Robert Sloan | 572a4e2 | 2017-04-17 10:52:19 -0700 | [diff] [blame] | 1 | // Copyright (c) 2017, Google Inc. |
| 2 | // |
| 3 | // Permission to use, copy, modify, and/or distribute this software for any |
| 4 | // purpose with or without fee is hereby granted, provided that the above |
| 5 | // copyright notice and this permission notice appear in all copies. |
| 6 | // |
| 7 | // THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES |
| 8 | // WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF |
| 9 | // MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY |
| 10 | // SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES |
| 11 | // WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION |
| 12 | // OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN |
| 13 | // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. */ |
| 14 | |
| 15 | // ar.go contains functions for parsing .a archive files. |
| 16 | |
| 17 | package main |
| 18 | |
| 19 | import ( |
| 20 | "bytes" |
| 21 | "errors" |
| 22 | "io" |
| 23 | "strconv" |
| 24 | "strings" |
| 25 | ) |
| 26 | |
| 27 | // ParseAR parses an archive file from r and returns a map from filename to |
| 28 | // contents, or else an error. |
| 29 | func ParseAR(r io.Reader) (map[string][]byte, error) { |
| 30 | // See https://en.wikipedia.org/wiki/Ar_(Unix)#File_format_details |
| 31 | const expectedMagic = "!<arch>\n" |
| 32 | var magic [len(expectedMagic)]byte |
| 33 | if _, err := io.ReadFull(r, magic[:]); err != nil { |
| 34 | return nil, err |
| 35 | } |
| 36 | if string(magic[:]) != expectedMagic { |
| 37 | return nil, errors.New("ar: not an archive file") |
| 38 | } |
| 39 | |
| 40 | const filenameTableName = "//" |
| 41 | const symbolTableName = "/" |
| 42 | var longFilenameTable []byte |
| 43 | ret := make(map[string][]byte) |
| 44 | |
| 45 | for { |
| 46 | var header [60]byte |
| 47 | if _, err := io.ReadFull(r, header[:]); err != nil { |
| 48 | if err == io.EOF { |
| 49 | break |
| 50 | } |
| 51 | return nil, errors.New("ar: error reading file header: " + err.Error()) |
| 52 | } |
| 53 | |
| 54 | name := strings.TrimRight(string(header[:16]), " ") |
| 55 | sizeStr := strings.TrimRight(string(header[48:58]), "\x00 ") |
| 56 | size, err := strconv.ParseUint(sizeStr, 10, 64) |
| 57 | if err != nil { |
| 58 | return nil, errors.New("ar: failed to parse file size: " + err.Error()) |
| 59 | } |
| 60 | |
| 61 | // File contents are padded to a multiple of two bytes |
| 62 | storedSize := size |
| 63 | if storedSize%2 == 1 { |
| 64 | storedSize++ |
| 65 | } |
| 66 | |
| 67 | contents := make([]byte, storedSize) |
| 68 | if _, err := io.ReadFull(r, contents); err != nil { |
| 69 | return nil, errors.New("ar: error reading file contents: " + err.Error()) |
| 70 | } |
| 71 | contents = contents[:size] |
| 72 | |
| 73 | switch { |
| 74 | case name == filenameTableName: |
| 75 | if longFilenameTable != nil { |
| 76 | return nil, errors.New("ar: two filename tables found") |
| 77 | } |
| 78 | longFilenameTable = contents |
| 79 | continue |
| 80 | |
| 81 | case name == symbolTableName: |
| 82 | continue |
| 83 | |
| 84 | case len(name) > 1 && name[0] == '/': |
| 85 | if longFilenameTable == nil { |
| 86 | return nil, errors.New("ar: long filename reference found before filename table") |
| 87 | } |
| 88 | |
| 89 | // A long filename is stored as "/" followed by a |
| 90 | // base-10 offset in the filename table. |
| 91 | offset, err := strconv.ParseUint(name[1:], 10, 64) |
| 92 | if err != nil { |
| 93 | return nil, errors.New("ar: failed to parse filename offset: " + err.Error()) |
| 94 | } |
| 95 | if offset > uint64((^uint(0))>>1) { |
| 96 | return nil, errors.New("ar: filename offset overflow") |
| 97 | } |
| 98 | |
| 99 | if int(offset) > len(longFilenameTable) { |
| 100 | return nil, errors.New("ar: filename offset out of bounds") |
| 101 | } |
| 102 | |
| 103 | filename := longFilenameTable[offset:] |
| 104 | if i := bytes.IndexByte(filename, '/'); i < 0 { |
| 105 | return nil, errors.New("ar: unterminated filename in table") |
| 106 | } else { |
| 107 | filename = filename[:i] |
| 108 | } |
| 109 | |
| 110 | name = string(filename) |
| 111 | |
| 112 | default: |
| 113 | name = strings.TrimRight(name, "/") |
| 114 | } |
| 115 | |
| 116 | ret[name] = contents |
| 117 | } |
| 118 | |
| 119 | return ret, nil |
| 120 | } |