xref: /titanic_50/usr/src/uts/common/zmod/crc32.c (revision 5c51f1241dbbdf2656d0e10011981411ed0c9673)
1 /*
2  * Copyright 2007 Sun Microsystems, Inc.  All rights reserved.
3  * Use is subject to license terms.
4  */
5 
6 /* crc32.c -- compute the CRC-32 of a data stream
7  * Copyright (C) 1995-2005 Mark Adler
8  * For conditions of distribution and use, see copyright notice in zlib.h
9  *
10  * Thanks to Rodney Brown <rbrown64@csc.com.au> for his contribution of faster
11  * CRC methods: exclusive-oring 32 bits of data at a time, and pre-computing
12  * tables for updating the shift register in one step with three exclusive-ors
13  * instead of four steps with four exclusive-ors.  This results in about a
14  * factor of two increase in speed on a Power PC G4 (PPC7455) using gcc -O3.
15  */
16 
17 #pragma ident	"%Z%%M%	%I%	%E% SMI"
18 
19 /*
20   Note on the use of DYNAMIC_CRC_TABLE: there is no mutex or semaphore
21   protection on the static variables used to control the first-use generation
22   of the crc tables.  Therefore, if you #define DYNAMIC_CRC_TABLE, you should
23   first call get_crc_table() to initialize the tables before allowing more than
24   one thread to use crc32().
25  */
26 
27 #ifdef MAKECRCH
28 #  include <stdio.h>
29 #  ifndef DYNAMIC_CRC_TABLE
30 #    define DYNAMIC_CRC_TABLE
31 #  endif /* !DYNAMIC_CRC_TABLE */
32 #endif /* MAKECRCH */
33 
34 #include "zutil.h"      /* for STDC and FAR definitions */
35 
36 #define local static
37 
38 /* Find a four-byte integer type for crc32_little() and crc32_big(). */
39 #ifndef NOBYFOUR
40 #  ifdef STDC           /* need ANSI C limits.h to determine sizes */
41 #    include <limits.h>
42 #    define BYFOUR
43 #    if (UINT_MAX == 0xffffffffUL)
44        typedef unsigned int u4;
45 #    else
46 #      if (ULONG_MAX == 0xffffffffUL)
47          typedef unsigned long u4;
48 #      else
49 #        if (USHRT_MAX == 0xffffffffUL)
50            typedef unsigned short u4;
51 #        else
52 #          undef BYFOUR     /* can't find a four-byte integer type! */
53 #        endif
54 #      endif
55 #    endif
56 #  endif /* STDC */
57 #endif /* !NOBYFOUR */
58 
59 /* Definitions for doing the crc four data bytes at a time. */
60 #ifdef BYFOUR
61 #  define REV(w) (((w)>>24)+(((w)>>8)&0xff00)+ \
62                 (((w)&0xff00)<<8)+(((w)&0xff)<<24))
63    local unsigned long crc32_little OF((unsigned long,
64                         const unsigned char FAR *, unsigned));
65    local unsigned long crc32_big OF((unsigned long,
66                         const unsigned char FAR *, unsigned));
67 #  define TBLS 8
68 #else
69 #  define TBLS 1
70 #endif /* BYFOUR */
71 
72 /* Local functions for crc concatenation */
73 local unsigned long gf2_matrix_times OF((unsigned long *mat,
74                                          unsigned long vec));
75 local void gf2_matrix_square OF((unsigned long *square, unsigned long *mat));
76 
77 #ifdef DYNAMIC_CRC_TABLE
78 
79 local volatile int crc_table_empty = 1;
80 local unsigned long FAR crc_table[TBLS][256];
81 local void make_crc_table OF((void));
82 #ifdef MAKECRCH
83    local void write_table OF((FILE *, const unsigned long FAR *));
84 #endif /* MAKECRCH */
85 /*
86   Generate tables for a byte-wise 32-bit CRC calculation on the polynomial:
87   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.
