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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 |
6 /* @(#) $Id$ */ | 6 /* @(#) $Id$ */ |
7 | 7 |
8 #include "zutil.h" | 8 #include "zutil.h" |
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 |
18 #define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;} | 18 #define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;} |
19 #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1); | 19 #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1); |
20 #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2); | 20 #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2); |
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 |
| 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) \ |
| 36 do { \ |
| 37 CHOP(a); \ |
| 38 if (a >= BASE) a -= BASE; \ |
| 39 } while (0) |
26 # define MOD(a) \ | 40 # define MOD(a) \ |
27 do { \ | 41 do { \ |
28 if (a >= (BASE << 16)) a -= (BASE << 16); \ | 42 CHOP(a); \ |
29 if (a >= (BASE << 15)) a -= (BASE << 15); \ | 43 MOD28(a); \ |
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; \ | |
45 } while (0) | 44 } while (0) |
46 # define MOD4(a) \ | 45 # define MOD63(a) \ |
47 do { \ | 46 do { /* this assumes a is not negative */ \ |
48 if (a >= (BASE << 4)) a -= (BASE << 4); \ | 47 z_off64_t tmp = a >> 32; \ |
49 if (a >= (BASE << 3)) a -= (BASE << 3); \ | 48 a &= 0xffffffffL; \ |
50 if (a >= (BASE << 2)) a -= (BASE << 2); \ | 49 a += (tmp << 8) - (tmp << 5) + tmp; \ |
51 if (a >= (BASE << 1)) a -= (BASE << 1); \ | 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 /* ========================================================================= */ |
60 uLong ZEXPORT adler32(adler, buf, len) | 65 uLong ZEXPORT adler32(adler, buf, len) |
61 uLong adler; | 66 uLong adler; |
62 const Bytef *buf; | 67 const Bytef *buf; |
63 uInt len; | 68 uInt len; |
64 { | 69 { |
65 unsigned long sum2; | 70 unsigned long sum2; |
66 unsigned n; | 71 unsigned n; |
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85 return 1L; | 90 return 1L; |
86 | 91 |
87 /* in case short lengths are provided, keep it somewhat fast */ | 92 /* in case short lengths are provided, keep it somewhat fast */ |
88 if (len < 16) { | 93 if (len < 16) { |
89 while (len--) { | 94 while (len--) { |
90 adler += *buf++; | 95 adler += *buf++; |
91 sum2 += adler; | 96 sum2 += adler; |
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 |
99 /* do length NMAX blocks -- requires just one modulo operation */ | 104 /* do length NMAX blocks -- requires just one modulo operation */ |
100 while (len >= NMAX) { | 105 while (len >= NMAX) { |
101 len -= NMAX; | 106 len -= NMAX; |
102 n = NMAX / 16; /* NMAX is divisible by 16 */ | 107 n = NMAX / 16; /* NMAX is divisible by 16 */ |
103 do { | 108 do { |
104 DO16(buf); /* 16 sums unrolled */ | 109 DO16(buf); /* 16 sums unrolled */ |
105 buf += 16; | 110 buf += 16; |
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130 /* ========================================================================= */ | 135 /* ========================================================================= */ |
131 local uLong adler32_combine_(adler1, adler2, len2) | 136 local uLong adler32_combine_(adler1, adler2, len2) |
132 uLong adler1; | 137 uLong adler1; |
133 uLong adler2; | 138 uLong adler2; |
134 z_off64_t len2; | 139 z_off64_t len2; |
135 { | 140 { |
136 unsigned long sum1; | 141 unsigned long sum1; |
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); |
145 sum1 += (adler2 & 0xffff) + BASE - 1; | 155 sum1 += (adler2 & 0xffff) + BASE - 1; |
146 sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; | 156 sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; |
147 if (sum1 >= BASE) sum1 -= BASE; | 157 if (sum1 >= BASE) sum1 -= BASE; |
148 if (sum1 >= BASE) sum1 -= BASE; | 158 if (sum1 >= BASE) sum1 -= BASE; |
149 if (sum2 >= (BASE << 1)) sum2 -= (BASE << 1); | 159 if (sum2 >= (BASE << 1)) sum2 -= (BASE << 1); |
150 if (sum2 >= BASE) sum2 -= BASE; | 160 if (sum2 >= BASE) sum2 -= BASE; |
151 return sum1 | (sum2 << 16); | 161 return sum1 | (sum2 << 16); |
152 } | 162 } |
153 | 163 |
154 /* ========================================================================= */ | 164 /* ========================================================================= */ |
155 uLong ZEXPORT adler32_combine(adler1, adler2, len2) | 165 uLong ZEXPORT adler32_combine(adler1, adler2, len2) |
156 uLong adler1; | 166 uLong adler1; |
157 uLong adler2; | 167 uLong adler2; |
158 z_off_t len2; | 168 z_off_t len2; |
159 { | 169 { |
160 return adler32_combine_(adler1, adler2, len2); | 170 return adler32_combine_(adler1, adler2, len2); |
161 } | 171 } |
162 | 172 |
163 uLong ZEXPORT adler32_combine64(adler1, adler2, len2) | 173 uLong ZEXPORT adler32_combine64(adler1, adler2, len2) |
164 uLong adler1; | 174 uLong adler1; |
165 uLong adler2; | 175 uLong adler2; |
166 z_off64_t len2; | 176 z_off64_t len2; |
167 { | 177 { |
168 return adler32_combine_(adler1, adler2, len2); | 178 return adler32_combine_(adler1, adler2, len2); |
169 } | 179 } |
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