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// Copyright 2016 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.
// Binary package export.
// This file was derived from $GOROOT/src/cmd/compile/internal/gc/bexport.go;
// see that file for specification of the format.
package gcimporter
import (
"bytes"
"encoding/binary"
"fmt"
"go/constant"
"go/token"
"go/types"
"math"
"math/big"
"sort"
"strings"
)
// If debugFormat is set, each integer and string value is preceded by a marker
// and position information in the encoding. This mechanism permits an importer
// to recognize immediately when it is out of sync. The importer recognizes this
// mode automatically (i.e., it can import export data produced with debugging
// support even if debugFormat is not set at the time of import). This mode will
// lead to massively larger export data (by a factor of 2 to 3) and should only
// be enabled during development and debugging.
//
// NOTE: This flag is the first flag to enable if importing dies because of
// (suspected) format errors, and whenever a change is made to the format.
const debugFormat = false // default: false
// Current export format version. Increase with each format change.
//
// Note: The latest binary (non-indexed) export format is at version 6.
// This exporter is still at level 4, but it doesn't matter since
// the binary importer can handle older versions just fine.
//
// 6: package height (CL 105038) -- NOT IMPLEMENTED HERE
// 5: improved position encoding efficiency (issue 20080, CL 41619) -- NOT IMPLEMENTED HERE
// 4: type name objects support type aliases, uses aliasTag
// 3: Go1.8 encoding (same as version 2, aliasTag defined but never used)
// 2: removed unused bool in ODCL export (compiler only)
// 1: header format change (more regular), export package for _ struct fields
// 0: Go1.7 encoding
const exportVersion = 4
// trackAllTypes enables cycle tracking for all types, not just named
// types. The existing compiler invariants assume that unnamed types
// that are not completely set up are not used, or else there are spurious
// errors.
// If disabled, only named types are tracked, possibly leading to slightly
// less efficient encoding in rare cases. It also prevents the export of
// some corner-case type declarations (but those are not handled correctly
// with with the textual export format either).
// TODO(gri) enable and remove once issues caused by it are fixed
const trackAllTypes = false
type exporter struct {
fset *token.FileSet
out bytes.Buffer
// object -> index maps, indexed in order of serialization
strIndex map[string]int
pkgIndex map[*types.Package]int
typIndex map[types.Type]int
// position encoding
posInfoFormat bool
prevFile string
prevLine int
// debugging support
written int // bytes written
indent int // for trace
}
// internalError represents an error generated inside this package.
type internalError string
func (e internalError) Error() string { return "gcimporter: " + string(e) }
func internalErrorf(format string, args ...interface{}) error {
return internalError(fmt.Sprintf(format, args...))
}
// BExportData returns binary export data for pkg.
// If no file set is provided, position info will be missing.
func BExportData(fset *token.FileSet, pkg *types.Package) (b []byte, err error) {
if !debug {
defer func() {
if e := recover(); e != nil {
if ierr, ok := e.(internalError); ok {
err = ierr
return
}
// Not an internal error; panic again.
panic(e)
}
}()
}
p := exporter{
fset: fset,
strIndex: map[string]int{"": 0}, // empty string is mapped to 0
pkgIndex: make(map[*types.Package]int),
typIndex: make(map[types.Type]int),
posInfoFormat: true, // TODO(gri) might become a flag, eventually
}
// write version info
// The version string must start with "version %d" where %d is the version
// number. Additional debugging information may follow after a blank; that
// text is ignored by the importer.
p.rawStringln(fmt.Sprintf("version %d", exportVersion))
var debug string
if debugFormat {
debug = "debug"
}
p.rawStringln(debug) // cannot use p.bool since it's affected by debugFormat; also want to see this clearly
p.bool(trackAllTypes)
p.bool(p.posInfoFormat)
// --- generic export data ---
// populate type map with predeclared "known" types
for index, typ := range predeclared() {
p.typIndex[typ] = index
}
if len(p.typIndex) != len(predeclared()) {
return nil, internalError("duplicate entries in type map?")
