1 /*
2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation. Oracle designates this
7 * particular file as subject to the "Classpath" exception as provided
8 * by Oracle in the LICENSE file that accompanied this code.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
22 * questions.
23 */
24
25 /* crc32.c -- compute the CRC-32 of a data stream
26 * Copyright (C) 1995-2006, 2010, 2011, 2012, 2016 Mark Adler
27 * For conditions of distribution and use, see copyright notice in zlib.h
28 *
29 * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
30 * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
31 * tables for updating the shift register in one step with three exclusive-ors
32 * instead of four steps with four exclusive-ors. This results in about a
33 * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
34 */
35
36 /* @(#) $Id$ */
37
38 /*
39 Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
40 protection on the static variables used to control the first-use generation
41 of the crc tables. Therefore, if you #define DYNAMIC_CRC_TABLE, you should
42 first call get_crc_table() to initialize the tables before allowing more than
43 one thread to use crc32().
44
45 DYNAMIC_CRC_TABLE and MAKECRCH can be #defined to write out crc32.h.
46 */
47
48 #ifdef MAKECRCH
49 # include <stdio.h>
50 # ifndef DYNAMIC_CRC_TABLE
51 # define DYNAMIC_CRC_TABLE
52 # endif /* !DYNAMIC_CRC_TABLE */
53 #endif /* MAKECRCH */
54
55 #include "zutil.h" /* for STDC and FAR definitions */
56
57 /* Definitions for doing the crc four data bytes at a time. */
58 #if !defined(NOBYFOUR) && defined(Z_U4)
59 # define BYFOUR
60 #endif
61 #ifdef BYFOUR
62 local unsigned long crc32_little OF((unsigned long,
63 const unsigned char FAR *, z_size_t));
64 local unsigned long crc32_big OF((unsigned long,
65 const unsigned char FAR *, z_size_t));
66 # define TBLS 8
67 #else
68 # define TBLS 1
69 #endif /* BYFOUR */
70
71 /* Local functions for crc concatenation */
72 local unsigned long gf2_matrix_times OF((unsigned long *mat,
73 unsigned long vec));
74 local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
75 local uLong crc32_combine_ OF((uLong crc1, uLong crc2, z_off64_t len2));
76
77
78 #ifdef DYNAMIC_CRC_TABLE
79
80 local volatile int crc_table_empty = 1;
81 local z_crc_t FAR crc_table[TBLS][256];
82 local void make_crc_table OF((void));
83 #ifdef MAKECRCH
84 local void write_table OF((FILE *, const z_crc_t FAR *));
85 #endif /* MAKECRCH */
86 /*
87 Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
88 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.
89
90 Polynomials over GF(2) are represented in binary, one bit per coefficient,
91 with the lowest powers in the most significant bit. Then adding polynomials
92 is just exclusive-or, and multiplying a polynomial by x is a right shift by
93 one. If we call the above polynomial p, and represent a byte as the
94 polynomial q, also with the lowest power in the most significant bit (so the
95 byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
96 where a mod b means the remainder after dividing a by b.
97
98 This calculation is done using the shift-register method of multiplying and
99 taking the remainder. The register is initialized to zero, and for each
100 incoming bit, x^32 is added mod p to the register if the bit is a one (where
101 x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
102 x (which is shifting right by one and adding x^32 mod p if the bit shifted
103 out is a one). We start with the highest power (least significant bit) of
104 q and repeat for all eight bits of q.
105
106 The first table is simply the CRC of all possible eight bit values. This is
107 all the information needed to generate CRCs on data a byte at a time for all
108 combinations of CRC register values and incoming bytes. The remaining tables
109 allow for word-at-a-time CRC calculation for both big-endian and little-
110 endian machines, where a word is four bytes.
