go_agent/src/code.google.com/p/go.tools/go/gcimporter/gcimporter.go
// Copyright 2011 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 gcimporter implements Import for gc-generated object files.
// Importing this package installs Import as go/types.DefaultImport.
package gcimporter
import (
"bufio"
"errors"
"fmt"
"go/ast"
"go/build"
"go/token"
"io"
"os"
"path/filepath"
"strconv"
"strings"
"text/scanner"
"code.google.com/p/go.tools/go/exact"
"code.google.com/p/go.tools/go/types"
)
// debugging/development support
const debug = false
func init() {
types.DefaultImport = Import
}
var pkgExts = [...]string{".a", ".5", ".6", ".8"}
// FindPkg returns the filename and unique package id for an import
// path based on package information provided by build.Import (using
// the build.Default build.Context).
// If no file was found, an empty filename is returned.
//
func FindPkg(path, srcDir string) (filename, id string) {
if len(path) == 0 {
return
}
id = path
var noext string
switch {
default:
// "x" -> "$GOPATH/pkg/$GOOS_$GOARCH/x.ext", "x"
// Don't require the source files to be present.
bp, _ := build.Import(path, srcDir, build.FindOnly|build.AllowBinary)
if bp.PkgObj == "" {
return
}
noext = strings.TrimSuffix(bp.PkgObj, ".a")
case build.IsLocalImport(path):
// "./x" -> "/this/directory/x.ext", "/this/directory/x"
noext = filepath.Join(srcDir, path)
id = noext
case filepath.IsAbs(path):
// for completeness only - go/build.Import
// does not support absolute imports
// "/x" -> "/x.ext", "/x"
noext = path
}
// try extensions
for _, ext := range pkgExts {
filename = noext + ext
if f, err := os.Stat(filename); err == nil && !f.IsDir() {
return
}
}
filename = "" // not found
return
}
// ImportData imports a package by reading the gc-generated export data,
// adds the corresponding package object to the imports map indexed by id,
// and returns the object.
//
// The imports map must contains all packages already imported. The data
// reader position must be the beginning of the export data section. The
// filename is only used in error messages.
//
// If imports[id] contains the completely imported package, that package
// can be used directly, and there is no need to call this function (but
// there is also no harm but for extra time used).
//
func ImportData(imports map[string]*types.Package, filename, id string, data io.Reader) (pkg *types.Package, err error) {
// support for parser error handling
defer func() {
switch r := recover().(type) {
case nil:
// nothing to do
case importError:
err = r
default:
panic(r) // internal error
}
}()
var p parser
p.init(filename, id, data, imports)
pkg = p.parseExport()
return
}
// Import imports a gc-generated package given its import path, adds the
// corresponding package object to the imports map, and returns the object.
// Local import paths are interpreted relative to the current working directory.
// The imports map must contains all packages already imported.
//
func Import(imports map[string]*types.Package, path string) (pkg *types.Package, err error) {
if path == "unsafe" {
return types.Unsafe, nil
}
srcDir := "."
if build.IsLocalImport(path) {
srcDir, err = os.Getwd()
if err != nil {
return
}
}
filename, id := FindPkg(path, srcDir)
if filename == "" {
err = fmt.Errorf("can't find import: %s", id)
return
}
// no need to re-import if the package was imported completely before
if pkg = imports[id]; pkg != nil && pkg.Complete() {
return
}
// open file
f, err := os.Open(filename)
if err != nil {
return
}
defer func() {
f.Close()
if err != nil {
// add file name to error
err = fmt.Errorf("reading export data: %s: %v", filename, err)
}
}()
buf := bufio.NewReader(f)
if err = FindExportData(buf); err != nil {
return
}
pkg, err = ImportData(imports, filename, id, buf)
return
}
// ----------------------------------------------------------------------------
// Parser
// TODO(gri) Imported objects don't have position information.
// Ideally use the debug table line info; alternatively
// create some fake position (or the position of the
// import). That way error messages referring to imported
// objects can print meaningful information.
