// Copyright 2009 The Go Authors. All rights reserved. // Use of this source code is governed by a BSD-style // license that can be found in the LICENSE file. package reflect import ( "errors" "internal/abi" "internal/goarch" "internal/itoa" "internal/unsafeheader" "math" "runtime" "unsafe" ) // Value is the reflection interface to a Go value. // // Not all methods apply to all kinds of values. Restrictions, // if any, are noted in the documentation for each method. // Use the Kind method to find out the kind of value before // calling kind-specific methods. Calling a method // inappropriate to the kind of type causes a run time panic. // // The zero Value represents no value. // Its [Value.IsValid] method returns false, its Kind method returns [Invalid], // its String method returns "", and all other methods panic. // Most functions and methods never return an invalid value. // If one does, its documentation states the conditions explicitly. // // A Value can be used concurrently by multiple goroutines provided that // the underlying Go value can be used concurrently for the equivalent // direct operations. // // To compare two Values, compare the results of the Interface method. // Using == on two Values does not compare the underlying values // they represent. type Value struct { // typ_ holds the type of the value represented by a Value. // Access using the typ method to avoid escape of v. typ_ *abi.Type // Pointer-valued data or, if flagIndir is set, pointer to data. // Valid when either flagIndir is set or typ.pointers() is true. ptr unsafe.Pointer // flag holds metadata about the value. // // The lowest five bits give the Kind of the value, mirroring typ.Kind(). // // The next set of bits are flag bits: // - flagStickyRO: obtained via unexported not embedded field, so read-only // - flagEmbedRO: obtained via unexported embedded field, so read-only // - flagIndir: val holds a pointer to the data // - flagAddr: v.CanAddr is true (implies flagIndir and ptr is non-nil) // - flagMethod: v is a method value. // If ifaceIndir(typ), code can assume that flagIndir is set. // // The remaining 22+ bits give a method number for method values. // If flag.kind() != Func, code can assume that flagMethod is unset. flag // A method value represents a curried method invocation // like r.Read for some receiver r. The typ+val+flag bits describe // the receiver r, but the flag's Kind bits say Func (methods are // functions), and the top bits of the flag give the method number // in r's type's method table. } type flag uintptr const ( flagKindWidth = 5 // there are 27 kinds flagKindMask flag = 1< len(prefix) && name[:len(prefix)] == prefix { methodName := name[len(prefix):] if len(methodName) > 0 && 'A' <= methodName[0] && methodName[0] <= 'Z' { return name } } } return "unknown method" } // nonEmptyInterface is the header for an interface value with methods. type nonEmptyInterface struct { itab *abi.ITab word unsafe.Pointer } // mustBe panics if f's kind is not expected. // Making this a method on flag instead of on Value // (and embedding flag in Value) means that we can write // the very clear v.mustBe(Bool) and have it compile into // v.flag.mustBe(Bool), which will only bother to copy the // single important word for the receiver. func (f flag) mustBe(expected Kind) { // TODO(mvdan): use f.kind() again once mid-stack inlining gets better if Kind(f&flagKindMask) != expected { panic(&ValueError{valueMethodName(), f.kind()}) } } // mustBeExported panics if f records that the value was obtained using // an unexported field. func (f flag) mustBeExported() { if f == 0 || f&flagRO != 0 { f.mustBeExportedSlow() } } func (f flag) mustBeExportedSlow() { if f == 0 { panic(&ValueError{valueMethodName(), Invalid}) } if f&flagRO != 0 { panic("reflect: " + valueMethodName() + " using value obtained using unexported field") } } // mustBeAssignable panics if f records that the value is not assignable, // which is to say that either it was obtained using an unexported field // or it is not addressable. func (f flag) mustBeAssignable() { if f&flagRO != 0 || f&flagAddr == 0 { f.mustBeAssignableSlow() } } func (f flag) mustBeAssignableSlow() { if f == 0 { panic(&ValueError{valueMethodName(), Invalid}) } // Assignable if addressable and not read-only. if f&flagRO != 0 { panic("reflect: " + valueMethodName() + " using value obtained using unexported field") } if f&flagAddr == 0 { panic("reflect: " + valueMethodName() + " using unaddressable value") } } // Addr returns a pointer value representing the address of v. // It panics if [Value.CanAddr] returns false. // Addr is typically used to obtain a pointer to a struct field // or slice element in order to call a method that requires a // pointer receiver. func (v Value) Addr() Value { if v.flag&flagAddr == 0 { panic("reflect.Value.Addr of unaddressable value") } // Preserve flagRO instead of using v.flag.ro() so that // v.Addr().Elem() is equivalent to v (#32772) fl := v.flag & flagRO return Value{ptrTo(v.typ()), v.ptr, fl | flag(Pointer)} } // Bool returns v's underlying value. // It panics if v's kind is not [Bool]. func (v Value) Bool() bool { // panicNotBool is split out to keep Bool inlineable. if v.kind() != Bool { v.panicNotBool() } return *(*bool)(v.ptr) } func (v Value) panicNotBool() { v.mustBe(Bool) } var bytesType = rtypeOf(([]byte)(nil)) // Bytes returns v's underlying value. // It panics if v's underlying value is not a slice of bytes or // an addressable array of bytes. func (v Value) Bytes() []byte { // bytesSlow is split out to keep Bytes inlineable for unnamed []byte. if v.typ_ == bytesType { // ok to use v.typ_ directly as comparison doesn't cause escape return *(*[]byte)(v.ptr) } return v.bytesSlow() } func (v Value) bytesSlow() []byte { switch v.kind() { case Slice: if v.typ().Elem().Kind() != abi.Uint8 { panic("reflect.Value.Bytes of non-byte slice") } // Slice is always bigger than a word; assume flagIndir. return *(*[]byte)(v.ptr) case Array: if v.typ().Elem().Kind() != abi.Uint8 { panic("reflect.Value.Bytes of non-byte array") } if !v.CanAddr() { panic("reflect.Value.Bytes of unaddressable byte array") } p := (*byte)(v.ptr) n := int((*arrayType)(unsafe.Pointer(v.typ())).Len) return unsafe.Slice(p, n) } panic(&ValueError{"reflect.Value.Bytes", v.kind()}) } // runes returns v's underlying value. // It panics if v's underlying value is not a slice of runes (int32s). func (v Value) runes() []rune { v.mustBe(Slice) if v.typ().Elem().Kind() != abi.Int32 { panic("reflect.Value.Bytes of non-rune slice") } // Slice is always bigger than a word; assume flagIndir. return *(*[]rune)(v.ptr) } // CanAddr reports whether the value's address can be obtained with [Value.Addr]. // Such values are called addressable. A value is addressable if it is // an element of a slice, an element of an addressable array, // a field of an addressable struct, or the result of dereferencing a pointer. // If CanAddr returns false, calling [Value.Addr] will panic. func (v Value) CanAddr() bool { return v.flag&flagAddr != 0 } // CanSet reports whether the value of v can be changed. // A [Value] can be changed only if it is addressable and was not // obtained by the use of unexported struct fields. // If CanSet returns false, calling [Value.Set] or any type-specific // setter (e.g., [Value.SetBool], [Value.SetInt]) will panic. func (v Value) CanSet() bool { return v.flag&(flagAddr|flagRO) == flagAddr } // Call calls the function v with the input arguments in. // For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]). // Call panics if v's Kind is not [Func]. // It returns the output results as Values. // As in Go, each input argument must be assignable to the // type of the function's corresponding input parameter. // If v is a variadic function, Call creates the variadic slice parameter // itself, copying in the corresponding values. func (v Value) Call(in []Value) []Value { v.mustBe(Func) v.mustBeExported() return v.call("Call", in) } // CallSlice calls the variadic function v with the input arguments in, // assigning the slice in[len(in)-1] to v's final variadic argument. // For example, if len(in) == 3, v.CallSlice(in) represents the Go call v(in[0], in[1], in[2]...). // CallSlice panics if v's Kind is not [Func] or if v is not variadic. // It returns the output results as Values. // As in Go, each input argument must be assignable to the // type of the function's corresponding input parameter. func (v Value) CallSlice(in []Value) []Value { v.mustBe(Func) v.mustBeExported() return v.call("CallSlice", in) } var callGC bool // for testing; see TestCallMethodJump and TestCallArgLive const debugReflectCall = false func (v Value) call(op string, in []Value) []Value { // Get function pointer, type. t := (*funcType)(unsafe.Pointer(v.typ())) var ( fn unsafe.Pointer rcvr Value rcvrtype *abi.Type ) if v.flag&flagMethod != 0 { rcvr = v rcvrtype, t, fn = methodReceiver(op, v, int(v.flag)>>flagMethodShift) } else if v.flag&flagIndir != 0 { fn = *(*unsafe.Pointer)(v.ptr) } else { fn = v.ptr } if fn == nil { panic("reflect.Value.Call: call of nil function") } isSlice := op == "CallSlice" n := t.NumIn() isVariadic := t.IsVariadic() if isSlice { if !isVariadic { panic("reflect: CallSlice of non-variadic function") } if len(in) < n { panic("reflect: CallSlice with too few input arguments") } if len(in) > n { panic("reflect: CallSlice with too many input arguments") } } else { if isVariadic { n-- } if len(in) < n { panic("reflect: Call with too few input arguments") } if !isVariadic && len(in) > n { panic("reflect: Call with too many input arguments") } } for _, x := range in { if x.Kind() == Invalid { panic("reflect: " + op + " using zero Value argument") } } for i := 0; i < n; i++ { if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(toRType(targ)) { panic("reflect: " + op + " using " + xt.String() + " as type " + stringFor(targ)) } } if !isSlice && isVariadic { // prepare slice for remaining values m := len(in) - n slice := MakeSlice(toRType(t.In(n)), m, m) elem := toRType(t.In(n)).Elem() // FIXME cast to slice type and Elem() for i := 0; i < m; i++ { x := in[n+i] if xt := x.Type(); !xt.AssignableTo(elem) { panic("reflect: cannot use " + xt.String() + " as type " + elem.String() + " in " + op) } slice.Index(i).Set(x) } origIn := in in = make([]Value, n+1) copy(in[:n], origIn) in[n] = slice } nin := len(in) if nin != t.NumIn() { panic("reflect.Value.Call: wrong argument count") } nout := t.NumOut() // Register argument space. var regArgs abi.RegArgs // Compute frame type. frametype, framePool, abid := funcLayout(t, rcvrtype) // Allocate a chunk of memory for frame if needed. var stackArgs unsafe.Pointer if frametype.Size() != 0 { if nout == 0 { stackArgs = framePool.Get().(unsafe.Pointer) } else { // Can't use pool if the function has return values. // We will leak pointer to args in ret, so its lifetime is not scoped. stackArgs = unsafe_New(frametype) } } frameSize := frametype.Size() if debugReflectCall { println("reflect.call", stringFor(&t.Type)) abid.dump() } // Copy inputs into args. // Handle receiver. inStart := 0 if rcvrtype != nil { // Guaranteed to only be one word in size, // so it will only take up exactly 1 abiStep (either // in a register or on the stack). switch st := abid.call.steps[0]; st.kind { case abiStepStack: storeRcvr(rcvr, stackArgs) case abiStepPointer: storeRcvr(rcvr, unsafe.Pointer(®Args.Ptrs[st.ireg])) fallthrough case abiStepIntReg: storeRcvr(rcvr, unsafe.Pointer(®Args.Ints[st.ireg])) case abiStepFloatReg: storeRcvr(rcvr, unsafe.Pointer(®Args.Floats[st.freg])) default: panic("unknown ABI parameter kind") } inStart = 1 } // Handle arguments. for i, v := range in { v.mustBeExported() targ := toRType(t.In(i)) // TODO(mknyszek): Figure out if it's possible to get some // scratch space for this assignment check. Previously, it // was possible to use space in the argument frame. v = v.assignTo("reflect.Value.Call", &targ.t, nil) stepsLoop: for _, st := range abid.call.stepsForValue(i + inStart) { switch st.kind { case abiStepStack: // Copy values to the "stack." addr := add(stackArgs, st.stkOff, "precomputed stack arg offset") if v.flag&flagIndir != 0 { typedmemmove(&targ.t, addr, v.ptr) } else { *(*unsafe.Pointer)(addr) = v.ptr } // There's only one step for a stack-allocated value. break stepsLoop case abiStepIntReg, abiStepPointer: // Copy values to "integer registers." if v.flag&flagIndir != 0 { offset := add(v.ptr, st.offset, "precomputed value offset") if st.kind == abiStepPointer { // Duplicate this pointer in the pointer area of the // register space. Otherwise, there's the potential for // this to be the last reference to v.ptr. regArgs.Ptrs[st.ireg] = *(*unsafe.Pointer)(offset) } intToReg(®Args, st.ireg, st.size, offset) } else { if st.kind == abiStepPointer { // See the comment in abiStepPointer case above. regArgs.Ptrs[st.ireg] = v.ptr } regArgs.Ints[st.ireg] = uintptr(v.ptr) } case abiStepFloatReg: // Copy values to "float registers." if v.flag&flagIndir == 0 { panic("attempted to copy pointer to FP register") } offset := add(v.ptr, st.offset, "precomputed value offset") floatToReg(®Args, st.freg, st.size, offset) default: panic("unknown ABI part kind") } } } // TODO(mknyszek): Remove this when we no longer have // caller reserved spill space. frameSize = align(frameSize, goarch.PtrSize) frameSize += abid.spill // Mark pointers in registers for the return path. regArgs.ReturnIsPtr = abid.outRegPtrs if debugReflectCall { regArgs.Dump() } // For testing; see TestCallArgLive. if callGC { runtime.GC() } // Call. call(frametype, fn, stackArgs, uint32(frametype.Size()), uint32(abid.retOffset), uint32(frameSize), ®Args) // For testing; see TestCallMethodJump. if callGC { runtime.GC() } var ret []Value if nout == 0 { if stackArgs != nil { typedmemclr(frametype, stackArgs) framePool.Put(stackArgs) } } else { if stackArgs != nil { // Zero the now unused input area of