}
// write package data
p.pkg(pkg, true)
if trace {
p.tracef("\n")
}
// write objects
objcount := 0
scope := pkg.Scope()
for _, name := range scope.Names() {
if !token.IsExported(name) {
continue
}
if trace {
p.tracef("\n")
}
p.obj(scope.Lookup(name))
objcount++
}
// indicate end of list
if trace {
p.tracef("\n")
}
p.tag(endTag)
// for self-verification only (redundant)
p.int(objcount)
if trace {
p.tracef("\n")
}
// --- end of export data ---
return p.out.Bytes(), nil
}
func (p *exporter) pkg(pkg *types.Package, emptypath bool) {
if pkg == nil {
panic(internalError("unexpected nil pkg"))
}
// if we saw the package before, write its index (>= 0)
if i, ok := p.pkgIndex[pkg]; ok {
p.index('P', i)
return
}
// otherwise, remember the package, write the package tag (< 0) and package data
if trace {
p.tracef("P%d = { ", len(p.pkgIndex))
defer p.tracef("} ")
}
p.pkgIndex[pkg] = len(p.pkgIndex)
p.tag(packageTag)
p.string(pkg.Name())
if emptypath {
p.string("")
} else {
p.string(pkg.Path())
}
}
func (p *exporter) obj(obj types.Object) {
switch obj := obj.(type) {
case *types.Const:
p.tag(constTag)
p.pos(obj)
p.qualifiedName(obj)
p.typ(obj.Type())
p.value(obj.Val())
case *types.TypeName:
if obj.IsAlias() {
p.tag(aliasTag)
p.pos(obj)
p.qualifiedName(obj)
} else {
p.tag(typeTag)
}
p.typ(obj.Type())
case *types.Var:
p.tag(varTag)
p.pos(obj)
p.qualifiedName(obj)
p.typ(obj.Type())
case *types.Func:
p.tag(funcTag)
p.pos(obj)
p.qualifiedName(obj)
sig := obj.Type().(*types.Signature)
p.paramList(sig.Params(), sig.Variadic())
p.paramList(sig.Results(), false)
default:
panic(internalErrorf("unexpected object %v (%T)", obj, obj))
}
}
func (p *exporter) pos(obj types.Object) {
if !p.posInfoFormat {
return
}
file, line := p.fileLine(obj)
if file == p.prevFile {
// common case: write line delta
// delta == 0 means different file or no line change
delta := line - p.prevLine
p.int(delta)
if delta == 0 {
p.int(-1) // -1 means no file change
}
} else {
// different file
p.int(0)
// Encode filename as length of common prefix with previous
// filename, followed by (possibly empty) suffix. Filenames
// frequently share path prefixes, so this can save a lot
// of space and make export data size less dependent on file
// path length. The suffix is unlikely to be empty because
// file names tend to end in ".go".
n := commonPrefixLen(p.prevFile, file)
p.int(n) // n >= 0
p.string(file[n:]) // write suffix only
p.prevFile = file
p.int(line)
}
p.prevLine = line
}
func (p *exporter) fileLine(obj types.Object) (file string, line int) {
if p.fset != nil {
pos := p.fset.Position(obj.Pos())
file = pos.Filename
line = pos.Line
}
return
}
func commonPrefixLen(a, b string) int {
if len(a) > len(b) {
a, b = b, a
}
// len(a) <= len(b)
i := 0
for i < len(a) && a[i] == b[i] {
i++
}
return i
}
func (p *exporter) qualifiedName(obj types.Object) {
p.string(obj.Name())
p.pkg(obj.Pkg(), false)
}
func (p *exporter) typ(t types.Type) {
if t == nil {
panic(internalError("nil type"))
}
// Possible optimization: Anonymous pointer types *T where
// T is a named type are common. We could canonicalize all
// such types *T to a single type PT = *T. This would lead
// to at most one *T entry in typIndex, and all future *T's
// would be encoded as the respective index directly. Would
// save 1 byte (pointerTag) per *T and reduce the typIndex
// size (at the cost of a canonicalization map). We can do
// this later, without encoding format change.
