1*b8382935SToomas Soome /* adler32.c -- compute the Adler-32 checksum of a data stream
2*b8382935SToomas Soome * Copyright (C) 1995-2011, 2016 Mark Adler
3*b8382935SToomas Soome * For conditions of distribution and use, see copyright notice in zlib.h
4*b8382935SToomas Soome */
5*b8382935SToomas Soome
6*b8382935SToomas Soome #include "zutil.h"
7*b8382935SToomas Soome
8*b8382935SToomas Soome local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2));
9*b8382935SToomas Soome
10*b8382935SToomas Soome #define BASE 65521U /* largest prime smaller than 65536 */
11*b8382935SToomas Soome #define NMAX 5552
12*b8382935SToomas Soome /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
13*b8382935SToomas Soome
14*b8382935SToomas Soome #define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;}
15*b8382935SToomas Soome #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
16*b8382935SToomas Soome #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
17*b8382935SToomas Soome #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
18*b8382935SToomas Soome #define DO16(buf) DO8(buf,0); DO8(buf,8);
19*b8382935SToomas Soome
20*b8382935SToomas Soome /* use NO_DIVIDE if your processor does not do division in hardware --
21*b8382935SToomas Soome try it both ways to see which is faster */
22*b8382935SToomas Soome #ifdef NO_DIVIDE
23*b8382935SToomas Soome /* note that this assumes BASE is 65521, where 65536 % 65521 == 15
24*b8382935SToomas Soome (thank you to John Reiser for pointing this out) */
25*b8382935SToomas Soome # define CHOP(a) \
26*b8382935SToomas Soome do { \
27*b8382935SToomas Soome unsigned long tmp = a >> 16; \
28*b8382935SToomas Soome a &= 0xffffUL; \
29*b8382935SToomas Soome a += (tmp << 4) - tmp; \
30*b8382935SToomas Soome } while (0)
31*b8382935SToomas Soome # define MOD28(a) \
32*b8382935SToomas Soome do { \
33*b8382935SToomas Soome CHOP(a); \
34*b8382935SToomas Soome if (a >= BASE) a -= BASE; \
35*b8382935SToomas Soome } while (0)
36*b8382935SToomas Soome # define MOD(a) \
37*b8382935SToomas Soome do { \
38*b8382935SToomas Soome CHOP(a); \
39*b8382935SToomas Soome MOD28(a); \
40*b8382935SToomas Soome } while (0)
41*b8382935SToomas Soome # define MOD63(a) \
42*b8382935SToomas Soome do { /* this assumes a is not negative */ \
43*b8382935SToomas Soome z_off64_t tmp = a >> 32; \
44*b8382935SToomas Soome a &= 0xffffffffL; \
45*b8382935SToomas Soome a += (tmp << 8) - (tmp << 5) + tmp; \
46*b8382935SToomas Soome tmp = a >> 16; \
47*b8382935SToomas Soome a &= 0xffffL; \
48*b8382935SToomas Soome a += (tmp << 4) - tmp; \
49*b8382935SToomas Soome tmp = a >> 16; \
50*b8382935SToomas Soome a &= 0xffffL; \
51*b8382935SToomas Soome a += (tmp << 4) - tmp; \
52*b8382935SToomas Soome if (a >= BASE) a -= BASE; \
53*b8382935SToomas Soome } while (0)
54*b8382935SToomas Soome #else
55*b8382935SToomas Soome # define MOD(a) a %= BASE
56*b8382935SToomas Soome # define MOD28(a) a %= BASE
57*b8382935SToomas Soome # define MOD63(a) a %= BASE
58*b8382935SToomas Soome #endif
59*b8382935SToomas Soome
60*b8382935SToomas Soome /* ========================================================================= */
adler32_z(uLong adler,const Bytef * buf,z_size_t len)61*b8382935SToomas Soome uLong ZEXPORT adler32_z(uLong adler, const Bytef *buf, z_size_t len)
62*b8382935SToomas Soome {
63*b8382935SToomas Soome unsigned long sum2;
64*b8382935SToomas Soome unsigned n;
65*b8382935SToomas Soome
66*b8382935SToomas Soome /* split Adler-32 into component sums */
67*b8382935SToomas Soome sum2 = (adler >> 16) & 0xffff;
68*b8382935SToomas Soome adler &= 0xffff;
69*b8382935SToomas Soome
70*b8382935SToomas Soome /* in case user likes doing a byte at a time, keep it fast */
71*b8382935SToomas Soome if (len == 1) {
72*b8382935SToomas Soome adler += buf[0];
73*b8382935SToomas Soome if (adler >= BASE)
74*b8382935SToomas Soome adler -= BASE;
75*b8382935SToomas Soome sum2 += adler;
76*b8382935SToomas Soome if (sum2 >= BASE)
77*b8382935SToomas Soome sum2 -= BASE;
78*b8382935SToomas Soome return adler | (sum2 << 16);
79*b8382935SToomas Soome }
80*b8382935SToomas Soome
81*b8382935SToomas Soome /* initial Adler-32 value (deferred check for len == 1 speed) */
82*b8382935SToomas Soome if (buf == Z_NULL)
83*b8382935SToomas Soome return 1L;
84*b8382935SToomas Soome
85*b8382935SToomas Soome /* in case short lengths are provided, keep it somewhat fast */
86*b8382935SToomas Soome if (len < 16) {
