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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 implements ExportData.
package types
import (
"bufio"
"fmt"
"io"
"os"
"strconv"
"strings"
)
func readGopackHeader(buf *bufio.Reader) (name string, size int, err os.Error) {
// See $GOROOT/include/ar.h.
hdr := make([]byte, 64+12+6+6+8+10+2)
_, err = io.ReadFull(buf, hdr)
if err != nil {
return
}
if trace {
fmt.Printf("header: %s", hdr)
}
s := strings.TrimSpace(string(hdr[64+12+6+6+8:][:10]))
size, err = strconv.Atoi(s)
if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' {
err = os.ErrorString("invalid archive header")
return
}
name = strings.TrimSpace(string(hdr[:64]))
return
}
type dataReader struct {
*bufio.Reader
io.Closer
}
// ExportData returns a readCloser positioned at the beginning of the
// export data section of the given object/archive file, or an error.
// It is the caller's responsibility to close the readCloser.
//
func ExportData(filename string) (rc io.ReadCloser, err os.Error) {
file, err := os.Open(filename)
if err != nil {
return
}
defer func() {
if err != nil {
file.Close()
// Add file name to error.
err = fmt.Errorf("reading export data: %s: %v", filename, err)
}
}()
buf := bufio.NewReader(file)
// Read first line to make sure this is an object file.
line, err := buf.ReadSlice('\n')
if err != nil {
return
}
if string(line) == "!<arch>\n" {
// Archive file. Scan to __.PKGDEF, which should
// be second archive entry.
var name string
var size int
// First entry should be __.SYMDEF.
// Read and discard.
if name, size, err = readGopackHeader(buf); err != nil {
return
}
if name != "__.SYMDEF" {
err = os.ErrorString("go archive does not begin with __.SYMDEF")
return
}
const block = 4096
tmp := make([]byte, block)
for size > 0 {
n := size
if n > block {
n = block
}
_, err = io.ReadFull(buf, tmp[:n])
if err != nil {
return
}
size -= n
}
// Second entry should be __.PKGDEF.
if name, size, err = readGopackHeader(buf); err != nil {
return
}
if name != "__.PKGDEF" {
err = os.ErrorString("go archive is missing __.PKGDEF")
return
}
// Read first line of __.PKGDEF data, so that line
// is once again the first line of the input.
line, err = buf.ReadSlice('\n')
if err != nil {
return
}
}
// Now at __.PKGDEF in archive or still at beginning of file.
// Either way, line should begin with "go object ".
if !strings.HasPrefix(string(line), "go object ") {
err = os.ErrorString("not a go object file")
return
}
// Skip over object header to export data.
// Begins after first line with $$.
for line[0] != '$' {
line, err = buf.ReadSlice('\n')
if err != nil {
return
}
}
rc = &dataReader{buf, file}
return
}
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