git clone https://git.lucas.co/go_mono.git
riff/example_test.go (2.2K)
1 // Copyright 2014 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 package riff_test
6
7 import (
8 "fmt"
9 "io"
10 "io/ioutil"
11 "log"
12 "strings"
13
14 "golang.org/x/image/riff"
15 )
16
17 func ExampleReader() {
18 formType, r, err := riff.NewReader(strings.NewReader(data))
19 if err != nil {
20 log.Fatal(err)
21 }
22 fmt.Printf("RIFF(%s)\n", formType)
23 if err := dump(r, ".\t"); err != nil {
24 log.Fatal(err)
25 }
26 // Output:
27 // RIFF(ROOT)
28 // . ZERO ""
29 // . ONE "a"
30 // . LIST(META)
31 // . . LIST(GOOD)
32 // . . . ONE "a"
33 // . . . FIVE "klmno"
34 // . . ZERO ""
35 // . . LIST(BAD )
36 // . . . THRE "def"
37 // . TWO "bc"
38 // . LIST(UGLY)
39 // . . FOUR "ghij"
40 // . . SIX "pqrstu"
41 }
42
43 func dump(r *riff.Reader, indent string) error {
44 for {
45 chunkID, chunkLen, chunkData, err := r.Next()
46 if err == io.EOF {
47 return nil
48 }
49 if err != nil {
50 return err
51 }
52 if chunkID == riff.LIST {
53 listType, list, err := riff.NewListReader(chunkLen, chunkData)
54 if err != nil {
55 return err
56 }
57 fmt.Printf("%sLIST(%s)\n", indent, listType)
58 if err := dump(list, indent+".\t"); err != nil {
59 return err
60 }
61 continue
62 }
63 b, err := ioutil.ReadAll(chunkData)
64 if err != nil {
65 return err
66 }
67 fmt.Printf("%s%s %q\n", indent, chunkID, b)
68 }
69 }
70
71 func encodeU32(u uint32) string {
72 return string([]byte{
73 byte(u >> 0),
74 byte(u >> 8),
75 byte(u >> 16),
76 byte(u >> 24),
77 })
78 }
79
80 func encode(chunkID, contents string) string {
81 n := len(contents)
82 if n&1 == 1 {
83 contents += "\x00"
84 }
85 return chunkID + encodeU32(uint32(n)) + contents
86 }
87
88 func encodeMulti(typ0, typ1 string, chunks ...string) string {
89 n := 4
90 for _, c := range chunks {
91 n += len(c)
92 }
93 s := typ0 + encodeU32(uint32(n)) + typ1
94 for _, c := range chunks {
95 s += c
96 }
97 return s
98 }
99
100 var (
101 d0 = encode("ZERO", "")
102 d1 = encode("ONE ", "a")
103 d2 = encode("TWO ", "bc")
104 d3 = encode("THRE", "def")
105 d4 = encode("FOUR", "ghij")
106 d5 = encode("FIVE", "klmno")
107 d6 = encode("SIX ", "pqrstu")
108 l0 = encodeMulti("LIST", "GOOD", d1, d5)
109 l1 = encodeMulti("LIST", "BAD ", d3)
110 l2 = encodeMulti("LIST", "UGLY", d4, d6)
111 l01 = encodeMulti("LIST", "META", l0, d0, l1)
112 data = encodeMulti("RIFF", "ROOT", d0, d1, l01, d2, l2)
113 )