Mercurial > projects > hoofbaby
comparison deps/Platinum/ThirdParty/Neptune/ThirdParty/zlib-1.2.3/adler32.c @ 0:3425707ddbf6
Initial import (hopefully this mercurial stuff works...)
author | fraserofthenight |
---|---|
date | Mon, 06 Jul 2009 08:06:28 -0700 |
parents | |
children |
comparison
equal
deleted
inserted
replaced
-1:000000000000 | 0:3425707ddbf6 |
---|---|
1 /* adler32.c -- compute the Adler-32 checksum of a data stream | |
2 * Copyright (C) 1995-2004 Mark Adler | |
3 * For conditions of distribution and use, see copyright notice in zlib.h | |
4 */ | |
5 | |
6 /* @(#) $Id: adler32.c 87 2008-08-15 19:03:36Z bok $ */ | |
7 | |
8 #define ZLIB_INTERNAL | |
9 #include "zlib.h" | |
10 | |
11 #define BASE 65521UL /* largest prime smaller than 65536 */ | |
12 #define NMAX 5552 | |
13 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ | |
14 | |
15 #define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;} | |
16 #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1); | |
17 #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2); | |
18 #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); | |
19 #define DO16(buf) DO8(buf,0); DO8(buf,8); | |
20 | |
21 /* use NO_DIVIDE if your processor does not do division in hardware */ | |
22 #ifdef NO_DIVIDE | |
23 # define MOD(a) \ | |
24 do { \ | |
25 if (a >= (BASE << 16)) a -= (BASE << 16); \ | |
26 if (a >= (BASE << 15)) a -= (BASE << 15); \ | |
27 if (a >= (BASE << 14)) a -= (BASE << 14); \ | |
28 if (a >= (BASE << 13)) a -= (BASE << 13); \ | |
29 if (a >= (BASE << 12)) a -= (BASE << 12); \ | |
30 if (a >= (BASE << 11)) a -= (BASE << 11); \ | |
31 if (a >= (BASE << 10)) a -= (BASE << 10); \ | |
32 if (a >= (BASE << 9)) a -= (BASE << 9); \ | |
33 if (a >= (BASE << 8)) a -= (BASE << 8); \ | |
34 if (a >= (BASE << 7)) a -= (BASE << 7); \ | |
35 if (a >= (BASE << 6)) a -= (BASE << 6); \ | |
36 if (a >= (BASE << 5)) a -= (BASE << 5); \ | |
37 if (a >= (BASE << 4)) a -= (BASE << 4); \ | |
38 if (a >= (BASE << 3)) a -= (BASE << 3); \ | |
39 if (a >= (BASE << 2)) a -= (BASE << 2); \ | |
40 if (a >= (BASE << 1)) a -= (BASE << 1); \ | |
41 if (a >= BASE) a -= BASE; \ | |
42 } while (0) | |
43 # define MOD4(a) \ | |
44 do { \ | |
45 if (a >= (BASE << 4)) a -= (BASE << 4); \ | |
46 if (a >= (BASE << 3)) a -= (BASE << 3); \ | |
47 if (a >= (BASE << 2)) a -= (BASE << 2); \ | |
48 if (a >= (BASE << 1)) a -= (BASE << 1); \ | |
49 if (a >= BASE) a -= BASE; \ | |
50 } while (0) | |
51 #else | |
52 # define MOD(a) a %= BASE | |
53 # define MOD4(a) a %= BASE | |
54 #endif | |
55 | |
56 /* ========================================================================= */ | |
57 uLong ZEXPORT adler32(adler, buf, len) | |
58 uLong adler; | |
59 const Bytef *buf; | |
60 uInt len; | |
61 { | |
62 unsigned long sum2; | |
63 unsigned n; | |
64 | |
65 /* split Adler-32 into component sums */ | |
66 sum2 = (adler >> 16) & 0xffff; | |
67 adler &= 0xffff; | |
68 | |
69 /* in case user likes doing a byte at a time, keep it fast */ | |
70 if (len == 1) { | |
71 adler += buf[0]; | |
72 if (adler >= BASE) | |
73 adler -= BASE; | |
74 sum2 += adler; | |
75 if (sum2 >= BASE) | |
76 sum2 -= BASE; | |
77 return adler | (sum2 << 16); | |
78 } | |
79 | |
80 /* initial Adler-32 value (deferred check for len == 1 speed) */ | |
81 if (buf == Z_NULL) | |
82 return 1L; | |
83 | |
84 /* in case short lengths are provided, keep it somewhat fast */ | |
85 if (len < 16) { | |
86 while (len--) { | |
87 adler += *buf++; | |
88 sum2 += adler; | |
89 } | |
90 if (adler >= BASE) | |
91 adler -= BASE; | |
92 MOD4(sum2); /* only added so many BASE's */ | |
93 return adler | (sum2 << 16); | |
94 } | |
95 | |
96 /* do length NMAX blocks -- requires just one modulo operation */ | |
97 while (len >= NMAX) { | |
98 len -= NMAX; | |
99 n = NMAX / 16; /* NMAX is divisible by 16 */ | |
100 do { | |
101 DO16(buf); /* 16 sums unrolled */ | |
102 buf += 16; | |
103 } while (--n); | |
104 MOD(adler); | |
105 MOD(sum2); | |
106 } | |
107 | |
108 /* do remaining bytes (less than NMAX, still just one modulo) */ | |
109 if (len) { /* avoid modulos if none remaining */ | |
110 while (len >= 16) { | |
111 len -= 16; | |
112 DO16(buf); | |
113 buf += 16; | |
114 } | |
115 while (len--) { | |
116 adler += *buf++; | |
117 sum2 += adler; | |
118 } | |
119 MOD(adler); | |
120 MOD(sum2); | |
121 } | |
122 | |
123 /* return recombined sums */ | |
124 return adler | (sum2 << 16); | |
125 } | |
126 | |
127 /* ========================================================================= */ | |
128 uLong ZEXPORT adler32_combine(adler1, adler2, len2) | |
129 uLong adler1; | |
130 uLong adler2; | |
131 z_off_t len2; | |
132 { | |
133 unsigned long sum1; | |
134 unsigned long sum2; | |
135 unsigned rem; | |
136 | |
137 /* the derivation of this formula is left as an exercise for the reader */ | |
138 rem = (unsigned)(len2 % BASE); | |
139 sum1 = adler1 & 0xffff; | |
140 sum2 = rem * sum1; | |
141 MOD(sum2); | |
142 sum1 += (adler2 & 0xffff) + BASE - 1; | |
143 sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; | |
144 if (sum1 > BASE) sum1 -= BASE; | |
145 if (sum1 > BASE) sum1 -= BASE; | |
146 if (sum2 > (BASE << 1)) sum2 -= (BASE << 1); | |
147 if (sum2 > BASE) sum2 -= BASE; | |
148 return sum1 | (sum2 << 16); | |
149 } |