forked from pierrre/imageserver
-
Notifications
You must be signed in to change notification settings - Fork 0
/
image.go
144 lines (124 loc) · 3.32 KB
/
image.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
package imageserver
import (
"bytes"
"encoding/binary"
"fmt"
)
const (
// ImageFormatMaxLen is the maximum length for the image's format.
ImageFormatMaxLen = 1 << 8 // 256 B
// ImageDataMaxLen is the maximum length for the image's data.
ImageDataMaxLen = 1 << 30 // 1 GiB
)
var (
imageByteOrder = binary.LittleEndian
)
// Image is a raw image.
//
//
// Binary encoding:
//
// - Format length (uint32)
//
// - Format (string)
//
// - Data length (uint32)
//
// - Data([]byte)
//
// Numbers are encoded using little-endian order.
type Image struct {
Format string // png, jpeg, bmp, gif, ...
Data []byte // raw image data
}
// MarshalBinary implements encoding.BinaryMarshaler.
func (im *Image) MarshalBinary() ([]byte, error) {
if len(im.Format) > ImageFormatMaxLen {
return nil, &ImageError{Message: fmt.Sprintf("marshal: format length %d is greater than the maximum value %d", len(im.Format), ImageFormatMaxLen)}
}
if len(im.Data) > ImageDataMaxLen {
return nil, &ImageError{Message: fmt.Sprintf("marshal: data length %d is greater than the maximum value %d", len(im.Data), ImageDataMaxLen)}
}
data := make([]byte, 0, 4+len(im.Format)+4+len(im.Data))
buf := make([]byte, 4)
imageByteOrder.PutUint32(buf, uint32(len(im.Format)))
data = append(data, buf...)
data = append(data, im.Format...)
imageByteOrder.PutUint32(buf, uint32(len(im.Data)))
data = append(data, buf...)
data = append(data, im.Data...)
return data, nil
}
// UnmarshalBinary implements encoding.BinaryUnmarshaler.
//
// It copies data then call UnmarshalBinaryNoCopy().
func (im *Image) UnmarshalBinary(data []byte) error {
dataCopy := make([]byte, len(data))
copy(dataCopy, data)
return im.UnmarshalBinaryNoCopy(dataCopy)
}
// UnmarshalBinaryNoCopy is like encoding.BinaryUnmarshaler but does no copy.
//
// The caller must not reuse data after that.
func (im *Image) UnmarshalBinaryNoCopy(data []byte) error {
readData := func(length int) ([]byte, error) {
if length > len(data) {
return nil, &ImageError{Message: "unmarshal: unexpected end of data"}
}
res := data[:length]
data = data[length:]
return res, nil
}
var buf []byte
var err error
buf, err = readData(4)
if err != nil {
return err
}
formatLen := imageByteOrder.Uint32(buf)
if formatLen > ImageFormatMaxLen {
return &ImageError{Message: fmt.Sprintf("unmarshal: format length %d is greater than the maximum value %d", formatLen, ImageFormatMaxLen)}
}
buf, err = readData(int(formatLen))
if err != nil {
return err
}
im.Format = string(buf)
buf, err = readData(4)
if err != nil {
return err
}
dataLen := imageByteOrder.Uint32(buf)
if dataLen > ImageDataMaxLen {
return &ImageError{Message: fmt.Sprintf("unmarshal: data length %d is greater than the maximum value %d", dataLen, ImageDataMaxLen)}
}
buf, err = readData(int(dataLen))
if err != nil {
return err
}
im.Data = buf
return nil
}
// ImageEqual compares two images and returns true if they are equal.
func ImageEqual(im1, im2 *Image) bool {
if im1 == im2 {
return true
}
if im1 == nil || im2 == nil {
return false
}
if im1.Format != im2.Format {
return false
}
if !bytes.Equal(im1.Data, im2.Data) {
return false
}
return true
}
// ImageError is an Image error.
type ImageError struct {
Message string
}
func (err *ImageError) Error() string {
return fmt.Sprintf("image error: %s", err.Message)
}