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authorMark Adler <madler@alumni.caltech.edu>2018-12-11 01:11:38 -0800
committerMark Adler <madler@alumni.caltech.edu>2018-12-26 12:26:52 -0800
commitf8719f5ae5acdc31d3794ddfea8ac963359de41e (patch)
tree70327ff8a4953abd605665ecd458a3c4b1a66443 /crc32.c
parent41d86c73b21191a3fa9ea5f476fc9f1fc5e4f8b3 (diff)
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Speed up software CRC-32 computation by a factor of 1.5 to 3.
Use the interleaved method of Kadatch and Jenkins in order to make use of pipelined instructions through multiple ALUs in a single core. This also speeds up and simplifies the combination of CRCs, and updates the functions to pre-calculate and use an operator for CRC combination.
Diffstat (limited to 'crc32.c')
-rw-r--r--crc32.c1070
1 files changed, 733 insertions, 337 deletions
diff --git a/crc32.c b/crc32.c
index 2d213b3..f41dc6d 100644
--- a/crc32.c
+++ b/crc32.c
@@ -2,11 +2,9 @@
2 * Copyright (C) 1995-2006, 2010, 2011, 2012, 2016, 2018 Mark Adler 2 * Copyright (C) 1995-2006, 2010, 2011, 2012, 2016, 2018 Mark Adler
3 * For conditions of distribution and use, see copyright notice in zlib.h 3 * For conditions of distribution and use, see copyright notice in zlib.h
4 * 4 *
5 * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster 5 * This interleaved implementation of a CRC makes use of pipelined multiple
6 * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing 6 * arithmetic-logic units, commonly found in modern CPU cores. It is due to
7 * tables for updating the shift register in one step with three exclusive-ors 7 * Kadatch and Jenkins (2010). See doc/crc-doc.1.0.pdf in this distribution.
8 * instead of four steps with four exclusive-ors. This results in about a
9 * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
10 */ 8 */
11 9
12/* @(#) $Id$ */ 10/* @(#) $Id$ */
@@ -14,13 +12,12 @@
14/* 12/*
15 Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore 13 Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
16 protection on the static variables used to control the first-use generation 14 protection on the static variables used to control the first-use generation
17 of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should 15 of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should
18 first call get_crc_table() to initialize the tables before allowing more than 16 first call get_crc_table() to initialize the tables before allowing more than
19 one thread to use crc32(). 17 one thread to use crc32().
20 18
21 DYNAMIC_CRC_TABLE and MAKECRCH can be #defined to write out crc32.h. A main() 19 MAKECRCH can be #defined to write out crc32.h. A main() routine is also
22 routine is also produced, so that this one source file can be compiled to an 20 produced, so that this one source file can be compiled to an executable.
23 executable.
24 */ 21 */
25 22
26#ifdef MAKECRCH 23#ifdef MAKECRCH
@@ -30,161 +27,164 @@
30# endif /* !DYNAMIC_CRC_TABLE */ 27# endif /* !DYNAMIC_CRC_TABLE */
31#endif /* MAKECRCH */ 28#endif /* MAKECRCH */
32 29
33#include "zutil.h" /* for STDC and FAR definitions */ 30#include "zutil.h" /* for Z_U4, Z_U8, z_crc_t, and FAR definitions */
31
32 /*
33 A CRC of a message is computed on N braids of words in the message, where
34 each word consists of W bytes (4 or 8). If N is 3, for example, then three
35 running sparse CRCs are calculated respectively on each braid, at these
36 indices in the array of words: 0, 3, 6, ..., 1, 4, 7, ..., and 2, 5, 8, ...
37 This is done starting at a word boundary, and continues until as many blocks
38 of N * W bytes as are available have been processed. The results are combined
39 into a single CRC at the end. For this code, N must be in the range 1..6 and
40 W must be 4 or 8. The upper limit on N can be increased if desired by adding
41 more #if blocks, extending the patterns apparent in the code. In addition,
42 crc32.h would need to be regenerated, if the maximum N value is increased.
43
44 N and W are chosen empirically by benchmarking the execution time on a given
45 processor. The choices for N and W below were based on testing on Intel Kaby
46 Lake i7, AMD Ryzen 7, ARM Cortex-A57, Sparc64-VII, PowerPC POWER9, and MIPS64
47 Octeon II processors. The Intel, AMD, and ARM processors were all fastest
48 with N=5, W=8. The Sparc, PowerPC, and MIPS64 were all fastest at N=5, W=4.
49 They were all tested with either gcc or clang, all using the -O3 optimization
50 level. Your mileage may vary.
51 */
34 52
35/* Definitions for doing the crc four data bytes at a time. */ 53/* Define N */
36#if !defined(NOBYFOUR) && defined(Z_U4) 54#ifdef Z_TESTN
37# define BYFOUR 55# define N Z_TESTN
38#endif
39#ifdef BYFOUR
40 local unsigned long crc32_little OF((unsigned long,
41 const unsigned char FAR *, z_size_t));
42 local unsigned long crc32_big OF((unsigned long,
43 const unsigned char FAR *, z_size_t));
44# define TBLS 8
45#else 56#else
46# define TBLS 1 57# define N 5
47#endif /* BYFOUR */ 58#endif
59#if N < 1 || N > 6
60# error N must be in 1..6
61#endif
48 62
49/* Local functions for crc concatenation */ 63/*
50#define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */ 64 z_crc_t must be at least 32 bits. z_word_t must be at least as long as
51local z_crc_t gf2_matrix_times OF((const z_crc_t *mat, z_crc_t vec)); 65 z_crc_t. It is assumed here that z_word_t is either 32 bits or 64 bits, and
52local uLong crc32_combine_ OF((uLong crc1, uLong crc2, z_off64_t len2)); 66 that bytes are eight bits.
53local void crc32_combine_gen_ OF((z_crc_t *op, z_off64_t len2)); 67 */
54 68
55/* ========================================================================= */ 69/*
56local z_crc_t gf2_matrix_times(mat, vec) 70 Define W and the associated z_word_t type. If W is not defined, then a
57 const z_crc_t *mat; 71 braided calculation is not used, and the associated tables and code are not
58 z_crc_t vec; 72 compiled.