// parser parses the exports inside a gc compiler-produced
// object/archive file and populates its scope with the results.
type parser struct {
scanner scanner.Scanner
tok rune // current token
lit string // literal string; only valid for Ident, Int, String tokens
id string // package id of imported package
imports map[string]*types.Package // package id -> package object
}
func (p *parser) init(filename, id string, src io.Reader, imports map[string]*types.Package) {
p.scanner.Init(src)
p.scanner.Error = func(_ *scanner.Scanner, msg string) { p.error(msg) }
p.scanner.Mode = scanner.ScanIdents | scanner.ScanInts | scanner.ScanChars | scanner.ScanStrings | scanner.ScanComments | scanner.SkipComments
p.scanner.Whitespace = 1<<'\t' | 1<<' '
p.scanner.Filename = filename // for good error messages
p.next()
p.id = id
p.imports = imports
if debug {
// check consistency of imports map
for _, pkg := range imports {
if pkg.Name() == "" {
fmt.Printf("no package name for %s\n", pkg.Path())
}
}
}
}
func (p *parser) next() {
p.tok = p.scanner.Scan()
switch p.tok {
case scanner.Ident, scanner.Int, scanner.Char, scanner.String, '·':
p.lit = p.scanner.TokenText()
default:
p.lit = ""
}
if debug {
fmt.Printf("%s: %q -> %q\n", scanner.TokenString(p.tok), p.scanner.TokenText(), p.lit)
}
}
func declTypeName(pkg *types.Package, name string) *types.TypeName {
scope := pkg.Scope()
if obj := scope.Lookup(name); obj != nil {
return obj.(*types.TypeName)
}
obj := types.NewTypeName(token.NoPos, pkg, name, nil)
// a named type may be referred to before the underlying type
// is known - set it up
types.NewNamed(obj, nil, nil)
scope.Insert(obj)
return obj
}
// ----------------------------------------------------------------------------
// Error handling
// Internal errors are boxed as importErrors.
type importError struct {
pos scanner.Position
err error
}
func (e importError) Error() string {
return fmt.Sprintf("import error %s (byte offset = %d): %s", e.pos, e.pos.Offset, e.err)
}
func (p *parser) error(err interface{}) {
if s, ok := err.(string); ok {
err = errors.New(s)
}
// panic with a runtime.Error if err is not an error
panic(importError{p.scanner.Pos(), err.(error)})
}
func (p *parser) errorf(format string, args ...interface{}) {
p.error(fmt.Sprintf(format, args...))
}
func (p *parser) expect(tok rune) string {
lit := p.lit
if p.tok != tok {
p.errorf("expected %s, got %s (%s)", scanner.TokenString(tok), scanner.TokenString(p.tok), lit)
}
p.next()
return lit
}
func (p *parser) expectSpecial(tok string) {
sep := 'x' // not white space
i := 0
for i < len(tok) && p.tok == rune(tok[i]) && sep > ' ' {
sep = p.scanner.Peek() // if sep <= ' ', there is white space before the next token
p.next()
i++
}
if i < len(tok) {
p.errorf("expected %q, got %q", tok, tok[0:i])
}
}
func (p *parser) expectKeyword(keyword string) {
lit := p.expect(scanner.Ident)
if lit != keyword {
p.errorf("expected keyword %s, got %q", keyword, lit)
}
}
// ----------------------------------------------------------------------------
// Qualified and unqualified names
// PackageId = string_lit .
//
func (p *parser) parsePackageId() string {
id, err := strconv.Unquote(p.expect(scanner.String))
if err != nil {
p.error(err)
}
// id == "" stands for the imported package id
// (only known at time of package installation)
if id == "" {
id = p.id
}
return id
}
// PackageName = ident .
//
func (p *parser) parsePackageName() string {
return p.expect(scanner.Ident)
}
// dotIdentifier = ( ident | '·' ) { ident | int | '·' } .
func (p *parser) parseDotIdent() string {
ident := ""
if p.tok != scanner.Int {
sep := 'x' // not white space
for (p.tok == scanner.Ident || p.tok == scanner.Int || p.tok == '·') && sep > ' ' {
ident += p.lit
sep = p.scanner.Peek() // if sep <= ' ', there is white space before the next token
p.next()
}
}
if ident == "" {
p.expect(scanner.Ident) // use expect() for error handling
}
return ident
}
// QualifiedName = "@" PackageId "." ( "?" | dotIdentifier ) .
