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author | Mark Adler <madler@alumni.caltech.edu> | 2011-09-11 11:04:49 -0700 |
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committer | Mark Adler <madler@alumni.caltech.edu> | 2011-09-11 11:04:49 -0700 |
commit | 10daf0d4d7815447799d555d04d30325836e1d44 (patch) | |
tree | 75579fbe11e42dc3197acca53f5f887ac3808b57 /adler32.c | |
parent | 9712272c78b9d9c93746d9c8e156a3728c65ca72 (diff) | |
download | zlib-10daf0d4d7815447799d555d04d30325836e1d44.tar.gz zlib-10daf0d4d7815447799d555d04d30325836e1d44.tar.bz2 zlib-10daf0d4d7815447799d555d04d30325836e1d44.zip |
zlib 1.2.5.1v1.2.5.1
Diffstat (limited to 'adler32.c')
-rw-r--r-- | adler32.c | 68 |
1 files changed, 39 insertions, 29 deletions
@@ -1,5 +1,5 @@ | |||
1 | /* adler32.c -- compute the Adler-32 checksum of a data stream | 1 | /* adler32.c -- compute the Adler-32 checksum of a data stream |
2 | * Copyright (C) 1995-2007 Mark Adler | 2 | * Copyright (C) 1995-2011 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 | 5 | ||
@@ -9,9 +9,9 @@ | |||
9 | 9 | ||
10 | #define local static | 10 | #define local static |
11 | 11 | ||
12 | local uLong adler32_combine_(uLong adler1, uLong adler2, z_off64_t len2); | 12 | local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2)); |
13 | 13 | ||
14 | #define BASE 65521UL /* largest prime smaller than 65536 */ | 14 | #define BASE 65521 /* largest prime smaller than 65536 */ |
15 | #define NMAX 5552 | 15 | #define NMAX 5552 |
16 | /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ | 16 | /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ |
17 | 17 | ||
@@ -21,39 +21,44 @@ local uLong adler32_combine_(uLong adler1, uLong adler2, z_off64_t len2); | |||
21 | #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); | 21 | #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); |
22 | #define DO16(buf) DO8(buf,0); DO8(buf,8); | 22 | #define DO16(buf) DO8(buf,0); DO8(buf,8); |
23 | 23 | ||
24 | /* use NO_DIVIDE if your processor does not do division in hardware */ | 24 | /* use NO_DIVIDE if your processor does not do division in hardware -- |
25 | try it both ways to see which is faster */ | ||
25 | #ifdef NO_DIVIDE | 26 | #ifdef NO_DIVIDE |
26 | # define MOD(a) \ | 27 | /* note that this assumes BASE is 65521, where 65536 % 65521 == 15 |
28 | (thank you to John Reiser for pointing this out) */ | ||
29 | # define CHOP(a) \ | ||
30 | do { \ | ||
31 | unsigned long tmp = a >> 16; \ | ||
32 | a &= 0xffffUL; \ | ||
33 | a += (tmp << 4) - tmp; \ | ||
34 | } while (0) | ||
35 | # define MOD28(a) \ | ||
27 | do { \ | 36 | do { \ |
28 | if (a >= (BASE << 16)) a -= (BASE << 16); \ | 37 | CHOP(a); \ |
29 | if (a >= (BASE << 15)) a -= (BASE << 15); \ | ||
30 | if (a >= (BASE << 14)) a -= (BASE << 14); \ | ||
31 | if (a >= (BASE << 13)) a -= (BASE << 13); \ | ||
32 | if (a >= (BASE << 12)) a -= (BASE << 12); \ | ||
33 | if (a >= (BASE << 11)) a -= (BASE << 11); \ | ||
34 | if (a >= (BASE << 10)) a -= (BASE << 10); \ | ||
