vfs_glusterfs: Implement AIO support
[Samba.git] / lib / zlib / adler32.c
blobb5333d7b8e39047fb6c23e721653de1226dca556
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 */
6 /* @(#) $Id$ */
8 #include "zutil.h"
10 #define BASE 65521UL /* largest prime smaller than 65536 */
11 #define NMAX 5552
12 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
14 #define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;}
15 #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
16 #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
17 #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
18 #define DO16(buf) DO8(buf,0); DO8(buf,8);
20 /* use NO_DIVIDE if your processor does not do division in hardware */
21 #ifdef NO_DIVIDE
22 # define MOD(a) \
23 do { \
24 if (a >= (BASE << 16)) a -= (BASE << 16); \
25 if (a >= (BASE << 15)) a -= (BASE << 15); \
26 if (a >= (BASE << 14)) a -= (BASE << 14); \
27 if (a >= (BASE << 13)) a -= (BASE << 13); \
28 if (a >= (BASE << 12)) a -= (BASE << 12); \
29 if (a >= (BASE << 11)) a -= (BASE << 11); \
30 if (a >= (BASE << 10)) a -= (BASE << 10); \
31 if (a >= (BASE << 9)) a -= (BASE << 9); \
32 if (a >= (BASE << 8)) a -= (BASE << 8); \
33 if (a >= (BASE << 7)) a -= (BASE << 7); \
34 if (a >= (BASE << 6)) a -= (BASE << 6); \
35 if (a >= (BASE << 5)) a -= (BASE << 5); \
36 if (a >= (BASE << 4)) a -= (BASE << 4); \
37 if (a >= (BASE << 3)) a -= (BASE << 3); \
38 if (a >= (BASE << 2)) a -= (BASE << 2); \
39 if (a >= (BASE << 1)) a -= (BASE << 1); \
40 if (a >= BASE) a -= BASE; \
41 } while (0)
42 # define MOD4(a) \
43 do { \
44 if (a >= (BASE << 4)) a -= (BASE << 4); \
45 if (a >= (BASE << 3)) a -= (BASE << 3); \
46 if (a >= (BASE << 2)) a -= (BASE << 2); \
47 if (a >= (BASE << 1)) a -= (BASE << 1); \
48 if (a >= BASE) a -= BASE; \
49 } while (0)
50 #else
51 # define MOD(a) a %= BASE
52 # define MOD4(a) a %= BASE
53 #endif
55 /* ========================================================================= */
56 uLong ZEXPORT adler32(adler, buf, len)
57 uLong adler;
58 const Bytef *buf;
59 uInt len;
61 unsigned long sum2;
62 unsigned n;
64 /* split Adler-32 into component sums */
65 sum2 = (adler >> 16) & 0xffff;
66 adler &= 0xffff;
68 /* in case user likes doing a byte at a time, keep it fast */
69 if (len == 1) {
70 adler += buf[0];
71 if (adler >= BASE)
72 adler -= BASE;
73 sum2 += adler;
74 if (sum2 >= BASE)
75 sum2 -= BASE;
76 return adler | (sum2 << 16);
79 /* initial Adler-32 value (deferred check for len == 1 speed) */
80 if (buf == Z_NULL)
81 return 1L;
83 /* in case short lengths are provided, keep it somewhat fast */
84 if (len < 16) {
85 while (len--) {
86 adler += *buf++;
87 sum2 += adler;
89 if (adler >= BASE)
90 adler -= BASE;
91 MOD4(sum2); /* only added so many BASE's */
92 return adler | (sum2 << 16);
95 /* do length NMAX blocks -- requires just one modulo operation */
96 while (len >= NMAX) {
97 len -= NMAX;
98 n = NMAX / 16; /* NMAX is divisible by 16 */
99 do {
100 DO16(buf); /* 16 sums unrolled */
101 buf += 16;
102 } while (--n);
103 MOD(adler);
104 MOD(sum2);
107 /* do remaining bytes (less than NMAX, still just one modulo) */
108 if (len) { /* avoid modulos if none remaining */
109 while (len >= 16) {
110 len -= 16;
111 DO16(buf);
112 buf += 16;
114 while (len--) {
115 adler += *buf++;
116 sum2 += adler;
118 MOD(adler);
119 MOD(sum2);
122 /* return recombined sums */
123 return adler | (sum2 << 16);
126 /* ========================================================================= */
127 uLong ZEXPORT adler32_combine(adler1, adler2, len2)
128 uLong adler1;
129 uLong adler2;
130 z_off_t len2;
132 unsigned long sum1;
133 unsigned long sum2;
134 unsigned rem;
136 /* the derivation of this formula is left as an exercise for the reader */
137 rem = (unsigned)(len2 % BASE);
138 sum1 = adler1 & 0xffff;
139 sum2 = rem * sum1;
140 MOD(sum2);
141 sum1 += (adler2 & 0xffff) + BASE - 1;
142 sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;
143 if (sum1 > BASE) sum1 -= BASE;
144 if (sum1 > BASE) sum1 -= BASE;
145 if (sum2 > (BASE << 1)) sum2 -= (BASE << 1);
146 if (sum2 > BASE) sum2 -= BASE;
147 return sum1 | (sum2 << 16);