// if we saw the type before, write its index (>= 0)
if i, ok := p.typIndex[t]; ok {
p.index('T', i)
return
}
// otherwise, remember the type, write the type tag (< 0) and type data
if trackAllTypes {
if trace {
p.tracef("T%d = {>\n", len(p.typIndex))
defer p.tracef("<\n} ")
}
p.typIndex[t] = len(p.typIndex)
}
switch t := t.(type) {
case *types.Named:
if !trackAllTypes {
// if we don't track all types, track named types now
p.typIndex[t] = len(p.typIndex)
}
p.tag(namedTag)
p.pos(t.Obj())
p.qualifiedName(t.Obj())
p.typ(t.Underlying())
if !types.IsInterface(t) {
p.assocMethods(t)
}
case *types.Array:
p.tag(arrayTag)
p.int64(t.Len())
p.typ(t.Elem())
case *types.Slice:
p.tag(sliceTag)
p.typ(t.Elem())
case *dddSlice:
p.tag(dddTag)
p.typ(t.elem)
case *types.Struct:
p.tag(structTag)
p.fieldList(t)
case *types.Pointer:
p.tag(pointerTag)
p.typ(t.Elem())
case *types.Signature:
p.tag(signatureTag)
p.paramList(t.Params(), t.Variadic())
p.paramList(t.Results(), false)
case *types.Interface:
p.tag(interfaceTag)
p.iface(t)
case *types.Map:
p.tag(mapTag)
p.typ(t.Key())
p.typ(t.Elem())
case *types.Chan:
p.tag(chanTag)
p.int(int(3 - t.Dir())) // hack
p.typ(t.Elem())
default:
panic(internalErrorf("unexpected type %T: %s", t, t))
}
}
func (p *exporter) assocMethods(named *types.Named) {
// Sort methods (for determinism).
var methods []*types.Func
for i := 0; i < named.NumMethods(); i++ {
methods = append(methods, named.Method(i))
}
sort.Sort(methodsByName(methods))
p.int(len(methods))
if trace && methods != nil {
p.tracef("associated methods {>\n")
}
for i, m := range methods {
if trace && i > 0 {
p.tracef("\n")
}
p.pos(m)
name := m.Name()
p.string(name)
if !exported(name) {
p.pkg(m.Pkg(), false)
}
sig := m.Type().(*types.Signature)
p.paramList(types.NewTuple(sig.Recv()), false)
p.paramList(sig.Params(), sig.Variadic())
p.paramList(sig.Results(), false)
p.int(0) // dummy value for go:nointerface pragma - ignored by importer
}
if trace && methods != nil {
p.tracef("<\n} ")
}
}
type methodsByName []*types.Func
func (x methodsByName) Len() int { return len(x) }
func (x methodsByName) Swap(i, j int) { x[i], x[j] = x[j], x[i] }
func (x methodsByName) Less(i, j int) bool { return x[i].Name() < x[j].Name() }
func (p *exporter) fieldList(t *types.Struct) {
if trace && t.NumFields() > 0 {
p.tracef("fields {>\n")
defer p.tracef("<\n} ")
}
p.int(t.NumFields())
for i := 0; i < t.NumFields(); i++ {
if trace && i > 0 {
p.tracef("\n")
}
p.field(t.Field(i))
p.string(t.Tag(i))
}
}
func (p *exporter) field(f *types.Var) {
if !f.IsField() {
panic(internalError("field expected"))
}
p.pos(f)
p.fieldName(f)
p.typ(f.Type())
}
func (p *exporter) iface(t *types.Interface) {
// TODO(gri): enable importer to load embedded interfaces,
// then emit Embeddeds and ExplicitMethods separately here.
p.int(0)
n := t.NumMethods()
if trace && n > 0 {
p.tracef("methods {>\n")
defer p.tracef("<\n} ")
}
p.int(n)
for i := 0; i < n; i++ {
if trace && i > 0 {
p.tracef("\n")
}
p.method(t.Method(i))
}
}
func (p *exporter) method(m *types.Func) {
sig := m.Type().(*types.Signature)
if sig.Recv() == nil {
panic(internalError("method expected"))
}
p.pos(m)
p.string(m.Name())
if m.Name() != "_" && !token.IsExported(m.Name()) {
p.pkg(m.Pkg(), false)
}
// interface method; no need to encode receiver.