args, // because the Values returned by this function contain pointers to the args object, // and will thus keep the args object alive indefinitely. typedmemclrpartial(frametype, stackArgs, 0, abid.retOffset) } // Wrap Values around return values in args. ret = make([]Value, nout) for i := 0; i < nout; i++ { tv := t.Out(i) if tv.Size() == 0 { // For zero-sized return value, args+off may point to the next object. // In this case, return the zero value instead. ret[i] = Zero(toRType(tv)) continue } steps := abid.ret.stepsForValue(i) if st := steps[0]; st.kind == abiStepStack { // This value is on the stack. If part of a value is stack // allocated, the entire value is according to the ABI. So // just make an indirection into the allocated frame. fl := flagIndir | flag(tv.Kind()) ret[i] = Value{tv, add(stackArgs, st.stkOff, "tv.Size() != 0"), fl} // Note: this does introduce false sharing between results - // if any result is live, they are all live. // (And the space for the args is live as well, but as we've // cleared that space it isn't as big a deal.) continue } // Handle pointers passed in registers. if !tv.IfaceIndir() { // Pointer-valued data gets put directly // into v.ptr. if steps[0].kind != abiStepPointer { print("kind=", steps[0].kind, ", type=", stringFor(tv), "\n") panic("mismatch between ABI description and types") } ret[i] = Value{tv, regArgs.Ptrs[steps[0].ireg], flag(tv.Kind())} continue } // All that's left is values passed in registers that we need to // create space for and copy values back into. // // TODO(mknyszek): We make a new allocation for each register-allocated // value, but previously we could always point into the heap-allocated // stack frame. This is a regression that could be fixed by adding // additional space to the allocated stack frame and storing the // register-allocated return values into the allocated stack frame and // referring there in the resulting Value. s := unsafe_New(tv) for _, st := range steps { switch st.kind { case abiStepIntReg: offset := add(s, st.offset, "precomputed value offset") intFromReg(®Args, st.ireg, st.size, offset) case abiStepPointer: s := add(s, st.offset, "precomputed value offset") *((*unsafe.Pointer)(s)) = regArgs.Ptrs[st.ireg] case abiStepFloatReg: offset := add(s, st.offset, "precomputed value offset") floatFromReg(®Args, st.freg, st.size, offset) case abiStepStack: panic("register-based return value has stack component") default: panic("unknown ABI part kind") } } ret[i] = Value{tv, s, flagIndir | flag(tv.Kind())} } } return ret } // callReflect is the call implementation used by a function // returned by MakeFunc. In many ways it is the opposite of the // method Value.call above. The method above converts a call using Values // into a call of a function with a concrete argument frame, while // callReflect converts a call of a function with a concrete argument // frame into a call using Values. // It is in this file so that it can be next to the call method above. // The remainder of the MakeFunc implementation is in makefunc.go. // // NOTE: This function must be marked as a "wrapper" in the generated code, // so that the linker can make it work correctly for panic and recover. // The gc compilers know to do that for the name "reflect.callReflect". // // ctxt is the "closure" generated by MakeFunc. // frame is a pointer to the arguments to that closure on the stack. // retValid points to a boolean which should be set when the results // section of frame is set. // // regs contains the argument values passed in registers and will contain // the values returned from ctxt.fn in registers. func callReflect(ctxt *makeFuncImpl, frame unsafe.Pointer, retValid *bool, regs *abi.RegArgs) { if callGC { // Call GC upon entry during testing. // Getting our stack scanned here is the biggest hazard, because // our caller (makeFuncStub) could have failed to place the last // pointer to a value in regs' pointer space, in which case it // won't be visible to the GC. runtime.GC() } ftyp := ctxt.ftyp f := ctxt.fn _, _, abid := funcLayout(ftyp, nil) // Copy arguments into Values. ptr := frame in := make([]Value, 0, int(ftyp.InCount)) for i, typ := range ftyp.InSlice() { if typ.Size() == 0 { in = append(in, Zero(toRType(typ))) continue } v := Value{typ, nil, flag(typ.Kind())} steps := abid.call.stepsForValue(i) if st := steps[0]; st.kind == abiStepStack { if typ.IfaceIndir() { // value cannot be inlined in interface data. // Must make a copy, because f might keep a reference to it, // and we cannot let f keep a reference to the stack frame // after this function returns, not even a read-only reference. v.ptr = unsafe_New(typ) if typ.Size() > 0 { typedmemmove(typ, v.ptr, add(ptr, st.stkOff, "typ.size > 0")) } v.flag |= flagIndir } else { v.ptr = *(*unsafe.Pointer)(add(ptr, st.stkOff, "1-ptr")) } } else { if typ.IfaceIndir() { // All that's left is values passed in registers that we need to // create space for the values. v.flag |= flagIndir v.ptr = unsafe_New(typ) for _, st := range steps { switch st.kind { case abiStepIntReg: offset := add(v.ptr, st.offset, "precomputed value offset") intFromReg(regs, st.ireg, st.size, offset) case abiStepPointer: s := add(v.ptr, st.offset, "precomputed value offset") *((*unsafe.Pointer)(s)) = regs.Ptrs[st.ireg] case abiStepFloatReg: offset := add(v.ptr, st.offset, "precomputed value offset") floatFromReg(regs, st.freg, st.size, offset) case abiStepStack: panic("register-based return value has stack component") default: panic("unknown ABI part kind") } } } else { // Pointer-valued data gets put directly // into v.ptr. if steps[0].kind != abiStepPointer { print("kind=", steps[0].kind, ", type=", stringFor(typ), "\n") panic("mismatch between ABI description and types") } v.ptr = regs.Ptrs[steps[0].ireg] } } in = append(in, v) } // Call underlying function. out := f(in) numOut := ftyp.NumOut() if len(out) != numOut { panic("reflect: wrong return count from function created by MakeFunc") } // Copy results back into argument frame and register space. if numOut > 0 { for i, typ := range ftyp.OutSlice() { v := out[i] if v.typ() == nil { panic("reflect: function created by MakeFunc using " + funcName(f) + " returned zero Value") } if v.flag&flagRO != 0 { panic("reflect: function created by MakeFunc using " + funcName(f) + " returned value obtained from unexported field") } if typ.Size() == 0 { continue } // Convert v to type typ if v is assignable to a variable // of type t in the language spec. // See issue 28761. // // // TODO(mknyszek): In the switch to the register ABI we lost // the scratch space here for the register cases (and // temporarily for all the cases). // // If/when this happens, take note of the following: // // We must clear the destination before calling assignTo, // in case assignTo writes (with memory barriers) to the // target location used as scratch space. See issue 39541. v = v.assignTo("reflect.MakeFunc", typ, nil) stepsLoop: for _, st := range abid.ret.stepsForValue(i) { switch st.kind { case abiStepStack: // Copy values to the "stack." addr := add(ptr, st.stkOff, "precomputed stack arg offset") // Do not use write barriers. The stack space used // for this call is not adequately zeroed, and we // are careful to keep the arguments alive until we // return to makeFuncStub's caller. if v.flag&flagIndir != 0 { memmove(addr, v.ptr, st.size) } else { // This case must be a pointer type. *(*uintptr)(addr) = uintptr(v.ptr) } // There's only one step for a stack-allocated value. break stepsLoop case abiStepIntReg, abiStepPointer: // Copy values to "integer registers." if v.flag&flagIndir != 0 { offset := add(v.ptr, st.offset, "precomputed value offset") intToReg(regs, st.ireg, st.size, offset) } else { // Only populate the Ints space on the return path. // This is safe because out is kept alive until the // end of this function, and the return path through // makeFuncStub has no preemption, so these pointers // are always visible to the GC. regs.Ints[st.ireg] = uintptr(v.ptr) } case abiStepFloatReg: // Copy values to "float registers." if v.flag&flagIndir == 0 { panic("attempted to copy pointer to FP register") } offset := add(v.ptr, st.offset, "precomputed value offset") floatToReg(regs, st.freg, st.size, offset) default: panic("unknown ABI part kind") } } } } // Announce that the return values are valid. // After this point the runtime can depend on the return values being valid. *retValid = true // We have to make sure that the out slice lives at least until // the runtime knows the return values are valid. Otherwise, the // return values might not be scanned by anyone during a GC. // (out would be dead, and the return slots not yet alive.) runtime.KeepAlive(out) // runtime.getArgInfo expects to be able to find ctxt on the // stack when it finds our caller, makeFuncStub. Make sure it // doesn't get garbage collected. runtime.KeepAlive(ctxt) } // methodReceiver returns information about the receiver // described by v. The Value v may or may not have the // flagMethod bit set, so the kind cached in v.flag should // not be used. // The return value rcvrtype gives the method's actual receiver type. // The return value t gives the method type signature (without the receiver). // The return value fn is a pointer to the method code. func methodReceiver(op string, v Value, methodIndex int) (rcvrtype *abi.Type, t *funcType, fn unsafe.Pointer) { i := methodIndex if v.typ().Kind() == abi.Interface { tt := (*interfaceType)(unsafe.Pointer(v.typ())) if uint(i) >= uint(len(tt.Methods)) { panic("reflect: internal error: invalid method index") } m := &tt.Methods[i] if !tt.nameOff(m.Name).IsExported() { panic("reflect: " + op + " of unexported method") } iface := (*nonEmptyInterface)(v.ptr) if iface.itab == nil { panic("reflect: " + op + " of method on nil interface value") } rcvrtype = iface.itab.Type fn = unsafe.Pointer(&unsafe.Slice(&iface.itab.Fun[0], i+1)[i]) t = (*funcType)(unsafe.Pointer(tt.typeOff(m.Typ))) } else { rcvrtype = v.typ() ms := v.typ().ExportedMethods() if uint(i) >= uint(len(ms)) { panic("reflect: internal error: invalid method index") } m := ms[i] if !nameOffFor(v.typ(), m.Name).IsExported() { panic("reflect: " + op + " of unexported method") } ifn := textOffFor(v.typ(), m.Ifn) fn = unsafe.Pointer(&ifn) t = (*funcType)(unsafe.Pointer(typeOffFor(v.typ(), m.Mtyp))) } return } // v is a method receiver. Store at p the word which is used to // encode that receiver at the start of the argument list. // Reflect uses the "interface" calling convention for // methods, which always uses one word to record the receiver. func storeRcvr(v Value, p unsafe.Pointer) { t := v.typ() if t.Kind() == abi.Interface { // the interface data word becomes the receiver word iface := (*nonEmptyInterface)(v.ptr) *(*unsafe.Pointer)(p) = iface.word } else if v.flag&flagIndir != 0 && !t.IfaceIndir() { *(*unsafe.Pointer)(p) = *(*unsafe.Pointer)(v.ptr) } else { *(*unsafe.Pointer)(p) = v.ptr } } // align returns the result of rounding x up to a multiple of n. // n must be a power of two. func align(x, n uintptr) uintptr { return (x + n - 1) &^ (n - 1) } // callMethod is the call implementation used by a function returned // by makeMethodValue (used by v.Method(i).Interface()). // It is a streamlined version of the usual reflect call: the caller has // already laid out the argument frame for us, so we don't have // to deal with individual Values for each argument. // It is in this file so that it can be next to the two similar functions above. // The remainder of the makeMethodValue implementation is in makefunc.go. // // NOTE: This function must be marked as a "wrapper" in the generated code, // so that the linker can make it work correctly for panic and recover. // The gc compilers know to do that for the name "reflect.callMethod". // // ctxt is the "closure" generated by makeMethodValue. // frame is a pointer to the arguments to that closure on the stack. // retValid points to a boolean which should be set when the results // section of frame is set. // // regs contains the argument values passed in registers and will contain // the values returned from ctxt.fn in registers. func callMethod(ctxt *methodValue, frame unsafe.Pointer, retValid *bool, regs *abi.RegArgs) { rcvr := ctxt.rcvr rcvrType, valueFuncType, methodFn := methodReceiver("call", rcvr, ctxt.method) // There are two ABIs at play here. // // methodValueCall was invoked with the ABI assuming there was no // receiver ("value ABI") and that's what frame and regs are holding. // // Meanwhile, we need to actually call the method with a receiver, which // has its own ABI ("method ABI"). Everything that follows is a translation // between the two. _, _, valueABI := funcLayout(valueFuncType, nil) valueFrame, valueRegs := frame, regs methodFrameType, methodFramePool, methodABI := funcLayout(valueFuncType, rcvrType) // Make a new frame that is one word bigger so we can store the receiver. // This space is used for both arguments and return values. methodFrame := methodFramePool.Get().