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// 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.
// This file is a reduced copy of $GOROOT/src/go/internal/gcimporter/gcimporter.go.
// Package gcimporter provides various functions for reading
// gc-generated object files that can be used to implement the
// Importer interface defined by the Go 1.5 standard library package.
//
// The encoding is deterministic: if the encoder is applied twice to
// the same types.Package data structure, both encodings are equal.
// This property may be important to avoid spurious changes in
// applications such as build systems.
//
// However, the encoder is not necessarily idempotent. Importing an
// exported package may yield a types.Package that, while it
// represents the same set of Go types as the original, may differ in
// the details of its internal representation. Because of these
// differences, re-encoding the imported package may yield a
// different, but equally valid, encoding of the package.
package gcimporter // import "golang.org/x/tools/internal/gcimporter"
import (
"bufio"
"bytes"
"fmt"
"go/build"
"go/token"
"go/types"
"io"
"os"
"os/exec"
"path/filepath"
"strings"
"sync"
)
const (
// Enable debug during development: it adds some additional checks, and
// prevents errors from being recovered.
debug = false
// If trace is set, debugging output is printed to std out.
trace = false
)
var exportMap sync.Map // package dir → func() (string, bool)
// lookupGorootExport returns the location of the export data
// (normally found in the build cache, but located in GOROOT/pkg
// in prior Go releases) for the package located in pkgDir.
//
// (We use the package's directory instead of its import path
// mainly to simplify handling of the packages in src/vendor
// and cmd/vendor.)
func lookupGorootExport(pkgDir string) (string, bool) {
f, ok := exportMap.Load(pkgDir)
if !ok {
var (
listOnce sync.Once
exportPath string
)
f, _ = exportMap.LoadOrStore(pkgDir, func() (string, bool) {
listOnce.Do(func() {
cmd := exec.Command("go", "list", "-export", "-f", "{{.Export}}", pkgDir)
cmd.Dir = build.Default.GOROOT
var output []byte
output, err := cmd.Output()
if err != nil {
return
}
exports := strings.Split(string(bytes.TrimSpace(output)), "\n")
if len(exports) != 1 {
return
}
exportPath = exports[0]
})
return exportPath, exportPath != ""
})
}
return f.(func() (string, bool))()
}
var pkgExts = [...]string{".a", ".o"}
// 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). A relative srcDir is interpreted
// relative to the current working directory.
// If no file was found, an empty filename is returned.
func FindPkg(path, srcDir string) (filename, id string) {
if path == "" {
return
}
var noext string
switch {
default:
// "x" -> "$GOPATH/pkg/$GOOS_$GOARCH/x.ext", "x"
// Don't require the source files to be present.
if abs, err := filepath.Abs(srcDir); err == nil { // see issue 14282
srcDir = abs
}
bp, _ := build.Import(path, srcDir, build.FindOnly|build.AllowBinary)
if bp.PkgObj == "" {
var ok bool
if bp.Goroot && bp.Dir != "" {
filename, ok = lookupGorootExport(bp.Dir)
}
if !ok {
id = path // make sure we have an id to print in error message
return
}
} else {
noext = strings.TrimSuffix(bp.PkgObj, ".a")
id = bp.ImportPath
}
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
id = path
}
if false { // for debugging
if path != id {
fmt.Printf("%s -> %s\n", path, id)
}
}
if filename != "" {
if f, err := os.Stat(filename); err == nil && !f.IsDir() {
return
}
}
// try extensions
for _, ext := range pkgExts {
filename = noext + ext
if f, err := os.Stat(filename); err == nil && !f.IsDir() {
return
}
}
filename = "" // not found
return
}
// Import imports a gc-generated package given its import path and srcDir, adds
// the corresponding package object to the packages map, and returns the object.
// The packages map must contain all packages already imported.
func Import(packages map[string]*types.Package, path, srcDir string, lookup func(path string) (io.ReadCloser, error)) (pkg *types.Package, err error) {
var rc io.ReadCloser
var filename, id string
if lookup != nil {
// With custom lookup specified, assume that caller has
// converted path to a canonical import path for use in the map.
if path == "unsafe" {
return types.Unsafe, nil
}
id = path
// No need to re-import if the package was imported completely before.
if pkg = packages[id]; pkg != nil && pkg.Complete() {
return
}
f, err := lookup(path)
if err != nil {
return nil, err
}
rc = f
} else {
filename, id = FindPkg(path, srcDir)
if filename == "" {
if path == "unsafe" {
return types.Unsafe, nil
}
return nil, fmt.Errorf("can't find import: %q", id)
}
// no need to re-import if the package was imported completely before
if pkg = packages[id]; pkg != nil && pkg.Complete() {
return
}
// open file
f, err := os.Open(filename)
if err != nil {
return nil, err
}
defer func() {
if err != nil {
// add file name to error
err = fmt.Errorf("%s: %v", filename, err)
}
}()
rc = f
}
defer rc.Close()
var hdr string
var size int64
buf := bufio.NewReader(rc)
if hdr, size, err = FindExportData(buf); err != nil {
return
}
switch hdr {
case "$$B\n":
var data []byte
data, err = io.ReadAll(buf)
if err != nil {
break
}
// TODO(gri): allow clients of go/importer to provide a FileSet.
// Or, define a new standard go/types/gcexportdata package.
fset := token.NewFileSet()
// Select appropriate importer.
if len(data) > 0 {
switch data[0] {
case 'v', 'c', 'd': // binary, till go1.10
return nil, fmt.Errorf("binary (%c) import format is no longer supported", data[0])
case 'i': // indexed, till go1.19
_, pkg, err := IImportData(fset, packages, data[1:], id)
return pkg, err
case 'u': // unified, from go1.20
_, pkg, err := UImportData(fset, packages, data[1:size], id)
return pkg, err
default:
l := len(data)
if l > 10 {
l = 10
}
return nil, fmt.Errorf("unexpected export data with prefix %q for path %s", string(data[:l]), id)
}
}
default:
err = fmt.Errorf("unknown export data header: %q", hdr)
}
return
}
type byPath []*types.Package
func (a byPath) Len() int { return len(a) }
func (a byPath) Swap(i, j int) { a[i], a[j] = a[j], a[i] }
func (a byPath) Less(i, j int) bool { return a[i].Path() < a[j].Path() }