59{ 73 */
60 z_crc_t sum; 74#ifdef Z_TESTW
61 75# if Z_TESTW-1 != -1
62 sum = 0; 76# define W Z_TESTW
63 while (vec) { 77# endif
64 if (vec & 1) 78#else
65 sum ^= *mat; 79# ifdef MAKECRCH
66 vec >>= 1; 80# define W 8 /* required for MAKECRCH */
67 mat++; 81# else
68 } 82# if defined(__x86_64__) || defined(__aarch64__)
69 return sum; 83# define W 8
70} 84# else
85# define W 4
86# endif
87# endif
88#endif
89#ifdef W
90# if W == 8 && defined(Z_U8)
91 typedef Z_U8 z_word_t;
92# elif defined(Z_U4)
93# undef W
94# define W 4
95 typedef Z_U4 z_word_t;
96# else
97# undef W
98# endif
99#endif
100
101/* Local functions. */
102local z_crc_t multmodp OF((z_crc_t a, z_crc_t b));
103local z_crc_t x2nmodp OF((z_off64_t n, unsigned k));
104#ifdef W
105 local z_word_t byte_swap OF((z_word_t word));
106 local z_crc_t crc_word OF((z_word_t data));
107 local z_word_t crc_word_big OF((z_word_t data));
108#endif /* W */
71 109
110/* CRC polynomial. */
111#define POLY 0xedb88320 /* p(x) reflected, with x^32 implied */
72 112
73#ifdef DYNAMIC_CRC_TABLE 113#ifdef DYNAMIC_CRC_TABLE
74 114
75local volatile int crc_table_empty = 1; 115local volatile int crc_table_empty = 1;
76local z_crc_t FAR crc_table[TBLS][256]; 116local z_crc_t FAR crc_table[256];
77local z_crc_t FAR crc_comb[GF2_DIM][GF2_DIM]; 117local z_crc_t FAR x2n_table[32];
78local void make_crc_table OF((void)); 118local void make_crc_table OF((void));
79local void gf2_matrix_square OF((z_crc_t *square, const z_crc_t *mat)); 119#ifdef W
120 local z_word_t FAR crc_big_table[256];
121 local z_crc_t FAR crc_braid_table[W][256];
122 local z_word_t FAR crc_braid_big_table[W][256];
123 local void braid OF((z_crc_t [][256], z_word_t [][256], int, int));
124#endif
80#ifdef MAKECRCH 125#ifdef MAKECRCH
81 local void write_table OF((FILE *, const z_crc_t FAR *, int)); 126 local void write_table OF((FILE *, const z_crc_t FAR *, int));
127 local void write_table32hi OF((FILE *, const z_word_t FAR *, int));
128 local void write_table64 OF((FILE *, const z_word_t FAR *, int));
82#endif /* MAKECRCH */ 129#endif /* MAKECRCH */
83 130
84/* ========================================================================= */
85local void gf2_matrix_square(square, mat)
86 z_crc_t *square;
87 const z_crc_t *mat;
88{
89 int n;
90
91 for (n = 0; n < GF2_DIM; n++)
92 square[n] = gf2_matrix_times(mat, mat[n]);
93}
94
95/* 131/*
96 Generate tables for a byte-wise 32-bit CRC calculation on the polynomial: 132 Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
97 x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1. 133 x^32+x^26+x^23+x^22+x^16+x^12+x^11+x^10+x^8+x^7+x^5+x^4+x^2+x+1.
98 134
99 Polynomials over GF(2) are represented in binary, one bit per coefficient, 135 Polynomials over GF(2) are represented in binary, one bit per coefficient,
100 with the lowest powers in the most significant bit. Then adding polynomials 136 with the lowest powers in the most significant bit. Then adding polynomials
101 is just exclusive-or, and multiplying a polynomial by x is a right shift by 137 is just exclusive-or, and multiplying a polynomial by x is a right shift by
102 one. If we call the above polynomial p, and represent a byte as the 138 one. If we call the above polynomial p, and represent a byte as the
103 polynomial q, also with the lowest power in the most significant bit (so the 139 polynomial q, also with the lowest power in the most significant bit (so the
104 byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p, 140 byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
105 where a mod b means the remainder after dividing a by b. 141 where a mod b means the remainder after dividing a by b.
106 142
107 This calculation is done using the shift-register method of multiplying and 143 This calculation is done using the shift-register method of multiplying and
108 taking the remainder. The register is initialized to zero, and for each 144 taking the remainder. The register is initialized to zero, and for each
109 incoming bit, x^32 is added mod p to the register if the bit is a one (where 145 incoming bit, x^32 is added mod p to the register if the bit is a one (where
110 x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by 146 x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by x
111 x (which is shifting right by one and adding x^32 mod p if the bit shifted 147 (which is shifting right by one and adding x^32 mod p if the bit shifted out
112 out is a one). We start with the highest power (least significant bit) of 148 is a one). We start with the highest power (least significant bit) of q and
113 q and repeat for all eight bits of q. 149 repeat for all eight bits of q.
114 150
115 The first table is simply the CRC of all possible eight bit values. This is 151 The table is simply the CRC of all possible eight bit values. This is all the
116 all the information needed to generate CRCs on data a byte at a time for all 152 information needed to generate CRCs on data a byte at a time for all
117 combinations of CRC register values and incoming bytes. The remaining tables 153 combinations of CRC register values and incoming bytes.
