| 1 | // Copyright 2011 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. |
| 4 | |
| 5 | // This file is a copy of $GOROOT/src/go/internal/gcimporter/exportdata.go. |
| 6 | |
| 7 | // This file implements FindExportData. |
| 8 | |
| 9 | package gcimporter |
| 10 | |
| 11 | import ( |
| 12 | "bufio" |
| 13 | "fmt" |
| 14 | "io" |
| 15 | "strconv" |
| 16 | "strings" |
| 17 | ) |
| 18 | |
| 19 | func readGopackHeader(r *bufio.Reader) (name string, size int64, err error) { |
| 20 | // See $GOROOT/include/ar.h. |
| 21 | hdr := make([]byte, 16+12+6+6+8+10+2) |
| 22 | _, err = io.ReadFull(r, hdr) |
| 23 | if err != nil { |
| 24 | return |
| 25 | } |
| 26 | // leave for debugging |
| 27 | if false { |
| 28 | fmt.Printf("header: %s", hdr) |
| 29 | } |
| 30 | s := strings.TrimSpace(string(hdr[16+12+6+6+8:][:10])) |
| 31 | length, err := strconv.Atoi(s) |
| 32 | size = int64(length) |
| 33 | if err != nil || hdr[len(hdr)-2] != '`' || hdr[len(hdr)-1] != '\n' { |
| 34 | err = fmt.Errorf("invalid archive header") |
| 35 | return |
| 36 | } |
| 37 | name = strings.TrimSpace(string(hdr[:16])) |
| 38 | return |
| 39 | } |
| 40 | |
| 41 | // FindExportData positions the reader r at the beginning of the |
| 42 | // export data section of an underlying GC-created object/archive |
| 43 | // file by reading from it. The reader must be positioned at the |
| 44 | // start of the file before calling this function. The hdr result |
| 45 | // is the string before the export data, either "$$" or "$$B". |
| 46 | // The size result is the length of the export data in bytes, or -1 if not known. |
| 47 | func FindExportData(r *bufio.Reader) (hdr string, size int64, err error) { |
| 48 | // Read first line to make sure this is an object file. |
| 49 | line, err := r.ReadSlice('\n') |
| 50 | if err != nil { |
| 51 | err = fmt.Errorf("can't find export data (%v)", err) |
| 52 | return |
| 53 | } |
| 54 | |
| 55 | if string(line) == "!<arch>\n" { |
| 56 | // Archive file. Scan to __.PKGDEF. |
| 57 | var name string |
| 58 | if name, size, err = readGopackHeader(r); err != nil { |
| 59 | return |
| 60 | } |
| 61 | |
| 62 | // First entry should be __.PKGDEF. |
| 63 | if name != "__.PKGDEF" { |
| 64 | err = fmt.Errorf("go archive is missing __.PKGDEF") |
| 65 | return |
| 66 | } |
| 67 | |
| 68 | // Read first line of __.PKGDEF data, so that line |
| 69 | // is once again the first line of the input. |
| 70 | if line, err = r.ReadSlice('\n'); err != nil { |
| 71 | err = fmt.Errorf("can't find export data (%v)", err) |
| 72 | return |
| 73 | } |
| 74 | size -= int64(len(line)) |
| 75 | } |
| 76 | |
| 77 | // Now at __.PKGDEF in archive or still at beginning of file. |
| 78 | // Either way, line should begin with "go object ". |
| 79 | if !strings.HasPrefix(string(line), "go object ") { |
| 80 | err = fmt.Errorf("not a Go object file") |
| 81 | return |
| 82 | } |
| 83 | |
| 84 | // Skip over object header to export data. |
| 85 | // Begins after first line starting with $$. |
| 86 | for line[0] != '$' { |
| 87 | if line, err = r.ReadSlice('\n'); err != nil { |
| 88 | err = fmt.Errorf("can't find export data (%v)", err) |
| 89 | return |
| 90 | } |
| 91 | size -= int64(len(line)) |
| 92 | } |
| 93 | hdr = string(line) |
| 94 | if size < 0 { |
| 95 | size = -1 |
| 96 | } |
| 97 | |
| 98 | return |
| 99 | } |
| 100 |
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