//
func (p *parser) parseQualifiedName() (id, name string) {
p.expect('@')
id = p.parsePackageId()
p.expect('.')
// Per rev f280b8a485fd (10/2/2013), qualified names may be used for anonymous fields.
if p.tok == '?' {
p.next()
} else {
name = p.parseDotIdent()
}
return
}
// getPkg returns the package for a given id. If the package is
// not found but we have a package name, create the package and
// add it to the p.imports map.
//
func (p *parser) getPkg(id, name string) *types.Package {
// package unsafe is not in the imports map - handle explicitly
if id == "unsafe" {
return types.Unsafe
}
pkg := p.imports[id]
if pkg == nil && name != "" {
pkg = types.NewPackage(id, name, types.NewScope(nil))
p.imports[id] = pkg
}
return pkg
}
// parseExportedName is like parseQualifiedName, but
// the package id is resolved to an imported *types.Package.
//
func (p *parser) parseExportedName() (pkg *types.Package, name string) {
id, name := p.parseQualifiedName()
pkg = p.getPkg(id, "")
if pkg == nil {
p.errorf("%s package not found", id)
}
return
}
// ----------------------------------------------------------------------------
// Types
// BasicType = identifier .
//
func (p *parser) parseBasicType() types.Type {
id := p.expect(scanner.Ident)
obj := types.Universe.Lookup(id)
if obj, ok := obj.(*types.TypeName); ok {
return obj.Type()
}
p.errorf("not a basic type: %s", id)
return nil
}
// ArrayType = "[" int_lit "]" Type .
//
func (p *parser) parseArrayType() types.Type {
// "[" already consumed and lookahead known not to be "]"
lit := p.expect(scanner.Int)
p.expect(']')
elem := p.parseType()
n, err := strconv.ParseInt(lit, 10, 64)
if err != nil {
p.error(err)
}
return types.NewArray(elem, n)
}
// MapType = "map" "[" Type "]" Type .
//
func (p *parser) parseMapType() types.Type {
p.expectKeyword("map")
p.expect('[')
key := p.parseType()
p.expect(']')
elem := p.parseType()
return types.NewMap(key, elem)
}
// Name = identifier | "?" | QualifiedName .
//
// If materializePkg is set, the returned package is guaranteed to be set.
// For fully qualified names, the returned package may be a fake package
// (without name, scope, and not in the p.imports map), created for the
// sole purpose of providing a package path. Fake packages are created
// when the package id is not found in the p.imports map; in that case
// we cannot create a real package because we don't have a package name.
// For non-qualified names, the returned package is the imported package.
//
func (p *parser) parseName(materializePkg bool) (pkg *types.Package, name string) {
switch p.tok {
case scanner.Ident:
pkg = p.imports[p.id]
name = p.lit
p.next()
case '?':
// anonymous
pkg = p.imports[p.id]
p.next()
case '@':
// exported name prefixed with package path
var id string
id, name = p.parseQualifiedName()
if materializePkg {
// we don't have a package name - if the package
// doesn't exist yet, create a fake package instead
pkg = p.getPkg(id, "")
if pkg == nil {
pkg = types.NewPackage(id, "", nil)
}
}
default:
p.error("name expected")
}
return
}
func deref(typ types.Type) types.Type {
if p, _ := typ.(*types.Pointer); p != nil {
return p.Elem()
}
return typ
}
// Field = Name Type [ string_lit ] .
//
func (p *parser) parseField() (*types.Var, string) {
pkg, name := p.parseName(true)
typ := p.parseType()
anonymous := false
if name == "" {
// anonymous field - typ must be T or *T and T must be a type name
switch typ := deref(typ).(type) {
case *types.Basic: // basic types are named types
pkg = nil
name = typ.Name()
case *types.Named:
obj := typ.Obj()
pkg = obj.Pkg() // TODO(gri) is this still correct?
name = obj.Name()
default:
p.errorf("anonymous field expected")
}
anonymous = true
}
tag := ""
if p.tok == scanner.String {
tag = p.expect(scanner.String)
}
return types.NewField(token.NoPos, pkg, name, typ, anonymous), tag
}
// StructType = "struct" "{" [ FieldList ] "}" .
