1 files changed, 284 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/noder/encoder.go b/src/cmd/compile/internal/noder/encoder.go
new file mode 100644
index 0000000000..d8ab0f6255
--- /dev/null
+++ b/src/cmd/compile/internal/noder/encoder.go
@@ -0,0 +1,284 @@
+// UNREVIEWED
+
+// Copyright 2021 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 noder
+
+import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
+	"go/constant"
+	"io"
+	"math/big"
+	"runtime"
+
+	"cmd/compile/internal/base"
+)
+
+type pkgEncoder struct {
+	elems [numRelocs][]string
+
+	stringsIdx map[string]int
+}
+
+func newPkgEncoder() pkgEncoder {
+	return pkgEncoder{
+		stringsIdx: make(map[string]int),
+	}
+}
+
+func (pw *pkgEncoder) dump(out io.Writer) {
+	writeUint32 := func(x uint32) {
+		assert(binary.Write(out, binary.LittleEndian, x) == nil)
+	}
+
+	var sum uint32
+	for _, elems := range &pw.elems {
+		sum += uint32(len(elems))
+		writeUint32(sum)
+	}
+
+	sum = 0
+	for _, elems := range &pw.elems {
+		for _, elem := range elems {
+			sum += uint32(len(elem))
+			writeUint32(sum)
+		}
+	}
+
+	for _, elems := range &pw.elems {
+		for _, elem := range elems {
+			_, err := io.WriteString(out, elem)
+			assert(err == nil)
+		}
+	}
+}
+
+func (pw *pkgEncoder) stringIdx(s string) int {
+	if idx, ok := pw.stringsIdx[s]; ok {
+		assert(pw.elems[relocString][idx] == s)
+		return idx
+	}
+
+	idx := len(pw.elems[relocString])
+	pw.elems[relocString] = append(pw.elems[relocString], s)
+	pw.stringsIdx[s] = idx
+	return idx
+}
+
+func (pw *pkgEncoder) newEncoder(k reloc, marker syncMarker) encoder {
+	e := pw.newEncoderRaw(k)
+	e.sync(marker)
+	return e
+}
+
+func (pw *pkgEncoder) newEncoderRaw(k reloc) encoder {
+	idx := len(pw.elems[k])
+	pw.elems[k] = append(pw.elems[k], "") // placeholder
+
+	return encoder{
+		p:   pw,
+		k:   k,
+		idx: idx,
+	}
+}
+
+// Encoders
+
+type encoder struct {
+	p *pkgEncoder
+
+	relocs []relocEnt
+	data   bytes.Buffer
+
+	encodingRelocHeader bool
+
+	k   reloc
+	idx int
+}
+
+func (w *encoder) flush() int {
+	var sb bytes.Buffer // TODO(mdempsky): strings.Builder after #44505 is resolved
+
+	// Backup the data so we write the relocations at the front.
+	var tmp bytes.Buffer
+	io.Copy(&tmp, &w.data)
+
+	// TODO(mdempsky): Consider writing these out separately so they're
+	// easier to strip, along with function bodies, so that we can prune
+	// down to just the data that's relevant to go/types.
+	if w.encodingRelocHeader {
+		base.Fatalf("encodingRelocHeader already true; recursive flush?")
+	}
+	w.encodingRelocHeader = true
+	w.sync(syncRelocs)
+	w.len(len(w.relocs))
+	for _, rent := range w.relocs {
+		w.sync(syncReloc)
+		w.len(int(rent.kind))
+		w.len(rent.idx)
+	}
+
+	io.Copy(&sb, &w.data)
+	io.Copy(&sb, &tmp)
+	w.p.elems[w.k][w.idx] = sb.String()
+
+	return w.idx
+}
+
+func (w *encoder) checkErr(err error) {
+	if err != nil {
+		base.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func (w *encoder) rawUvarint(x uint64) {
+	var buf [binary.MaxVarintLen64]byte
+	n := binary.PutUvarint(buf[:], x)
+	_, err := w.data.Write(buf[:n])
+	w.checkErr(err)
+}
+
+func (w *encoder) rawVarint(x int64) {
+	// Zig-zag encode.
