-
Notifications
You must be signed in to change notification settings - Fork 117
/
varint.h
164 lines (146 loc) · 4.7 KB
/
varint.h
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
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
#ifndef _VARINT_H_
#define _VARINT_H_
#include <stdint.h>
#include "macros.h"
// read unsigned varint32 from buffer. assumes the buffer will have enough size
inline const uint8_t *
read_uvint32_slow(const uint8_t *buf, uint32_t *value)
{
const uint8_t *p;
uint32_t b, result;
p = buf;
b = *p++; result = (b & 0x7F) ; if (likely(b < 0x80)) goto done;
b = *p++; result |= (b & 0x7F) << 7; if (likely(b < 0x80)) goto done;
b = *p++; result |= (b & 0x7F) << 14; if (likely(b < 0x80)) goto done;
b = *p++; result |= (b & 0x7F) << 21; if (likely(b < 0x80)) goto done;
b = *p++; result |= b << 28; if (likely(b < 0x80)) goto done;
ALWAYS_ASSERT(false); // should not reach here (improper encoding)
done:
*value = result;
return p;
}
/**
* Read a uvint32 from buf into value, returning the
* next position in buf after the value has been read.
*
* Assumes buf points to a well encoded varint
*/
inline ALWAYS_INLINE const uint8_t *
read_uvint32(const uint8_t *buf, uint32_t *value)
{
if (likely(*buf < 0x80)) {
*value = *buf;
return buf + 1;
}
return read_uvint32_slow(buf, value);
}
inline const uint8_t *
failsafe_read_uvint32_slow(
const uint8_t *buf, size_t nbytes, uint32_t *value)
{
const uint8_t *p;
uint32_t b, result;
p = buf;
if (unlikely(!nbytes--)) return nullptr;
b = *p++; result = (b & 0x7F) ; if (likely(b < 0x80)) goto done;
if (unlikely(!nbytes--)) return nullptr;
b = *p++; result |= (b & 0x7F) << 7; if (likely(b < 0x80)) goto done;
if (unlikely(!nbytes--)) return nullptr;
b = *p++; result |= (b & 0x7F) << 14; if (likely(b < 0x80)) goto done;
if (unlikely(!nbytes--)) return nullptr;
b = *p++; result |= (b & 0x7F) << 21; if (likely(b < 0x80)) goto done;
if (unlikely(!nbytes--)) return nullptr;
b = *p++; result |= b << 28; if (likely(b < 0x80)) goto done;
done:
*value = result;
return p;
}
inline ALWAYS_INLINE const uint8_t *
failsafe_read_uvint32(
const uint8_t *stream, size_t nbytes, uint32_t *value)
{
if (unlikely(!nbytes))
return nullptr;
const uint8_t ch = *stream;
if (likely(ch < 0x80)) {
*value = ch;
return stream + 1;
}
return failsafe_read_uvint32_slow(stream, nbytes, value);
}
inline ALWAYS_INLINE size_t
skip_uvint32(const uint8_t *stream, uint8_t *rawv)
{
if (rawv) {
if (likely((rawv[0] = stream[0]) < 0x80)) return 1;
if (likely((rawv[1] = stream[1]) < 0x80)) return 2;
if (likely((rawv[2] = stream[2]) < 0x80)) return 3;
if (likely((rawv[3] = stream[3]) < 0x80)) return 4;
if (likely((rawv[4] = stream[4]) < 0x80)) return 5;
} else {
if (likely(stream[0] < 0x80)) return 1;
if (likely(stream[1] < 0x80)) return 2;
if (likely(stream[2] < 0x80)) return 3;
if (likely(stream[3] < 0x80)) return 4;
if (likely(stream[4] < 0x80)) return 5;
}
ALWAYS_ASSERT(false);
return 0;
}
inline ALWAYS_INLINE size_t
failsafe_skip_uvint32(const uint8_t *stream, size_t nbytes, uint8_t *rawv)
{
if (rawv) {
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[0] = stream[0]) < 0x80)) return 1;
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[1] = stream[1]) < 0x80)) return 2;
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[2] = stream[2]) < 0x80)) return 3;
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[3] = stream[3]) < 0x80)) return 4;
if (unlikely(!nbytes--)) return 0;
if (likely((rawv[4] = stream[4]) < 0x80)) return 5;
} else {
if (unlikely(!nbytes--)) return 0;
if (likely(stream[0] < 0x80)) return 1;
if (unlikely(!nbytes--)) return 0;
if (likely(stream[1] < 0x80)) return 2;
if (unlikely(!nbytes--)) return 0;
if (likely(stream[2] < 0x80)) return 3;
if (unlikely(!nbytes--)) return 0;
if (likely(stream[3] < 0x80)) return 4;
if (unlikely(!nbytes--)) return 0;
if (likely(stream[4] < 0x80)) return 5;
}
ALWAYS_ASSERT(false);
return 0;
}
/**
* write uint32_t as unsigned varint32 to buffer. assumes the buffer will have
* enough size. returns the position in buf after the value has been written
*/
inline uint8_t *
write_uvint32(uint8_t *buf, uint32_t value)
{
while (value > 0x7F) {
*buf++ = (((uint8_t) value) & 0x7F) | 0x80;
value >>= 7;
}
*buf++ = ((uint8_t) value) & 0x7F;
return buf;
}
inline size_t
size_uvint32(uint32_t value)
{
if (likely(value <= 0x7F)) return 1;
if (likely(value <= ((0x7F << 7) | 0x7F))) return 2;
if (likely(value <= ((0x7F << 14) | (0x7F << 7) | 0x7F))) return 3;
if (likely(value <= ((0x7F << 21) | (0x7F << 14) | (0x7F << 7) | 0x7F))) return 4;
return 5;
}
class varint {
public:
static void Test();
};
#endif /* _VARINT_H_ */