1 | /* |
2 | * Copyright (c) 2008-2016 Apple Inc. All rights reserved. |
3 | * |
4 | * @APPLE_OSREFERENCE_LICENSE_HEADER_START@ |
5 | * |
6 | * This file contains Original Code and/or Modifications of Original Code |
7 | * as defined in and that are subject to the Apple Public Source License |
8 | * Version 2.0 (the 'License'). You may not use this file except in |
9 | * compliance with the License. The rights granted to you under the License |
10 | * may not be used to create, or enable the creation or redistribution of, |
11 | * unlawful or unlicensed copies of an Apple operating system, or to |
12 | * circumvent, violate, or enable the circumvention or violation of, any |
13 | * terms of an Apple operating system software license agreement. |
14 | * |
15 | * Please obtain a copy of the License at |
16 | * http://www.opensource.apple.com/apsl/ and read it before using this file. |
17 | * |
18 | * The Original Code and all software distributed under the License are |
19 | * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER |
20 | * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, |
21 | * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, |
22 | * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. |
23 | * Please see the License for the specific language governing rights and |
24 | * limitations under the License. |
25 | * |
26 | * @APPLE_OSREFERENCE_LICENSE_HEADER_END@ |
27 | */ |
28 | /* adler32.c -- compute the Adler-32 checksum of a data stream |
29 | * Copyright (C) 1995-2004 Mark Adler |
30 | * For conditions of distribution and use, see copyright notice in zlib.h |
31 | */ |
32 | |
33 | /* @(#) $Id$ */ |
34 | |
35 | |
36 | #define ZLIB_INTERNAL |
37 | #if KERNEL |
38 | #include <libkern/zlib.h> |
39 | #else |
40 | #include "zlib.h" |
41 | #endif /* KERNEL */ |
42 | |
43 | |
44 | #define BASE 65521UL /* largest prime smaller than 65536 */ |
45 | #define NMAX 5552 |
46 | /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ |
47 | |
48 | #define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;} |
49 | #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1); |
50 | #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2); |
51 | #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); |
52 | #define DO16(buf) DO8(buf,0); DO8(buf,8); |
53 | |
54 | /* use NO_DIVIDE if your processor does not do division in hardware */ |
55 | #ifdef NO_DIVIDE |
56 | # define MOD(a) \ |
57 | do { \ |
58 | if (a >= (BASE << 16)) a -= (BASE << 16); \ |
59 | if (a >= (BASE << 15)) a -= (BASE << 15); \ |
60 | if (a >= (BASE << 14)) a -= (BASE << 14); \ |
61 | if (a >= (BASE << 13)) a -= (BASE << 13); \ |
62 | if (a >= (BASE << 12)) a -= (BASE << 12); \ |
63 | if (a >= (BASE << 11)) a -= (BASE << 11); \ |
64 | if (a >= (BASE << 10)) a -= (BASE << 10); \ |
65 | if (a >= (BASE << 9)) a -= (BASE << 9); \ |
66 | if (a >= (BASE << 8)) a -= (BASE << 8); \ |
67 | if (a >= (BASE << 7)) a -= (BASE << 7); \ |
68 | if (a >= (BASE << 6)) a -= (BASE << 6); \ |
69 | if (a >= (BASE << 5)) a -= (BASE << 5); \ |
70 | if (a >= (BASE << 4)) a -= (BASE << 4); \ |
71 | if (a >= (BASE << 3)) a -= (BASE << 3); \ |
72 | if (a >= (BASE << 2)) a -= (BASE << 2); \ |
