384 lines
9.4 KiB
Go
384 lines
9.4 KiB
Go
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// Copyright 2021 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package pkgbits
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import (
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"bytes"
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"crypto/md5"
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"encoding/binary"
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"go/constant"
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"io"
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"math/big"
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"runtime"
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)
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// currentVersion is the current version number.
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//
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// - v0: initial prototype
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//
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// - v1: adds the flags uint32 word
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const currentVersion uint32 = 1
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// A PkgEncoder provides methods for encoding a package's Unified IR
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// export data.
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type PkgEncoder struct {
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// elems holds the bitstream for previously encoded elements.
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elems [numRelocs][]string
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// stringsIdx maps previously encoded strings to their index within
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// the RelocString section, to allow deduplication. That is,
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// elems[RelocString][stringsIdx[s]] == s (if present).
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stringsIdx map[string]Index
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// syncFrames is the number of frames to write at each sync
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// marker. A negative value means sync markers are omitted.
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syncFrames int
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}
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// SyncMarkers reports whether pw uses sync markers.
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func (pw *PkgEncoder) SyncMarkers() bool { return pw.syncFrames >= 0 }
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// NewPkgEncoder returns an initialized PkgEncoder.
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//
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// syncFrames is the number of caller frames that should be serialized
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// at Sync points. Serializing additional frames results in larger
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// export data files, but can help diagnosing desync errors in
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// higher-level Unified IR reader/writer code. If syncFrames is
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// negative, then sync markers are omitted entirely.
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func NewPkgEncoder(syncFrames int) PkgEncoder {
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return PkgEncoder{
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stringsIdx: make(map[string]Index),
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syncFrames: syncFrames,
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}
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}
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// DumpTo writes the package's encoded data to out0 and returns the
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// package fingerprint.
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func (pw *PkgEncoder) DumpTo(out0 io.Writer) (fingerprint [8]byte) {
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h := md5.New()
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out := io.MultiWriter(out0, h)
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writeUint32 := func(x uint32) {
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assert(binary.Write(out, binary.LittleEndian, x) == nil)
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}
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writeUint32(currentVersion)
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var flags uint32
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if pw.SyncMarkers() {
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flags |= flagSyncMarkers
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}
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writeUint32(flags)
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// Write elemEndsEnds.
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var sum uint32
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for _, elems := range &pw.elems {
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sum += uint32(len(elems))
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writeUint32(sum)
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}
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// Write elemEnds.
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sum = 0
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for _, elems := range &pw.elems {
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for _, elem := range elems {
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sum += uint32(len(elem))
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writeUint32(sum)
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}
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}
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// Write elemData.
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for _, elems := range &pw.elems {
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for _, elem := range elems {
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_, err := io.WriteString(out, elem)
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assert(err == nil)
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}
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}
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// Write fingerprint.
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copy(fingerprint[:], h.Sum(nil))
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_, err := out0.Write(fingerprint[:])
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assert(err == nil)
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return
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}
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// StringIdx adds a string value to the strings section, if not
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// already present, and returns its index.
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func (pw *PkgEncoder) StringIdx(s string) Index {
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if idx, ok := pw.stringsIdx[s]; ok {
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assert(pw.elems[RelocString][idx] == s)
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return idx
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}
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idx := Index(len(pw.elems[RelocString]))
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pw.elems[RelocString] = append(pw.elems[RelocString], s)
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pw.stringsIdx[s] = idx
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return idx
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}
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// NewEncoder returns an Encoder for a new element within the given
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// section, and encodes the given SyncMarker as the start of the
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// element bitstream.
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func (pw *PkgEncoder) NewEncoder(k RelocKind, marker SyncMarker) Encoder {
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e := pw.NewEncoderRaw(k)
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e.Sync(marker)
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return e
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}
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// NewEncoderRaw returns an Encoder for a new element within the given
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// section.
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//
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// Most callers should use NewEncoder instead.
