go.tools/cmd/godex: a tool to dump export information
Initial implementation. Lots of missing pieces.
Example use:
godex math
godex math.Sin
godex math.Sin math.Cos
LGTM=adonovan
R=adonovan
CC=golang-codereviews
https://golang.org/cl/76890044
diff --git a/cmd/godex/gccgo.go b/cmd/godex/gccgo.go
new file mode 100644
index 0000000..8c200e6
--- /dev/null
+++ b/cmd/godex/gccgo.go
@@ -0,0 +1,88 @@
+// Copyright 2014 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 implements access to gccgo-generated export data.
+
+package main
+
+import (
+ "debug/elf"
+ "fmt"
+ "io"
+ "os"
+
+ "code.google.com/p/go.tools/go/gccgoimporter"
+ "code.google.com/p/go.tools/go/importer"
+ "code.google.com/p/go.tools/go/types"
+)
+
+func init() {
+ // importer for default gccgo
+ var inst gccgoimporter.GccgoInstallation
+ inst.InitFromDriver("gccgo")
+ register("gccgo", protect(inst.GetImporter(nil)))
+
+ // importer for gccgo using condensed export format (experimental)
+ register("gccgo-new", protect(gccgoNewImporter))
+}
+
+func gccgoNewImporter(packages map[string]*types.Package, path string) (*types.Package, error) {
+ reader, closer, err := openGccgoExportFile(path)
+ if err != nil {
+ return nil, err
+ }
+ defer closer.Close()
+
+ // TODO(gri) importer.ImportData takes a []byte instead of an io.Reader;
+ // hence the need to read some amount of data. At the same time we don't
+ // want to read the entire, potentially very large object file. For now,
+ // read 10K. Fix this!
+ var data = make([]byte, 10<<10)
+ n, err := reader.Read(data)
+ if err != nil && err != io.EOF {
+ return nil, err
+ }
+
+ return importer.ImportData(packages, data[:n])
+}
+
+// openGccgoExportFile was copied from gccgoimporter.
+func openGccgoExportFile(fpath string) (reader io.ReadSeeker, closer io.Closer, err error) {
+ f, err := os.Open(fpath)
+ if err != nil {
+ return
+ }
+ defer func() {
+ if err != nil {
+ f.Close()
+ }
+ }()
+ closer = f
+
+ var magic [4]byte
+ _, err = f.ReadAt(magic[:], 0)
+ if err != nil {
+ return
+ }
+
+ if string(magic[:]) == "v1;\n" {
+ // Raw export data.
+ reader = f
+ return
+ }
+
+ ef, err := elf.NewFile(f)
+ if err != nil {
+ return
+ }
+
+ sec := ef.Section(".go_export")
+ if sec == nil {
+ err = fmt.Errorf("%s: .go_export section not found", fpath)
+ return
+ }
+
+ reader = sec.Open()
+ return
+}
