1 // Copyright 2016 The Go Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style
3 // license that can be found in the LICENSE file.
5 // Package gcexportdata provides functions for locating, reading, and
6 // writing export data files containing type information produced by the
7 // gc compiler. This package supports go1.7 export data format and all
10 // Although it might seem convenient for this package to live alongside
11 // go/types in the standard library, this would cause version skew
12 // problems for developer tools that use it, since they must be able to
13 // consume the outputs of the gc compiler both before and after a Go
14 // update such as from Go 1.7 to Go 1.8. Because this package lives in
15 // golang.org/x/tools, sites can update their version of this repo some
16 // time before the Go 1.8 release and rebuild and redeploy their
17 // developer tools, which will then be able to consume both Go 1.7 and
18 // Go 1.8 export data files, so they will work before and after the
19 // Go update. (See discussion at https://golang.org/issue/15651.)
21 package gcexportdata // import "golang.org/x/tools/go/gcexportdata"
32 "golang.org/x/tools/go/internal/gcimporter"
35 // Find returns the name of an object (.o) or archive (.a) file
36 // containing type information for the specified import path,
37 // using the workspace layout conventions of go/build.
38 // If no file was found, an empty filename is returned.
40 // A relative srcDir is interpreted relative to the current working directory.
42 // Find also returns the package's resolved (canonical) import path,
43 // reflecting the effects of srcDir and vendoring on importPath.
44 func Find(importPath, srcDir string) (filename, path string) {
45 return gcimporter.FindPkg(importPath, srcDir)
48 // NewReader returns a reader for the export data section of an object
49 // (.o) or archive (.a) file read from r. The new reader may provide
50 // additional trailing data beyond the end of the export data.
51 func NewReader(r io.Reader) (io.Reader, error) {
52 buf := bufio.NewReader(r)
53 _, err := gcimporter.FindExportData(buf)
54 // If we ever switch to a zip-like archive format with the ToC
55 // at the end, we can return the correct portion of export data,
56 // but for now we must return the entire rest of the file.
60 // Read reads export data from in, decodes it, and returns type
61 // information for the package.
62 // The package name is specified by path.
63 // File position information is added to fset.
65 // Read may inspect and add to the imports map to ensure that references
66 // within the export data to other packages are consistent. The caller
67 // must ensure that imports[path] does not exist, or exists but is
68 // incomplete (see types.Package.Complete), and Read inserts the
69 // resulting package into this map entry.
71 // On return, the state of the reader is undefined.
72 func Read(in io.Reader, fset *token.FileSet, imports map[string]*types.Package, path string) (*types.Package, error) {
73 data, err := ioutil.ReadAll(in)
75 return nil, fmt.Errorf("reading export data for %q: %v", path, err)
78 if bytes.HasPrefix(data, []byte("!<arch>")) {
79 return nil, fmt.Errorf("can't read export data for %q directly from an archive file (call gcexportdata.NewReader first to extract export data)", path)
82 // The App Engine Go runtime v1.6 uses the old export data format.
83 // TODO(adonovan): delete once v1.7 has been around for a while.
84 if bytes.HasPrefix(data, []byte("package ")) {
85 return gcimporter.ImportData(imports, path, path, bytes.NewReader(data))
88 // The indexed export format starts with an 'i'; the older
89 // binary export format starts with a 'c', 'd', or 'v'
90 // (from "version"). Select appropriate importer.
91 if len(data) > 0 && data[0] == 'i' {
92 _, pkg, err := gcimporter.IImportData(fset, imports, data[1:], path)
96 _, pkg, err := gcimporter.BImportData(fset, imports, data, path)
100 // Write writes encoded type information for the specified package to out.
101 // The FileSet provides file position information for named objects.
102 func Write(out io.Writer, fset *token.FileSet, pkg *types.Package) error {
103 b, err := gcimporter.IExportData(fset, pkg)
107 _, err = out.Write(b)