varnish-cache/lib/libvgz/crc32.c
1
/* crc32.c -- compute the CRC-32 of a data stream
2
 * Copyright (C) 1995-2006, 2010, 2011, 2012, 2016 Mark Adler
3
 * For conditions of distribution and use, see copyright notice in zlib.h
4
 *
5
 * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
6
 * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
7
 * tables for updating the shift register in one step with three exclusive-ors
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
 */
11
12
/* @(#) $Id$ */
13
14
/*
15
  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
17
  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
19
  one thread to use crc32().
20
21
  DYNAMIC_CRC_TABLE and MAKECRCH can be #defined to write out crc32.h.
22
 */
23
24
#ifdef MAKECRCH
25
#  include <stdio.h>
26
#  ifndef DYNAMIC_CRC_TABLE
27
#    define DYNAMIC_CRC_TABLE
28
#  endif /* !DYNAMIC_CRC_TABLE */
29
#endif /* MAKECRCH */
30
31
#include "zutil.h"      /* for STDC and FAR definitions */
32
33
/* Definitions for doing the crc four data bytes at a time. */
34
#if !defined(NOBYFOUR) && defined(Z_U4)
35
#  define BYFOUR
36
#endif
37
#ifdef BYFOUR
38
   local unsigned long crc32_little OF((unsigned long,
39
                        const unsigned char FAR *, z_size_t));
40
   local unsigned long crc32_big OF((unsigned long,
41
                        const unsigned char FAR *, z_size_t));
42
#  define TBLS 8
43
#else
44
#  define TBLS 1
45
#endif /* BYFOUR */
46
47
/* Local functions for crc concatenation */
48
local unsigned long gf2_matrix_times OF((unsigned long *mat,
49
                                         unsigned long vec));
50
local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
51
local uLong crc32_combine_ OF((uLong crc1, uLong crc2, z_off64_t len2));
52
53
54
#ifdef DYNAMIC_CRC_TABLE
55
56
local volatile int crc_table_empty = 1;
57
local z_crc_t FAR crc_table[TBLS][256];
58
local void make_crc_table OF((void));
59
#ifdef MAKECRCH
60
   local void write_table OF((FILE *, const z_crc_t FAR *));
61
#endif /* MAKECRCH */
62
/*
63
  Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
64
  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.
65
66
  Polynomials over GF(2) are represented in binary, one bit per coefficient,
67
  with the lowest powers in the most significant bit.  Then adding polynomials
68
  is just exclusive-or, and multiplying a polynomial by x is a right shift by
69
  one.  If we call the above polynomial p, and represent a byte as the
70
  polynomial q, also with the lowest power in the most significant bit (so the
71
  byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
72
  where a mod b means the remainder after dividing a by b.
73
74
  This calculation is done using the shift-register method of multiplying and
75
  taking the remainder.  The register is initialized to zero, and for each
76
  incoming bit, x^32 is added mod p to the register if the bit is a one (where
77
  x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
78
  x (which is shifting right by one and adding x^32 mod p if the bit shifted
79
  out is a one).  We start with the highest power (least significant bit) of
80
  q and repeat for all eight bits of q.
81
82
  The first table is simply the CRC of all possible eight bit values.  This is
83
  all the information needed to generate CRCs on data a byte at a time for all
84
  combinations of CRC register values and incoming bytes.  The remaining tables
85
  allow for word-at-a-time CRC calculation for both big-endian and little-
86
  endian machines, where a word is four bytes.