(unsafe.Pointer) var methodRegs abi.RegArgs // Deal with the receiver. It's guaranteed to only be one word in size. switch st := methodABI.call.steps[0]; st.kind { case abiStepStack: // Only copy the receiver to the stack if the ABI says so. // Otherwise, it'll be in a register already. storeRcvr(rcvr, methodFrame) case abiStepPointer: // Put the receiver in a register. storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Ptrs[st.ireg])) fallthrough case abiStepIntReg: storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Ints[st.ireg])) case abiStepFloatReg: storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Floats[st.freg])) default: panic("unknown ABI parameter kind") } // Translate the rest of the arguments. for i, t := range valueFuncType.InSlice() { valueSteps := valueABI.call.stepsForValue(i) methodSteps := methodABI.call.stepsForValue(i + 1) // Zero-sized types are trivial: nothing to do. if len(valueSteps) == 0 { if len(methodSteps) != 0 { panic("method ABI and value ABI do not align") } continue } // There are four cases to handle in translating each // argument: // 1. Stack -> stack translation. // 2. Stack -> registers translation. // 3. Registers -> stack translation. // 4. Registers -> registers translation. // If the value ABI passes the value on the stack, // then the method ABI does too, because it has strictly // fewer arguments. Simply copy between the two. if vStep := valueSteps[0]; vStep.kind == abiStepStack { mStep := methodSteps[0] // Handle stack -> stack translation. if mStep.kind == abiStepStack { if vStep.size != mStep.size { panic("method ABI and value ABI do not align") } typedmemmove(t, add(methodFrame, mStep.stkOff, "precomputed stack offset"), add(valueFrame, vStep.stkOff, "precomputed stack offset")) continue } // Handle stack -> register translation. for _, mStep := range methodSteps { from := add(valueFrame, vStep.stkOff+mStep.offset, "precomputed stack offset") switch mStep.kind { case abiStepPointer: // Do the pointer copy directly so we get a write barrier. methodRegs.Ptrs[mStep.ireg] = *(*unsafe.Pointer)(from) fallthrough // We need to make sure this ends up in Ints, too. case abiStepIntReg: intToReg(&methodRegs, mStep.ireg, mStep.size, from) case abiStepFloatReg: floatToReg(&methodRegs, mStep.freg, mStep.size, from) default: panic("unexpected method step") } } continue } // Handle register -> stack translation. if mStep := methodSteps[0]; mStep.kind == abiStepStack { for _, vStep := range valueSteps { to := add(methodFrame, mStep.stkOff+vStep.offset, "precomputed stack offset") switch vStep.kind { case abiStepPointer: // Do the pointer copy directly so we get a write barrier. *(*unsafe.Pointer)(to) = valueRegs.Ptrs[vStep.ireg] case abiStepIntReg: intFromReg(valueRegs, vStep.ireg, vStep.size, to) case abiStepFloatReg: floatFromReg(valueRegs, vStep.freg, vStep.size, to) default: panic("unexpected value step") } } continue } // Handle register -> register translation. if len(valueSteps) != len(methodSteps) { // Because it's the same type for the value, and it's assigned // to registers both times, it should always take up the same // number of registers for each ABI. panic("method ABI and value ABI don't align") } for i, vStep := range valueSteps { mStep := methodSteps[i] if mStep.kind != vStep.kind { panic("method ABI and value ABI don't align") } switch vStep.kind { case abiStepPointer: // Copy this too, so we get a write barrier. methodRegs.Ptrs[mStep.ireg] = valueRegs.Ptrs[vStep.ireg] fallthrough case abiStepIntReg: methodRegs.Ints[mStep.ireg] = valueRegs.Ints[vStep.ireg] case abiStepFloatReg: methodRegs.Floats[mStep.freg] = valueRegs.Floats[vStep.freg] default: panic("unexpected value step") } } } methodFrameSize := methodFrameType.Size() // TODO(mknyszek): Remove this when we no longer have // caller reserved spill space. methodFrameSize = align(methodFrameSize, goarch.PtrSize) methodFrameSize += methodABI.spill // Mark pointers in registers for the return path. methodRegs.ReturnIsPtr = methodABI.outRegPtrs // Call. // Call copies the arguments from scratch to the stack, calls fn, // and then copies the results back into scratch. call(methodFrameType, methodFn, methodFrame, uint32(methodFrameType.Size()), uint32(methodABI.retOffset), uint32(methodFrameSize), &methodRegs) // Copy return values. // // This is somewhat simpler because both ABIs have an identical // return value ABI (the types are identical). As a result, register // results can simply be copied over. Stack-allocated values are laid // out the same, but are at different offsets from the start of the frame // Ignore any changes to args. // Avoid constructing out-of-bounds pointers if there are no return values. // because the arguments may be laid out differently. if valueRegs != nil { *valueRegs = methodRegs } if retSize := methodFrameType.Size() - methodABI.retOffset; retSize > 0 { valueRet := add(valueFrame, valueABI.retOffset, "valueFrame's size > retOffset") methodRet := add(methodFrame, methodABI.retOffset, "methodFrame's size > retOffset") // This copies to the stack. Write barriers are not needed. memmove(valueRet, methodRet, retSize) } // Tell the runtime it can now depend on the return values // being properly initialized. *retValid = true // Clear the scratch space and put it back in the pool. // This must happen after the statement above, so that the return // values will always be scanned by someone. typedmemclr(methodFrameType, methodFrame) methodFramePool.Put(methodFrame) // See the comment in callReflect. runtime.KeepAlive(ctxt) // Keep valueRegs alive because it may hold live pointer results. // The caller (methodValueCall) has it as a stack object, which is only // scanned when there is a reference to it. runtime.KeepAlive(valueRegs) } // funcName returns the name of f, for use in error messages. func funcName(f func([]Value) []Value) string { pc := *(*uintptr)(unsafe.Pointer(&f)) rf := runtime.FuncForPC(pc) if rf != nil { return rf.Name() } return "closure" } // Cap returns v's capacity. // It panics if v's Kind is not [Array], [Chan], [Slice] or pointer to [Array]. func (v Value) Cap() int { // capNonSlice is split out to keep Cap inlineable for slice kinds. if v.kind() == Slice { return (*unsafeheader.Slice)(v.ptr).Cap } return v.capNonSlice() } func (v Value) capNonSlice() int { k := v.kind() switch k { case Array: return v.typ().Len() case Chan: return chancap(v.pointer()) case Ptr: if v.typ().Elem().Kind() == abi.Array { return v.typ().Elem().Len() } panic("reflect: call of reflect.Value.Cap on ptr to non-array Value") } panic(&ValueError{"reflect.Value.Cap", v.kind()}) } // Close closes the channel v. // It panics if v's Kind is not [Chan] or // v is a receive-only channel. func (v Value) Close() { v.mustBe(Chan) v.mustBeExported() tt := (*chanType)(unsafe.Pointer(v.typ())) if ChanDir(tt.Dir)&SendDir == 0 { panic("reflect: close of receive-only channel") } chanclose(v.pointer()) } // CanComplex reports whether [Value.Complex] can be used without panicking. func (v Value) CanComplex() bool { switch v.kind() { case Complex64, Complex128: return true default: return false } } // Complex returns v's underlying value, as a complex128. // It panics if v's Kind is not [Complex64] or [Complex128] func (v Value) Complex() complex128 { k := v.kind() switch k { case Complex64: return complex128(*(*complex64)(v.ptr)) case Complex128: return *(*complex128)(v.ptr) } panic(&ValueError{"reflect.Value.Complex", v.kind()}) } // Elem returns the value that the interface v contains // or that the pointer v points to. // It panics if v's Kind is not [Interface] or [Pointer]. // It returns the zero Value if v is nil. func (v Value) Elem() Value { k := v.kind() switch k { case Interface: var eface any if v.typ().NumMethod() == 0 { eface = *(*any)(v.ptr) } else { eface = (any)(*(*interface { M() })(v.ptr)) } x := unpackEface(eface) if x.flag != 0 { x.flag |= v.flag.ro() } return x case Pointer: ptr := v.ptr if v.flag&flagIndir != 0 { if v.typ().IfaceIndir() { // This is a pointer to a not-in-heap object. ptr points to a uintptr // in the heap. That uintptr is the address of a not-in-heap object. // In general, pointers to not-in-heap objects can be total junk. // But Elem() is asking to dereference it, so the user has asserted // that at least it is a valid pointer (not just an integer stored in // a pointer slot). So let's check, to make sure that it isn't a pointer // that the runtime will crash on if it sees it during GC or write barriers. // Since it is a not-in-heap pointer, all pointers to the heap are // forbidden! That makes the test pretty easy. // See issue 48399. if !verifyNotInHeapPtr(*(*uintptr)(ptr)) { panic("reflect: reflect.Value.Elem on an invalid notinheap pointer") } } ptr = *(*unsafe.Pointer)(ptr) } // The returned value's address is v's value. if ptr == nil { return Value{} } tt := (*ptrType)(unsafe.Pointer(v.typ())) typ := tt.Elem fl := v.flag&flagRO | flagIndir | flagAddr fl |= flag(typ.Kind()) return Value{typ, ptr, fl} } panic(&ValueError{"reflect.Value.Elem", v.kind()}) } // Field returns the i'th field of the struct v. // It panics if v's Kind is not [Struct] or i is out of range. func (v Value) Field(i int) Value { if v.kind() != Struct { panic(&ValueError{"reflect.Value.Field", v.kind()}) } tt := (*structType)(unsafe.Pointer(v.typ())) if uint(i) >= uint(len(tt.Fields)) { panic("reflect: Field index out of range") } field := &tt.Fields[i] typ := field.Typ // Inherit permission bits from v, but clear flagEmbedRO. fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind()) // Using an unexported field forces flagRO. if !field.Name.IsExported() { if field.Embedded() { fl |= flagEmbedRO } else { fl |= flagStickyRO } } // Either flagIndir is set and v.ptr points at struct, // or flagIndir is not set and v.ptr is the actual struct data. // In the former case, we want v.ptr + offset. // In the latter case, we must have field.offset = 0, // so v.ptr + field.offset is still the correct address. ptr := add(v.ptr, field.Offset, "same as non-reflect &v.field") return Value{typ, ptr, fl} } // FieldByIndex returns the nested field corresponding to index. // It panics if evaluation requires stepping through a nil // pointer or a field that is not a struct. func (v Value) FieldByIndex(index []int) Value { if len(index) == 1 { return v.Field(index[0]) } v.mustBe(Struct) for i, x := range index { if i > 0 { if v.Kind() == Pointer && v.typ().Elem().Kind() == abi.Struct { if v.IsNil() { panic("reflect: indirection through nil pointer to embedded struct") } v = v.Elem() } } v = v.Field(x) } return v } // FieldByIndexErr returns the nested field corresponding to index. // It returns an error if evaluation requires stepping through a nil // pointer, but panics if it must step through a field that // is not a struct. func (v Value) FieldByIndexErr(index []int) (Value, error) { if len(index) == 1 { return v.Field(index[0]), nil } v.mustBe(Struct) for i, x := range index { if i > 0 { if v.Kind() == Ptr && v.typ().Elem().Kind() == abi.Struct { if v.IsNil() { return Value{}, errors.New("reflect: indirection through nil pointer to embedded struct field " + nameFor(v.typ().Elem())) } v = v.Elem() } } v = v.Field(x) } return v, nil } // FieldByName returns the struct field with the given name. // It returns the zero Value if no field was found. // It panics if v's Kind is not [Struct]. func (v Value) FieldByName(name string) Value { v.mustBe(Struct) if f, ok := toRType(v.typ()).FieldByName(name); ok { return v.FieldByIndex(f.Index) } return Value{} } // FieldByNameFunc returns the struct field with a name // that satisfies the match function. // It panics if v's Kind is not [Struct]. // It returns the zero Value if no field was found. func (v Value) FieldByNameFunc(match func(string) bool) Value { if f, ok := toRType(v.typ()).FieldByNameFunc(match); ok { return v.FieldByIndex(f.Index) } return Value{} } // CanFloat reports whether [Value.Float] can be used without panicking. func (v Value) CanFloat() bool { switch v.kind() { case Float32, Float64: return true default: return false } } // Float returns v's underlying value, as a float64. // It panics if v's Kind is not [Float32] or [Float64] func (v Value) Float() float64 { k := v.kind() switch k { case Float32: return float64(*(*float32)(v.ptr)) case Float64: return *(*float64)(v.ptr) } panic(&ValueError{"reflect.Value.Float", v.kind()}) } var uint8Type = rtypeOf(uint8(0)) // Index returns v's i'th element. // It panics if v's Kind is not [Array], [Slice], or [String] or i is out of range. func (v Value) Index(i int) Value { switch v.kind() { case Array: tt := (*arrayType)(unsafe.Pointer(v.typ())) if uint(i) >= uint(tt.Len) { panic("reflect: array index out of range") } typ := tt.Elem offset := uintptr(i) * typ.Size() // Either flagIndir is set and v.ptr points at array, // or flagIndir is not set and v.ptr is the actual array data. // In the former case, we want v.ptr + offset. // In the latter case, we must be doing Index(0), so offset = 0, // so v.ptr + offset is still the correct address. val := add(v.ptr, offset, "same as &v[i], i < tt.len") fl := v.flag&(flagIndir|flagAddr) | v.flag.ro() | flag(typ.Kind()) // bits same as overall array return Value{typ, val, fl} case Slice: // Element flag same as Elem of Pointer. // Addressable, indirect, possibly read-only. s := (*unsafeheader.Slice)(v.ptr) if uint(i) >= uint(s.Len) { panic("reflect: slice index out of range") } tt := (*sliceType)(unsafe.Pointer(v.typ())) typ := tt.Elem val := arrayAt(s.Data, i, typ.Size(), "i < s.Len") fl := flagAddr | flagIndir | v.flag.ro() | flag(typ.Kind()) return Value{typ, val, fl} case String: s := (*unsafeheader.String)(v.ptr) if uint(i) >= uint(s.Len) { panic("reflect: string index out of range") } p := arrayAt(s.Data, i, 1, "i < s.Len") fl := v.flag.ro() | flag(Uint8) | flagIndir return Value{uint8Type, p, fl} } panic(&ValueError{"reflect.Value.Index", v.kind()}) } // CanInt reports whether Int can be used without panicking. func (v Value) CanInt() bool { switch v.kind() { case Int, Int8, Int16, Int32, Int64: return true default: return false } } // Int returns v's underlying value, as an int64. // It panics if v's Kind is not [Int], [Int8], [Int16], [Int32], or [Int64]. func (v Value) Int() int64 { k := v.kind() p := v.ptr switch k { case Int: return int64(*(*int)(p)) case Int8: return int64(*(*int8)(p)) case Int16: return int64(*(*int16)(p)) case Int32: return int64(*(*int32)(p)) case Int64: return *(*int64)(p) } panic(&ValueError{"reflect.Value.Int", v.kind()}) } // CanInterface reports whether [Value.Interface] can be used without panicking. func (v Value) CanInterface() bool { if v.flag == 0 { panic(&ValueError{"reflect.Value.CanInterface", Invalid}) } return v.flag&flagRO == 0 } // Interface returns v's current value as