// FieldList = Field { ";" Field } .
//
func (p *parser) parseStructType() types.Type {
var fields []*types.Var
var tags []string
p.expectKeyword("struct")
p.expect('{')
for i := 0; p.tok != '}'; i++ {
if i > 0 {
p.expect(';')
}
fld, tag := p.parseField()
if tag != "" && tags == nil {
tags = make([]string, i)
}
if tags != nil {
tags = append(tags, tag)
}
fields = append(fields, fld)
}
p.expect('}')
return types.NewStruct(fields, tags)
}
// Parameter = ( identifier | "?" ) [ "..." ] Type [ string_lit ] .
//
func (p *parser) parseParameter() (par *types.Var, isVariadic bool) {
_, name := p.parseName(false)
if name == "" {
name = "_" // cannot access unnamed identifiers
}
if p.tok == '.' {
p.expectSpecial("...")
isVariadic = true
}
typ := p.parseType()
if isVariadic {
typ = types.NewSlice(typ)
}
// ignore argument tag (e.g. "noescape")
if p.tok == scanner.String {
p.next()
}
// TODO(gri) should we provide a package?
par = types.NewVar(token.NoPos, nil, name, typ)
return
}
// Parameters = "(" [ ParameterList ] ")" .
// ParameterList = { Parameter "," } Parameter .
//
func (p *parser) parseParameters() (list []*types.Var, isVariadic bool) {
p.expect('(')
for p.tok != ')' {
if len(list) > 0 {
p.expect(',')
}
par, variadic := p.parseParameter()
list = append(list, par)
if variadic {
if isVariadic {
p.error("... not on final argument")
}
isVariadic = true
}
}
p.expect(')')
return
}
// Signature = Parameters [ Result ] .
// Result = Type | Parameters .
//
func (p *parser) parseSignature(recv *types.Var) *types.Signature {
params, isVariadic := p.parseParameters()
// optional result type
var results []*types.Var
if p.tok == '(' {
var variadic bool
results, variadic = p.parseParameters()
if variadic {
p.error("... not permitted on result type")
}
}
return types.NewSignature(nil, recv, types.NewTuple(params...), types.NewTuple(results...), isVariadic)
}
// InterfaceType = "interface" "{" [ MethodList ] "}" .
// MethodList = Method { ";" Method } .
// Method = Name Signature .
//
// The methods of embedded interfaces are always "inlined"
// by the compiler and thus embedded interfaces are never
// visible in the export data.
//
func (p *parser) parseInterfaceType() types.Type {
var methods []*types.Func
p.expectKeyword("interface")
p.expect('{')
for i := 0; p.tok != '}'; i++ {
if i > 0 {
p.expect(';')
}
pkg, name := p.parseName(true)
sig := p.parseSignature(nil)
methods = append(methods, types.NewFunc(token.NoPos, pkg, name, sig))
}
p.expect('}')
return types.NewInterface(methods, nil)
}
// ChanType = ( "chan" [ "<-" ] | "<-" "chan" ) Type .
//
func (p *parser) parseChanType() types.Type {
dir := ast.SEND | ast.RECV
if p.tok == scanner.Ident {
p.expectKeyword("chan")
if p.tok == '<' {
p.expectSpecial("<-")
dir = ast.SEND
}
} else {
p.expectSpecial("<-")
p.expectKeyword("chan")
dir = ast.RECV
}
elem := p.parseType()
return types.NewChan(dir, elem)
}
// Type =
// BasicType | TypeName | ArrayType | SliceType | StructType |
// PointerType | FuncType | InterfaceType | MapType | ChanType |
// "(" Type ")" .
//
// BasicType = ident .
// TypeName = ExportedName .
// SliceType = "[" "]" Type .
// PointerType = "*" Type .
// FuncType = "func" Signature .