111 */
112 local void make_crc_table()
113 {
114 z_crc_t c;
115 int n, k;
116 z_crc_t poly; /* polynomial exclusive-or pattern */
117 /* terms of polynomial defining this crc (except x^32): */
118 static volatile int first = 1; /* flag to limit concurrent making */
119 static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
120
121 /* See if another task is already doing this (not thread-safe, but better
122 than nothing -- significantly reduces duration of vulnerability in
123 case the advice about DYNAMIC_CRC_TABLE is ignored) */
124 if (first) {
125 first = 0;
126
127 /* make exclusive-or pattern from polynomial (0xedb88320UL) */
128 poly = 0;
129 for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++)
130 poly |= (z_crc_t)1 << (31 - p[n]);
131
132 /* generate a crc for every 8-bit value */
133 for (n = 0; n < 256; n++) {
134 c = (z_crc_t)n;
135 for (k = 0; k < 8; k++)
136 c = c & 1 ? poly ^ (c >> 1) : c >> 1;
137 crc_table[0][n] = c;
138 }
139
140 #ifdef BYFOUR
141 /* generate crc for each value followed by one, two, and three zeros,
142 and then the byte reversal of those as well as the first table */
143 for (n = 0; n < 256; n++) {
144 c = crc_table[0][n];
145 crc_table[4][n] = ZSWAP32(c);
146 for (k = 1; k < 4; k++) {
147 c = crc_table[0][c & 0xff] ^ (c >> 8);
148 crc_table[k][n] = c;
149 crc_table[k + 4][n] = ZSWAP32(c);
150 }
151 }
152 #endif /* BYFOUR */
153
154 crc_table_empty = 0;
155 }
156 else { /* not first */
157 /* wait for the other guy to finish (not efficient, but rare) */
158 while (crc_table_empty)
159 ;
160 }
161
162 #ifdef MAKECRCH
163 /* write out CRC tables to crc32.h */
164 {
165 FILE *out;
166
167 out = fopen("crc32.h", "w");
168 if (out == NULL) return;
169 fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
170 fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
171 fprintf(out, "local const z_crc_t FAR ");
172 fprintf(out, "crc_table[TBLS][256] =\n{\n {\n");
173 write_table(out, crc_table[0]);
174 # ifdef BYFOUR
175 fprintf(out, "#ifdef BYFOUR\n");
176 for (k = 1; k < 8; k++) {
177 fprintf(out, " },\n {\n");
178 write_table(out, crc_table[k]);
179 }
180 fprintf(out, "#endif\n");
181 # endif /* BYFOUR */
182 fprintf(out, " }\n};\n");
183 fclose(out);
184 }
185 #endif /* MAKECRCH */
186 }
187
188 #ifdef MAKECRCH
189 local void write_table(out, table)
190 FILE *out;
191 const z_crc_t FAR *table;
192 {
193 int n;
194
195 for (n = 0; n < 256; n++)
196 fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : " ",
197 (unsigned long)(table[n]),
198 n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
199 }
200 #endif /* MAKECRCH */
201
202 #else /* !DYNAMIC_CRC_TABLE */
203 /* ========================================================================
204 * Tables of CRC-32s of all single-byte values, made by make_crc_table().
205 */
206 #include "crc32.h"
207 #endif /* DYNAMIC_CRC_TABLE */
208
209 /* =========================================================================
210 * This function can be used by asm versions of crc32()
211 */
212 const z_crc_t FAR * ZEXPORT get_crc_table()
213 {
214 #ifdef DYNAMIC_CRC_TABLE
215 if (crc_table_empty)
216 make_crc_table();
217 #endif /* DYNAMIC_CRC_TABLE */
218 return (const z_crc_t FAR *)crc_table;
219 }
220
221 /* ========================================================================= */
222 #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
223 #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
224
225 /* ========================================================================= */
226 uLong ZEXPORT crc32_z(crc, buf, len)
227 uLong crc;
228 const unsigned char FAR *buf;
229 z_size_t len;
230 {
231 if (buf == Z_NULL) return 0UL;
232
233 #ifdef DYNAMIC_CRC_TABLE
234 if (crc_table_empty)
235 make_crc_table();
236 #endif /* DYNAMIC_CRC_TABLE */
237
238 #ifdef BYFOUR
239 if (sizeof(void *) == sizeof(ptrdiff_t)) {
240 z_crc_t endian;
241
242 endian = 1;
243 if (*((unsigned char *)(&endian)))
244 return (uLong)crc32_little(crc, buf, len);
245 else
246 return (uLong)crc32_big(crc, buf, len);
247 }
248 #endif /* BYFOUR */
249 crc = crc ^ 0xffffffffUL;
250 while (len >= 8) {
251 DO8;
252 len -= 8;
253 }
254 if (len) do {
255 DO1;
256 } while (--len);
257 return crc ^ 0xffffffffUL;
258 }
259
260 /* ========================================================================= */
261 uLong ZEXPORT crc32(crc, buf, len)
262 uLong crc;
263 const unsigned char FAR *buf;
264 uInt len;
265 {
266 return crc32_z(crc, buf, len);
267 }
268
269 #ifdef BYFOUR
270
271 /*
272 This BYFOUR code accesses the passed unsigned char * buffer with a 32-bit
273 integer pointer type. This violates the strict aliasing rule, where a
274 compiler can assume, for optimization purposes, that two pointers to
275 fundamentally different types won't ever point to the same memory. This can
276 manifest as a problem only if one of the pointers is written to. This code
277 only reads from those pointers. So long as this code remains isolated in
278 this compilation unit, there won't be a problem. For this reason, this code
279 should not be copied and pasted into a compilation unit in which other code
280 writes to the buffer that is passed to these routines.