87
*/
88
local void make_crc_table()
89
{
90
    z_crc_t c;
91
    int n, k;
92
    z_crc_t poly;                       /* polynomial exclusive-or pattern */
93
    /* terms of polynomial defining this crc (except x^32): */
94
    static volatile int first = 1;      /* flag to limit concurrent making */
95
    static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
96
97
    /* See if another task is already doing this (not thread-safe, but better
98
       than nothing -- significantly reduces duration of vulnerability in
99
       case the advice about DYNAMIC_CRC_TABLE is ignored) */
100
    if (first) {
101
        first = 0;
102
103
        /* make exclusive-or pattern from polynomial (0xedb88320UL) */
104
        poly = 0;
105
        for (n = 0; n < (int)(sizeof(p)/sizeof(unsigned char)); n++)
106
            poly |= (z_crc_t)1 << (31 - p[n]);
107
108
        /* generate a crc for every 8-bit value */
109
        for (n = 0; n < 256; n++) {
110
            c = (z_crc_t)n;
111
            for (k = 0; k < 8; k++)
112
                c = c & 1 ? poly ^ (c >> 1) : c >> 1;
113
            crc_table[0][n] = c;
114
        }
115
116
#ifdef BYFOUR
117
        /* generate crc for each value followed by one, two, and three zeros,
118
           and then the byte reversal of those as well as the first table */
119
        for (n = 0; n < 256; n++) {
120
            c = crc_table[0][n];
121
            crc_table[4][n] = ZSWAP32(c);
122
            for (k = 1; k < 4; k++) {
123
                c = crc_table[0][c & 0xff] ^ (c >> 8);
124
                crc_table[k][n] = c;
125
                crc_table[k + 4][n] = ZSWAP32(c);
126
            }
127
        }
128
#endif /* BYFOUR */
129
130
        crc_table_empty = 0;
131
    }
132
    else {      /* not first */
133
        /* wait for the other guy to finish (not efficient, but rare) */
134
        while (crc_table_empty)
135
            ;
136
    }
137
138
#ifdef MAKECRCH
139
    /* write out CRC tables to crc32.h */
140
    {
141
        FILE *out;
142
143
        out = fopen("crc32.h", "w");
144
        if (out == NULL) return;
145
        fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
146
        fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
147
        fprintf(out, "local const z_crc_t FAR ");
148
        fprintf(out, "crc_table[TBLS][256] =\n{\n  {\n");
149
        write_table(out, crc_table[0]);
150
#  ifdef BYFOUR
151
        fprintf(out, "#ifdef BYFOUR\n");
152
        for (k = 1; k < 8; k++) {
153
            fprintf(out, "  },\n  {\n");
154
            write_table(out, crc_table[k]);
155
        }
156
        fprintf(out, "#endif\n");
157
#  endif /* BYFOUR */
158
        fprintf(out, "  }\n};\n");
159
        fclose(out);
160
    }
161
#endif /* MAKECRCH */
162
}
163
164
#ifdef MAKECRCH
165
local void write_table(out, table)
166
    FILE *out;
167
    const z_crc_t FAR *table;
168
{
169
    int n;
170
171
    for (n = 0; n < 256; n++)
172
        fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : "    ",
173
                (unsigned long)(table[n]),
174
                n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
175
}
176
#endif /* MAKECRCH */
177
178
#else /* !DYNAMIC_CRC_TABLE */
179
/* ========================================================================
180
 * Tables of CRC-32s of all single-byte values, made by make_crc_table().