118 allow for word-at-a-time CRC calculation for both big-endian and little- 154 */
119 endian machines, where a word is four bytes. 155
120*/
121local void make_crc_table() 156local void make_crc_table()
122{ 157{
123 z_crc_t c; 158 z_crc_t p;
124 int n, k;
125 z_crc_t poly; /* polynomial exclusive-or pattern */
126 /* terms of polynomial defining this crc (except x^32): */
127 static volatile int first = 1; /* flag to limit concurrent making */ 159 static volatile int first = 1; /* flag to limit concurrent making */
128 static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
129 160
130 /* See if another task is already doing this (not thread-safe, but better 161 /* See if another task is already doing this (not thread-safe, but better
131 than nothing -- significantly reduces duration of vulnerability in 162 than nothing -- significantly reduces duration of vulnerability in
132 case the advice about DYNAMIC_CRC_TABLE is ignored) */ 163 case the advice about DYNAMIC_CRC_TABLE is ignored) */
133 if (first) { 164 if (first) {
165 unsigned i, j, n;
134 first = 0; 166 first = 0;
135 167
136 /* make exclusive-or pattern from polynomial (0xedb88320UL) */ 168 /* initialize the CRC of bytes tables */
137 poly = 0; 169 for (i = 0; i < 256; i++) {
138 for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++) 170 p = i;
139 poly |= (z_crc_t)1 << (31 - p[n]); 171 for (j = 0; j < 8; j++)
140 172 p = p & 1 ? (p >> 1) ^ POLY : p >> 1;
141 /* generate a crc for every 8-bit value */ 173 crc_table[i] = p;
142 for (n = 0; n < 256; n++) { 174#ifdef W
143 c = (z_crc_t)n; 175 crc_big_table[i] = byte_swap(p);
144 for (k = 0; k < 8; k++) 176#endif
145 c = c & 1 ? poly ^ (c >> 1) : c >> 1;
146 crc_table[0][n] = c;
147 }
148
149#ifdef BYFOUR
150 /* generate crc for each value followed by one, two, and three zeros,
151 and then the byte reversal of those as well as the first table */
152 for (n = 0; n < 256; n++) {
153 c = crc_table[0][n];
154 crc_table[4][n] = ZSWAP32(c);
155 for (k = 1; k < 4; k++) {
156 c = crc_table[0][c & 0xff] ^ (c >> 8);
157 crc_table[k][n] = c;
158 crc_table[k + 4][n] = ZSWAP32(c);
159 }
160 }
161#endif /* BYFOUR */
162
163 /* generate zero operators table for crc32_combine() */
164
165 /* generate the operator to apply a single zero bit to a CRC -- the
166 first row adds the polynomial if the low bit is a 1, and the
167 remaining rows shift the CRC right one bit */
168 k = GF2_DIM - 3;
169 crc_comb[k][0] = 0xedb88320UL; /* CRC-32 polynomial */
170 z_crc_t row = 1;
171 for (n = 1; n < GF2_DIM; n++) {
172 crc_comb[k][n] = row;
173 row <<= 1;
174 } 177 }
175 178
176 /* generate operators that apply 2, 4, and 8 zeros to a CRC, putting 179 /* initialize the x^2^n mod p(x) table */
177 the last one, the operator for one zero byte, at the 0 position */ 180 p = (z_crc_t)1 << 30; /* x^1 */
178 gf2_matrix_square(crc_comb[k + 1], crc_comb[k]); 181 x2n_table[0] = p;
179 gf2_matrix_square(crc_comb[k + 2], crc_comb[k + 1]); 182 for (n = 1; n < 32; n++)
180 gf2_matrix_square(crc_comb[0], crc_comb[k + 2]); 183 x2n_table[n] = p = multmodp(p, p);
181 184#ifdef W
182 /* generate operators for applying 2^n zero bytes to a CRC, filling out 185 /* initialize the braiding tables -- needs x2n_table[] */
183 the remainder of the table -- the operators repeat after GF2_DIM 186 braid(crc_braid_table, crc_braid_big_table, N, W);
184 values of n, so the table only needs GF2_DIM entries, regardless of 187#endif
185 the size of the length being processed */
186 for (n = 1; n < k; n++)
187 gf2_matrix_square(crc_comb[n], crc_comb[n - 1]);
188 188
189 /* mark tables as complete, in case someone else is waiting */ 189 /* mark tables as complete, in case someone else is waiting */
190 crc_table_empty = 0; 190 crc_table_empty = 0;
@@ -196,42 +196,145 @@ local void make_crc_table()
196 } 196 }
197#ifdef MAKECRCH 197#ifdef MAKECRCH
198 { 198 {
199 /*
200 The crc32.h header file contains tables for both 32-bit and 64-bit
201 z_word_t's, and so requires a 64-bit type be available. In that case,
202 z_word_t must be defined to be 64-bits. This code then also generates
203 and writes out the tables for the case that z_word_t is 32 bits.
204 */
205#if !defined(W) || W != 8
206# error Need a 64-bit integer type in order to generate crc32.h.