281 */
282
283 /* ========================================================================= */
284 #define DOLIT4 c ^= *buf4++; \
285 c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
286 crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
287 #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
288
289 /* ========================================================================= */
290 local unsigned long crc32_little(crc, buf, len)
291 unsigned long crc;
292 const unsigned char FAR *buf;
293 z_size_t len;
294 {
295 register z_crc_t c;
296 register const z_crc_t FAR *buf4;
297
298 c = (z_crc_t)crc;
299 c = ~c;
300 while (len && ((ptrdiff_t)buf & 3)) {
301 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
302 len--;
303 }
304
305 buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
306 while (len >= 32) {
307 DOLIT32;
308 len -= 32;
309 }
310 while (len >= 4) {
311 DOLIT4;
312 len -= 4;
313 }
314 buf = (const unsigned char FAR *)buf4;
315
316 if (len) do {
317 c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
318 } while (--len);
319 c = ~c;
320 return (unsigned long)c;
321 }
322
323 /* ========================================================================= */
324 #define DOBIG4 c ^= *buf4++; \
325 c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
326 crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
327 #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
328
329 /* ========================================================================= */
330 local unsigned long crc32_big(crc, buf, len)
331 unsigned long crc;
332 const unsigned char FAR *buf;
333 z_size_t len;
334 {
335 register z_crc_t c;
336 register const z_crc_t FAR *buf4;
337
338 c = ZSWAP32((z_crc_t)crc);
339 c = ~c;
340 while (len && ((ptrdiff_t)buf & 3)) {
341 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
342 len--;
343 }
344
345 buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
346 while (len >= 32) {
347 DOBIG32;
348 len -= 32;
349 }
350 while (len >= 4) {
351 DOBIG4;
352 len -= 4;
353 }
354 buf = (const unsigned char FAR *)buf4;
355
356 if (len) do {
357 c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
358 } while (--len);
359 c = ~c;
360 return (unsigned long)(ZSWAP32(c));
361 }
362
363 #endif /* BYFOUR */
364
365 #define GF2_DIM 32 /* dimension of GF(2) vectors (length of CRC) */
366
367 /* ========================================================================= */
368 local unsigned long gf2_matrix_times(mat, vec)
369 unsigned long *mat;
370 unsigned long vec;
371 {
372 unsigned long sum;
373
374 sum = 0;
375 while (vec) {
376 if (vec & 1)
377 sum ^= *mat;
378 vec >>= 1;
379 mat++;
380 }
381 return sum;
382 }
383
384 /* ========================================================================= */
385 local void gf2_matrix_square(square, mat)
386 unsigned long *square;
387 unsigned long *mat;
388 {
389 int n;
390
391 for (n = 0; n < GF2_DIM; n++)
392 square[n] = gf2_matrix_times(mat, mat[n]);
393 }
394
395 /* ========================================================================= */
396 local uLong crc32_combine_(crc1, crc2, len2)
397 uLong crc1;
398 uLong crc2;
399 z_off64_t len2;
400 {
401 int n;
402 unsigned long row;
403 unsigned long even[GF2_DIM]; /* even-power-of-two zeros operator */
404 unsigned long odd[GF2_DIM]; /* odd-power-of-two zeros operator */
405
406 /* degenerate case (also disallow negative lengths) */
407 if (len2 <= 0)
408 return crc1;
409
410 /* put operator for one zero bit in odd */
411 odd[0] = 0xedb88320UL; /* CRC-32 polynomial */
412 row = 1;
413 for (n = 1; n < GF2_DIM; n++) {
414 odd[n] = row;
415 row <<= 1;
416 }
417
418 /* put operator for two zero bits in even */
419 gf2_matrix_square(even, odd);
420
421 /* put operator for four zero bits in odd */
422 gf2_matrix_square(odd, even);
423
424 /* apply len2 zeros to crc1 (first square will put the operator for one
425 zero byte, eight zero bits, in even) */
426 do {
427 /* apply zeros operator for this bit of len2 */
428 gf2_matrix_square(even, odd);
429 if (len2 & 1)
430 crc1 = gf2_matrix_times(even, crc1);
431 len2 >>= 1;
432
433 /* if no more bits set, then done */
434 if (len2 == 0)
435 break;
436
437 /* another iteration of the loop with odd and even swapped */
438 gf2_matrix_square(odd, even);
439 if (len2 & 1)
440 crc1 = gf2_matrix_times(odd, crc1);
441 len2 >>= 1;
442
443 /* if no more bits set, then done */
444 } while (len2 != 0);
445
446 /* return combined crc */
447 crc1 ^= crc2;
448 return crc1;
449 }
450
451 /* ========================================================================= */
452 uLong ZEXPORT crc32_combine(crc1, crc2, len2)
453 uLong crc1;
454 uLong crc2;
455 z_off_t len2;
456 {
457 return crc32_combine_(crc1, crc2, len2);
458 }
459
460 uLong ZEXPORT crc32_combine64(crc1, crc2, len2)
461 uLong crc1;
462 uLong crc2;
463 z_off64_t len2;
464 {
465 return crc32_combine_(crc1, crc2, len2);
466 }