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
|
package proto
import (
"encoding/binary"
"errors"
"io"
"unsafe"
)
// DecodeTag reverses the encoding applied by EncodeTag.
func DecodeTag(tag uint64) (FieldNumber, WireType) {
return FieldNumber(tag >> 3), WireType(tag & 7)
}
// DecodeZigZag reverses the encoding applied by EncodeZigZag.
func DecodeZigZag(v uint64) int64 {
return decodeZigZag64(v)
}
func decodeZigZag64(v uint64) int64 {
return int64(v>>1) ^ -(int64(v) & 1)
}
func decodeZigZag32(v uint32) int32 {
return int32(v>>1) ^ -(int32(v) & 1)
}
type decodeFunc = func([]byte, unsafe.Pointer, flags) (int, error)
var errVarintOverflow = errors.New("varint overflowed 64 bits integer")
func decodeVarint(b []byte) (uint64, int, error) {
if len(b) != 0 && b[0] < 0x80 {
// Fast-path for decoding the common case of varints that fit on a
// single byte.
//
// This path is ~60% faster than calling binary.Uvarint.
return uint64(b[0]), 1, nil
}
var x uint64
var s uint
for i, c := range b {
if c < 0x80 {
if i > 9 || i == 9 && c > 1 {
return 0, i, errVarintOverflow
}
return x | uint64(c)<<s, i + 1, nil
}
x |= uint64(c&0x7f) << s
s += 7
}
return x, len(b), io.ErrUnexpectedEOF
}
func decodeVarintZigZag(b []byte) (int64, int, error) {
v, n, err := decodeVarint(b)
return decodeZigZag64(v), n, err
}
func decodeLE32(b []byte) (uint32, int, error) {
if len(b) < 4 {
return 0, 0, io.ErrUnexpectedEOF
}
return binary.LittleEndian.Uint32(b), 4, nil
}
func decodeLE64(b []byte) (uint64, int, error) {
if len(b) < 8 {
return 0, 0, io.ErrUnexpectedEOF
}
return binary.LittleEndian.Uint64(b), 8, nil
}
func decodeTag(b []byte) (f fieldNumber, t wireType, n int, err error) {
v, n, err := decodeVarint(b)
return fieldNumber(v >> 3), wireType(v & 7), n, err
}
func decodeVarlen(b []byte) ([]byte, int, error) {
v, n, err := decodeVarint(b)
if err != nil {
return nil, n, err
}
if v > uint64(len(b)-n) {
return nil, n, io.ErrUnexpectedEOF
}
return b[n : n+int(v)], n + int(v), nil
}
|
