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 } 121