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func (pw *PkgEncoder) NewEncoderRaw(k RelocKind) Encoder {
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idx := Index(len(pw.elems[k]))
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pw.elems[k] = append(pw.elems[k], "") // placeholder
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return Encoder{
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p: pw,
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k: k,
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Idx: idx,
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}
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}
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// An Encoder provides methods for encoding an individual element's
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// bitstream data.
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type Encoder struct {
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p *PkgEncoder
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Relocs []RelocEnt
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RelocMap map[RelocEnt]uint32
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Data bytes.Buffer // accumulated element bitstream data
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encodingRelocHeader bool
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k RelocKind
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Idx Index // index within relocation section
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}
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// Flush finalizes the element's bitstream and returns its Index.
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func (w *Encoder) Flush() Index {
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var sb bytes.Buffer // TODO(mdempsky): strings.Builder after #44505 is resolved
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// Backup the data so we write the relocations at the front.
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var tmp bytes.Buffer
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io.Copy(&tmp, &w.Data)
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// TODO(mdempsky): Consider writing these out separately so they're
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// easier to strip, along with function bodies, so that we can prune
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// down to just the data that's relevant to go/types.
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if w.encodingRelocHeader {
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panic("encodingRelocHeader already true; recursive flush?")
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}
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w.encodingRelocHeader = true
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w.Sync(SyncRelocs)
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w.Len(len(w.Relocs))
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for _, rEnt := range w.Relocs {
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w.Sync(SyncReloc)
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w.Len(int(rEnt.Kind))
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w.Len(int(rEnt.Idx))
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}
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io.Copy(&sb, &w.Data)
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io.Copy(&sb, &tmp)
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w.p.elems[w.k][w.Idx] = sb.String()
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return w.Idx
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}
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func (w *Encoder) checkErr(err error) {
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if err != nil {
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errorf("unexpected encoding error: %v", err)
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}
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}
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func (w *Encoder) rawUvarint(x uint64) {
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var buf [binary.MaxVarintLen64]byte
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n := binary.PutUvarint(buf[:], x)
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_, err := w.Data.Write(buf[:n])
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w.checkErr(err)
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}
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func (w *Encoder) rawVarint(x int64) {
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// Zig-zag encode.
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ux := uint64(x) << 1
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if x < 0 {
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ux = ^ux
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}
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w.rawUvarint(ux)
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}
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func (w *Encoder) rawReloc(r RelocKind, idx Index) int {
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e := RelocEnt{r, idx}
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if w.RelocMap != nil {
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if i, ok := w.RelocMap[e]; ok {
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return int(i)
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}
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} else {
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w.RelocMap = make(map[RelocEnt]uint32)
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}
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i := len(w.Relocs)
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w.RelocMap[e] = uint32(i)
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w.Relocs = append(w.Relocs, e)
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return i
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}
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func (w *Encoder) Sync(m SyncMarker) {
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if !w.p.SyncMarkers() {
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return
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}
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// Writing out stack frame string references requires working
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// relocations, but writing out the relocations themselves involves
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// sync markers. To prevent infinite recursion, we simply trim the
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// stack frame for sync markers within the relocation header.
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var frames []string
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if !w.encodingRelocHeader && w.p.syncFrames > 0 {
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pcs := make([]uintptr, w.p.syncFrames)
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n := runtime.Callers(2, pcs)
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frames = fmtFrames(pcs[:n]...)
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}
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// TODO(mdempsky): Save space by writing out stack frames as a
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// linked list so we can share common stack frames.
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w.rawUvarint(uint64(m))
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w.rawUvarint(uint64(len(frames)))
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for _, frame := range frames {
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w.rawUvarint(uint64(w.rawReloc(RelocString, w.p.StringIdx(frame))))
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}
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}
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// Bool encodes and writes a bool value into the element bitstream,
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// and then returns the bool value.