87*b8382935SToomas Soome while (len--) {
88*b8382935SToomas Soome adler += *buf++;
89*b8382935SToomas Soome sum2 += adler;
90*b8382935SToomas Soome }
91*b8382935SToomas Soome if (adler >= BASE)
92*b8382935SToomas Soome adler -= BASE;
93*b8382935SToomas Soome MOD28(sum2); /* only added so many BASE's */
94*b8382935SToomas Soome return adler | (sum2 << 16);
95*b8382935SToomas Soome }
96*b8382935SToomas Soome
97*b8382935SToomas Soome /* do length NMAX blocks -- requires just one modulo operation */
98*b8382935SToomas Soome while (len >= NMAX) {
99*b8382935SToomas Soome len -= NMAX;
100*b8382935SToomas Soome n = NMAX / 16; /* NMAX is divisible by 16 */
101*b8382935SToomas Soome do {
102*b8382935SToomas Soome DO16(buf); /* 16 sums unrolled */
103*b8382935SToomas Soome buf += 16;
104*b8382935SToomas Soome } while (--n);
105*b8382935SToomas Soome MOD(adler);
106*b8382935SToomas Soome MOD(sum2);
107*b8382935SToomas Soome }
108*b8382935SToomas Soome
109*b8382935SToomas Soome /* do remaining bytes (less than NMAX, still just one modulo) */
110*b8382935SToomas Soome if (len) { /* avoid modulos if none remaining */
111*b8382935SToomas Soome while (len >= 16) {
112*b8382935SToomas Soome len -= 16;
113*b8382935SToomas Soome DO16(buf);
114*b8382935SToomas Soome buf += 16;
115*b8382935SToomas Soome }
116*b8382935SToomas Soome while (len--) {
117*b8382935SToomas Soome adler += *buf++;
118*b8382935SToomas Soome sum2 += adler;
119*b8382935SToomas Soome }
120*b8382935SToomas Soome MOD(adler);
121*b8382935SToomas Soome MOD(sum2);
122*b8382935SToomas Soome }
123*b8382935SToomas Soome
124*b8382935SToomas Soome /* return recombined sums */
125*b8382935SToomas Soome return adler | (sum2 << 16);
126*b8382935SToomas Soome }
127*b8382935SToomas Soome
128*b8382935SToomas Soome /* ========================================================================= */
adler32(uLong adler,const Bytef * buf,uInt len)129*b8382935SToomas Soome uLong ZEXPORT adler32(uLong adler, const Bytef *buf, uInt len)
130*b8382935SToomas Soome {
131*b8382935SToomas Soome return adler32_z(adler, buf, len);
132*b8382935SToomas Soome }
133*b8382935SToomas Soome
134*b8382935SToomas Soome /* ========================================================================= */
adler32_combine_(uLong adler1,uLong adler2,z_off64_t len2)135*b8382935SToomas Soome local uLong adler32_combine_(uLong adler1, uLong adler2, z_off64_t len2)
136*b8382935SToomas Soome {
137*b8382935SToomas Soome unsigned long sum1;
138*b8382935SToomas Soome unsigned long sum2;
139*b8382935SToomas Soome unsigned rem;
140*b8382935SToomas Soome
141*b8382935SToomas Soome /* for negative len, return invalid adler32 as a clue for debugging */
142*b8382935SToomas Soome if (len2 < 0)
143*b8382935SToomas Soome return 0xffffffffUL;
144*b8382935SToomas Soome
145*b8382935SToomas Soome /* the derivation of this formula is left as an exercise for the reader */
146*b8382935SToomas Soome MOD63(len2); /* assumes len2 >= 0 */
147*b8382935SToomas Soome rem = (unsigned)len2;
148*b8382935SToomas Soome sum1 = adler1 & 0xffff;
149*b8382935SToomas Soome sum2 = rem * sum1;
150*b8382935SToomas Soome MOD(sum2);
151*b8382935SToomas Soome sum1 += (adler2 & 0xffff) + BASE - 1;
152*b8382935SToomas Soome sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;
153*b8382935SToomas Soome if (sum1 >= BASE) sum1 -= BASE;
154*b8382935SToomas Soome if (sum1 >= BASE) sum1 -= BASE;
155*b8382935SToomas Soome if (sum2 >= ((unsigned long)BASE << 1)) sum2 -= ((unsigned long)BASE << 1);
156*b8382935SToomas Soome if (sum2 >= BASE) sum2 -= BASE;
157*b8382935SToomas Soome return sum1 | (sum2 << 16);
158*b8382935SToomas Soome }
159*b8382935SToomas Soome
160*b8382935SToomas Soome /* ========================================================================= */
adler32_combine(uLong adler1,uLong adler2,z_off_t len2)161*b8382935SToomas Soome uLong ZEXPORT adler32_combine(uLong adler1, uLong adler2, z_off_t len2)
162*b8382935SToomas Soome {
163*b8382935SToomas Soome return adler32_combine_(adler1, adler2, len2);
164*b8382935SToomas Soome }
165*b8382935SToomas Soome
adler32_combine64(uLong adler1,uLong adler2,z_off64_t len2)166*b8382935SToomas Soome uLong ZEXPORT adler32_combine64(uLong adler1, uLong adler2, z_off64_t len2)
167*b8382935SToomas Soome {
168*b8382935SToomas Soome return adler32_combine_(adler1, adler2, len2);
169*b8382935SToomas Soome }
170