forked from rurban/smhasher
-
Notifications
You must be signed in to change notification settings - Fork 10
/
crc32_hw1.c
316 lines (276 loc) · 10.1 KB
/
crc32_hw1.c
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
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
/* Compile with gcc -O3 -msse4.2 ... */
/* crc32c.c -- compute CRC-32C using the Intel crc32 instruction
* Copyright (C) 2013 Mark Adler
* Version 1.1 1 Aug 2013 Mark Adler
*/
/*
This software is provided 'as-is', without any express or implied
warranty. In no event will the author be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
Mark Adler
*/
/* Use hardware CRC instruction on Intel SSE 4.2 processors. This computes a
CRC-32C, *not* the CRC-32 used by Ethernet and zip, gzip, etc.
*/
/* Version history:
1.0 10 Feb 2013 First version
1.1 1 Aug 2013 Correct comments on why three crc instructions in parallel
*/
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#ifndef _MSC_VER
#include <unistd.h>
#include <pthread.h>
#endif
/* CRC-32C (iSCSI) polynomial in reversed bit order. */
#define POLY 0x82f63b78
/* Table for a quadword-at-a-time software crc. */
static pthread_once_t crc32c_once_sw = PTHREAD_ONCE_INIT;
static uint32_t crc32c_table[8][256];
/* Construct table for software CRC-32C calculation. */
static void crc32c_init_sw(void)
{
uint32_t n, crc, k;
for (n = 0; n < 256; n++) {
crc = n;
crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
crc = crc & 1 ? (crc >> 1) ^ POLY : crc >> 1;
crc32c_table[0][n] = crc;
}
for (n = 0; n < 256; n++) {
crc = crc32c_table[0][n];
for (k = 1; k < 8; k++) {
crc = crc32c_table[0][crc & 0xff] ^ (crc >> 8);
crc32c_table[k][n] = crc;
}
}
}
/* Table-driven software version as a fall-back. This is about 15 times slower
than using the hardware instructions. This assumes little-endian integers,
as is the case on Intel processors that the assembler code here is for. */
static uint32_t crc32c_sw(uint32_t crci, const void *buf, size_t len)
{
const unsigned char *next = buf;
uint64_t crc;
pthread_once(&crc32c_once_sw, crc32c_init_sw);
crc = crci ^ 0xffffffff;
while (len && ((uintptr_t)next & 7) != 0) {
crc = crc32c_table[0][(crc ^ *next++) & 0xff] ^ (crc >> 8);
len--;
}
while (len >= 8) {
crc ^= *(uint64_t *)next;
crc = crc32c_table[7][crc & 0xff] ^
crc32c_table[6][(crc >> 8) & 0xff] ^
crc32c_table[5][(crc >> 16) & 0xff] ^
crc32c_table[4][(crc >> 24) & 0xff] ^
crc32c_table[3][(crc >> 32) & 0xff] ^
crc32c_table[2][(crc >> 40) & 0xff] ^
crc32c_table[1][(crc >> 48) & 0xff] ^
crc32c_table[0][crc >> 56];
next += 8;
len -= 8;
}
while (len) {
crc = crc32c_table[0][(crc ^ *next++) & 0xff] ^ (crc >> 8);
len--;
}
return (uint32_t)crc ^ 0xffffffff;
}
/* Block sizes for three-way parallel crc computation. LONG and SHORT must
both be powers of two. The associated string constants must be set
accordingly, for use in constructing the assembler instructions. */
#define LONG 8192
#define LONGx1 "8192"
#define LONGx2 "16384"
#define SHORT 256
#define SHORTx1 "256"
#define SHORTx2 "512"
/* Tables for hardware crc that shift a crc by LONG and SHORT zeros. */
static pthread_once_t crc32c_once_hw = PTHREAD_ONCE_INIT;
static uint32_t crc32c_long[4][256];
static uint32_t crc32c_short[4][256];
/* Multiply a matrix times a vector over the Galois field of two elements,
GF(2). Each element is a bit in an unsigned integer. mat must have at
least as many entries as the power of two for most significant one bit in
vec. */
static inline uint32_t gf2_matrix_times(uint32_t *mat, uint32_t vec)
{
uint32_t sum;
sum = 0;
while (vec) {
if (vec & 1)
sum ^= *mat;
vec >>= 1;
mat++;
}
return sum;
}
/* Multiply a matrix by itself over GF(2). Both mat and square must have 32
rows. */
static inline void gf2_matrix_square(uint32_t *square, uint32_t *mat)
{
int n;
for (n = 0; n < 32; n++)
square[n] = gf2_matrix_times(mat, mat[n]);
}
/* Construct an operator to apply len zeros to a crc. len must be a power of
two. If len is not a power of two, then the result is the same as for the
largest power of two less than len. The result for len == 0 is the same as