207#endif
199 FILE *out; 208 FILE *out;
209 int k, n;
210 z_crc_t ltl[8][256];
211 z_word_t big[8][256];
200 212
201 out = fopen("crc32.h", "w"); 213 out = fopen("crc32.h", "w");
202 if (out == NULL) return; 214 if (out == NULL) return;
203 215
204 /* write out CRC table to crc32.h */ 216 /* write out little-endian CRC table to crc32.h */
205 fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n"); 217 fprintf(out,
206 fprintf(out, " * Generated automatically by crc32.c\n */\n\n"); 218 "/* crc32.h -- tables for rapid CRC calculation\n"
207 fprintf(out, "local const z_crc_t FAR "); 219 " * Generated automatically by crc32.c\n */\n"
208 fprintf(out, "crc_table[%d][256] =\n{\n {\n", TBLS); 220 "\n"
209 write_table(out, crc_table[0], 256); 221 "local const z_crc_t FAR crc_table[] = {\n"
210# ifdef BYFOUR 222 " ");
211 fprintf(out, "#ifdef BYFOUR\n"); 223 write_table(out, crc_table, 256);
212 for (k = 1; k < 8; k++) { 224 fprintf(out,
213 fprintf(out, " },\n {\n"); 225 "};\n");
214 write_table(out, crc_table[k], 256); 226
215 } 227 /* write out big-endian CRC table for 64-bit z_word_t to crc32.h */
216 fprintf(out, "#endif\n"); 228 fprintf(out,
217# endif /* BYFOUR */ 229 "\n"
218 fprintf(out, " }\n};\n"); 230 "#ifdef W\n"
219 231 "\n"
220 /* write out zero operator table to crc32.h */ 232 "#if W == 8\n"
221 fprintf(out, "\nlocal const z_crc_t FAR "); 233 "\n"
222 fprintf(out, "crc_comb[%d][%d] =\n{\n {\n", GF2_DIM, GF2_DIM); 234 "local const z_word_t FAR crc_big_table[] = {\n"
223 write_table(out, crc_comb[0], GF2_DIM); 235 " ");
224 for (k = 1; k < GF2_DIM; k++) { 236 write_table64(out, crc_big_table, 256);
225 fprintf(out, " },\n {\n"); 237 fprintf(out,
226 write_table(out, crc_comb[k], GF2_DIM); 238 "};\n");
239
240 /* write out big-endian CRC table for 32-bit z_word_t to crc32.h */
241 fprintf(out,
242 "\n"
243 "#else /* W == 4 */\n"
244 "\n"
245 "local const z_word_t FAR crc_big_table[] = {\n"
246 " ");
247 write_table32hi(out, crc_big_table, 256);
248 fprintf(out,
249 "};\n"
250 "\n"
251 "#endif\n");
252
253 /* write out braid tables for each value of N */
254 for (n = 1; n <= 6; n++) {
255 fprintf(out,
256 "\n"
257 "#if N == %d\n", n);
258
259 /* compute braid tables for this N and 64-bit word_t */
260 braid(ltl, big, n, 8);
261
262 /* write out braid tables for 64-bit z_word_t to crc32.h */
263 fprintf(out,
264 "\n"
265 "#if W == 8\n"
266 "\n"
267 "local const z_crc_t FAR crc_braid_table[][256] = {\n");
268 for (k = 0; k < 8; k++) {
269 fprintf(out, " {");
270 write_table(out, ltl[k], 256);
271 fprintf(out, "}%s", k < 7 ? ",\n" : "");
272 }
273 fprintf(out,
274 "};\n"
275 "\n"
276 "local const z_word_t FAR crc_braid_big_table[][256] = {\n");
277 for (k = 0; k < 8; k++) {
278 fprintf(out, " {");
279 write_table64(out, big[k], 256);
280 fprintf(out, "}%s", k < 7 ? ",\n" : "");
281 }
282 fprintf(out,
283 "};\n");
284
285 /* compute braid tables for this N and 32-bit word_t */
286 braid(ltl, big, n, 4);
287
288 /* write out braid tables for 32-bit z_word_t to crc32.h */
289 fprintf(out,
290 "\n"
291 "#else /* W == 4 */\n"
292 "\n"
293 "local const z_crc_t FAR crc_braid_table[][256] = {\n");
294 for (k = 0; k < 4; k++) {
295 fprintf(out, " {");
296 write_table(out, ltl[k], 256);
297 fprintf(out, "}%s", k < 3 ? ",\n" : "");
298 }
299 fprintf(out,
300 "};\n"
301 "\n"
302 "local const z_word_t FAR crc_braid_big_table[][256] = {\n");
303 for (k = 0; k < 4; k++) {
304 fprintf(out, " {");
305 write_table32hi(out, big[k], 256);
306 fprintf(out, "}%s", k < 3 ? ",\n" : "");
307 }
308 fprintf(out,
309 "};\n"
310 "\n"
311 "#endif\n"
312 "\n"
313 "#endif\n");
227 } 314 }
228 fprintf(out, " }\n};\n"); 315 fprintf(out,
316 "\n"
317 "#endif\n");
318
319 /* write out zeros operator table to crc32.h */
320 fprintf(out,
321 "\n"
322 "local const z_crc_t FAR x2n_table[] = {\n"
323 " ");
324 write_table(out, x2n_table, 32);
325 fprintf(out,
326 "};\n");
229 fclose(out); 327 fclose(out);
230 } 328 }
231#endif /* MAKECRCH */ 329#endif /* MAKECRCH */
232} 330}
233 331
234#ifdef MAKECRCH 332#ifdef MAKECRCH
333
334/*
335 Write the 32-bit values in table[0..k-1] to out, five per line in
336 hexadecimal separated by commas.
337 */
235local void write_table(out, table, k) 338local void write_table(out, table, k)
236 FILE *out; 339 FILE *out;
237 const z_crc_t FAR *table; 340 const z_crc_t FAR *table;
@@ -240,26 +343,194 @@ local void write_table(out, table, k)
240 int n; 343 int n;
241 344
242 for (n = 0; n < k; n++) 345 for (n = 0; n < k; n++)
243 fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ", 346 fprintf(out, "%s0x%08lx%s", n == 0 || n % 5 ? "" : " ",
244 (unsigned long)(table[n]), 347 (unsigned long)(table[n]),
245 n == k - 1 ? "\n" : (n % 5 == 4 ? ",\n" : ", ")); 348 n == k - 1 ? "" : (n % 5 == 4 ? ",\n" : ", "));
349}
350
351/*
352 Write the high 32-bits of each value in table[0..k-1] to out, five per line
353 in hexadecimal separated by commas.
354 */
355local void write_table32hi(out, table, k)
356FILE *out;
357const z_word_t FAR *table;
358int k;
359{
360 int n;
361
362 for (n = 0; n < k; n++)
363 fprintf(out, "%s0x%08lx%s", n == 0 || n % 5 ? "" : " ",
364 (unsigned long)(table[n] >> 32),
365 n == k - 1 ? "" : (n % 5 == 4 ? ",\n" : ", "));
246} 366}
247 367
368/*
369 Write the 64-bit values in table[0..k-1] to out, three per line in
370 hexadecimal separated by commas. This assumes that if there is a 64-bit
371 type, then there is also a long long integer type, and it is at least 64
372 bits. If not, then the type cast and format string can be adjusted
373 accordingly.