//
func (p *parser) parseType() types.Type {
switch p.tok {
case scanner.Ident:
switch p.lit {
default:
return p.parseBasicType()
case "struct":
return p.parseStructType()
case "func":
// FuncType
p.next()
return p.parseSignature(nil)
case "interface":
return p.parseInterfaceType()
case "map":
return p.parseMapType()
case "chan":
return p.parseChanType()
}
case '@':
// TypeName
pkg, name := p.parseExportedName()
return declTypeName(pkg, name).Type()
case '[':
p.next() // look ahead
if p.tok == ']' {
// SliceType
p.next()
return types.NewSlice(p.parseType())
}
return p.parseArrayType()
case '*':
// PointerType
p.next()
return types.NewPointer(p.parseType())
case '<':
return p.parseChanType()
case '(':
// "(" Type ")"
p.next()
typ := p.parseType()
p.expect(')')
return typ
}
p.errorf("expected type, got %s (%q)", scanner.TokenString(p.tok), p.lit)
return nil
}
// ----------------------------------------------------------------------------
// Declarations
// ImportDecl = "import" PackageName PackageId .
//
func (p *parser) parseImportDecl() {
p.expectKeyword("import")
name := p.parsePackageName()
p.getPkg(p.parsePackageId(), name)
}
// int_lit = [ "+" | "-" ] { "0" ... "9" } .
//
func (p *parser) parseInt() string {
s := ""
switch p.tok {
case '-':
s = "-"
p.next()
case '+':
p.next()
}
return s + p.expect(scanner.Int)
}
// number = int_lit [ "p" int_lit ] .
//
func (p *parser) parseNumber() (typ *types.Basic, val exact.Value) {
// mantissa
mant := exact.MakeFromLiteral(p.parseInt(), token.INT)
if mant == nil {
panic("invalid mantissa")
}
if p.lit == "p" {
// exponent (base 2)
p.next()
exp, err := strconv.ParseInt(p.parseInt(), 10, 0)
if err != nil {
p.error(err)
}
if exp < 0 {
denom := exact.MakeInt64(1)
denom = exact.Shift(denom, token.SHL, uint(-exp))
typ = types.Typ[types.UntypedFloat]
val = exact.BinaryOp(mant, token.QUO, denom)
return
}
if exp > 0 {
mant = exact.Shift(mant, token.SHL, uint(exp))
}
typ = types.Typ[types.UntypedFloat]
val = mant
return
}
typ = types.Typ[types.UntypedInt]
val = mant
return
}
// ConstDecl = "const" ExportedName [ Type ] "=" Literal .
// Literal = bool_lit | int_lit | float_lit | complex_lit | rune_lit | string_lit .
// bool_lit = "true" | "false" .
// complex_lit = "(" float_lit "+" float_lit "i" ")" .
// rune_lit = "(" int_lit "+" int_lit ")" .
// string_lit = `"` { unicode_char } `"` .
//
func (p *parser) parseConstDecl() {
p.expectKeyword("const")
pkg, name := p.parseExportedName()
var typ0 types.Type
if p.tok != '=' {
typ0 = p.parseType()
}
p.expect('=')
var typ types.Type
var val exact.Value
switch p.tok {
case scanner.Ident:
// bool_lit
if p.lit != "true" && p.lit != "false" {
p.error("expected true or false")
}
typ = types.Typ[types.UntypedBool]
val = exact.MakeBool(p.lit == "true")
p.next()
case '-', scanner.Int:
// int_lit
typ, val = p.parseNumber()
case '(':
// complex_lit or rune_lit
p.next()
if p.tok == scanner.Char {
p.next()
p.expect('+')
typ = types.Typ[types.UntypedRune]
_, val = p.parseNumber()
p.expect(')')
break
}
_, re := p.parseNumber()
p.expect('+')
_, im := p.parseNumber()
p.expectKeyword("i")
p.expect(')')
typ = types.Typ[types.UntypedComplex]
val = exact.BinaryOp(re, token.ADD, exact.MakeImag(im))
case scanner.Char:
// rune_lit
typ = types.Typ[types.UntypedRune]
val = exact.MakeFromLiteral(p.lit, token.CHAR)
p.next()
case scanner.String:
// string_lit
typ = types.Typ[types.UntypedString]
val = exact.MakeFromLiteral(p.lit, token.STRING)
p.next()
default:
p.errorf("expected literal got %s", scanner.TokenString(p.tok))
}
if typ0 == nil {
typ0 = typ
}
pkg.Scope().Insert(types.NewConst(token.NoPos, pkg, name, typ0, val))
}
// TypeDecl = "type" ExportedName Type .