for len == 1. A version of this routine could be easily written for any
len, but that is not needed for this application. */
static void crc32c_zeros_op(uint32_t *even, size_t len)
{
int n;
uint32_t row;
uint32_t odd[32]; /* odd-power-of-two zeros operator */
/* put operator for one zero bit in odd */
odd[0] = POLY; /* CRC-32C polynomial */
row = 1;
for (n = 1; n < 32; n++) {
odd[n] = row;
row <<= 1;
}
/* put operator for two zero bits in even */
gf2_matrix_square(even, odd);
/* put operator for four zero bits in odd */
gf2_matrix_square(odd, even);
/* first square will put the operator for one zero byte (eight zero bits),
in even -- next square puts operator for two zero bytes in odd, and so
on, until len has been rotated down to zero */
do {
gf2_matrix_square(even, odd);
len >>= 1;
if (len == 0)
return;
gf2_matrix_square(odd, even);
len >>= 1;
} while (len);
/* answer ended up in odd -- copy to even */
for (n = 0; n < 32; n++)
even[n] = odd[n];
}
/* Take a length and build four lookup tables for applying the zeros operator
for that length, byte-by-byte on the operand. */
static void crc32c_zeros(uint32_t zeros[][256], size_t len)
{
uint32_t n;
uint32_t op[32];
crc32c_zeros_op(op, len);
for (n = 0; n < 256; n++) {
zeros[0][n] = gf2_matrix_times(op, n);
zeros[1][n] = gf2_matrix_times(op, n << 8);
zeros[2][n] = gf2_matrix_times(op, n << 16);
zeros[3][n] = gf2_matrix_times(op, n << 24);
}
}
/* Apply the zeros operator table to crc. */
static inline uint32_t crc32c_shift(uint32_t zeros[][256], uint32_t crc)
{
return zeros[0][crc & 0xff] ^ zeros[1][(crc >> 8) & 0xff] ^
zeros[2][(crc >> 16) & 0xff] ^ zeros[3][crc >> 24];
}
/* Initialize tables for shifting crcs. */
static void crc32c_init_hw(void)
{
crc32c_zeros(crc32c_long, LONG);
crc32c_zeros(crc32c_short, SHORT);
}
/* Compute CRC-32C using the Intel hardware instruction. */
uint32_t crc32c(const void *buf, size_t len, uint32_t crc)
{
const unsigned char *next = buf;
const unsigned char *end;
uint64_t crc0, crc1, crc2; /* need to be 64 bits for crc32q */
/* populate shift tables the first time through */
pthread_once(&crc32c_once_hw, crc32c_init_hw);
/* pre-process the crc */
crc0 = crc ^ 0xffffffff;
/* compute the crc for up to seven leading bytes to bring the data pointer
to an eight-byte boundary */
while (len && ((uintptr_t)next & 7) != 0) {
__asm__("crc32b\t" "(%1), %0"
: "=r"(crc0)
: "r"(next), "0"(crc0));
next++;
len--;
}
/* compute the crc on sets of LONG*3 bytes, executing three independent crc
instructions, each on LONG bytes -- this is optimized for the Nehalem,
Westmere, Sandy Bridge, and Ivy Bridge architectures, which have a
throughput of one crc per cycle, but a latency of three cycles */
while (len >= LONG*3) {
crc1 = 0;
crc2 = 0;
end = next + LONG;
do {
__asm__("crc32q\t" "(%3), %0\n\t"
"crc32q\t" LONGx1 "(%3), %1\n\t"
"crc32q\t" LONGx2 "(%3), %2"
: "=r"(crc0), "=r"(crc1), "=r"(crc2)
: "r"(next), "0"(crc0), "1"(crc1), "2"(crc2));
next += 8;
} while (next < end);
crc0 = crc32c_shift(crc32c_long, crc0) ^ crc1;
crc0 = crc32c_shift(crc32c_long, crc0) ^ crc2;
next += LONG*2;
len -= LONG*3;
}
/* do the same thing, but now on SHORT*3 blocks for the remaining data less
than a LONG*3 block */
while (len >= SHORT*3) {
crc1 = 0;
crc2 = 0;
end = next + SHORT;
do {
__asm__("crc32q\t" "(%3), %0\n\t"
"crc32q\t" SHORTx1 "(%3), %1\n\t"
"crc32q\t" SHORTx2 "(%3), %2"
: "=r"(crc0), "=r"(crc1), "=r"(crc2)
: "r"(next), "0"(crc0), "1"(crc1), "2"(crc2));
next += 8;
} while (next < end);
crc0 = crc32c_shift(crc32c_short, crc0) ^ crc1;
crc0 = crc32c_shift(crc32c_short, crc0) ^ crc2;
next += SHORT*2;
len -= SHORT*3;
}
/* compute the crc on the remaining eight-byte units less than a SHORT*3
block */
end = next + (len - (len & 7));
while (next < end) {
__asm__("crc32q\t" "(%1), %0"
: "=r"(crc0)
: "r"(next), "0"(crc0));
next += 8;
}
len &= 7;
/* compute the crc for up to seven trailing bytes */
while (len) {
__asm__("crc32b\t" "(%1), %0"
: "=r"(crc0)
: "r"(next), "0"(crc0));
next++;
len--;
}
/* return a post-processed crc */
return (uint32_t)(crc0 ^ 0xffffffff);
}