an interface{}. // It is equivalent to: // // var i interface{} = (v's underlying value) // // It panics if the Value was obtained by accessing // unexported struct fields. func (v Value) Interface() (i any) { return valueInterface(v, true) } func valueInterface(v Value, safe bool) any { if v.flag == 0 { panic(&ValueError{"reflect.Value.Interface", Invalid}) } if safe && v.flag&flagRO != 0 { // Do not allow access to unexported values via Interface, // because they might be pointers that should not be // writable or methods or function that should not be callable. panic("reflect.Value.Interface: cannot return value obtained from unexported field or method") } if v.flag&flagMethod != 0 { v = makeMethodValue("Interface", v) } if v.kind() == Interface { // Special case: return the element inside the interface. // Empty interface has one layout, all interfaces with // methods have a second layout. if v.NumMethod() == 0 { return *(*any)(v.ptr) } return *(*interface { M() })(v.ptr) } return packEface(v) } // InterfaceData returns a pair of unspecified uintptr values. // It panics if v's Kind is not Interface. // // In earlier versions of Go, this function returned the interface's // value as a uintptr pair. As of Go 1.4, the implementation of // interface values precludes any defined use of InterfaceData. // // Deprecated: The memory representation of interface values is not // compatible with InterfaceData. func (v Value) InterfaceData() [2]uintptr { v.mustBe(Interface) // The compiler loses track as it converts to uintptr. Force escape. escapes(v.ptr) // We treat this as a read operation, so we allow // it even for unexported data, because the caller // has to import "unsafe" to turn it into something // that can be abused. // Interface value is always bigger than a word; assume flagIndir. return *(*[2]uintptr)(v.ptr) } // IsNil reports whether its argument v is nil. The argument must be // a chan, func, interface, map, pointer, or slice value; if it is // not, IsNil panics. Note that IsNil is not always equivalent to a // regular comparison with nil in Go. For example, if v was created // by calling [ValueOf] with an uninitialized interface variable i, // i==nil will be true but v.IsNil will panic as v will be the zero // Value. func (v Value) IsNil() bool { k := v.kind() switch k { case Chan, Func, Map, Pointer, UnsafePointer: if v.flag&flagMethod != 0 { return false } ptr := v.ptr if v.flag&flagIndir != 0 { ptr = *(*unsafe.Pointer)(ptr) } return ptr == nil case Interface, Slice: // Both interface and slice are nil if first word is 0. // Both are always bigger than a word; assume flagIndir. return *(*unsafe.Pointer)(v.ptr) == nil } panic(&ValueError{"reflect.Value.IsNil", v.kind()}) } // IsValid reports whether v represents a value. // It returns false if v is the zero Value. // If [Value.IsValid] returns false, all other methods except String panic. // Most functions and methods never return an invalid Value. // If one does, its documentation states the conditions explicitly. func (v Value) IsValid() bool { return v.flag != 0 } // IsZero reports whether v is the zero value for its type. // It panics if the argument is invalid. func (v Value) IsZero() bool { switch v.kind() { case Bool: return !v.Bool() case Int, Int8, Int16, Int32, Int64: return v.Int() == 0 case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return v.Uint() == 0 case Float32, Float64: return v.Float() == 0 case Complex64, Complex128: return v.Complex() == 0 case Array: if v.flag&flagIndir == 0 { return v.ptr == nil } typ := (*abi.ArrayType)(unsafe.Pointer(v.typ())) // If the type is comparable, then compare directly with zero. if typ.Equal != nil && typ.Size() <= abi.ZeroValSize { // v.ptr doesn't escape, as Equal functions are compiler generated // and never escape. The escape analysis doesn't know, as it is a // function pointer call. return typ.Equal(abi.NoEscape(v.ptr), unsafe.Pointer(&zeroVal[0])) } if typ.TFlag&abi.TFlagRegularMemory != 0 { // For some types where the zero value is a value where all bits of this type are 0 // optimize it. return isZero(unsafe.Slice(((*byte)(v.ptr)), typ.Size())) } n := int(typ.Len) for i := 0; i < n; i++ { if !v.Index(i).IsZero() { return false } } return true case Chan, Func, Interface, Map, Pointer, Slice, UnsafePointer: return v.IsNil() case String: return v.Len() == 0 case Struct: if v.flag&flagIndir == 0 { return v.ptr == nil } typ := (*abi.StructType)(unsafe.Pointer(v.typ())) // If the type is comparable, then compare directly with zero. if typ.Equal != nil && typ.Size() <= abi.ZeroValSize { // See noescape justification above. return typ.Equal(abi.NoEscape(v.ptr), unsafe.Pointer(&zeroVal[0])) } if typ.TFlag&abi.TFlagRegularMemory != 0 { // For some types where the zero value is a value where all bits of this type are 0 // optimize it. return isZero(unsafe.Slice(((*byte)(v.ptr)), typ.Size())) } n := v.NumField() for i := 0; i < n; i++ { if !v.Field(i).IsZero() && v.Type().Field(i).Name != "_" { return false } } return true default: // This should never happen, but will act as a safeguard for later, // as a default value doesn't makes sense here. panic(&ValueError{"reflect.Value.IsZero", v.Kind()}) } } // isZero For all zeros, performance is not as good as // return bytealg.Count(b, byte(0)) == len(b) func isZero(b []byte) bool { if len(b) == 0 { return true } const n = 32 // Align memory addresses to 8 bytes. for uintptr(unsafe.Pointer(&b[0]))%8 != 0 { if b[0] != 0 { return false } b = b[1:] if len(b) == 0 { return true } } for len(b)%8 != 0 { if b[len(b)-1] != 0 { return false } b = b[:len(b)-1] } if len(b) == 0 { return true } w := unsafe.Slice((*uint64)(unsafe.Pointer(&b[0])), len(b)/8) for len(w)%n != 0 { if w[0] != 0 { return false } w = w[1:] } for len(w) >= n { if w[0] != 0 || w[1] != 0 || w[2] != 0 || w[3] != 0 || w[4] != 0 || w[5] != 0 || w[6] != 0 || w[7] != 0 || w[8] != 0 || w[9] != 0 || w[10] != 0 || w[11] != 0 || w[12] != 0 || w[13] != 0 || w[14] != 0 || w[15] != 0 || w[16] != 0 || w[17] != 0 || w[18] != 0 || w[19] != 0 || w[20] != 0 || w[21] != 0 || w[22] != 0 || w[23] != 0 || w[24] != 0 || w[25] != 0 || w[26] != 0 || w[27] != 0 || w[28] != 0 || w[29] != 0 || w[30] != 0 || w[31] != 0 { return false } w = w[n:] } return true } // SetZero sets v to be the zero value of v's type. // It panics if [Value.CanSet] returns false. func (v Value) SetZero() { v.mustBeAssignable() switch v.kind() { case Bool: *(*bool)(v.ptr) = false case Int: *(*int)(v.ptr) = 0 case Int8: *(*int8)(v.ptr) = 0 case Int16: *(*int16)(v.ptr) = 0 case Int32: *(*int32)(v.ptr) = 0 case Int64: *(*int64)(v.ptr) = 0 case Uint: *(*uint)(v.ptr) = 0 case Uint8: *(*uint8)(v.ptr) = 0 case Uint16: *(*uint16)(v.ptr) = 0 case Uint32: *(*uint32)(v.ptr) = 0 case Uint64: *(*uint64)(v.ptr) = 0 case Uintptr: *(*uintptr)(v.ptr) = 0 case Float32: *(*float32)(v.ptr) = 0 case Float64: *(*float64)(v.ptr) = 0 case Complex64: *(*complex64)(v.ptr) = 0 case Complex128: *(*complex128)(v.ptr) = 0 case String: *(*string)(v.ptr) = "" case Slice: *(*unsafeheader.Slice)(v.ptr) = unsafeheader.Slice{} case Interface: *(*abi.EmptyInterface)(v.ptr) = abi.EmptyInterface{} case Chan, Func, Map, Pointer, UnsafePointer: *(*unsafe.Pointer)(v.ptr) = nil case Array, Struct: typedmemclr(v.typ(), v.ptr) default: // This should never happen, but will act as a safeguard for later, // as a default value doesn't makes sense here. panic(&ValueError{"reflect.Value.SetZero", v.Kind()}) } } // Kind returns v's Kind. // If v is the zero Value ([Value.IsValid] returns false), Kind returns Invalid. func (v Value) Kind() Kind { return v.kind() } // Len returns v's length. // It panics if v's Kind is not [Array], [Chan], [Map], [Slice], [String], or pointer to [Array]. func (v Value) Len() int { // lenNonSlice is split out to keep Len inlineable for slice kinds. if v.kind() == Slice { return (*unsafeheader.Slice)(v.ptr).Len } return v.lenNonSlice() } func (v Value) lenNonSlice() int { switch k := v.kind(); k { case Array: tt := (*arrayType)(unsafe.Pointer(v.typ())) return int(tt.Len) case Chan: return chanlen(v.pointer()) case Map: return maplen(v.pointer()) case String: // String is bigger than a word; assume flagIndir. return (*unsafeheader.String)(v.ptr).Len case Ptr: if v.typ().Elem().Kind() == abi.Array { return v.typ().Elem().Len() } panic("reflect: call of reflect.Value.Len on ptr to non-array Value") } panic(&ValueError{"reflect.Value.Len", v.kind()}) } var stringType = rtypeOf("") // MapIndex returns the value associated with key in the map v. // It panics if v's Kind is not [Map]. // It returns the zero Value if key is not found in the map or if v represents a nil map. // As in Go, the key's value must be assignable to the map's key type. func (v Value) MapIndex(key Value) Value { v.mustBe(Map) tt := (*mapType)(unsafe.Pointer(v.typ())) // Do not require key to be exported, so that DeepEqual // and other programs can use all the keys returned by // MapKeys as arguments to MapIndex. If either the map // or the key is unexported, though, the result will be // considered unexported. This is consistent with the // behavior for structs, which allow read but not write // of unexported fields. var e unsafe.Pointer if (tt.Key == stringType || key.kind() == String) && tt.Key == key.typ() && tt.Elem.Size() <= abi.MapMaxElemBytes { k := *(*string)(key.ptr) e = mapaccess_faststr(v.typ(), v.pointer(), k) } else { key = key.assignTo("reflect.Value.MapIndex", tt.Key, nil) var k unsafe.Pointer if key.flag&flagIndir != 0 { k = key.ptr } else { k = unsafe.Pointer(&key.ptr) } e = mapaccess(v.typ(), v.pointer(), k) } if e == nil { return Value{} } typ := tt.Elem fl := (v.flag | key.flag).ro() fl |= flag(typ.Kind()) return copyVal(typ, fl, e) } // MapKeys returns a slice containing all the keys present in the map, // in unspecified order. // It panics if v's Kind is not [Map]. // It returns an empty slice if v represents a nil map. func (v Value) MapKeys() []Value { v.mustBe(Map) tt := (*mapType)(unsafe.Pointer(v.typ())) keyType := tt.Key fl := v.flag.ro() | flag(keyType.Kind()) m := v.pointer() mlen := int(0) if m != nil { mlen = maplen(m) } var it hiter mapiterinit(v.typ(), m, &it) a := make([]Value, mlen) var i int for i = 0; i < len(a); i++ { key := mapiterkey(&it) if key == nil { // Someone deleted an entry from the map since we // called maplen above. It's a data race, but nothing // we can do about it. break } a[i] = copyVal(keyType, fl, key) mapiternext(&it) } return a[:i] } // hiter's structure matches runtime.hiter's structure. // Having a clone here allows us to embed a map iterator // inside type MapIter so that MapIters can be re-used // without doing any allocations. type hiter struct { key unsafe.Pointer elem unsafe.Pointer t unsafe.Pointer h unsafe.Pointer buckets unsafe.Pointer bptr unsafe.Pointer overflow *[]unsafe.Pointer oldoverflow *[]unsafe.Pointer startBucket uintptr offset uint8 wrapped bool B uint8 i uint8 bucket uintptr checkBucket uintptr } func (h *hiter) initialized() bool { return h.t != nil } // A MapIter is an iterator for ranging over a map. // See [Value.MapRange]. type MapIter struct { m Value hiter hiter } // Key returns the key of iter's current map entry. func (iter *MapIter) Key() Value { if !iter.hiter.initialized() { panic("MapIter.Key called before Next") } iterkey := mapiterkey(&iter.hiter) if iterkey == nil { panic("MapIter.Key called on exhausted iterator") } t := (*mapType)(unsafe.Pointer(iter.m.typ())) ktype := t.Key return copyVal(ktype, iter.m.flag.ro()|flag(ktype.Kind()), iterkey) } // SetIterKey assigns to v the key of iter's current map entry. // It is equivalent to v.Set(iter.Key()), but it avoids allocating a new Value. // As in Go, the key must be assignable to v's type and // must not be derived from an unexported field. func (v Value) SetIterKey(iter *MapIter) { if !iter.hiter.initialized() { panic("reflect: Value.SetIterKey called before Next") } iterkey := mapiterkey(&iter.hiter) if iterkey == nil { panic("reflect: Value.SetIterKey called on exhausted iterator") } v.mustBeAssignable() var target unsafe.Pointer if v.kind() == Interface { target = v.ptr } t := (*mapType)(unsafe.Pointer(iter.m.typ())) ktype := t.Key iter.m.mustBeExported() // do not let unexported m leak key := Value{ktype, iterkey, iter.m.flag | flag(ktype.Kind()) | flagIndir} key = key.assignTo("reflect.MapIter.SetKey", v.typ(), target) typedmemmove(v.typ(), v.ptr, key.ptr) } // Value returns the value of iter's current map entry. func (iter *MapIter) Value() Value { if !iter.hiter.initialized() { panic("MapIter.Value called before Next") } iterelem := mapiterelem(&iter.hiter) if iterelem == nil { panic("MapIter.Value called on exhausted iterator") } t := (*mapType)(unsafe.Pointer(iter.m.typ())) vtype := t.Elem return copyVal(vtype, iter.m.flag.ro()|flag(vtype.Kind()), iterelem) } // SetIterValue assigns to v the value of iter's current map entry. // It is equivalent to v.Set(iter.Value()), but it avoids allocating a new Value. // As in Go, the value must be assignable to v's type and // must not be derived from an unexported field. func (v Value) SetIterValue(iter *MapIter) { if !iter.hiter.initialized() { panic("reflect: Value.SetIterValue called before Next") } iterelem := mapiterelem(&iter.hiter) if iterelem == nil { panic("reflect: Value.SetIterValue called on exhausted iterator") } v.mustBeAssignable() var target unsafe.Pointer if v.kind() == Interface { target = v.ptr } t := (*mapType)(unsafe.Pointer(iter.m.typ())) vtype := t.Elem iter.m.mustBeExported() // do not let unexported m leak elem := Value{vtype, iterelem, iter.m.flag | flag(vtype.Kind()) | flagIndir} elem = elem.assignTo("reflect.MapIter.SetValue", v.typ(), target) typedmemmove(v.typ(), v.ptr, elem.ptr) } // Next advances the map iterator and reports whether there is another // entry. It returns false when iter is exhausted; subsequent // calls to [MapIter.Key], [MapIter.Value], or [MapIter.Next] will panic. func (iter *MapIter) Next() bool { if !iter.m.IsValid() { panic("MapIter.Next called on an iterator that does not have an associated map Value") } if !iter.hiter.initialized() { mapiterinit(iter.m.typ(), iter.m.pointer(), &iter.hiter) } else { if mapiterkey(&iter.hiter) == nil { panic("MapIter.Next called on exhausted iterator") } mapiternext(&iter.hiter) } return mapiterkey(&iter.hiter) != nil } // Reset modifies iter to iterate over v. // It panics if v's Kind is not [Map] and v is not the zero Value. // Reset(Value{}) causes iter to not to refer to any map, // which may allow the previously iterated-over map to be garbage collected. func (iter *MapIter) Reset(v Value) { if v.IsValid() { v.mustBe(Map) } iter.m = v iter.hiter = hiter{} } // MapRange returns a range iterator for a map. // It panics if v's Kind is not [Map]. // // Call [MapIter.Next] to advance the iterator, and [MapIter.Key]/[MapIter.Value] to access each entry. // [MapIter.Next] returns false when the iterator is exhausted. // MapRange follows the same iteration semantics as a range statement. // // Example: // // iter := reflect.ValueOf(m).MapRange() // for iter.Next() { // k := iter.Key() // v := iter.Value() // ... // } func (v Value) MapRange() *MapIter { // This is inlinable to take advantage of "function outlining". // The allocation of MapIter can be stack allocated if the caller // does not allow it to escape. // See https://blog.filippo.io/efficient-go-apis-with-the-inliner/ if v.kind() != Map { v.panicNotMap() } return &MapIter{m: v} } // Force slow panicking path not inlined, so it won't add to the // inlining budget of the caller. // TODO: undo when the inliner is no longer bottom-up only. // //go:noinline func (f flag) panicNotMap() { f.mustBe(Map) } // copyVal returns a Value containing the map key or value at ptr, // allocating a new variable as needed. func copyVal(typ *abi.Type, fl flag, ptr unsafe.Pointer) Value { if typ.IfaceIndir() { // Copy result so future changes to the map // won't change the underlying value. c := unsafe_New(typ) typedmemmove(typ, c, ptr) return Value{typ, c, fl | flagIndir} } return Value{typ, *(*unsafe.Pointer)(ptr), fl} } // Method returns a function value corresponding to v's i'th method. // The arguments to a Call on the returned function should not include // a receiver; the returned function will always use v as the receiver. // Method panics if i is out of range or if v is a nil interface value. func (v Value) Method(i int) Value { if v.typ() == nil { panic(&ValueError{"reflect.Value.Method", Invalid}) } if v.flag&flagMethod != 0 || uint(i) >= uint(toRType(v.typ()).NumMethod()) { panic("reflect: Method index out of range") } if v.typ().Kind() == abi.Interface && v.IsNil() { panic("reflect: Method on nil interface value") } fl := v.flag.ro() | (v.flag & flagIndir) fl |= flag(Func) fl |= flag(i)<> (64 - bitSize) return x != trunc } panic(&ValueError{"reflect.Value.OverflowInt", v.kind()}) } // OverflowUint reports whether the uint64 x cannot be represented by v's type. // It panics if v's Kind is not [Uint], [Uintptr], [Uint8], [Uint16], [Uint32], or [Uint64]. func (v Value) OverflowUint(x uint64) bool { k := v.kind() switch k { case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64: bitSize := v.typ_.Size() * 8 // ok to use v.typ_ directly as Size doesn't escape trunc := (x << (64 - bitSize)) >> (64 - bitSize) return x != trunc } panic(&ValueError{"reflect.Value.OverflowUint", v.kind()}) } //go:nocheckptr // This prevents inlining Value.Pointer when -d=checkptr is enabled, // which ensures cmd/compile can recognize unsafe.Pointer(v.Pointer()) // and make an exception. // Pointer returns v's value as a uintptr. // It panics if v's Kind is not [Chan], [Func], [Map], [Pointer], [Slice], [String], or [UnsafePointer]. // // If v's Kind is [Func], the returned pointer is an underlying // code pointer, but not necessarily enough to identify a // single function uniquely. The only guarantee is that the // result is zero if and only if v is a nil func Value. // // If v's Kind is [Slice], the returned pointer is to the first // element of the slice. If the slice is nil the returned value // is 0. If the slice is empty but non-nil the return value is non-zero. // // If v's Kind is [String], the returned pointer is to the first // element of the underlying bytes of string. // // It's preferred to use uintptr(Value.UnsafePointer()) to get the equivalent result. func (v Value) Pointer() uintptr { // The compiler loses track as it converts to uintptr. Force escape. escapes(v.ptr) k := v.kind() switch k { case Pointer: if !v.typ().Pointers() { val := *(*uintptr)(v.ptr) // Since it is a not-in-heap pointer, all pointers to the heap are // forbidden! See comment in Value.Elem and issue #48399. if !verifyNotInHeapPtr(val) { panic("reflect: reflect.Value.Pointer on an invalid notinheap pointer") } return val } fallthrough case Chan, Map, UnsafePointer: return uintptr(v.pointer()) case Func: if v.flag&flagMethod != 0 { // As the doc comment says, the returned pointer is an // underlying code pointer but not necessarily enough to // identify a single function uniquely. All method expressions // created via reflect have the same underlying code pointer, // so their Pointers are equal. The function used here must // match the one used in makeMethodValue. return methodValueCallCodePtr() } p := v.pointer() // Non-nil func value points at data block. // First word of data block is actual code. if p != nil { p = *(*unsafe.Pointer)(p) } return uintptr(p) case Slice: return uintptr((*unsafeheader.Slice)(v.ptr).Data) case String: return uintptr((*unsafeheader.String)(v.ptr).Data) } panic(&ValueError{"reflect.Value.Pointer", v.kind()}) } // Recv receives and returns a value from the channel v. // It panics if v's Kind is not [Chan]. // The receive blocks until a value is ready. // The boolean value ok is true if the value x corresponds to a send // on the channel, false if it is a zero value received because the channel is closed. func (v Value) Recv() (x Value, ok bool) { v.mustBe(Chan) v.mustBeExported() return v.recv(false) } // internal recv, possibly non-blocking (nb). // v is known to be a channel. func (v Value) recv(nb bool) (val Value, ok bool) { tt := (*chanType)(unsafe.Pointer(v.typ())) if ChanDir(tt.Dir)&RecvDir == 0 { panic("reflect: recv on send-only channel") } t := tt.Elem val = Value{t, nil, flag(t.Kind())} var p unsafe.Pointer if t.IfaceIndir() { p = unsafe_New(t) val.ptr = p val.flag |= flagIndir } else { p = unsafe.Pointer(&val.ptr) } selected, ok := chanrecv(v.pointer(), nb, p) if !selected { val = Value{} } return } // Send sends x on the channel v. // It panics if v's kind is not [Chan] or if x's type is not the same type as v's element type. // As in Go, x's value must be assignable to the channel's element type. func (v Value) Send(x Value) { v.mustBe(Chan) v.mustBeExported() v.send(x, false) } // internal send, possibly non-blocking. // v is known to be a channel. func (v Value) send(x Value, nb bool) (selected bool) { tt := (*chanType)(unsafe.Pointer(v.typ())) if ChanDir(tt.Dir)&SendDir == 0 { panic("reflect: send on recv-only channel") } x.mustBeExported() x = x.assignTo("reflect.Value.Send", tt.Elem, nil) var p unsafe.Pointer if x.flag&flagIndir != 0 { p = x.ptr } else { p = unsafe.Pointer(&x.ptr) } return chansend(v.pointer(), p, nb) } // Set assigns x to the value v. // It panics if [Value.CanSet] returns false. // As in Go, x's value must be assignable to v's type and // must not be derived from an unexported field. func (v Value) Set(x Value) { v.mustBeAssignable() x.mustBeExported() // do not let unexported x leak var target unsafe.Pointer if v.kind() == Interface { target = v.ptr } x = x.assignTo("reflect.Set", v.typ(), target) if x.flag&flagIndir != 0 { if x.ptr == unsafe.Pointer(&zeroVal[0]) { typedmemclr(v.typ(), v.ptr) } else { typedmemmove(v.typ(), v.ptr, x.ptr) } } else { *(*unsafe.Pointer)(v.ptr) = x.ptr } } // SetBool sets v's underlying value. // It panics if v's Kind is not [Bool] or if [Value.CanSet] returns false. func (v Value) SetBool(x bool) { v.mustBeAssignable() v.mustBe(Bool) *(*bool)(v.ptr) = x } // SetBytes sets v's underlying value. // It panics if v's underlying value is not a slice of bytes. func (v Value) SetBytes(x []byte) { v.mustBeAssignable() v.mustBe(Slice) if toRType(v.typ()).Elem().Kind() != Uint8 { // TODO add Elem method, fix mustBe(Slice) to return slice. panic("reflect.Value.SetBytes of non-byte slice") } *(*[]byte)(v.ptr) = x } // setRunes sets v's underlying value. // It panics if v's underlying value is not a slice of runes (int32s). func (v Value) setRunes(x []rune) { v.mustBeAssignable() v.mustBe(Slice) if v.typ().Elem().Kind() != abi.Int32 { panic("reflect.Value.setRunes of non-rune slice") } *(*[]rune)(v.ptr) = x } // SetComplex sets v's underlying value to x. // It panics if v's Kind is not [Complex64] or [Complex128], or if [Value.CanSet] returns false. func (v Value) SetComplex(x complex128) { v.mustBeAssignable() switch k := v.kind(); k { default: panic(&ValueError{"reflect.Value.SetComplex", v.kind()}) case Complex64: *(*complex64)(v.ptr) = complex64(x) case Complex128: *(*complex128)(v.ptr) = x } } // SetFloat sets v's underlying value to x. // It panics if v's Kind is not [Float32] or [Float64], or if [Value.CanSet] returns false. func (v Value) SetFloat(x float64) { v.mustBeAssignable() switch k := v.kind(); k { default: panic(&ValueError{"reflect.Value.SetFloat", v.kind()}) case Float32: *(*float32)(v.ptr) = float32(x) case Float64: *(*float64)(v.ptr) = x } } // SetInt sets v's underlying value to x. // It panics if v's Kind is not [Int], [Int8], [Int16], [Int32], or [Int64], or if [Value.CanSet] returns false. func (v Value) SetInt(x int64) { v.mustBeAssignable() switch k := v.kind(); k { default: panic(&ValueError{"reflect.Value.SetInt", v.kind()}) case Int: *(*int)(v.ptr) = int(x) case Int8: *(*int8)(v.ptr) = int8(x) case Int16: *(*int16)(v.ptr) = int16(x) case Int32: *(*int32)(v.ptr) = int32(x) case Int64: *(*int64)(v.ptr) = x } } // SetLen sets v's length to n. // It panics if v's Kind is not [Slice] or if n is negative or // greater than the capacity of the slice. func (v Value) SetLen(n int) { v.mustBeAssignable() v.mustBe(Slice) s := (*unsafeheader.Slice)(v.ptr) if uint(n) > uint(s.Cap) { panic("reflect: slice length out of range in SetLen") } s.Len = n } // SetCap sets v's capacity to n. // It panics if v's Kind is not [Slice] or if n is smaller than the length or // greater than the capacity of the slice. func (v Value) SetCap(n int) { v.mustBeAssignable() v.mustBe(Slice) s := (*unsafeheader.Slice)(v.ptr) if n < s.Len || n > s.Cap { panic("reflect: slice capacity out of range in SetCap") } s.Cap = n } // SetMapIndex sets the element associated with key in the map v to elem. // It panics if v's Kind is not [Map]. // If elem is the zero Value, SetMapIndex deletes the key from the map. // Otherwise if v holds a nil map, SetMapIndex will panic. // As in Go, key's elem must be assignable to the map's key type, // and elem's value must be assignable to the map's elem type. func (v Value) SetMapIndex(key, elem Value) { v.mustBe(Map) v.mustBeExported() key.mustBeExported() tt := (*mapType)(unsafe.Pointer(v.typ())) if (tt.Key == stringType || key.kind() == String) && tt.Key == key.typ() && tt.Elem.Size() <= abi.MapMaxElemBytes { k := *(*string)(key.ptr) if elem.typ() == nil { mapdelete_faststr(v.typ(), v.pointer(), k) return } elem.mustBeExported() elem = elem.assignTo("reflect.Value.SetMapIndex", tt.Elem, nil) var e unsafe.Pointer if elem.flag&flagIndir != 0 { e = elem.ptr } else { e = unsafe.Pointer(&elem.ptr) } mapassign_faststr(v.typ(), v.pointer(), k, e) return } key = key.assignTo("reflect.Value.SetMapIndex", tt.Key, nil) var k unsafe.Pointer if key.flag&flagIndir != 0 { k = key.ptr } else { k = unsafe.Pointer(&key.ptr) } if elem.typ() == nil { mapdelete(v.typ(), v.pointer(), k) return } elem.mustBeExported() elem = elem.assignTo("reflect.Value.SetMapIndex", tt.Elem, nil) var e unsafe.Pointer if elem.flag&flagIndir != 0 { e = elem.ptr } else { e = unsafe.Pointer(&elem.ptr) } mapassign(v.typ(), v.pointer(), k, e) } // SetUint sets v's underlying value to x. // It panics if v's Kind is not [Uint], [Uintptr], [Uint8], [Uint16], [Uint32], or [Uint64], or if [Value.CanSet] returns false. func (v Value) SetUint(x uint64) { v.mustBeAssignable() switch k := v.kind(); k { default: panic(&ValueError{"reflect.Value.SetUint", v.kind()}) case Uint: *(*uint)(v.ptr) = uint(x) case Uint8: *(*uint8)(v.ptr) = uint8(x) case Uint16: *(*uint16)(v.ptr) = uint16(x) case Uint32: *(*uint32)(v.ptr) = uint32(x) case Uint64: *(*uint64)(v.ptr) = x case Uintptr: *(*uintptr)(v.ptr) = uintptr(x) } } // SetPointer sets the [unsafe.Pointer] value v to x. // It panics if v's Kind is not [UnsafePointer]. func (v Value) SetPointer(x unsafe.Pointer) { v.mustBeAssignable() v.mustBe(UnsafePointer) *(*unsafe.Pointer)(v.ptr) = x } // SetString sets v's underlying value to x. // It panics if v's Kind is not [String] or if [Value.CanSet] returns false. func (v Value) SetString(x string) { v.mustBeAssignable() v.mustBe(String) *(*string)(v.ptr) = x } // Slice returns v[i:j]. // It panics if v's Kind is not [Array], [Slice] or [String], or if v is an unaddressable array, // or if the indexes are out of bounds. func (v Value) Slice(i, j int) Value { var ( cap int typ *sliceType base unsafe.Pointer ) switch kind := v.kind(); kind { default: panic(&ValueError{"reflect.Value.Slice", v.kind()}) case Array: if v.flag&flagAddr == 0 { panic("reflect.Value.Slice: slice of unaddressable array") } tt := (*arrayType)(unsafe.Pointer(v.typ())) cap = int(tt.Len) typ = (*sliceType)(unsafe.Pointer(tt.Slice)) base = v.ptr case Slice: typ = (*sliceType)(unsafe.Pointer(v.typ())) s := (*unsafeheader.Slice)(v.ptr) base = s.Data cap = s.Cap case