//
func (p *parser) parseTypeDecl() {
p.expectKeyword("type")
pkg, name := p.parseExportedName()
obj := declTypeName(pkg, name)
// The type object may have been imported before and thus already
// have a type associated with it. We still need to parse the type
// structure, but throw it away if the object already has a type.
// This ensures that all imports refer to the same type object for
// a given type declaration.
typ := p.parseType()
if name := obj.Type().(*types.Named); name.Underlying() == nil {
name.SetUnderlying(typ)
}
}
// VarDecl = "var" ExportedName Type .
//
func (p *parser) parseVarDecl() {
p.expectKeyword("var")
pkg, name := p.parseExportedName()
typ := p.parseType()
pkg.Scope().Insert(types.NewVar(token.NoPos, pkg, name, typ))
}
// Func = Signature [ Body ] .
// Body = "{" ... "}" .
//
func (p *parser) parseFunc(recv *types.Var) *types.Signature {
sig := p.parseSignature(recv)
if p.tok == '{' {
p.next()
for i := 1; i > 0; p.next() {
switch p.tok {
case '{':
i++
case '}':
i--
}
}
}
return sig
}
// MethodDecl = "func" Receiver Name Func .
// Receiver = "(" ( identifier | "?" ) [ "*" ] ExportedName ")" .
//
func (p *parser) parseMethodDecl() {
// "func" already consumed
p.expect('(')
recv, _ := p.parseParameter() // receiver
p.expect(')')
// determine receiver base type object
base := deref(recv.Type()).(*types.Named)
// parse method name, signature, and possibly inlined body
pkg, name := p.parseName(true)
sig := p.parseFunc(recv)
// add method to type unless type was imported before
// and method exists already
// TODO(gri) This leads to a quadratic algorithm - ok for now because method counts are small.
base.AddMethod(types.NewFunc(token.NoPos, pkg, name, sig))
}
// FuncDecl = "func" ExportedName Func .
//
func (p *parser) parseFuncDecl() {
// "func" already consumed
pkg, name := p.parseExportedName()
typ := p.parseFunc(nil)
pkg.Scope().Insert(types.NewFunc(token.NoPos, pkg, name, typ))
}
// Decl = [ ImportDecl | ConstDecl | TypeDecl | VarDecl | FuncDecl | MethodDecl ] "\n" .
//
func (p *parser) parseDecl() {
if p.tok == scanner.Ident {
switch p.lit {
case "import":
p.parseImportDecl()
case "const":
p.parseConstDecl()
case "type":
p.parseTypeDecl()
case "var":
p.parseVarDecl()
case "func":
p.next() // look ahead
if p.tok == '(' {
p.parseMethodDecl()
} else {
p.parseFuncDecl()
}
}
}
p.expect('\n')
}
// ----------------------------------------------------------------------------
// Export
// Export = "PackageClause { Decl } "$$" .
// PackageClause = "package" PackageName [ "safe" ] "\n" .
//
func (p *parser) parseExport() *types.Package {
p.expectKeyword("package")
name := p.parsePackageName()
if p.tok == scanner.Ident && p.lit == "safe" {
// package was compiled with -u option - ignore
p.next()
}
p.expect('\n')
pkg := p.getPkg(p.id, name)
for p.tok != '$' && p.tok != scanner.EOF {
p.parseDecl()
}
if ch := p.scanner.Peek(); p.tok != '$' || ch != '$' {
// don't call next()/expect() since reading past the
// export data may cause scanner errors (e.g. NUL chars)
p.errorf("expected '$$', got %s %c", scanner.TokenString(p.tok), ch)
}
if n := p.scanner.ErrorCount; n != 0 {
p.errorf("expected no scanner errors, got %d", n)
}
// package was imported completely and without errors
pkg.MarkComplete()
return pkg
}