diff options
Diffstat (limited to 'vendor/github.com/google/go-cmp/cmp/path.go')
| -rw-r--r-- | vendor/github.com/google/go-cmp/cmp/path.go | 80 |
1 files changed, 75 insertions, 5 deletions
diff --git a/vendor/github.com/google/go-cmp/cmp/path.go b/vendor/github.com/google/go-cmp/cmp/path.go index 96fffd2..f01eff3 100644 --- a/vendor/github.com/google/go-cmp/cmp/path.go +++ b/vendor/github.com/google/go-cmp/cmp/path.go @@ -1,6 +1,6 @@ // Copyright 2017, 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.md file. +// license that can be found in the LICENSE file. package cmp @@ -10,6 +10,8 @@ import ( "strings" "unicode" "unicode/utf8" + + "github.com/google/go-cmp/cmp/internal/value" ) // Path is a list of PathSteps describing the sequence of operations to get @@ -41,7 +43,7 @@ type PathStep interface { // In some cases, one or both may be invalid or have restrictions: // • For StructField, both are not interface-able if the current field // is unexported and the struct type is not explicitly permitted by - // AllowUnexported to traverse unexported fields. + // an Exporter to traverse unexported fields. // • For SliceIndex, one may be invalid if an element is missing from // either the x or y slice. // • For MapIndex, one may be invalid if an entry is missing from @@ -175,7 +177,8 @@ type structField struct { // pvx, pvy, and field are only valid if unexported is true. unexported bool mayForce bool // Forcibly allow visibility - pvx, pvy reflect.Value // Parent values + paddr bool // Was parent addressable? + pvx, pvy reflect.Value // Parent values (always addressible) field reflect.StructField // Field information } @@ -187,8 +190,8 @@ func (sf StructField) Values() (vx, vy reflect.Value) { // Forcibly obtain read-write access to an unexported struct field. if sf.mayForce { - vx = retrieveUnexportedField(sf.pvx, sf.field) - vy = retrieveUnexportedField(sf.pvy, sf.field) + vx = retrieveUnexportedField(sf.pvx, sf.field, sf.paddr) + vy = retrieveUnexportedField(sf.pvy, sf.field, sf.paddr) return vx, vy // CanInterface reports true } return sf.vx, sf.vy // CanInterface reports false @@ -207,6 +210,7 @@ type SliceIndex struct{ *sliceIndex } type sliceIndex struct { pathStep xkey, ykey int + isSlice bool // False for reflect.Array } func (si SliceIndex) Type() reflect.Type { return si.typ } @@ -301,6 +305,72 @@ func (tf Transform) Func() reflect.Value { return tf.trans.fnc } // The == operator can be used to detect the exact option used. func (tf Transform) Option() Option { return tf.trans } +// pointerPath represents a dual-stack of pointers encountered when +// recursively traversing the x and y values. This data structure supports +// detection of cycles and determining whether the cycles are equal. +// In Go, cycles can occur via pointers, slices, and maps. +// +// The pointerPath uses a map to represent a stack; where descension into a +// pointer pushes the address onto the stack, and ascension from a pointer +// pops the address from the stack. Thus, when traversing into a pointer from +// reflect.Ptr, reflect.Slice element, or reflect.Map, we can detect cycles +// by checking whether the pointer has already been visited. The cycle detection +// uses a separate stack for the x and y values. +// +// If a cycle is detected we need to determine whether the two pointers +// should be considered equal. The definition of equality chosen by Equal +// requires two graphs to have the same structure. To determine this, both the +// x and y values must have a cycle where the previous pointers were also +// encountered together as a pair. +// +// Semantically, this is equivalent to augmenting Indirect, SliceIndex, and +// MapIndex with pointer information for the x and y values. +// Suppose px and py are two pointers to compare, we then search the +// Path for whether px was ever encountered in the Path history of x, and +// similarly so with py. If either side has a cycle, the comparison is only +// equal if both px and py have a cycle resulting from the same PathStep. +// +// Using a map as a stack is more performant as we can perform cycle detection +// in O(1) instead of O(N) where N is len(Path). +type pointerPath struct { + // mx is keyed by x pointers, where the value is the associated y pointer. + mx map[value.Pointer]value.Pointer + // my is keyed by y pointers, where the value is the associated x pointer. + my map[value.Pointer]value.Pointer +} + +func (p *pointerPath) Init() { + p.mx = make(map[value.Pointer]value.Pointer) + p.my = make(map[value.Pointer]value.Pointer) +} + +// Push indicates intent to descend into pointers vx and vy where +// visited reports whether either has been seen before. If visited before, +// equal reports whether both pointers were encountered together. +// Pop must be called if and only if the pointers were never visited. +// +// The pointers vx and vy must be a reflect.Ptr, reflect.Slice, or reflect.Map +// and be non-nil. +func (p pointerPath) Push(vx, vy reflect.Value) (equal, visited bool) { + px := value.PointerOf(vx) + py := value.PointerOf(vy) + _, ok1 := p.mx[px] + _, ok2 := p.my[py] + if ok1 || ok2 { + equal = p.mx[px] == py && p.my[py] == px // Pointers paired together + return equal, true + } + p.mx[px] = py + p.my[py] = px + return false, false +} + +// Pop ascends from pointers vx and vy. +func (p pointerPath) Pop(vx, vy reflect.Value) { + delete(p.mx, value.PointerOf(vx)) + delete(p.my, value.PointerOf(vy)) +} + // isExported reports whether the identifier is exported. func isExported(id string) bool { r, _ := utf8.DecodeRuneInString(id) |