1 /*
2 Copyright (c) 2013 Blake Smith <blakesmith0@gmail.com>
3 4 Permission is hereby granted, free of charge, to any person obtaining a copy
5 of this software and associated documentation files (the "Software"), to deal
6 in the Software without restriction, including without limitation the rights
7 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
8 copies of the Software, and to permit persons to whom the Software is
9 furnished to do so, subject to the following conditions:
10 11 The above copyright notice and this permission notice shall be included in
12 all copies or substantial portions of the Software.
13 14 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
15 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
16 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
17 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
18 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
19 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
20 THE SOFTWARE.
21 */
22 package ar
23 24 import (
25 "errors"
26 "io"
27 "strconv"
28 )
29 30 var (
31 ErrWriteTooLong = errors.New("ar: write too long")
32 )
33 34 // Writer provides sequential writing of an ar archive.
35 // An ar archive is sequence of header file pairs
36 // Call WriteHeader to begin writing a new file, then call Write to supply the file's data
37 //
38 // Example:
39 // archive := ar.NewWriter(writer)
40 // archive.WriteGlobalHeader()
41 // header := new(ar.Header)
42 // header.Size = 15 // bytes
43 // if err := archive.WriteHeader(header); err != nil {
44 // return err
45 // }
46 // io.Copy(archive, data)
47 type Writer struct {
48 w io.Writer
49 nb int64 // number of unwritten bytes for the current file entry
50 }
51 52 // Create a new ar writer that writes to w
53 func NewWriter(w io.Writer) *Writer { return &Writer{w: w} }
54 55 func (aw *Writer) numeric(b []byte, x int64) {
56 s := strconv.FormatInt(x, 10)
57 for len(s) < len(b) {
58 s = s + " "
59 }
60 copy(b, []byte(s))
61 }
62 63 func (aw *Writer) octal(b []byte, x int64) {
64 s := "100" + strconv.FormatInt(x, 8)
65 for len(s) < len(b) {
66 s = s + " "
67 }
68 copy(b, []byte(s))
69 }
70 71 func (aw *Writer) string(b []byte, str string) {
72 s := str
73 for len(s) < len(b) {
74 s = s + " "
75 }
76 copy(b, []byte(s))
77 }
78 79 // Writes to the current entry in the ar archive
80 // Returns ErrWriteTooLong if more than header.Size
81 // bytes are written after a call to WriteHeader
82 func (aw *Writer) Write(b []byte) (n int, err error) {
83 if int64(len(b)) > aw.nb {
84 b = b[0:aw.nb]
85 err = ErrWriteTooLong
86 }
87 n, werr := aw.w.Write(b)
88 aw.nb -= int64(n)
89 if werr != nil {
90 return n, werr
91 }
92 93 if len(b)%2 == 1 { // data size must be aligned to an even byte
94 n2, _ := aw.w.Write([]byte{'\n'})
95 return n+n2, err
96 }
97 98 return
99 }
100 101 func (aw *Writer) WriteGlobalHeader() error {
102 _, err := aw.w.Write([]byte(GLOBAL_HEADER))
103 return err
104 }
105 106 // Writes the header to the underlying writer and prepares
107 // to receive the file payload
108 func (aw *Writer) WriteHeader(hdr *Header) error {
109 aw.nb = int64(hdr.Size)
110 header := make([]byte, HEADER_BYTE_SIZE)
111 s := slicer(header)
112 113 aw.string(s.next(16), hdr.Name)
114 aw.numeric(s.next(12), hdr.ModTime.Unix())
115 aw.numeric(s.next(6), int64(hdr.Uid))
116 aw.numeric(s.next(6), int64(hdr.Gid))
117 aw.octal(s.next(8), hdr.Mode)
118 aw.numeric(s.next(10), hdr.Size)
119 aw.string(s.next(2), "`\n")
120 121 _, err := aw.w.Write(header)
122 123 return err
124 }
125