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//
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// For simple, 2-alternative encodings, the idiomatic way to call Bool
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// is something like:
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//
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// if w.Bool(x != 0) {
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// // alternative #1
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// } else {
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// // alternative #2
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// }
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//
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// For multi-alternative encodings, use Code instead.
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func (w *Encoder) Bool(b bool) bool {
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w.Sync(SyncBool)
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var x byte
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if b {
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x = 1
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}
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err := w.Data.WriteByte(x)
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w.checkErr(err)
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return b
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}
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// Int64 encodes and writes an int64 value into the element bitstream.
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func (w *Encoder) Int64(x int64) {
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w.Sync(SyncInt64)
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w.rawVarint(x)
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}
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// Uint64 encodes and writes a uint64 value into the element bitstream.
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func (w *Encoder) Uint64(x uint64) {
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w.Sync(SyncUint64)
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w.rawUvarint(x)
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}
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// Len encodes and writes a non-negative int value into the element bitstream.
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func (w *Encoder) Len(x int) { assert(x >= 0); w.Uint64(uint64(x)) }
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// Int encodes and writes an int value into the element bitstream.
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func (w *Encoder) Int(x int) { w.Int64(int64(x)) }
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// Len encodes and writes a uint value into the element bitstream.
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func (w *Encoder) Uint(x uint) { w.Uint64(uint64(x)) }
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// Reloc encodes and writes a relocation for the given (section,
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// index) pair into the element bitstream.
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//
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// Note: Only the index is formally written into the element
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// bitstream, so bitstream decoders must know from context which
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// section an encoded relocation refers to.
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func (w *Encoder) Reloc(r RelocKind, idx Index) {
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w.Sync(SyncUseReloc)
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w.Len(w.rawReloc(r, idx))
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}
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// Code encodes and writes a Code value into the element bitstream.
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func (w *Encoder) Code(c Code) {
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w.Sync(c.Marker())
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w.Len(c.Value())
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}
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// String encodes and writes a string value into the element
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// bitstream.
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//
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// Internally, strings are deduplicated by adding them to the strings
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// section (if not already present), and then writing a relocation
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// into the element bitstream.
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func (w *Encoder) String(s string) {
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w.Sync(SyncString)
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w.Reloc(RelocString, w.p.StringIdx(s))
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}
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// Strings encodes and writes a variable-length slice of strings into
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// the element bitstream.
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func (w *Encoder) Strings(ss []string) {
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w.Len(len(ss))
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for _, s := range ss {
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w.String(s)
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}
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}
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// Value encodes and writes a constant.Value into the element
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// bitstream.
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func (w *Encoder) Value(val constant.Value) {
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w.Sync(SyncValue)
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if w.Bool(val.Kind() == constant.Complex) {
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w.scalar(constant.Real(val))
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w.scalar(constant.Imag(val))
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} else {
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w.scalar(val)
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}
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}
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func (w *Encoder) scalar(val constant.Value) {
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switch v := constant.Val(val).(type) {
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default:
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errorf("unhandled %v (%v)", val, val.Kind())
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case bool:
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w.Code(ValBool)
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w.Bool(v)
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case string:
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w.Code(ValString)
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w.String(v)
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case int64:
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w.Code(ValInt64)
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w.Int64(v)
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case *big.Int:
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w.Code(ValBigInt)
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w.bigInt(v)
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case *big.Rat:
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w.Code(ValBigRat)
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w.bigInt(v.Num())
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w.bigInt(v.Denom())
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case *big.Float:
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w.Code(ValBigFloat)
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w.bigFloat(v)
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}
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}
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func (w *Encoder) bigInt(v *big.Int) {
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b := v.Bytes()
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w.String(string(b)) // TODO: More efficient encoding.
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w.Bool(v.Sign() < 0)
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}
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func (w *Encoder) bigFloat(v *big.Float) {
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b := v.Append(nil, 'p', -1)
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w.String(string(b)) // TODO: More efficient encoding.
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}
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