88 
89   Polynomials over GF(2) are represented in binary, one bit per coefficient,
90   with the lowest powers in the most significant bit.  Then adding polynomials
91   is just exclusive-or, and multiplying a polynomial by x is a right shift by
92   one.  If we call the above polynomial p, and represent a byte as the
93   polynomial q, also with the lowest power in the most significant bit (so the
94   byte 0xb1 is the polynomial x^7+x^3+x+1), then the CRC is (q*x^32) mod p,
95   where a mod b means the remainder after dividing a by b.
96 
97   This calculation is done using the shift-register method of multiplying and
98   taking the remainder.  The register is initialized to zero, and for each
99   incoming bit, x^32 is added mod p to the register if the bit is a one (where
100   x^32 mod p is p+x^32 = x^26+...+1), and the register is multiplied mod p by
101   x (which is shifting right by one and adding x^32 mod p if the bit shifted
102   out is a one).  We start with the highest power (least significant bit) of
103   q and repeat for all eight bits of q.
104 
105   The first table is simply the CRC of all possible eight bit values.  This is
106   all the information needed to generate CRCs on data a byte at a time for all
107   combinations of CRC register values and incoming bytes.  The remaining tables
108   allow for word-at-a-time CRC calculation for both big-endian and little-
109   endian machines, where a word is four bytes.
110 */
111 local void make_crc_table()
112 {
113     unsigned long c;
114     int n, k;
115     unsigned long poly;                 /* polynomial exclusive-or pattern */
116     /* terms of polynomial defining this crc (except x^32): */
117     static volatile int first = 1;      /* flag to limit concurrent making */
118     static const unsigned char p[] = {0,1,2,4,5,7,8,10,11,12,16,22,23,26};
119 
120     /* See if another task is already doing this (not thread-safe, but better
121        than nothing -- significantly reduces duration of vulnerability in
122        case the advice about DYNAMIC_CRC_TABLE is ignored) */
123     if (first) {
124         first = 0;
125 
126         /* make exclusive-or pattern from polynomial (0xedb88320UL) */
127         poly = 0UL;
128         for (n = 0; n < sizeof(p)/sizeof(unsigned char); n++)
129             poly |= 1UL << (31 - p[n]);
130 
131         /* generate a crc for every 8-bit value */
132         for (n = 0; n < 256; n++) {
133             c = (unsigned long)n;
134             for (k = 0; k < 8; k++)
135                 c = c & 1 ? poly ^ (c >> 1) : c >> 1;
136             crc_table[0][n] = c;
137         }
138 
139 #ifdef BYFOUR
140         /* generate crc for each value followed by one, two, and three zeros,
141            and then the byte reversal of those as well as the first table */
142         for (n = 0; n < 256; n++) {
143             c = crc_table[0][n];
144             crc_table[4][n] = REV(c);
145             for (k = 1; k < 4; k++) {
146                 c = crc_table[0][c & 0xff] ^ (c >> 8);
147                 crc_table[k][n] = c;
148                 crc_table[k + 4][n] = REV(c);
149             }
150         }
151 #endif /* BYFOUR */
152 
153         crc_table_empty = 0;
154     }
155     else {      /* not first */
156         /* wait for the other guy to finish (not efficient, but rare) */
157         while (crc_table_empty)
158             ;
159     }
160 
161 #ifdef MAKECRCH
162     /* write out CRC tables to crc32.h */
163     {
164         FILE *out;
165 
166         out = fopen("crc32.h", "w");
167         if (out == NULL) return;
168         fprintf(out, "/* crc32.h -- tables for rapid CRC calculation\n");
169         fprintf(out, " * Generated automatically by crc32.c\n */\n\n");
170         fprintf(out, "local const unsigned long FAR ");
171         fprintf(out, "crc_table[TBLS][256] =\n{\n  {\n");
172         write_table(out, crc_table[0]);
173 #  ifdef BYFOUR
174         fprintf(out, "#ifdef BYFOUR\n");
175         for (k = 1; k < 8; k++) {
176             fprintf(out, "  },\n  {\n");
177             write_table(out, crc_table[k]);
178         }
179         fprintf(out, "#endif\n");
180 #  endif /* BYFOUR */
181         fprintf(out, "  }\n};\n");
182         fclose(out);
183     }
184 #endif /* MAKECRCH */
185 }
186 
187 #ifdef MAKECRCH
188 local void write_table(out, table)
189     FILE *out;
190     const unsigned long FAR *table;
191 {
192     int n;
193 
194     for (n = 0; n < 256; n++)
195         fprintf(out, "%s0x%08lxUL%s", n % 5 ? "" : "    ", table[n],
196                 n == 255 ? "\n" : (n % 5 == 4 ? ",\n" : ", "));
197 }
198 #endif /* MAKECRCH */
199 
200 #else /* !DYNAMIC_CRC_TABLE */
201 /* ========================================================================
202  * Tables of CRC-32s of all single-byte values, made by make_crc_table().