p.paramList(sig.Params(), sig.Variadic())
p.paramList(sig.Results(), false)
}
func (p *exporter) fieldName(f *types.Var) {
name := f.Name()
if f.Anonymous() {
// anonymous field - we distinguish between 3 cases:
// 1) field name matches base type name and is exported
// 2) field name matches base type name and is not exported
// 3) field name doesn't match base type name (alias name)
bname := basetypeName(f.Type())
if name == bname {
if token.IsExported(name) {
name = "" // 1) we don't need to know the field name or package
} else {
name = "?" // 2) use unexported name "?" to force package export
}
} else {
// 3) indicate alias and export name as is
// (this requires an extra "@" but this is a rare case)
p.string("@")
}
}
p.string(name)
if name != "" && !token.IsExported(name) {
p.pkg(f.Pkg(), false)
}
}
func basetypeName(typ types.Type) string {
switch typ := deref(typ).(type) {
case *types.Basic:
return typ.Name()
case *types.Named:
return typ.Obj().Name()
default:
return "" // unnamed type
}
}
func (p *exporter) paramList(params *types.Tuple, variadic bool) {
// use negative length to indicate unnamed parameters
// (look at the first parameter only since either all
// names are present or all are absent)
n := params.Len()
if n > 0 && params.At(0).Name() == "" {
n = -n
}
p.int(n)
for i := 0; i < params.Len(); i++ {
q := params.At(i)
t := q.Type()
if variadic && i == params.Len()-1 {
t = &dddSlice{t.(*types.Slice).Elem()}
}
p.typ(t)
if n > 0 {
name := q.Name()
p.string(name)
if name != "_" {
p.pkg(q.Pkg(), false)
}
}
p.string("") // no compiler-specific info
}
}
func (p *exporter) value(x constant.Value) {
if trace {
p.tracef("= ")
}
switch x.Kind() {
case constant.Bool:
tag := falseTag
if constant.BoolVal(x) {
tag = trueTag
}
p.tag(tag)
case constant.Int:
if v, exact := constant.Int64Val(x); exact {
// common case: x fits into an int64 - use compact encoding
p.tag(int64Tag)
p.int64(v)
return
}
// uncommon case: large x - use float encoding
// (powers of 2 will be encoded efficiently with exponent)
p.tag(floatTag)
p.float(constant.ToFloat(x))
case constant.Float:
p.tag(floatTag)
p.float(x)
case constant.Complex:
p.tag(complexTag)
p.float(constant.Real(x))
p.float(constant.Imag(x))
case constant.String:
p.tag(stringTag)
p.string(constant.StringVal(x))
case constant.Unknown:
// package contains type errors
p.tag(unknownTag)
default:
panic(internalErrorf("unexpected value %v (%T)", x, x))
}
}
func (p *exporter) float(x constant.Value) {
if x.Kind() != constant.Float {
panic(internalErrorf("unexpected constant %v, want float", x))
}
// extract sign (there is no -0)
sign := constant.Sign(x)
if sign == 0 {
// x == 0
p.int(0)
return
}
// x != 0
var f big.Float
if v, exact := constant.Float64Val(x); exact {
// float64
f.SetFloat64(v)
} else if num, denom := constant.Num(x), constant.Denom(x); num.Kind() == constant.Int {
// TODO(gri): add big.Rat accessor to constant.Value.
r := valueToRat(num)
f.SetRat(r.Quo(r, valueToRat(denom)))
} else {
// Value too large to represent as a fraction => inaccessible.
// TODO(gri): add big.Float accessor to constant.Value.
f.SetFloat64(math.MaxFloat64) // FIXME
}
// extract exponent such that 0.5 <= m < 1.0
var m big.Float
exp := f.MantExp(&m)
// extract mantissa as *big.Int
// - set exponent large enough so mant satisfies mant.IsInt()
// - get *big.Int from mant
m.SetMantExp(&m, int(m.MinPrec()))
mant, acc := m.Int(nil)
if acc != big.Exact {
panic(internalError("internal error"))
}
p.int(sign)
p.int(exp)
p.string(string(mant.Bytes()))
}
func valueToRat(x constant.Value) *big.Rat {
// Convert little-endian to big-endian.