374 */
375local void write_table64(out, table, k)
376 FILE *out;
377 const z_word_t FAR *table;
378 int k;
379{
380 int n;
381
382 for (n = 0; n < k; n++)
383 fprintf(out, "%s0x%016llx%s", n == 0 || n % 3 ? "" : " ",
384 (unsigned long long)(table[n]),
385 n == k - 1 ? "" : (n % 3 == 2 ? ",\n" : ", "));
386}
387
388/* Actually do the deed. */
248int main() 389int main()
249{ 390{
250 make_crc_table(); 391 make_crc_table();
251 return 0; 392 return 0;
252} 393}
394
253#endif /* MAKECRCH */ 395#endif /* MAKECRCH */
254 396
397#ifdef W
398/*
399 Generate the little and big-endian braid tables for the given n and z_word_t
400 size w. Each array must have room for w blocks of 256 elements.
401 */
402local void braid(ltl, big, n, w)
403 z_crc_t ltl[][256];
404 z_word_t big[][256];
405 int n;
406 int w;
407{
408 int k;
409 z_crc_t i, p, q;
410 for (k = 0; k < w; k++) {
411 p = x2nmodp((n * w + 3 - k) << 3, 0);
412 ltl[k][0] = 0;
413 big[w - 1 - k][0] = 0;
414 for (i = 1; i < 256; i++) {
415 ltl[k][i] = q = multmodp(i << 24, p);
416 big[w - 1 - k][i] = byte_swap(q);
417 }
418 }
419}
420#endif
421
255#else /* !DYNAMIC_CRC_TABLE */ 422#else /* !DYNAMIC_CRC_TABLE */
256/* ======================================================================== 423/* ========================================================================
257 * Tables of CRC-32s of all single-byte values, made by make_crc_table(), 424 * Tables for byte-wise and braided CRC-32 calculations, and a table of powers
258 * and tables of zero operator matrices for crc32_combine(). 425 * of x for combining CRC-32s, all made by make_crc_table().
259 */ 426 */
260#include "crc32.h" 427#include "crc32.h"
261#endif /* DYNAMIC_CRC_TABLE */ 428#endif /* DYNAMIC_CRC_TABLE */
262 429
430/* ========================================================================
431 * Routines used for CRC calculation. Some are also required for the table
432 * generation above.
433 */
434
435/*
436 Return a(x) multiplied by b(x) modulo p(x), where p(x) is the CRC polynomial,
437 reflected. For speed, this requires that a not be zero.
438 */
439local z_crc_t multmodp(a, b)
440 z_crc_t a;
441 z_crc_t b;
442{
443 z_crc_t m, p;
444
445 m = (z_crc_t)1 << 31;
446 p = 0;
447 for (;;) {
448 if (a & m) {
449 p ^= b;
450 if ((a & (m - 1)) == 0)
451 break;
452 }
453 m >>= 1;
454 b = b & 1 ? (b >> 1) ^ POLY : b >> 1;
455 }
456 return p;
457}
458
459/*
460 Return x^(n+k) modulo p(x). Requires that x2n_table[] has been initialized.
461 */
462local z_crc_t x2nmodp(n, k)
463 z_off64_t n;
464 unsigned k;
465{
466 z_crc_t p;
467
468 p = (z_crc_t)1 << 31; /* x^0 == 1 */
469 while (n) {
470 if (n & 1)
471 p = multmodp(x2n_table[k & 31], p);
472 n >>= 1;
473 k++;
474 }
475 return p;
476}
477
478#ifdef W
479
480/*
481 Swap the bytes in a z_word_t to convert between little and big endian. Any
482 self-respecting compiler will optimize this to a single machine byte-swap
483 instruction, if one is available. This assumes that word_t is either 32 bits
484 or 64 bits.
485 */
486local z_word_t byte_swap(word)
487 z_word_t word;
488{
489#if W == 8
490 return
491 (word & 0xff00000000000000) >> 56 |
492 (word & 0xff000000000000) >> 40 |
493 (word & 0xff0000000000) >> 24 |
494 (word & 0xff00000000) >> 8 |
495 (word & 0xff000000) << 8 |
496 (word & 0xff0000) << 24 |
497 (word & 0xff00) << 40 |
498 (word & 0xff) << 56;
499#else /* W == 4 */
500 return
501 (word & 0xff000000) >> 24 |
502 (word & 0xff0000) >> 8 |
503 (word & 0xff00) << 8 |
504 (word & 0xff) << 24;
505#endif
506}
507
508/*
509 Return the CRC of the W bytes in the word_t data, taking the
510 least-significant byte of the word as the first byte of data, without any pre
511 or post conditioning. This is used to combine the CRCs of each braid.