181
 */
182
#include "crc32.h"
183
#endif /* DYNAMIC_CRC_TABLE */
184
185
/* =========================================================================
186
 * This function can be used by asm versions of crc32()
187
 */
188 0
const z_crc_t FAR * ZEXPORT get_crc_table()
189
{
190
#ifdef DYNAMIC_CRC_TABLE
191
    if (crc_table_empty)
192
        make_crc_table();
193
#endif /* DYNAMIC_CRC_TABLE */
194 0
    return (const z_crc_t FAR *)crc_table;
195
}
196
197
/* ========================================================================= */
198
#define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
199
#define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
200
201
/* ========================================================================= */
202 143405
unsigned long ZEXPORT crc32_z(crc, buf, len)
203
    unsigned long crc;
204
    const unsigned char FAR *buf;
205
    z_size_t len;
206
{
207 143405
    if (buf == Z_NULL) return 0UL;
208
209
#ifdef DYNAMIC_CRC_TABLE
210
    if (crc_table_empty)
211
        make_crc_table();
212
#endif /* DYNAMIC_CRC_TABLE */
213
214
#ifdef BYFOUR
215
    if (sizeof(void *) == sizeof(ptrdiff_t)) {
216
        z_crc_t endian;
217
218 104609
        endian = 1;
219 104609
        if (*((unsigned char *)(&endian)))
220 104609
            return crc32_little(crc, buf, len);
221
        else
222 0
            return crc32_big(crc, buf, len);
223
    }
224
#endif /* BYFOUR */
225
    crc = crc ^ 0xffffffffUL;
226
    while (len >= 8) {
227
        DO8;
228
        len -= 8;
229
    }
230
    if (len) do {
231
        DO1;
232
    } while (--len);
233
    return crc ^ 0xffffffffUL;
234
}
235
236
/* ========================================================================= */
237 143405
unsigned long ZEXPORT crc32(crc, buf, len)
238
    unsigned long crc;
239
    const unsigned char FAR *buf;
240
    uInt len;
241
{
242 143405
    return crc32_z(crc, buf, len);
243
}
244
245
#ifdef BYFOUR
246
247
/*
248
   This BYFOUR code accesses the passed unsigned char * buffer with a 32-bit
249
   integer pointer type. This violates the strict aliasing rule, where a
250
   compiler can assume, for optimization purposes, that two pointers to
251
   fundamentally different types won't ever point to the same memory. This can
252
   manifest as a problem only if one of the pointers is written to. This code
253
   only reads from those pointers. So long as this code remains isolated in
254
   this compilation unit, there won't be a problem. For this reason, this code
255
   should not be copied and pasted into a compilation unit in which other code
256
   writes to the buffer that is passed to these routines.
257
 */
258
259
/* ========================================================================= */
260
#define DOLIT4 c ^= *buf4++; \
261
        c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
262
            crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
263
#define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
264
265
/* ========================================================================= */
266 104609
local unsigned long crc32_little(crc, buf, len)
267
    unsigned long crc;
268
    const unsigned char FAR *buf;
269
    z_size_t len;
270
{
271
    register z_crc_t c;
272
    register const z_crc_t FAR *buf4;
273
274 104609
    c = (z_crc_t)crc;
275 104609
    c = ~c;
276 294074
    while (len && ((ptrdiff_t)buf & 3)) {
277 84856
        c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
278 84856
        len--;
279
    }
280
281 104609
    buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
282 1455713
    while (len >= 32) {
283 1246495
        DOLIT32;
284 1246495
        len -= 32;
285
    }
286 406397
    while (len >= 4) {
287 197179
        DOLIT4;
288 197179
        len -= 4;
289
    }
290 104609
    buf = (const unsigned char FAR *)buf4;
291
292 104609
    if (len) do {
293 141372
        c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
294 141372
    } while (--len);
295 104609
    c = ~c;
296 104609
    return (unsigned long)c;
297
}
298
299
/* ========================================================================= */
300
#define DOBIG4 c ^= *buf4++; \
301
        c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
302
            crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