String: s := (*unsafeheader.String)(v.ptr) if i < 0 || j < i || j > s.Len { panic("reflect.Value.Slice: string slice index out of bounds") } var t unsafeheader.String if i < s.Len { t = unsafeheader.String{Data: arrayAt(s.Data, i, 1, "i < s.Len"), Len: j - i} } return Value{v.typ(), unsafe.Pointer(&t), v.flag} } if i < 0 || j < i || j > cap { panic("reflect.Value.Slice: slice index out of bounds") } // Declare slice so that gc can see the base pointer in it. var x []unsafe.Pointer // Reinterpret as *unsafeheader.Slice to edit. s := (*unsafeheader.Slice)(unsafe.Pointer(&x)) s.Len = j - i s.Cap = cap - i if cap-i > 0 { s.Data = arrayAt(base, i, typ.Elem.Size(), "i < cap") } else { // do not advance pointer, to avoid pointing beyond end of slice s.Data = base } fl := v.flag.ro() | flagIndir | flag(Slice) return Value{typ.Common(), unsafe.Pointer(&x), fl} } // Slice3 is the 3-index form of the slice operation: it returns v[i:j:k]. // It panics if v's Kind is not [Array] or [Slice], or if v is an unaddressable array, // or if the indexes are out of bounds. func (v Value) Slice3(i, j, k int) Value { var ( cap int typ *sliceType base unsafe.Pointer ) switch kind := v.kind(); kind { default: panic(&ValueError{"reflect.Value.Slice3", v.kind()}) case Array: if v.flag&flagAddr == 0 { panic("reflect.Value.Slice3: slice of unaddressable array") } tt := (*arrayType)(unsafe.Pointer(v.typ())) cap = int(tt.Len) typ = (*sliceType)(unsafe.Pointer(tt.Slice)) base = v.ptr case Slice: typ = (*sliceType)(unsafe.Pointer(v.typ())) s := (*unsafeheader.Slice)(v.ptr) base = s.Data cap = s.Cap } if i < 0 || j < i || k < j || k > cap { panic("reflect.Value.Slice3: slice index out of bounds") } // Declare slice so that the garbage collector // can see the base pointer in it. var x []unsafe.Pointer // Reinterpret as *unsafeheader.Slice to edit. s := (*unsafeheader.Slice)(unsafe.Pointer(&x)) s.Len = j - i s.Cap = k - i if k-i > 0 { s.Data = arrayAt(base, i, typ.Elem.Size(), "i < k <= cap") } else { // do not advance pointer, to avoid pointing beyond end of slice s.Data = base } fl := v.flag.ro() | flagIndir | flag(Slice) return Value{typ.Common(), unsafe.Pointer(&x), fl} } // String returns the string v's underlying value, as a string. // String is a special case because of Go's String method convention. // Unlike the other getters, it does not panic if v's Kind is not [String]. // Instead, it returns a string of the form "" where T is v's type. // The fmt package treats Values specially. It does not call their String // method implicitly but instead prints the concrete values they hold. func (v Value) String() string { // stringNonString is split out to keep String inlineable for string kinds. if v.kind() == String { return *(*string)(v.ptr) } return v.stringNonString() } func (v Value) stringNonString() string { if v.kind() == Invalid { return "" } // If you call String on a reflect.Value of other type, it's better to // print something than to panic. Useful in debugging. return "<" + v.Type().String() + " Value>" } // TryRecv attempts to receive a value from the channel v but will not block. // It panics if v's Kind is not [Chan]. // If the receive delivers a value, x is the transferred value and ok is true. // If the receive cannot finish without blocking, x is the zero Value and ok is false. // If the channel is closed, x is the zero value for the channel's element type and ok is false. func (v Value) TryRecv() (x Value, ok bool) { v.mustBe(Chan) v.mustBeExported() return v.recv(true) } // TrySend attempts to send x on the channel v but will not block. // It panics if v's Kind is not [Chan]. // It reports whether the value was sent. // As in Go, x's value must be assignable to the channel's element type. func (v Value) TrySend(x Value) bool { v.mustBe(Chan) v.mustBeExported() return v.send(x, true) } // Type returns v's type. func (v Value) Type() Type { if v.flag != 0 && v.flag&flagMethod == 0 { return (*rtype)(noescape(unsafe.Pointer(v.typ_))) // inline of toRType(v.typ()), for own inlining in inline test } return v.typeSlow() } func (v Value) typeSlow() Type { if v.flag == 0 { panic(&ValueError{"reflect.Value.Type", Invalid}) } typ := v.typ() if v.flag&flagMethod == 0 { return toRType(v.typ()) } // Method value. // v.typ describes the receiver, not the method type. i := int(v.flag) >> flagMethodShift if v.typ().Kind() == abi.Interface { // Method on interface. tt := (*interfaceType)(unsafe.Pointer(typ)) if uint(i) >= uint(len(tt.Methods)) { panic("reflect: internal error: invalid method index") } m := &tt.Methods[i] return toRType(typeOffFor(typ, m.Typ)) } // Method on concrete type. ms := typ.ExportedMethods() if uint(i) >= uint(len(ms)) { panic("reflect: internal error: invalid method index") } m := ms[i] return toRType(typeOffFor(typ, m.Mtyp)) } // CanUint reports whether [Value.Uint] can be used without panicking. func (v Value) CanUint() bool { switch v.kind() { case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return true default: return false } } // Uint returns v's underlying value, as a uint64. // It panics if v's Kind is not [Uint], [Uintptr], [Uint8], [Uint16], [Uint32], or [Uint64]. func (v Value) Uint() uint64 { k := v.kind() p := v.ptr switch k { case Uint: return uint64(*(*uint)(p)) case Uint8: return uint64(*(*uint8)(p)) case Uint16: return uint64(*(*uint16)(p)) case Uint32: return uint64(*(*uint32)(p)) case Uint64: return *(*uint64)(p) case Uintptr: return uint64(*(*uintptr)(p)) } panic(&ValueError{"reflect.Value.Uint", v.kind()}) } //go:nocheckptr // This prevents inlining Value.UnsafeAddr when -d=checkptr is enabled, // which ensures cmd/compile can recognize unsafe.Pointer(v.UnsafeAddr()) // and make an exception. // UnsafeAddr returns a pointer to v's data, as a uintptr. // It panics if v is not addressable. // // It's preferred to use uintptr(Value.Addr().UnsafePointer()) to get the equivalent result. func (v Value) UnsafeAddr() uintptr { if v.typ() == nil { panic(&ValueError{"reflect.Value.UnsafeAddr", Invalid}) } if v.flag&flagAddr == 0 { panic("reflect.Value.UnsafeAddr of unaddressable value") } // The compiler loses track as it converts to uintptr. Force escape. escapes(v.ptr) return uintptr(v.ptr) } // UnsafePointer returns v's value as a [unsafe.Pointer]. // It panics if v's Kind is not [Chan], [Func], [Map], [Pointer], [Slice], [String] or [UnsafePointer]. // // If v's Kind is [Func], the returned pointer is an underlying // code pointer, but not necessarily enough to identify a // single function uniquely. The only guarantee is that the // result is zero if and only if v is a nil func Value. // // If v's Kind is [Slice], the returned pointer is to the first // element of the slice. If the slice is nil the returned value // is nil. If the slice is empty but non-nil the return value is non-nil. // // If v's Kind is [String], the returned pointer is to the first // element of the underlying bytes of string. func (v Value) UnsafePointer() unsafe.Pointer { k := v.kind() switch k { case Pointer: if !v.typ().Pointers() { // Since it is a not-in-heap pointer, all pointers to the heap are // forbidden! See comment in Value.Elem and issue #48399. if !verifyNotInHeapPtr(*(*uintptr)(v.ptr)) { panic("reflect: reflect.Value.UnsafePointer on an invalid notinheap pointer") } return *(*unsafe.Pointer)(v.ptr) } fallthrough case Chan, Map, UnsafePointer: return v.pointer() case Func: if v.flag&flagMethod != 0 { // As the doc comment says, the returned pointer is an // underlying code pointer but not necessarily enough to // identify a single function uniquely. All method expressions // created via reflect have the same underlying code pointer, // so their Pointers are equal. The function used here must // match the one used in makeMethodValue. code := methodValueCallCodePtr() return *(*unsafe.Pointer)(unsafe.Pointer(&code)) } p := v.pointer() // Non-nil func value points at data block. // First word of data block is actual code. if p != nil { p = *(*unsafe.Pointer)(p) } return p case Slice: return (*unsafeheader.Slice)(v.ptr).Data case String: return (*unsafeheader.String)(v.ptr).Data } panic(&ValueError{"reflect.Value.UnsafePointer", v.kind()}) } // StringHeader is the runtime representation of a string. // It cannot be used safely or portably and its representation may // change in a later release. // Moreover, the Data field is not sufficient to guarantee the data // it references will not be garbage collected, so programs must keep // a separate, correctly typed pointer to the underlying data. // // Deprecated: Use unsafe.String or unsafe.StringData instead. type StringHeader struct { Data uintptr Len int } // SliceHeader is the runtime representation of a slice. // It cannot be used safely or portably and its representation may // change in a later release. // Moreover, the Data field is not sufficient to guarantee the data // it references will not be garbage collected, so programs must keep // a separate, correctly typed pointer to the underlying data. // // Deprecated: Use unsafe.Slice or unsafe.SliceData instead. type SliceHeader struct { Data uintptr Len int Cap int } func typesMustMatch(what string, t1, t2 Type) { if t1 != t2 { panic(what + ": " + t1.String() + " != " + t2.String()) } } // arrayAt returns the i-th element of p, // an array whose elements are eltSize bytes wide. // The array pointed at by p must have at least i+1 elements: // it is invalid (but impossible to check here) to pass i >= len, // because then the result will point outside the array. // whySafe must explain why i < len. (Passing "i < len" is fine; // the benefit is to surface this assumption at the call site.) func arrayAt(p unsafe.Pointer, i int, eltSize uintptr, whySafe string) unsafe.Pointer { return add(p, uintptr(i)*eltSize, "i < len") } // Grow increases the slice's capacity, if necessary, to guarantee space for // another n elements. After Grow(n), at least n elements can be appended // to the slice without another allocation. // // It panics if v's Kind is not a [Slice] or if n is negative or too large to // allocate the memory. func (v Value) Grow(n int) { v.mustBeAssignable() v.mustBe(Slice) v.grow(n) } // grow is identical to Grow but does not check for assignability. func (v Value) grow(n int) { p := (*unsafeheader.Slice)(v.ptr) switch { case n < 0: panic("reflect.Value.Grow: negative len") case p.Len+n < 0: panic("reflect.Value.Grow: slice overflow") case p.Len+n > p.Cap: t := v.typ().Elem() *p = growslice(t, *p, n) } } // extendSlice extends a slice by n elements. // // Unlike Value.grow, which modifies the slice in place and // does not change the length of the slice in place, // extendSlice returns a new slice value with the length // incremented by the number of specified elements. func (v Value) extendSlice(n int) Value { v.mustBeExported() v.mustBe(Slice) // Shallow copy the slice header to avoid mutating the source slice. sh := *(*unsafeheader.Slice)(v.ptr) s := &sh v.ptr = unsafe.Pointer(s) v.flag = flagIndir | flag(Slice) // equivalent flag to MakeSlice v.grow(n) // fine to treat as assignable since we allocate a new slice header s.Len += n return v } // Clear clears the contents of a map or zeros the contents of a slice. // // It panics if v's Kind is not [Map] or [Slice]. func (v Value) Clear() { switch v.Kind() { case Slice: sh := *(*unsafeheader.Slice)(v.ptr) st := (*sliceType)(unsafe.Pointer(v.typ())) typedarrayclear(st.Elem, sh.Data, sh.Len) case Map: mapclear(v.typ(), v.pointer()) default: panic(&ValueError{"reflect.Value.Clear", v.Kind()}) } } // Append appends the values x to a slice s and returns the resulting slice. // As in Go, each x's value must be assignable to the slice's element type. func Append(s Value, x ...Value) Value { s.mustBe(Slice) n := s.Len() s = s.extendSlice(len(x)) for i, v := range x { s.Index(n + i).Set(v) } return s } // AppendSlice appends a slice t to a slice s and returns the resulting slice. // The slices s and t must have the same element type. func AppendSlice(s, t Value) Value { s.mustBe(Slice) t.mustBe(Slice) typesMustMatch("reflect.AppendSlice", s.Type().Elem(), t.Type().Elem()) ns := s.Len() nt := t.Len() s = s.extendSlice(nt) Copy(s.Slice(ns, ns+nt), t) return s } // Copy copies the contents of src into dst until either // dst has been filled or src has been exhausted. // It returns the number of elements copied. // Dst and src each must have kind [Slice] or [Array], and // dst and src must have the same element type. // // As a special case, src can have kind [String] if the element type of dst is kind [Uint8]. func Copy(dst, src Value) int { dk := dst.kind() if dk != Array && dk != Slice { panic(&ValueError{"reflect.Copy", dk}) } if dk == Array { dst.mustBeAssignable() } dst.mustBeExported() sk := src.kind() var stringCopy bool if sk != Array && sk != Slice { stringCopy = sk == String && dst.typ().Elem().Kind() == abi.Uint8 if !stringCopy { panic(&ValueError{"reflect.Copy", sk}) } } src.mustBeExported() de := dst.typ().Elem() if !stringCopy { se := src.typ().Elem() typesMustMatch("reflect.Copy", toType(de), toType(se)) } var ds, ss unsafeheader.Slice if dk == Array { ds.Data = dst.ptr ds.Len = dst.Len() ds.Cap = ds.Len } else { ds = *(*unsafeheader.Slice)(dst.ptr) } if sk == Array { ss.Data = src.ptr ss.Len = src.Len() ss.Cap = ss.Len } else if sk == Slice { ss = *(*unsafeheader.Slice)(src.ptr) } else { sh := *(*unsafeheader.String)(src.ptr) ss.Data = sh.Data ss.Len = sh.Len ss.Cap = sh.Len } return typedslicecopy(de.Common(), ds, ss) } // A runtimeSelect is a single case passed to rselect. // This must match ../runtime/select.go:/runtimeSelect type runtimeSelect struct { dir SelectDir // SelectSend, SelectRecv or SelectDefault typ *rtype // channel type ch unsafe.Pointer // channel val unsafe.Pointer // ptr to data (SendDir) or ptr to receive buffer (RecvDir) } // rselect runs a select. It returns the index of the chosen case. // If the case was