512 */
513local z_crc_t crc_word(data)
514 z_word_t data;
515{
516 int k;
517 for (k = 0; k < W; k++)
518 data = (data >> 8) ^ crc_table[data & 0xff];
519 return (z_crc_t)data;
520}
521
522local z_word_t crc_word_big(data)
523 z_word_t data;
524{
525 int k;
526 for (k = 0; k < W; k++)
527 data = (data << 8) ^
528 crc_big_table[(data >> ((W - 1) << 3)) & 0xff];
529 return data;
530}
531
532#endif /* W */
533
263/* ========================================================================= 534/* =========================================================================
264 * This function can be used by asm versions of crc32() 535 * This function can be used by asm versions of crc32()
265 */ 536 */
@@ -273,168 +544,348 @@ const z_crc_t FAR * ZEXPORT get_crc_table()
273} 544}
274 545
275/* ========================================================================= */ 546/* ========================================================================= */
276#define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
277#define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
278
279/* ========================================================================= */
280unsigned long ZEXPORT crc32_z(crc, buf, len) 547unsigned long ZEXPORT crc32_z(crc, buf, len)
281 unsigned long crc; 548 unsigned long crc;
282 const unsigned char FAR *buf; 549 const unsigned char FAR *buf;
283 z_size_t len; 550 z_size_t len;
284{ 551{
285 if (buf == Z_NULL) return 0UL; 552 /* Return initial CRC, if requested. */
553 if (buf == Z_NULL) return 0;
286 554
287#ifdef DYNAMIC_CRC_TABLE 555#ifdef DYNAMIC_CRC_TABLE
288 if (crc_table_empty) 556 if (crc_table_empty)
289 make_crc_table(); 557 make_crc_table();
290#endif /* DYNAMIC_CRC_TABLE */ 558#endif /* DYNAMIC_CRC_TABLE */
291 559
292#ifdef BYFOUR 560 /* Pre-condition the CRC */
293 if (sizeof(void *) == sizeof(z_size_t)) { 561 crc ^= 0xffffffff;
294 z_crc_t endian; 562
563#ifdef W
564
565 /* If provided enough bytes, do a braided CRC calculation. */
566 if (len >= N * W + W - 1) {
567 z_size_t blks;
568 z_word_t const *words;
569 unsigned endian;
570 int k;
571
572 /* Compute the CRC up to a z_word_t boundary. */
573 while (len && ((z_size_t)buf & (W - 1)) != 0) {
574 len--;
575 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
576 }
577
578 /* Compute the CRC on as many N z_word_t blocks as are available. */
579 blks = len / (N * W);
580 len -= blks * N * W;
581 words = (z_word_t const *)buf;
295 582
583 /* Do endian check at execution time instead of compile time, since ARM
584 processors can change the endianess at execution time. If the
585 compiler knows what the endianess will be, it can optimize out the
586 check and the unused branch. */
296 endian = 1; 587 endian = 1;
297 if (*((unsigned char *)(&endian))) 588 if (*(unsigned char *)&endian) {
298 return crc32_little(crc, buf, len); 589 /* Little endian. */
299 else 590
300 return crc32_big(crc, buf, len); 591 z_crc_t crc0;
301 } 592 z_word_t word0;
302#endif /* BYFOUR */ 593#if N > 1
303 crc = crc ^ 0xffffffffUL; 594 z_crc_t crc1;
304 while (len >= 8) { 595 z_word_t word1;
305 DO8; 596#if N > 2
306 len -= 8; 597 z_crc_t crc2;
307 } 598 z_word_t word2;
308 if (len) do { 599#if N > 3
309 DO1; 600 z_crc_t crc3;
310 } while (--len); 601 z_word_t word3;
311 return crc ^ 0xffffffffUL; 602#if N > 4
312} 603 z_crc_t crc4;
604 z_word_t word4;
605#if N > 5
606 z_crc_t crc5;
607 z_word_t word5;
608#endif
609#endif
610#endif
611#endif
612#endif
313 613
314/* ========================================================================= */ 614 /* Initialize the CRC for each braid. */
315unsigned long ZEXPORT crc32(crc, buf, len) 615 crc0 = crc;
316 unsigned long crc; 616#if N > 1
317 const unsigned char FAR *buf; 617 crc1 = 0;
318 uInt len; 618#if N > 2
319{ 619 crc2 = 0;
320 return crc32_z(crc, buf, len); 620#if N > 3
321} 621 crc3 = 0;
622#if N > 4
623 crc4 = 0;
624#if N > 5
625 crc5 = 0;
626#endif
627#endif
628#endif
629#endif
630#endif
322 631
323#ifdef BYFOUR 632 /*
633 Process the first blks-1 blocks, computing the CRCs on each braid
634 independently.
635 */
636 while (--blks) {
637 /* Load the word for each braid into registers. */
638 word0 = crc0 ^ words[0];
639#if N > 1
640 word1 = crc1 ^ words[1];
641#if N > 2
642 word2 = crc2 ^ words[2];
643#if N > 3
644 word3 = crc3 ^ words[3];
645#if N > 4
646 word4 = crc4 ^ words[4];
647#if N > 5
648 word5 = crc5 ^ words[5];
649#endif
650#endif
651#endif
652#endif
653#endif
654 words += N;
655
656 /* Compute and update the CRC for each word. The loop should
657 get unrolled. */
658 crc0 = crc_braid_table[0][word0 & 0xff];
659#if N > 1
660 crc1 = crc_braid_table[0][word1 & 0xff];
661#if N > 2
662 crc2 = crc_braid_table[0][word2 & 0xff];
663#if N > 3
664 crc3 = crc_braid_table[0][word3 & 0xff];
665#if N > 4
666 crc4 = crc_braid_table[0][word4 & 0xff];
667#if N > 5
668 crc5 = crc_braid_table[0][word5 & 0xff];
669#endif
670#endif
671#endif
672#endif
673#endif
674 for (k = 1; k < W; k++) {
675 crc0 ^= crc_braid_table[k][(word0 >> (k << 3)) & 0xff];
676#if N > 1
677 crc1 ^= crc_braid_table[k][(word1 >> (k << 3)) & 0xff];
678#if N > 2
679 crc2 ^= crc_braid_table[k][(word2 >> (k << 3)) & 0xff];
680#if N > 3
681 crc3 ^= crc_braid_table[k][(word3 >> (k << 3)) & 0xff];
682#if N > 4
683 crc4 ^= crc_braid_table[k][(word4 >> (k << 3)) & 0xff];
684#if N > 5
685 crc5 ^= crc_braid_table[k][(word5 >> (k << 3)) & 0xff];
686#endif
687#endif
688#endif
689#endif
690#endif
691 }
692 }
324 693
325/* 694 /*
326 This BYFOUR code accesses the passed unsigned char * buffer with a 32-bit 695 Process the last block, combining the CRCs of the N braids at the
327 integer pointer type. This violates the strict aliasing rule, where a 696 same time.