73 | if (a >= (BASE << 1)) a -= (BASE << 1); \ |
74 | if (a >= BASE) a -= BASE; \ |
75 | } while (0) |
76 | # define MOD4(a) \ |
77 | do { \ |
78 | if (a >= (BASE << 4)) a -= (BASE << 4); \ |
79 | if (a >= (BASE << 3)) a -= (BASE << 3); \ |
80 | if (a >= (BASE << 2)) a -= (BASE << 2); \ |
81 | if (a >= (BASE << 1)) a -= (BASE << 1); \ |
82 | if (a >= BASE) a -= BASE; \ |
83 | } while (0) |
84 | #else |
85 | # define MOD(a) a %= BASE |
86 | # define MOD4(a) a %= BASE |
87 | #endif |
88 | |
89 | /* ========================================================================= */ |
90 | uLong ZEXPORT |
91 | adler32(uLong adler, const Bytef *buf, uInt len) |
92 | { |
93 | unsigned long sum2; |
94 | unsigned n; |
95 | |
96 | /* split Adler-32 into component sums */ |
97 | sum2 = (adler >> 16) & 0xffff; |
98 | adler &= 0xffff; |
99 | |
100 | /* in case user likes doing a byte at a time, keep it fast */ |
101 | if (len == 1) { |
102 | adler += buf[0]; |
103 | if (adler >= BASE) |
104 | adler -= BASE; |
105 | sum2 += adler; |
106 | if (sum2 >= BASE) |
107 | sum2 -= BASE; |
108 | return adler | (sum2 << 16); |
109 | } |
110 | |
111 | /* initial Adler-32 value (deferred check for len == 1 speed) */ |
112 | if (buf == Z_NULL) |
113 | return 1L; |
114 | |
115 | /* in case short lengths are provided, keep it somewhat fast */ |
116 | if (len < 16) { |
117 | while (len--) { |
118 | adler += *buf++; |
119 | sum2 += adler; |
120 | } |
121 | if (adler >= BASE) |
122 | adler -= BASE; |
123 | MOD4(sum2); /* only added so many BASE's */ |
124 | return adler | (sum2 << 16); |
125 | } |
126 | |
127 | |
128 | /* do length NMAX blocks -- requires just one modulo operation */ |
129 | while (len >= NMAX) { |
130 | len -= NMAX; |
131 | n = NMAX / 16; /* NMAX is divisible by 16 */ |
132 | do { |
133 | DO16(buf); /* 16 sums unrolled */ |
134 | buf += 16; |
135 | } while (--n); |
136 | MOD(adler); |
137 | MOD(sum2); |
138 | } |
139 | |
140 | /* do remaining bytes (less than NMAX, still just one modulo) */ |
141 | if (len) { /* avoid modulos if none remaining */ |
142 | while (len >= 16) { |
143 | len -= 16; |
144 | DO16(buf); |
145 | buf += 16; |
146 | } |
147 | while (len--) { |
148 | adler += *buf++; |
149 | sum2 += adler; |
150 | } |
151 | MOD(adler); |
152 | MOD(sum2); |
153 | } |
154 | |
155 | /* return recombined sums */ |
156 | return adler | (sum2 << 16); |
157 | } |
158 | |
159 | /* ========================================================================= */ |
160 | uLong ZEXPORT |
161 | adler32_combine(uLong adler1, uLong adler2, z_off_t len2) |
162 | { |
163 | unsigned long sum1; |
164 | unsigned long sum2; |
165 | unsigned rem; |
166 | |
167 | /* the derivation of this formula is left as an exercise for the reader */ |
168 | rem = (unsigned)(len2 % BASE); |
169 | sum1 = adler1 & 0xffff; |
170 | sum2 = rem * sum1; |
171 | MOD(sum2); |
172 | sum1 += (adler2 & 0xffff) + BASE - 1; |
173 | sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; |
174 | if (sum1 > BASE) sum1 -= BASE; |
175 | if (sum1 > BASE) sum1 -= BASE; |
176 | if (sum2 > (BASE << 1)) sum2 -= (BASE << 1); |
177 | if (sum2 > BASE) sum2 -= BASE; |
178 | return sum1 | (sum2 << 16); |
179 | } |
180 | |