303
#define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
304
305
/* ========================================================================= */
306 0
local unsigned long crc32_big(crc, buf, len)
307
    unsigned long crc;
308
    const unsigned char FAR *buf;
309
    z_size_t len;
310
{
311
    register z_crc_t c;
312
    register const z_crc_t FAR *buf4;
313
314 0
    c = ZSWAP32((z_crc_t)crc);
315 0
    c = ~c;
316 0
    while (len && ((ptrdiff_t)buf & 3)) {
317 0
        c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
318 0
        len--;
319
    }
320
321 0
    buf4 = (const z_crc_t FAR *)(const void FAR *)buf;
322 0
    while (len >= 32) {
323 0
        DOBIG32;
324 0
        len -= 32;
325
    }
326 0
    while (len >= 4) {
327 0
        DOBIG4;
328 0
        len -= 4;
329
    }
330 0
    buf = (const unsigned char FAR *)buf4;
331
332 0
    if (len) do {
333 0
        c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
334 0
    } while (--len);
335 0
    c = ~c;
336 0
    return (unsigned long)(ZSWAP32(c));
337
}
338
339
#endif /* BYFOUR */
340
341
#define GF2_DIM 32      /* dimension of GF(2) vectors (length of CRC) */
342
343
/* ========================================================================= */
344 17917
local unsigned long gf2_matrix_times(mat, vec)
345
    unsigned long *mat;
346
    unsigned long vec;
347
{
348
    unsigned long sum;
349
350 17917
    sum = 0;
351 383675
    while (vec) {
352 347841
        if (vec & 1)
353 94804
            sum ^= *mat;
354 347841
        vec >>= 1;
355 347841
        mat++;
356
    }
357 17917
    return sum;
358
}
359
360
/* ========================================================================= */
361 553
local void gf2_matrix_square(square, mat)
362
    unsigned long *square;
363
    unsigned long *mat;
364
{
365
    int n;
366
367 18249
    for (n = 0; n < GF2_DIM; n++)
368 17696
        square[n] = gf2_matrix_times(mat, mat[n]);
369 553
}
370
371
/* ========================================================================= */
372 101
local uLong crc32_combine_(crc1, crc2, len2)
373
    uLong crc1;
374
    uLong crc2;
375
    z_off64_t len2;
376
{
377
    int n;
378
    unsigned long row;
379
    unsigned long even[GF2_DIM];    /* even-power-of-two zeros operator */
380
    unsigned long odd[GF2_DIM];     /* odd-power-of-two zeros operator */
381
382
    /* degenerate case (also disallow negative lengths) */
383 101
    if (len2 <= 0)
384 0
        return crc1;
385
386
    /* put operator for one zero bit in odd */
387 101
    odd[0] = 0xedb88320UL;          /* CRC-32 polynomial */
388 101
    row = 1;
389 3232
    for (n = 1; n < GF2_DIM; n++) {
390 3131
        odd[n] = row;
391 3131
        row <<= 1;
392
    }
393
394
    /* put operator for two zero bits in even */
395 101
    gf2_matrix_square(even, odd);
396
397
    /* put operator for four zero bits in odd */
398 101
    gf2_matrix_square(odd, even);
399
400
    /* apply len2 zeros to crc1 (first square will put the operator for one
401
       zero byte, eight zero bits, in even) */
402
    do {
403
        /* apply zeros operator for this bit of len2 */
404 194
        gf2_matrix_square(even, odd);
405 194
        if (len2 & 1)
406 123
            crc1 = gf2_matrix_times(even, crc1);
407 194
        len2 >>= 1;
408
409
        /* if no more bits set, then done */
410 194
        if (len2 == 0)
411 37
            break;
412
413
        /* another iteration of the loop with odd and even swapped */
414 157
        gf2_matrix_square(odd, even);
415 157
        if (len2 & 1)
416 98
            crc1 = gf2_matrix_times(odd, crc1);
417 157
        len2 >>= 1;
418
419
        /* if no more bits set, then done */
420 157
    } while (len2 != 0);
421
422
    /* return combined crc */
423 101
    crc1 ^= crc2;
424 101
    return crc1;
425
}
426
427
/* ========================================================================= */
428 101
uLong ZEXPORT crc32_combine(crc1, crc2, len2)
429
    uLong crc1;
430
    uLong crc2;
431
    z_off_t len2;
432
{
433 101
    return crc32_combine_(crc1, crc2, len2);
434
}
435
436 0
uLong ZEXPORT crc32_combine64(crc1, crc2, len2)
437
    uLong crc1;
438
    uLong crc2;
439
    z_off64_t len2;
440
{
441 0
    return crc32_combine_(crc1, crc2, len2);
442
}