328 compiler can assume, for optimization purposes, that two pointers to 697 */
329 fundamentally different types won't ever point to the same memory. This can 698 crc = crc_word(crc0 ^ words[0]);
330 manifest as a problem only if one of the pointers is written to. This code 699#if N > 1
331 only reads from those pointers. So long as this code remains isolated in 700 crc = crc_word(crc1 ^ words[1] ^ crc);
332 this compilation unit, there won't be a problem. For this reason, this code 701#if N > 2
333 should not be copied and pasted into a compilation unit in which other code 702 crc = crc_word(crc2 ^ words[2] ^ crc);
334 writes to the buffer that is passed to these routines. 703#if N > 3
335 */ 704 crc = crc_word(crc3 ^ words[3] ^ crc);
705#if N > 4
706 crc = crc_word(crc4 ^ words[4] ^ crc);
707#if N > 5
708 crc = crc_word(crc5 ^ words[5] ^ crc);
709#endif
710#endif
711#endif
712#endif
713#endif
714 words += N;
715 }
716 else {
717 /* Big endian. */
718
719 z_word_t crc0, word0, comb;
720#if N > 1
721 z_word_t crc1, word1;
722#if N > 2
723 z_word_t crc2, word2;
724#if N > 3
725 z_word_t crc3, word3;
726#if N > 4
727 z_word_t crc4, word4;
728#if N > 5
729 z_word_t crc5, word5;
730#endif
731#endif
732#endif
733#endif
734#endif
336 735
337/* ========================================================================= */ 736 /* Initialize the CRC for each braid. */
338#define DOLIT4 c ^= *buf4++; \ 737 crc0 = byte_swap(crc);
339 c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \ 738#if N > 1
340 crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24] 739 crc1 = 0;
341#define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4 740#if N > 2
741 crc2 = 0;
742#if N > 3
743 crc3 = 0;
744#if N > 4
745 crc4 = 0;
746#if N > 5
747 crc5 = 0;
748#endif
749#endif
750#endif
751#endif
752#endif
342 753
343/* ========================================================================= */ 754 /*
344local unsigned long crc32_little(crc, buf, len) 755 Process the first blks-1 blocks, computing the CRCs on each braid
345 unsigned long crc; 756 independently.
346 const unsigned char FAR *buf; 757 */
347 z_size_t len; 758 while (--blks) {
348{ 759 /* Load the word for each braid into registers. */
349 register z_crc_t c; 760 word0 = crc0 ^ words[0];
350 register const z_crc_t FAR *buf4; 761#if N > 1
762 word1 = crc1 ^ words[1];
763#if N > 2
764 word2 = crc2 ^ words[2];
765#if N > 3
766 word3 = crc3 ^ words[3];
767#if N > 4
768 word4 = crc4 ^ words[4];
769#if N > 5
770 word5 = crc5 ^ words[5];
771#endif
772#endif
773#endif
774#endif
775#endif
776 words += N;
777
778 /* Compute and update the CRC for each word. The loop should
779 get unrolled. */
780 crc0 = crc_braid_big_table[0][word0 & 0xff];
781#if N > 1
782 crc1 = crc_braid_big_table[0][word1 & 0xff];
783#if N > 2
784 crc2 = crc_braid_big_table[0][word2 & 0xff];
785#if N > 3
786 crc3 = crc_braid_big_table[0][word3 & 0xff];
787#if N > 4
788 crc4 = crc_braid_big_table[0][word4 & 0xff];
789#if N > 5
790 crc5 = crc_braid_big_table[0][word5 & 0xff];
791#endif
792#endif
793#endif
794#endif
795#endif
796 for (k = 1; k < W; k++) {
797 crc0 ^= crc_braid_big_table[k][(word0 >> (k << 3)) & 0xff];
798#if N > 1
799 crc1 ^= crc_braid_big_table[k][(word1 >> (k << 3)) & 0xff];
800#if N > 2
801 crc2 ^= crc_braid_big_table[k][(word2 >> (k << 3)) & 0xff];
802#if N > 3
803 crc3 ^= crc_braid_big_table[k][(word3 >> (k << 3)) & 0xff];
804#if N > 4
805 crc4 ^= crc_braid_big_table[k][(word4 >> (k << 3)) & 0xff];
806#if N > 5
807 crc5 ^= crc_braid_big_table[k][(word5 >> (k << 3)) & 0xff];
808#endif
809#endif
810#endif
811#endif
812#endif
813 }
814 }
351 815
352 c = (z_crc_t)crc; 816 /*
353 c = ~c; 817 Process the last block, combining the CRCs of the N braids at the
354 while (len && ((z_size_t)buf & 3)) { 818 same time.
355 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8); 819 */
356 len--; 820 comb = crc_word_big(crc0 ^ words[0]);
821#if N > 1
822 comb = crc_word_big(crc1 ^ words[1] ^ comb);
823#if N > 2
824 comb = crc_word_big(crc2 ^ words[2] ^ comb);
825#if N > 3
826 comb = crc_word_big(crc3 ^ words[3] ^ comb);
827#if N > 4
828 comb = crc_word_big(crc4 ^ words[4] ^ comb);
829#if N > 5
830 comb = crc_word_big(crc5 ^ words[5] ^ comb);
831#endif
832#endif
833#endif
834#endif
835#endif
836 words += N;
837 crc = byte_swap(comb);