a receive, val is filled in with the received value. // The conventional OK bool indicates whether the receive corresponds // to a sent value. // // rselect generally doesn't escape the runtimeSelect slice, except // that for the send case the value to send needs to escape. We don't // have a way to represent that in the function signature. So we handle // that with a forced escape in function Select. // //go:noescape func rselect([]runtimeSelect) (chosen int, recvOK bool) // A SelectDir describes the communication direction of a select case. type SelectDir int // NOTE: These values must match ../runtime/select.go:/selectDir. const ( _ SelectDir = iota SelectSend // case Chan <- Send SelectRecv // case <-Chan: SelectDefault // default ) // A SelectCase describes a single case in a select operation. // The kind of case depends on Dir, the communication direction. // // If Dir is SelectDefault, the case represents a default case. // Chan and Send must be zero Values. // // If Dir is SelectSend, the case represents a send operation. // Normally Chan's underlying value must be a channel, and Send's underlying value must be // assignable to the channel's element type. As a special case, if Chan is a zero Value, // then the case is ignored, and the field Send will also be ignored and may be either zero // or non-zero. // // If Dir is [SelectRecv], the case represents a receive operation. // Normally Chan's underlying value must be a channel and Send must be a zero Value. // If Chan is a zero Value, then the case is ignored, but Send must still be a zero Value. // When a receive operation is selected, the received Value is returned by Select. type SelectCase struct { Dir SelectDir // direction of case Chan Value // channel to use (for send or receive) Send Value // value to send (for send) } // Select executes a select operation described by the list of cases. // Like the Go select statement, it blocks until at least one of the cases // can proceed, makes a uniform pseudo-random choice, // and then executes that case. It returns the index of the chosen case // and, if that case was a receive operation, the value received and a // boolean indicating whether the value corresponds to a send on the channel // (as opposed to a zero value received because the channel is closed). // Select supports a maximum of 65536 cases. func Select(cases []SelectCase) (chosen int, recv Value, recvOK bool) { if len(cases) > 65536 { panic("reflect.Select: too many cases (max 65536)") } // NOTE: Do not trust that caller is not modifying cases data underfoot. // The range is safe because the caller cannot modify our copy of the len // and each iteration makes its own copy of the value c. var runcases []runtimeSelect if len(cases) > 4 { // Slice is heap allocated due to runtime dependent capacity. runcases = make([]runtimeSelect, len(cases)) } else { // Slice can be stack allocated due to constant capacity. runcases = make([]runtimeSelect, len(cases), 4) } haveDefault := false for i, c := range cases { rc := &runcases[i] rc.dir = c.Dir switch c.Dir { default: panic("reflect.Select: invalid Dir") case SelectDefault: // default if haveDefault { panic("reflect.Select: multiple default cases") } haveDefault = true if c.Chan.IsValid() { panic("reflect.Select: default case has Chan value") } if c.Send.IsValid() { panic("reflect.Select: default case has Send value") } case SelectSend: ch := c.Chan if !ch.IsValid() { break } ch.mustBe(Chan) ch.mustBeExported() tt := (*chanType)(unsafe.Pointer(ch.typ())) if ChanDir(tt.Dir)&SendDir == 0 { panic("reflect.Select: SendDir case using recv-only channel") } rc.ch = ch.pointer() rc.typ = toRType(&tt.Type) v := c.Send if !v.IsValid() { panic("reflect.Select: SendDir case missing Send value") } v.mustBeExported() v = v.assignTo("reflect.Select", tt.Elem, nil) if v.flag&flagIndir != 0 { rc.val = v.ptr } else { rc.val = unsafe.Pointer(&v.ptr) } // The value to send needs to escape. See the comment at rselect for // why we need forced escape. escapes(rc.val) case SelectRecv: if c.Send.IsValid() { panic("reflect.Select: RecvDir case has Send value") } ch := c.Chan if !ch.IsValid() { break } ch.mustBe(Chan) ch.mustBeExported() tt := (*chanType)(unsafe.Pointer(ch.typ())) if ChanDir(tt.Dir)&RecvDir == 0 { panic("reflect.Select: RecvDir case using send-only channel") } rc.ch = ch.pointer() rc.typ = toRType(&tt.Type) rc.val = unsafe_New(tt.Elem) } } chosen, recvOK = rselect(runcases) if runcases[chosen].dir == SelectRecv { tt := (*chanType)(unsafe.Pointer(runcases[chosen].typ)) t := tt.Elem p := runcases[chosen].val fl := flag(t.Kind()) if t.IfaceIndir() { recv = Value{t, p, fl | flagIndir} } else { recv = Value{t, *(*unsafe.Pointer)(p), fl} } } return chosen, recv, recvOK } /* * constructors */ // implemented in package runtime //go:noescape func unsafe_New(*abi.Type) unsafe.Pointer //go:noescape func unsafe_NewArray(*abi.Type, int) unsafe.Pointer // MakeSlice creates a new zero-initialized slice value // for the specified slice type, length, and capacity. func MakeSlice(typ Type, len, cap int) Value { if typ.Kind() != Slice { panic("reflect.MakeSlice of non-slice type") } if len < 0 { panic("reflect.MakeSlice: negative len") } if cap < 0 { panic("reflect.MakeSlice: negative cap") } if len > cap { panic("reflect.MakeSlice: len > cap") } s := unsafeheader.Slice{Data: unsafe_NewArray(&(typ.Elem().(*rtype).t), cap), Len: len, Cap: cap} return Value{&typ.(*rtype).t, unsafe.Pointer(&s), flagIndir | flag(Slice)} } // SliceAt returns a [Value] representing a slice whose underlying // data starts at p, with length and capacity equal to n. // // This is like [unsafe.Slice]. func SliceAt(typ Type, p unsafe.Pointer, n int) Value { unsafeslice(typ.common(), p, n) s := unsafeheader.Slice{Data: p, Len: n, Cap: n} return Value{SliceOf(typ).common(), unsafe.Pointer(&s), flagIndir | flag(Slice)} } // MakeChan creates a new channel with the specified type and buffer size. func MakeChan(typ Type, buffer int) Value { if typ.Kind() != Chan { panic("reflect.MakeChan of non-chan type") } if buffer < 0 { panic("reflect.MakeChan: negative buffer size") } if typ.ChanDir() != BothDir { panic("reflect.MakeChan: unidirectional channel type") } t := typ.common() ch := makechan(t, buffer) return Value{t, ch, flag(Chan)} } // MakeMap creates a new map with the specified type. func MakeMap(typ Type) Value { return MakeMapWithSize(typ, 0) } // MakeMapWithSize creates a new map with the specified type // and initial space for approximately n elements. func MakeMapWithSize(typ Type, n int) Value { if typ.Kind() != Map { panic("reflect.MakeMapWithSize of non-map type") } t := typ.common() m := makemap(t, n) return Value{t, m, flag(Map)} } // Indirect returns the value that v points to. // If v is a nil pointer, Indirect returns a zero Value. // If v is not a pointer, Indirect returns v. func Indirect(v Value) Value { if v.Kind() != Pointer { return v } return v.Elem() } // ValueOf returns a new Value initialized to the concrete value // stored in the interface i. ValueOf(nil) returns the zero Value. func ValueOf(i any) Value { if i == nil { return Value{} } return unpackEface(i) } // Zero returns a Value representing the zero value for the specified type. // The result is different from the zero value of the Value struct, // which represents no value at all. // For example, Zero(TypeOf(42)) returns a Value with Kind [Int] and value 0. // The returned value is neither addressable nor settable. func Zero(typ Type) Value { if typ == nil { panic("reflect: Zero(nil)") } t := &typ.(*rtype).t fl := flag(t.Kind()) if t.IfaceIndir() { var p unsafe.Pointer if t.Size() <= abi.ZeroValSize { p = unsafe.Pointer(&zeroVal[0]) } else { p = unsafe_New(t) } return Value{t, p, fl | flagIndir} } return Value{t, nil, fl} } //go:linkname zeroVal runtime.zeroVal var zeroVal [abi.ZeroValSize]byte // New returns a Value representing a pointer to a new zero value // for the specified type. That is, the returned Value's Type is [PointerTo](typ). func New(typ Type) Value { if typ == nil { panic("reflect: New(nil)") } t := &typ.(*rtype).t pt := ptrTo(t) if pt.IfaceIndir() { // This is a pointer to a not-in-heap type. panic("reflect: New of type that may not be allocated in heap (possibly undefined cgo C type)") } ptr := unsafe_New(t) fl := flag(Pointer) return Value{pt, ptr, fl} } // NewAt returns a Value representing a pointer to a value of the // specified type, using p as that pointer. func NewAt(typ Type, p unsafe.Pointer) Value { fl := flag(Pointer) t := typ.(*rtype) return Value{t.ptrTo(), p, fl} } // assignTo returns a value v that can be assigned directly to dst. // It panics if v is not assignable to dst. // For a conversion to an interface type, target, if not nil, // is a suggested scratch space to use. // target must be initialized memory (or nil). func (v Value) assignTo(context string, dst *abi.Type, target unsafe.Pointer) Value { if v.flag&flagMethod != 0 { v = makeMethodValue(context, v) } switch { case directlyAssignable(dst, v.typ()): // Overwrite type so that they match. // Same memory layout, so no harm done. fl := v.flag&(flagAddr|flagIndir) | v.flag.ro() fl |= flag(dst.Kind()) return Value{dst, v.ptr, fl} case implements(dst, v.typ()): if v.Kind() == Interface && v.IsNil() { // A nil ReadWriter passed to nil Reader is OK, // but using ifaceE2I below will panic. // Avoid the panic by returning a nil dst (e.g., Reader) explicitly. return Value{dst, nil, flag(Interface)} } x := valueInterface(v, false) if target == nil { target = unsafe_New(dst) } if dst.NumMethod() == 0 { *(*any)(target) = x } else { ifaceE2I(dst, x, target) } return Value{dst, target, flagIndir | flag(Interface)} } // Failed. panic(context + ": value of type " + stringFor(v.typ()) + " is not assignable to type " + stringFor(dst)) } // Convert returns the value v converted to type t. // If the usual Go conversion rules do not allow conversion // of the value v to type t, or if converting v to type t panics, Convert panics. func (v Value) Convert(t Type) Value { if v.flag&flagMethod != 0 { v = makeMethodValue("Convert", v) } op := convertOp(t.common(), v.typ()) if op == nil { panic("reflect.Value.Convert: value of type " + stringFor(v.typ()) + " cannot be converted to type " + t.String()) } return op(v, t) } // CanConvert reports whether the value v can be converted to type t. // If v.CanConvert(t) returns true then v.Convert(t) will not panic. func (v Value) CanConvert(t Type) bool { vt := v.Type() if !vt.ConvertibleTo(t) { return false } // Converting from slice to array or to pointer-to-array can panic // depending on the value. switch { case vt.Kind() == Slice && t.Kind() == Array: if t.Len() > v.Len() { return false } case vt.Kind() == Slice && t.Kind() == Pointer && t.Elem().Kind() == Array: n := t.Elem().Len() if n > v.Len() { return false } } return true } // Comparable reports whether the value v is comparable. // If the type of v is an interface, this checks the dynamic type. // If this reports true then v.Interface() == x will not panic for any x, // nor will v.Equal(u) for any Value u. func (v Value) Comparable() bool { k := v.Kind() switch k { case Invalid: return false case Array: switch v.Type().Elem().Kind() { case Interface, Array, Struct: for i := 0; i < v.Type().Len(); i++ { if !v.Index(i).Comparable() { return false } } return true } return v.Type().Comparable() case Interface: return v.IsNil() || v.Elem().Comparable() case Struct: for i := 0; i < v.NumField(); i++ { if !v.Field(i).Comparable() { return false } } return true default: return v.Type().Comparable() } } // Equal reports true if v is equal to u. // For two invalid values, Equal will report true. // For an interface value, Equal will compare the value within the interface. // Otherwise, If the values have different types, Equal will report false. // Otherwise, for arrays and structs Equal will compare each element in order, // and report false if it finds non-equal elements. // During all comparisons, if values of the same type are compared, // and the type is not comparable, Equal will panic. func (v Value) Equal(u Value) bool { if v.Kind() == Interface { v = v.Elem() } if u.Kind() == Interface { u = u.Elem() } if !v.IsValid() || !u.IsValid() { return v.IsValid() == u.IsValid() } if v.Kind() != u.Kind() || v.Type() != u.Type() { return false } // Handle each Kind directly rather than calling valueInterface // to avoid allocating. switch v.Kind() { default: panic("reflect.Value.Equal: invalid Kind") case Bool: return v.Bool() == u.Bool() case Int, Int8, Int16, Int32, Int64: return v.Int() == u.Int() case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return v.Uint() == u.Uint() case Float32, Float64: return v.Float() == u.Float() case Complex64, Complex128: return v.Complex() == u.Complex() case String: return v.String() == u.String() case Chan, Pointer, UnsafePointer: return v.Pointer() == u.Pointer() case Array: // u and v have the same type so they have the same length vl := v.Len() if vl == 0 { // panic on [0]func() if !v.Type().Elem().Comparable() { break } return true } for i := 0; i < vl; i++ { if !v.Index(i).Equal(u.Index(i)) { return false } } return true case Struct: // u and v have the same type so they have the same fields nf := v.NumField() for i := 0; i < nf; i++ { if !v.Field(i).Equal(u.Field(i)) { return false } } return true case Func, Map, Slice: break } panic("reflect.Value.Equal: values of type " + v.Type().String() + " are not comparable") } // convertOp returns the function to convert a value of type src // to a value of type dst. If the conversion is illegal, convertOp returns nil. func convertOp(dst, src *abi.Type) func(Value, Type) Value { switch Kind(src.Kind()) { case Int, Int8, Int16, Int32, Int64: switch Kind(dst.Kind()) { case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return cvtInt case Float32, Float64: return cvtIntFloat case String: return cvtIntString } case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: switch Kind(dst.Kind()) { case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return cvtUint case Float32, Float64: return cvtUintFloat case String: return cvtUintString } case Float32, Float64: switch Kind(dst.Kind()) { case Int, Int8, Int16, Int32, Int64: return cvtFloatInt case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr: return cvtFloatUint case Float32, Float64: return cvtFloat } case Complex64, Complex128: switch Kind(dst.Kind()) { case Complex64, Complex128: return cvtComplex } case String: if dst.Kind() == abi.Slice && pkgPathFor(dst.Elem()) == "" { switch Kind(dst.Elem().Kind()) { case Uint8: return cvtStringBytes case Int32: return cvtStringRunes } } case Slice: if dst.Kind() == abi.String && pkgPathFor(src.Elem()) == "" { switch Kind(src.Elem().Kind()) { case Uint8: return cvtBytesString case Int32: return cvtRunesString } } // "x is a slice, T is a pointer-to-array type, // and the slice and array types have identical element types." if dst.Kind() == abi.Pointer && dst.Elem().Kind() == abi.Array && src.Elem() == dst.Elem().Elem() { return cvtSliceArrayPtr } // "x is a slice, T is an array type, // and the slice and array types have identical element types." if dst.Kind() == abi.Array && src.Elem() == dst.Elem() { return cvtSliceArray } case Chan: if dst.Kind() == abi.Chan && specialChannelAssignability(dst, src) { return cvtDirect } } // dst and src have same underlying type. if haveIdenticalUnderlyingType(dst, src, false) { return cvtDirect } // dst and src are non-defined pointer types with same underlying base type. if dst.Kind() == abi.Pointer && nameFor(dst) == "" && src.Kind() == abi.Pointer && nameFor(src) == "" && haveIdenticalUnderlyingType(elem(dst), elem(src), false) { return cvtDirect } if implements(dst, src) { if src.Kind() == abi.Interface { return cvtI2I } return cvtT2I } return nil } // makeInt returns a Value of type t equal to bits (possibly truncated), // where t is a signed or unsigned int type. func makeInt(f flag, bits uint64, t Type) Value { typ := t.common() ptr := unsafe_New(typ) switch typ.Size() { case 1: *(*uint8)(ptr) = uint8(bits) case 2: *(*uint16)(ptr) = uint16(bits) case 4: *(*uint32)(ptr) = uint32(bits) case 8: *(*uint64)(ptr) = bits } return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} } // makeFloat returns a Value of type t equal to v (possibly truncated to float32), // where t is a float32 or float64 type. func makeFloat(f flag, v float64, t Type) Value { typ := t.common() ptr := unsafe_New(typ) switch typ.Size() { case 4: *(*float32)(ptr) = float32(v) case 8: *(*float64)(ptr) = v } return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} } // makeFloat32 returns a Value of type t equal to v, where t is a float32 type. func makeFloat32(f flag, v float32, t Type) Value { typ := t.common() ptr := unsafe_New(typ) *(*float32)(ptr) = v return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} } // makeComplex returns a Value of type t equal to v (possibly truncated to complex64), // where t is a complex64 or complex128 type. func makeComplex(f flag, v complex128, t Type) Value { typ := t.common() ptr := unsafe_New(typ) switch typ.Size() { case 8: *(*complex64)(ptr) = complex64(v) case 16: *(*complex128)(ptr) = v } return Value{typ, ptr, f | flagIndir | flag(typ.Kind())} } func makeString(f flag, v string, t Type) Value { ret := New(t).Elem() ret.SetString(v) ret.flag = ret.flag&^flagAddr | f return ret } func makeBytes(f flag, v []byte, t Type) Value { ret := New(t).Elem() ret.SetBytes(v) ret.flag = ret.flag&^flagAddr | f return ret } func makeRunes(f flag, v []rune, t Type) Value { ret := New(t).Elem() ret.setRunes(v) ret.flag = ret.flag&^flagAddr | f return ret } // These conversion functions are returned by convertOp // for classes of conversions. For example, the first function, cvtInt, // takes any value v of signed int type and returns the value converted // to type t, where t is any signed or unsigned int type. // convertOp: intXX -> [u]intXX func cvtInt(v Value, t Type) Value { return makeInt(v.flag.ro(), uint64(v.Int()), t) } // convertOp: uintXX -> [u]intXX func cvtUint(v Value, t Type) Value { return makeInt(v.flag.ro(), v.Uint(), t) } // convertOp: floatXX -> intXX func cvtFloatInt(v Value, t Type) Value { return makeInt(v.flag.ro(), uint64(int64(v.Float())), t) } // convertOp: floatXX -> uintXX func cvtFloatUint(v Value, t Type) Value { return makeInt(v.flag.ro(), uint64(v.Float()), t) } // convertOp: intXX -> floatXX func cvtIntFloat(v Value, t Type) Value { return makeFloat(v.flag.ro(), float64(v.Int()), t) } // convertOp: uintXX -> floatXX func cvtUintFloat(v Value, t Type) Value { return makeFloat(v.flag.ro(), float64(v.Uint()), t) } // convertOp: floatXX -> floatXX func cvtFloat(v Value, t Type) Value { if v.Type().Kind() == Float32 && t.Kind() == Float32 { // Don't do any conversion if both types have underlying type float32. // This avoids converting to float64 and back, which will // convert a signaling NaN to a quiet NaN. See issue 36400. return makeFloat32(v.flag.ro(), *(*float32)(v.ptr), t) } return makeFloat(v.flag.ro(), v.Float(), t) } // convertOp: complexXX -> complexXX func cvtComplex(v Value, t Type) Value { return makeComplex(v.flag.ro(), v.Complex(), t) } // convertOp: intXX -> string func cvtIntString(v Value, t Type) Value { s := "\uFFFD" if x := v.Int(); int64(rune(x)) == x { s = string(rune(x)) } return makeString(v.flag.ro(), s, t) } // convertOp: uintXX -> string func cvtUintString(v Value, t Type) Value { s := "\uFFFD" if x := v.Uint(); uint64(rune(x)) == x { s = string(rune(x)) } return makeString(v.flag.ro(), s, t) } // convertOp: []byte -> string func cvtBytesString(v Value, t Type) Value { return makeString(v.flag.ro(), string(v.Bytes()), t) } // convertOp: string -> []byte func cvtStringBytes(v Value, t Type) Value { return makeBytes(v.flag.ro(), []byte(v.String()), t) } // convertOp: []rune -> string func cvtRunesString(v Value, t Type) Value { return makeString(v.flag.ro(), string(v.runes()), t) } // convertOp: string -> []rune func cvtStringRunes(v Value, t Type) Value { return makeRunes(v.flag.ro(), []rune(v.String()), t) } // convertOp: []T -> *[N]T func cvtSliceArrayPtr(v Value, t Type) Value { n := t.Elem().Len() if n > v.Len() { panic("reflect: cannot convert slice with length " + itoa.Itoa(v.Len()) + " to pointer to array with length " + itoa.Itoa(n)) } h := (*unsafeheader.Slice)(v.ptr) return Value{t.common(), h.Data, v.flag&^(flagIndir|flagAddr|flagKindMask) | flag(Pointer)} } // convertOp: []T -> [N]T func cvtSliceArray(v Value, t Type) Value { n := t.Len() if n > v.Len() { panic("reflect: cannot convert slice with length " + itoa.Itoa(v.Len()) + " to array with length " + itoa.Itoa(n)) } h := (*unsafeheader.Slice)(v.ptr) typ := t.common() ptr := h.Data c := unsafe_New(typ) typedmemmove(typ, c, ptr) ptr = c return Value{typ, ptr, v.flag&^(flagAddr|flagKindMask) | flag(Array)} } // convertOp: direct copy func cvtDirect(v Value, typ Type) Value { f := v.flag t := typ.common() ptr := v.ptr if f&flagAddr != 0 { // indirect, mutable word - make a copy c := unsafe_New(t) typedmemmove(t, c, ptr) ptr = c f &^= flagAddr } return Value{t, ptr, v.flag.ro() | f} // v.flag.ro()|f == f? } // convertOp: concrete -> interface func cvtT2I(v Value, typ Type) Value { target := unsafe_New(typ.common()) x := valueInterface(v, false) if typ.NumMethod() == 0 { *(*any)(target) = x } else { ifaceE2I(typ.common(), x, target) } return Value{typ.common(), target, v.flag.ro() | flagIndir | flag(Interface)} } // convertOp: interface -> interface func cvtI2I(v Value, typ Type) Value { if v.IsNil() { ret := Zero(typ) ret.flag |= v.flag.ro() return ret } return cvtT2I(v.Elem(), typ) } // implemented in ../runtime // //go:noescape func chancap(ch unsafe.Pointer) int //go:noescape func chanclose(ch unsafe.Pointer) //go:noescape func chanlen(ch unsafe.Pointer) int // Note: some of the noescape annotations below are technically a lie, // but safe in the context of this package. Functions like chansend0 // and mapassign0 don't escape the referent, but may escape anything // the referent points to (they do shallow copies of the referent). // We add a 0 to their names and wrap them in functions with the // proper escape behavior. //go:noescape func chanrecv(ch unsafe.Pointer, nb bool, val unsafe.Pointer) (selected, received bool) //go:noescape func chansend0(ch unsafe.Pointer, val unsafe.Pointer, nb bool) bool func chansend(ch unsafe.Pointer, val unsafe.Pointer, nb bool) bool { contentEscapes(val) return chansend0(ch, val, nb) } func makechan(typ *abi.Type, size int) (ch unsafe.Pointer) func makemap(t *abi.Type, cap int) (m unsafe.Pointer) //go:noescape func mapaccess(t *abi.Type, m unsafe.Pointer, key unsafe.Pointer) (val unsafe.Pointer) //go:noescape func mapaccess_faststr(t *abi.Type, m unsafe.Pointer, key string) (val unsafe.Pointer) //go:noescape func mapassign0(t *abi.Type, m unsafe.Pointer, key, val unsafe.Pointer) // mapassign should be an internal detail, // but widely used packages access it using linkname. // Notable members of the hall of shame include: // - github.com/modern-go/reflect2 // - github.com/goccy/go-json // // Do not remove or change the type signature. // See go.dev/issue/67401. // //go:linkname mapassign func mapassign(t *abi.Type, m unsafe.Pointer, key, val unsafe.Pointer) { contentEscapes(key) contentEscapes(val) mapassign0(t, m, key, val) } //go:noescape func mapassign_faststr0(t *abi.Type, m unsafe.Pointer, key string, val unsafe.Pointer) func mapassign_faststr(t *abi.Type, m unsafe.Pointer, key string, val unsafe.Pointer) { contentEscapes((*unsafeheader.String)(unsafe.Pointer(&key)).Data) contentEscapes(val) mapassign_faststr0(t, m, key, val) } //go:noescape func mapdelete(t *abi.Type, m unsafe.Pointer, key unsafe.Pointer) //go:noescape func mapdelete_faststr(t *abi.Type, m unsafe.Pointer, key string) //go:noescape func mapiterinit(t *abi.Type, m unsafe.Pointer, it *hiter) //go:noescape func mapiterkey(it *hiter) (key unsafe.Pointer) //go:noescape func mapiterelem(it *hiter) (elem unsafe.Pointer) //go:noescape func mapiternext(it *hiter) //go:noescape func maplen(m unsafe.Pointer) int func mapclear(t *abi.Type, m unsafe.Pointer) // call calls fn with "stackArgsSize" bytes of stack arguments laid out // at stackArgs and register arguments laid out in regArgs. frameSize is // the total amount of stack space that will be reserved by call, so this // should include enough space to spill register arguments to the stack in // case of preemption. // // After fn returns, call copies stackArgsSize-stackRetOffset result bytes // back into stackArgs+stackRetOffset before returning, for any return // values passed on the stack. Register-based return values will be found // in the same regArgs structure. // // regArgs must also be prepared with an appropriate ReturnIsPtr bitmap // indicating which registers will contain pointer-valued return values. The // purpose of this bitmap is to keep pointers visible to the GC between // returning from reflectcall and actually using them. // // If copying result bytes back from the stack, the caller must pass the // argument frame type as stackArgsType, so that call can execute appropriate // write barriers during the copy. // // Arguments passed through to call do not escape. The type is used only in a // very limited callee of call, the stackArgs are copied, and regArgs is only // used in the call frame. // //go:noescape //go:linkname call runtime.reflectcall func call(stackArgsType *abi.Type, f, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs) func ifaceE2I(t *abi.Type, src any, dst unsafe.Pointer) // memmove copies size bytes to dst from src. No write barriers are used. // //go:noescape func memmove(dst, src unsafe.Pointer, size uintptr) // typedmemmove copies a value of type t to dst from src. // //go:noescape func typedmemmove(t *abi.Type, dst, src unsafe.Pointer) // typedmemclr zeros the value at ptr of type t. // //go:noescape func typedmemclr(t *abi.Type, ptr unsafe.Pointer) // typedmemclrpartial is like typedmemclr but assumes that // dst points off bytes into the value and only clears size bytes. // //go:noescape func typedmemclrpartial(t *abi.Type, ptr unsafe.Pointer, off, size uintptr) // typedslicecopy copies a slice of elemType values from src to dst, // returning the number of elements copied. // //go:noescape func typedslicecopy(t *abi.Type, dst, src unsafeheader.Slice) int // typedarrayclear zeroes the value at ptr of an array of elemType, // only clears len elem. // //go:noescape func typedarrayclear(elemType *abi.Type, ptr unsafe.Pointer, len int) //go:noescape func typehash(t *abi.Type, p unsafe.Pointer, h uintptr) uintptr func verifyNotInHeapPtr(p uintptr) bool //go:noescape func growslice(t *abi.Type, old unsafeheader.Slice, num int) unsafeheader.Slice //go:noescape func unsafeslice(t *abi.Type, ptr unsafe.Pointer, len int) // Dummy annotation marking that the value x escapes, // for use in cases where the reflect code is so clever that // the compiler cannot follow. func escapes(x any) { if dummy.b { dummy.x = x } } var dummy struct { b bool x any } // Dummy annotation marking that the content of value x // escapes (i.e. modeling roughly heap=*x), // for use in cases where the reflect code is so clever that // the compiler cannot follow. func contentEscapes(x unsafe.Pointer) { if dummy.b { escapes(*(*any)(x)) // the dereference may not always be safe, but never executed } } // This is just a wrapper around abi.NoEscape. The inlining heuristics are // finnicky and for whatever reason treat the local call to noescape as much // lower cost with respect to the inliner budget. (That is, replacing calls to // noescape with abi.NoEscape will cause inlining tests to fail.) // //go:nosplit func noescape(p unsafe.Pointer) unsafe.Pointer { return abi.NoEscape(p) }