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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.
// package importer implements Import for gc-generated object files.
package importer
import (
"bufio"
"bytes"
"fmt"
"go/build"
"internal/pkgbits"
"io"
"os"
"os/exec"
"path/filepath"
"strings"
"sync"
"cmd/compile/internal/types2"
)
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(filepath.Join(build.Default.GOROOT, "bin", "go"), "list", "-export", "-f", "{{.Export}}", pkgDir)
cmd.Dir = build.Default.GOROOT
cmd.Env = append(os.Environ(), "PWD="+cmd.Dir, "GOROOT="+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"} // a file from the build cache will have no extension
// 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]*types2.Package, path, srcDir string, lookup func(path string) (io.ReadCloser, error)) (pkg *types2.Package, err error) {
var rc io.ReadCloser
var 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 types2.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 {
var filename string
filename, id = FindPkg(path, srcDir)
if filename == "" {
if path == "unsafe" {
return types2.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()
buf := bufio.NewReader(rc)
hdr, size, err := FindExportData(buf)
if err != nil {
return
}
switch hdr {
case "$$\n":
err = fmt.Errorf("import %q: old textual export format no longer supported (recompile library)", path)
case "$$B\n":
var data []byte
var r io.Reader = buf
if size >= 0 {
r = io.LimitReader(r, int64(size))
}
data, err = io.ReadAll(r)
if err != nil {
break
}
if len(data) == 0 {
err = fmt.Errorf("import %q: missing export data", path)
break
}
exportFormat := data[0]
s := string(data[1:])
// The indexed export format starts with an 'i'; the older
// binary export format starts with a 'c', 'd', or 'v'
// (from "version"). Select appropriate importer.
switch exportFormat {
case 'u':
s = s[:strings.Index(s, "\n$$\n")]
input := pkgbits.NewPkgDecoder(id, s)
pkg = ReadPackage(nil, packages, input)
case 'i':
pkg, err = ImportData(packages, s, id)
default:
err = fmt.Errorf("import %q: old binary export format no longer supported (recompile library)", path)
}
default:
err = fmt.Errorf("import %q: unknown export data header: %q", path, hdr)
}
return
}
type byPath []*types2.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() }