838 }
839
840 /*
841 Update the pointer to the remaining bytes to process.
842 */
843 buf = (unsigned char const *)words;
357 } 844 }
358 845
359 buf4 = (const z_crc_t FAR *)(const void FAR *)buf; 846#endif /* W */
360 while (len >= 32) { 847
361 DOLIT32; 848 /* Complete the computation of the CRC on any remaining bytes. */
362 len -= 32; 849 while (len >= 8) {
850 len -= 8;
851 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
852 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
853 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
854 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
855 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
856 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
857 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
858 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
363 } 859 }
364 while (len >= 4) { 860 while (len) {
365 DOLIT4; 861 len--;
366 len -= 4; 862 crc = (crc >> 8) ^ crc_table[(crc ^ *buf++) & 0xff];
367 } 863 }
368 buf = (const unsigned char FAR *)buf4;
369 864
370 if (len) do { 865 /* Return the CRC, post-conditioned. */
371 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8); 866 return crc ^ 0xffffffff;
372 } while (--len);
373 c = ~c;
374 return (unsigned long)c;
375} 867}
376 868
377/* ========================================================================= */ 869/* ========================================================================= */
378#define DOBIG4 c ^= *buf4++; \ 870unsigned long ZEXPORT crc32(crc, buf, len)
379 c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
380 crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
381#define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
382
383/* ========================================================================= */
384local unsigned long crc32_big(crc, buf, len)
385 unsigned long crc; 871 unsigned long crc;
386 const unsigned char FAR *buf; 872 const unsigned char FAR *buf;
387 z_size_t len; 873 uInt len;
388{ 874{
389 register z_crc_t c; 875 return crc32_z(crc, buf, len);
390 register const z_crc_t FAR *buf4;
391
392 c = ZSWAP32((z_crc_t)crc);
393 c = ~c;
394 while (len && ((z_size_t)buf & 3)) {
395 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
396 len--;
397 }
398
399 buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
400 while (len >= 32) {
401 DOBIG32;
402 len -= 32;
403 }
404 while (len >= 4) {
405 DOBIG4;
406 len -= 4;
407 }
408 buf = (const unsigned char FAR *)buf4;
409
410 if (len) do {
411 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
412 } while (--len);
413 c = ~c;
414 return (unsigned long)(ZSWAP32(c));
415} 876}
416 877
417#endif /* BYFOUR */
418
419/* ========================================================================= */ 878/* ========================================================================= */
420local uLong crc32_combine_(crc1, crc2, len2) 879uLong ZEXPORT crc32_combine64(crc1, crc2, len2)
421 uLong crc1; 880 uLong crc1;
422 uLong crc2; 881 uLong crc2;
423 z_off64_t len2; 882 z_off64_t len2;
424{ 883{
425 int n;
426
427#ifdef DYNAMIC_CRC_TABLE 884#ifdef DYNAMIC_CRC_TABLE
428 if (crc_table_empty) 885 if (crc_table_empty)
429 make_crc_table(); 886 make_crc_table();
430#endif /* DYNAMIC_CRC_TABLE */ 887#endif /* DYNAMIC_CRC_TABLE */
431 888 return multmodp(x2nmodp(len2, 3), crc1) ^ crc2;
432 if (len2 > 0)
433 /* operator for 2^n zeros repeats every GF2_DIM n values */
434 for (n = 0; len2; n = (n + 1) % GF2_DIM, len2 >>= 1)
435 if (len2 & 1)
436 crc1 = gf2_matrix_times(crc_comb[n], crc1);
437 return crc1 ^ crc2;
438} 889}
439 890
440/* ========================================================================= */ 891/* ========================================================================= */
@@ -443,87 +894,32 @@ uLong ZEXPORT crc32_combine(crc1, crc2, len2)
443 uLong crc2; 894 uLong crc2;
444 z_off_t len2; 895 z_off_t len2;
445{ 896{
446 return crc32_combine_(crc1, crc2, len2); 897 return crc32_combine64(crc1, crc2, len2);
447}
448
449uLong ZEXPORT crc32_combine64(crc1, crc2, len2)
450 uLong crc1;
451 uLong crc2;
452 z_off64_t len2;
453{
454 return crc32_combine_(crc1, crc2, len2);
455} 898}
456 899
457/* ========================================================================= */ 900/* ========================================================================= */
458local void crc32_combine_gen_(op, len2) 901uLong ZEXPORT crc32_combine_gen64(len2)
459 z_crc_t *op;
460 z_off64_t len2; 902 z_off64_t len2;
461{ 903{
462 z_crc_t row;
463 int j;
464 unsigned i;
465
466#ifdef DYNAMIC_CRC_TABLE 904#ifdef DYNAMIC_CRC_TABLE
467 if (crc_table_empty) 905 if (crc_table_empty)
468 make_crc_table(); 906 make_crc_table();
469#endif /* DYNAMIC_CRC_TABLE */ 907#endif /* DYNAMIC_CRC_TABLE */
470 908 return x2nmodp(len2, 3);
471 /* if len2 is zero or negative, return the identity matrix */
472 if (len2 <= 0) {
473 row = 1;
474 for (j = 0; j < GF2_DIM; j++) {
475 op[j] = row;
476 row <<= 1;
477 }
478 return;
479 }
480
481 /* at least one bit in len2 is set -- find it, and copy the operator
482 corresponding to that position into op */
483 i = 0;
484 for (;;) {
485 if (len2 & 1) {
486 for (j = 0; j < GF2_DIM; j++)
487 op[j] = crc_comb[i][j];
488 break;
489 }
490 len2 >>= 1;
491 i = (i + 1) % GF2_DIM;
492 }
493
494 /* for each remaining bit set in len2 (if any), multiply op by the operator
495 corresponding to that position */
496 for (;;) {
497 len2 >>= 1;
498 i = (i + 1) % GF2_DIM;
499 if (len2 == 0)
500 break;
501 if (len2 & 1)
502 for (j = 0; j < GF2_DIM; j++)
503 op[j] = gf2_matrix_times(crc_comb[i], op[j]);
504 }
505} 909}
506 910
507/* ========================================================================= */ 911/* ========================================================================= */
508void ZEXPORT crc32_combine_gen(op, len2) 912uLong ZEXPORT crc32_combine_gen(len2)
509 z_crc_t *op;
510 z_off_t len2; 913 z_off_t len2;
511{ 914{
512 crc32_combine_gen_(op, len2); 915 return crc32_combine_gen64(len2);
513}
514
515void ZEXPORT crc32_combine_gen64(op, len2)
516 z_crc_t *op;
517 z_off64_t len2;
518{
519 crc32_combine_gen_(op, len2);
520} 916}
521 917
522/* ========================================================================= */ 918/* ========================================================================= */
523uLong crc32_combine_op(crc1, crc2, op) 919uLong crc32_combine_op(crc1, crc2, op)
524 uLong crc1; 920 uLong crc1;
525 uLong crc2; 921 uLong crc2;
526 const z_crc_t *op; 922 uLong op;
527{ 923{
528 return gf2_matrix_times(op, crc1) ^ crc2; 924 return multmodp(op, crc1) ^ crc2;
529} 925}