// I can't believe this is necessary.
bytes := constant.Bytes(x)
for i := 0; i < len(bytes)/2; i++ {
bytes[i], bytes[len(bytes)-1-i] = bytes[len(bytes)-1-i], bytes[i]
}
return new(big.Rat).SetInt(new(big.Int).SetBytes(bytes))
}
func (p *exporter) bool(b bool) bool {
if trace {
p.tracef("[")
defer p.tracef("= %v] ", b)
}
x := 0
if b {
x = 1
}
p.int(x)
return b
}
// ----------------------------------------------------------------------------
// Low-level encoders
func (p *exporter) index(marker byte, index int) {
if index < 0 {
panic(internalError("invalid index < 0"))
}
if debugFormat {
p.marker('t')
}
if trace {
p.tracef("%c%d ", marker, index)
}
p.rawInt64(int64(index))
}
func (p *exporter) tag(tag int) {
if tag >= 0 {
panic(internalError("invalid tag >= 0"))
}
if debugFormat {
p.marker('t')
}
if trace {
p.tracef("%s ", tagString[-tag])
}
p.rawInt64(int64(tag))
}
func (p *exporter) int(x int) {
p.int64(int64(x))
}
func (p *exporter) int64(x int64) {
if debugFormat {
p.marker('i')
}
if trace {
p.tracef("%d ", x)
}
p.rawInt64(x)
}
func (p *exporter) string(s string) {
if debugFormat {
p.marker('s')
}
if trace {
p.tracef("%q ", s)
}
// if we saw the string before, write its index (>= 0)
// (the empty string is mapped to 0)
if i, ok := p.strIndex[s]; ok {
p.rawInt64(int64(i))
return
}
// otherwise, remember string and write its negative length and bytes
p.strIndex[s] = len(p.strIndex)
p.rawInt64(-int64(len(s)))
for i := 0; i < len(s); i++ {
p.rawByte(s[i])
}
}
// marker emits a marker byte and position information which makes
// it easy for a reader to detect if it is "out of sync". Used for
// debugFormat format only.
func (p *exporter) marker(m byte) {
p.rawByte(m)
// Enable this for help tracking down the location
// of an incorrect marker when running in debugFormat.
if false && trace {
p.tracef("#%d ", p.written)
}
p.rawInt64(int64(p.written))
}
// rawInt64 should only be used by low-level encoders.
func (p *exporter) rawInt64(x int64) {
var tmp [binary.MaxVarintLen64]byte
n := binary.PutVarint(tmp[:], x)
for i := 0; i < n; i++ {
p.rawByte(tmp[i])
}
}
// rawStringln should only be used to emit the initial version string.
func (p *exporter) rawStringln(s string) {
for i := 0; i < len(s); i++ {
p.rawByte(s[i])
}
p.rawByte('\n')
}
// rawByte is the bottleneck interface to write to p.out.
// rawByte escapes b as follows (any encoding does that
// hides '$'):
//
// '$' => '|' 'S'
// '|' => '|' '|'
//
// Necessary so other tools can find the end of the
// export data by searching for "$$".
// rawByte should only be used by low-level encoders.
func (p *exporter) rawByte(b byte) {
switch b {
case '$':
// write '$' as '|' 'S'
b = 'S'
fallthrough
case '|':
// write '|' as '|' '|'
p.out.WriteByte('|')
p.written++
}
p.out.WriteByte(b)
p.written++
}
// tracef is like fmt.Printf but it rewrites the format string
// to take care of indentation.
func (p *exporter) tracef(format string, args ...interface{}) {
if strings.ContainsAny(format, "<>\n") {
var buf bytes.Buffer
for i := 0; i < len(format); i++ {
// no need to deal with runes
ch := format[i]
switch ch {
case '>':
p.indent++
continue
case '<':
p.indent--
continue
}
buf.WriteByte(ch)
if ch == '\n' {
for j := p.indent; j > 0; j-- {
buf.WriteString(". ")
}
}
}
format = buf.String()
}
fmt.Printf(format, args...)
}
// Debugging support.
// (tagString is only used when tracing is enabled)
var tagString = [...]string{
// Packages
-packageTag: "package",
// Types
-namedTag: "named type",
-arrayTag: "array",
-sliceTag: "slice",
-dddTag: "ddd",
-structTag: "struct",
-pointerTag: "pointer",
-signatureTag: "signature",
-interfaceTag: "interface",
-mapTag: "map",
-chanTag: "chan",
// Values
-falseTag: "false",
-trueTag: "true",
-int64Tag: "int64",
-floatTag: "float",
-fractionTag: "fraction",
-complexTag: "complex",
-stringTag: "string",
-unknownTag: "unknown",
// Type aliases
-aliasTag: "alias",
}