203  */
204 #include "crc32.h"
205 #endif /* DYNAMIC_CRC_TABLE */
206 
207 /* =========================================================================
208  * This function can be used by asm versions of crc32()
209  */
210 const unsigned long FAR * ZEXPORT get_crc_table()
211 {
212 #ifdef DYNAMIC_CRC_TABLE
213     if (crc_table_empty)
214         make_crc_table();
215 #endif /* DYNAMIC_CRC_TABLE */
216     return (const unsigned long FAR *)crc_table;
217 }
218 
219 /* ========================================================================= */
220 #define DO1 crc = crc_table[0][((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8)
221 #define DO8 DO1; DO1; DO1; DO1; DO1; DO1; DO1; DO1
222 
223 /* ========================================================================= */
224 unsigned long ZEXPORT crc32(crc, buf, len)
225     unsigned long crc;
226     const unsigned char FAR *buf;
227     unsigned len;
228 {
229     if (buf == Z_NULL) return 0UL;
230 
231 #ifdef DYNAMIC_CRC_TABLE
232     if (crc_table_empty)
233         make_crc_table();
234 #endif /* DYNAMIC_CRC_TABLE */
235 
236 #ifdef BYFOUR
237     if (sizeof(void *) == sizeof(ptrdiff_t)) {
238         u4 endian;
239 
240         endian = 1;
241         if (*((unsigned char *)(&endian)))
242             return crc32_little(crc, buf, len);
243         else
244             return crc32_big(crc, buf, len);
245     }
246 #endif /* BYFOUR */
247     crc = crc ^ 0xffffffffUL;
248     while (len >= 8) {
249         DO8;
250         len -= 8;
251     }
252     if (len) do {
253         DO1;
254     } while (--len);
255     return crc ^ 0xffffffffUL;
256 }
257 
258 #ifdef BYFOUR
259 
260 /* ========================================================================= */
261 #define DOLIT4 c ^= *buf4++; \
262         c = crc_table[3][c & 0xff] ^ crc_table[2][(c >> 8) & 0xff] ^ \
263             crc_table[1][(c >> 16) & 0xff] ^ crc_table[0][c >> 24]
264 #define DOLIT32 DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4; DOLIT4
265 
266 /* ========================================================================= */
267 local unsigned long crc32_little(crc, buf, len)
268     unsigned long crc;
269     const unsigned char FAR *buf;
270     unsigned len;
271 {
272     register u4 c;
273     register const u4 FAR *buf4;
274 
275     c = (u4)crc;
276     c = ~c;
277     while (len && ((ptrdiff_t)buf & 3)) {
278         c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
279         len--;
280     }
281 
282     buf4 = (const u4 FAR *)(const void FAR *)buf;
283     while (len >= 32) {
284         DOLIT32;
285         len -= 32;
286     }
287     while (len >= 4) {
288         DOLIT4;
289         len -= 4;
290     }
291     buf = (const unsigned char FAR *)buf4;
292 
293     if (len) do {
294         c = crc_table[0][(c ^ *buf++) & 0xff] ^ (c >> 8);
295     } while (--len);
296     c = ~c;
297     return (unsigned long)c;
298 }
299 
300 /* ========================================================================= */
301 #define DOBIG4 c ^= *++buf4; \
302         c = crc_table[4][c & 0xff] ^ crc_table[5][(c >> 8) & 0xff] ^ \
303             crc_table[6][(c >> 16) & 0xff] ^ crc_table[7][c >> 24]
304 #define DOBIG32 DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4; DOBIG4
305 
306 /* ========================================================================= */
307 local unsigned long crc32_big(crc, buf, len)