+	ux := uint64(x) << 1
+	if x < 0 {
+		ux = ^ux
+	}
+
+	w.rawUvarint(ux)
+}
+
+func (w *encoder) rawReloc(r reloc, idx int) int {
+	// TODO(mdempsky): Use map for lookup.
+	for i, rent := range w.relocs {
+		if rent.kind == r && rent.idx == idx {
+			return i
+		}
+	}
+
+	i := len(w.relocs)
+	w.relocs = append(w.relocs, relocEnt{r, idx})
+	return i
+}
+
+func (w *encoder) sync(m syncMarker) {
+	if !enableSync {
+		return
+	}
+
+	// Writing out stack frame string references requires working
+	// relocations, but writing out the relocations themselves involves
+	// sync markers. To prevent infinite recursion, we simply trim the
+	// stack frame for sync markers within the relocation header.
+	var frames []string
+	if !w.encodingRelocHeader && base.Debug.SyncFrames > 0 {
+		pcs := make([]uintptr, base.Debug.SyncFrames)
+		n := runtime.Callers(2, pcs)
+		frames = fmtFrames(pcs[:n]...)
+	}
+
+	// TODO(mdempsky): Save space by writing out stack frames as a
+	// linked list so we can share common stack frames.
+	w.rawUvarint(uint64(m))
+	w.rawUvarint(uint64(len(frames)))
+	for _, frame := range frames {
+		w.rawUvarint(uint64(w.rawReloc(relocString, w.p.stringIdx(frame))))
+	}
+}
+
+func (w *encoder) bool(b bool) bool {
+	w.sync(syncBool)
+	var x byte
+	if b {
+		x = 1
+	}
+	err := w.data.WriteByte(x)
+	w.checkErr(err)
+	return b
+}
+
+func (w *encoder) int64(x int64) {
+	w.sync(syncInt64)
+	w.rawVarint(x)
+}
+
+func (w *encoder) uint64(x uint64) {
+	w.sync(syncUint64)
+	w.rawUvarint(x)
+}
+
+func (w *encoder) len(x int)   { assert(x >= 0); w.uint64(uint64(x)) }
+func (w *encoder) int(x int)   { w.int64(int64(x)) }
+func (w *encoder) uint(x uint) { w.uint64(uint64(x)) }
+
+func (w *encoder) reloc(r reloc, idx int) {
+	w.sync(syncUseReloc)
+	w.len(w.rawReloc(r, idx))
+}
+
+func (w *encoder) code(c code) {
+	w.sync(c.marker())
+	w.len(c.value())
+}
+
+func (w *encoder) string(s string) {
+	w.sync(syncString)
+	w.reloc(relocString, w.p.stringIdx(s))
+}
+
+func (w *encoder) strings(ss []string) {
+	w.len(len(ss))
+	for _, s := range ss {
+		w.string(s)
+	}
+}
+
+func (w *encoder) rawValue(val constant.Value) {
+	if w.bool(val.Kind() == constant.Complex) {
+		w.scalar(constant.Real(val))
+		w.scalar(constant.Imag(val))
+	} else {
+		w.scalar(val)
+	}
+}
+
+func (w *encoder) scalar(val constant.Value) {
+	switch v := constant.Val(val).(type) {
+	default:
+		panic(fmt.Sprintf("unhandled %v (%v)", val, val.Kind()))
+	case bool:
+		w.code(valBool)
+		w.bool(v)
+	case string:
+		w.code(valString)
+		w.string(v)
+	case int64:
+		w.code(valInt64)
+		w.int64(v)
+	case *big.Int:
+		w.code(valBigInt)
+		w.bigInt(v)
+	case *big.Rat:
+		w.code(valBigRat)
+		w.bigInt(v.Num())
+		w.bigInt(v.Denom())
+	case *big.Float:
+		w.code(valBigFloat)
+		w.bigFloat(v)
+	}
+}
+
+func (w *encoder) bigInt(v *big.Int) {
+	b := v.Bytes()
+	w.string(string(b)) // TODO: More efficient encoding.
+	w.bool(v.Sign() < 0)
+}
+
+func (w *encoder) bigFloat(v *big.Float) {
+	b := v.Append(nil, 'p', -1)
+	w.string(string(b)) // TODO: More efficient encoding.
+}