35 | if (a >= (BASE << 9)) a -= (BASE << 9); \ | ||
36 | if (a >= (BASE << 8)) a -= (BASE << 8); \ | ||
37 | if (a >= (BASE << 7)) a -= (BASE << 7); \ | ||
38 | if (a >= (BASE << 6)) a -= (BASE << 6); \ | ||
39 | if (a >= (BASE << 5)) a -= (BASE << 5); \ | ||
40 | if (a >= (BASE << 4)) a -= (BASE << 4); \ | ||
41 | if (a >= (BASE << 3)) a -= (BASE << 3); \ | ||
42 | if (a >= (BASE << 2)) a -= (BASE << 2); \ | ||
43 | if (a >= (BASE << 1)) a -= (BASE << 1); \ | ||
44 | if (a >= BASE) a -= BASE; \ | 38 | if (a >= BASE) a -= BASE; \ |
45 | } while (0) | 39 | } while (0) |
46 | # define MOD4(a) \ | 40 | # define MOD(a) \ |
47 | do { \ | 41 | do { \ |
48 | if (a >= (BASE << 4)) a -= (BASE << 4); \ | 42 | CHOP(a); \ |
49 | if (a >= (BASE << 3)) a -= (BASE << 3); \ | 43 | MOD28(a); \ |
50 | if (a >= (BASE << 2)) a -= (BASE << 2); \ | 44 | } while (0) |
51 | if (a >= (BASE << 1)) a -= (BASE << 1); \ | 45 | # define MOD63(a) \ |
46 | do { /* this assumes a is not negative */ \ | ||
47 | z_off64_t tmp = a >> 32; \ | ||
48 | a &= 0xffffffffL; \ | ||
49 | a += (tmp << 8) - (tmp << 5) + tmp; \ | ||
50 | tmp = a >> 16; \ | ||
51 | a &= 0xffffL; \ | ||
52 | a += (tmp << 4) - tmp; \ | ||
53 | tmp = a >> 16; \ | ||
54 | a &= 0xffffL; \ | ||
55 | a += (tmp << 4) - tmp; \ | ||
52 | if (a >= BASE) a -= BASE; \ | 56 | if (a >= BASE) a -= BASE; \ |
53 | } while (0) | 57 | } while (0) |
54 | #else | 58 | #else |
55 | # define MOD(a) a %= BASE | 59 | # define MOD(a) a %= BASE |
56 | # define MOD4(a) a %= BASE | 60 | # define MOD28(a) a %= BASE |
61 | # define MOD63(a) a %= BASE | ||
57 | #endif | 62 | #endif |
58 | 63 | ||
59 | /* ========================================================================= */ | 64 | /* ========================================================================= */ |
@@ -92,7 +97,7 @@ uLong ZEXPORT adler32(adler, buf, len) | |||
92 | } | 97 | } |
93 | if (adler >= BASE) | 98 | if (adler >= BASE) |
94 | adler -= BASE; | 99 | adler -= BASE; |
95 | MOD4(sum2); /* only added so many BASE's */ | 100 | MOD28(sum2); /* only added so many BASE's */ |
96 | return adler | (sum2 << 16); | 101 | return adler | (sum2 << 16); |
97 | } | 102 | } |
98 | 103 | ||
@@ -137,8 +142,13 @@ local uLong adler32_combine_(adler1, adler2, len2) | |||
137 | unsigned long sum2; | 142 | unsigned long sum2; |
138 | unsigned rem; | 143 | unsigned rem; |
139 | 144 | ||
145 | /* for negative len, return invalid adler32 as a clue for debugging */ | ||
146 | if (len2 < 0) | ||
147 | return 0xffffffffUL; | ||
148 | |||
140 | /* the derivation of this formula is left as an exercise for the reader */ | 149 | /* the derivation of this formula is left as an exercise for the reader */ |
141 | rem = (unsigned)(len2 % BASE); | 150 | MOD63(len2); /* assumes len2 >= 0 */ |
151 | rem = (unsigned)len2; | ||
142 | sum1 = adler1 & 0xffff; | 152 | sum1 = adler1 & 0xffff; |
143 | sum2 = rem * sum1; | 153 | sum2 = rem * sum1; |
144 | MOD(sum2); | 154 | MOD(sum2); |