308     unsigned long crc;
309     const unsigned char FAR *buf;
310     unsigned len;
311 {
312     register u4 c;
313     register const u4 FAR *buf4;
314 
315     c = REV((u4)crc);
316     c = ~c;
317     while (len && ((ptrdiff_t)buf & 3)) {
318         c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
319         len--;
320     }
321 
322     buf4 = (const u4 FAR *)(const void FAR *)buf;
323     buf4--;
324     while (len >= 32) {
325         DOBIG32;
326         len -= 32;
327     }
328     while (len >= 4) {
329         DOBIG4;
330         len -= 4;
331     }
332     buf4++;
333     buf = (const unsigned char FAR *)buf4;
334 
335     if (len) do {
336         c = crc_table[4][(c >> 24) ^ *buf++] ^ (c << 8);
337     } while (--len);
338     c = ~c;
339     return (unsigned long)(REV(c));
340 }
341 
342 #endif /* BYFOUR */
343 
344 #define GF2_DIM 32      /* dimension of GF(2) vectors (length of CRC) */
345 
346 /* ========================================================================= */
347 local unsigned long gf2_matrix_times(mat, vec)
348     unsigned long *mat;
349     unsigned long vec;
350 {
351     unsigned long sum;
352 
353     sum = 0;
354     while (vec) {
355         if (vec & 1)
356             sum ^= *mat;
357         vec >>= 1;
358         mat++;
359     }
360     return sum;
361 }
362 
363 /* ========================================================================= */
364 local void gf2_matrix_square(square, mat)
365     unsigned long *square;
366     unsigned long *mat;
367 {
368     int n;
369 
370     for (n = 0; n < GF2_DIM; n++)
371         square[n] = gf2_matrix_times(mat, mat[n]);
372 }
373 
374 /* ========================================================================= */
375 uLong ZEXPORT crc32_combine(crc1, crc2, len2)
376     uLong crc1;
377     uLong crc2;
378     z_off_t len2;
379 {
380     int n;
381     unsigned long row;
382     unsigned long even[GF2_DIM];    /* even-power-of-two zeros operator */
383     unsigned long odd[GF2_DIM];     /* odd-power-of-two zeros operator */
384 
385     /* degenerate case */
386     if (len2 == 0)
387         return crc1;
388 
389     /* put operator for one zero bit in odd */
390     odd[0] = 0xedb88320UL;          /* CRC-32 polynomial */
391     row = 1;
392     for (n = 1; n < GF2_DIM; n++) {
393         odd[n] = row;
394         row <<= 1;
395     }
396 
397     /* put operator for two zero bits in even */
398     gf2_matrix_square(even, odd);
399 
400     /* put operator for four zero bits in odd */
401     gf2_matrix_square(odd, even);
402 
403     /* apply len2 zeros to crc1 (first square will put the operator for one
404        zero byte, eight zero bits, in even) */
405     do {
406         /* apply zeros operator for this bit of len2 */
407         gf2_matrix_square(even, odd);
408         if (len2 & 1)
409             crc1 = gf2_matrix_times(even, crc1);
410         len2 >>= 1;
411 
412         /* if no more bits set, then done */
413         if (len2 == 0)
414             break;
415 
416         /* another iteration of the loop with odd and even swapped */
417         gf2_matrix_square(odd, even);
418         if (len2 & 1)
419             crc1 = gf2_matrix_times(odd, crc1);
420         len2 >>= 1;
421 
422         /* if no more bits set, then done */
423     } while (len2 != 0);
424 
425     /* return combined crc */
426     crc1 ^= crc2;
427     return crc1;
428 }
429