1 files changed, 174 insertions, 0 deletions
diff --git a/src/go/internal/gcimporter/gcimporter.go b/src/go/internal/gcimporter/gcimporter.go
new file mode 100644
index 0000000..b74daca
--- /dev/null
+++ b/src/go/internal/gcimporter/gcimporter.go
@@ -0,0 +1,174 @@
+// 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.
+package gcimporter // import "go/internal/gcimporter"
+
+import (
+	"bufio"
+	"fmt"
+	"go/build"
+	"go/token"
+	"go/types"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// debugging/development support
+const debug = false
+
+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 == "" {
+			id = path // make sure we have an id to print in error message
+			return
+		}
+		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)
+		}
+	}
+
+	// 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(fset *token.FileSet, 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 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 {
+		var filename string
+		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
+	buf := bufio.NewReader(rc)
+	if hdr, err = FindExportData(buf); 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
+		data, err = io.ReadAll(buf)
+		if err != nil {
+			break
+		}
+
+		// 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.
+		if len(data) > 0 && data[0] == 'i' {
+			_, pkg, err = iImportData(fset, packages, data[1:], id)
+		} else {
+			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 []*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() }