| /* |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This code is free software; you can redistribute it and/or modify it |
| * under the terms of the GNU General Public License version 2 only, as |
| * published by the Free Software Foundation. Oracle designates this |
| * particular file as subject to the "Classpath" exception as provided |
| * by Oracle in the LICENSE file that accompanied this code. |
| * |
| * This code is distributed in the hope that it will be useful, but WITHOUT |
| * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
| * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
| * version 2 for more details (a copy is included in the LICENSE file that |
| * accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License version |
| * 2 along with this work; if not, write to the Free Software Foundation, |
| * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
| * |
| * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| */ |
| |
| /* adler32.c -- compute the Adler-32 checksum of a data stream |
| * Copyright (C) 1995-2011 Mark Adler |
| * For conditions of distribution and use, see copyright notice in zlib.h |
| */ |
| |
| /* @(#) $Id$ */ |
| |
| #include "zutil.h" |
| |
| #define local static |
| |
| local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2)); |
| |
| #define BASE 65521 /* largest prime smaller than 65536 */ |
| #define NMAX 5552 |
| /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ |
| |
| #define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;} |
| #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1); |
| #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2); |
| #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); |
| #define DO16(buf) DO8(buf,0); DO8(buf,8); |
| |
| /* use NO_DIVIDE if your processor does not do division in hardware -- |
| try it both ways to see which is faster */ |
| #ifdef NO_DIVIDE |
| /* note that this assumes BASE is 65521, where 65536 % 65521 == 15 |
| (thank you to John Reiser for pointing this out) */ |
| # define CHOP(a) \ |
| do { \ |
| unsigned long tmp = a >> 16; \ |
| a &= 0xffffUL; \ |
| a += (tmp << 4) - tmp; \ |
| } while (0) |
| # define MOD28(a) \ |
| do { \ |
| CHOP(a); \ |
| if (a >= BASE) a -= BASE; \ |
| } while (0) |
| # define MOD(a) \ |
| do { \ |
| CHOP(a); \ |
| MOD28(a); \ |
| } while (0) |
| # define MOD63(a) \ |
| do { /* this assumes a is not negative */ \ |
| z_off64_t tmp = a >> 32; \ |
| a &= 0xffffffffL; \ |
| a += (tmp << 8) - (tmp << 5) + tmp; \ |
| tmp = a >> 16; \ |
| a &= 0xffffL; \ |
| a += (tmp << 4) - tmp; \ |
| tmp = a >> 16; \ |
| a &= 0xffffL; \ |
| a += (tmp << 4) - tmp; \ |
| if (a >= BASE) a -= BASE; \ |
| } while (0) |
| #else |
| # define MOD(a) a %= BASE |
| # define MOD28(a) a %= BASE |
| # define MOD63(a) a %= BASE |
| #endif |
| |
| /* ========================================================================= */ |
| uLong ZEXPORT adler32(adler, buf, len) |
| uLong adler; |
| const Bytef *buf; |
| uInt len; |
| { |
| unsigned long sum2; |
| unsigned n; |
| |
| /* split Adler-32 into component sums */ |
| sum2 = (adler >> 16) & 0xffff; |
| adler &= 0xffff; |
| |
| /* in case user likes doing a byte at a time, keep it fast */ |
| if (len == 1) { |
| adler += buf[0]; |
| if (adler >= BASE) |
| adler -= BASE; |
| sum2 += adler; |
| if (sum2 >= BASE) |
| sum2 -= BASE; |
| return adler | (sum2 << 16); |
| } |
| |
| /* initial Adler-32 value (deferred check for len == 1 speed) */ |
| if (buf == Z_NULL) |
| return 1L; |
| |
| /* in case short lengths are provided, keep it somewhat fast */ |
| if (len < 16) { |
| while (len--) { |
| adler += *buf++; |
| sum2 += adler; |
| } |
| if (adler >= BASE) |
| adler -= BASE; |
| MOD28(sum2); /* only added so many BASE's */ |
| return adler | (sum2 << 16); |
| } |
| |
| /* do length NMAX blocks -- requires just one modulo operation */ |
| while (len >= NMAX) { |
| len -= NMAX; |
| n = NMAX / 16; /* NMAX is divisible by 16 */ |
| do { |
| DO16(buf); /* 16 sums unrolled */ |
| buf += 16; |
| } while (--n); |
| MOD(adler); |
| MOD(sum2); |
| } |
| |
| /* do remaining bytes (less than NMAX, still just one modulo) */ |
| if (len) { /* avoid modulos if none remaining */ |
| while (len >= 16) { |
| len -= 16; |
| DO16(buf); |
| buf += 16; |
| } |
| while (len--) { |
| adler += *buf++; |
| sum2 += adler; |
| } |
| MOD(adler); |
| MOD(sum2); |
| } |
| |
| /* return recombined sums */ |
| return adler | (sum2 << 16); |
| } |
| |
| /* ========================================================================= */ |
| local uLong adler32_combine_(adler1, adler2, len2) |
| uLong adler1; |
| uLong adler2; |
| z_off64_t len2; |
| { |
| unsigned long sum1; |
| unsigned long sum2; |
| unsigned rem; |
| |
| /* for negative len, return invalid adler32 as a clue for debugging */ |
| if (len2 < 0) |
| return 0xffffffffUL; |
| |
| /* the derivation of this formula is left as an exercise for the reader */ |
| MOD63(len2); /* assumes len2 >= 0 */ |
| rem = (unsigned)len2; |
| sum1 = adler1 & 0xffff; |
| sum2 = rem * sum1; |
| MOD(sum2); |
| sum1 += (adler2 & 0xffff) + BASE - 1; |
| sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; |
| if (sum1 >= BASE) sum1 -= BASE; |
| if (sum1 >= BASE) sum1 -= BASE; |
| if (sum2 >= (BASE << 1)) sum2 -= (BASE << 1); |
| if (sum2 >= BASE) sum2 -= BASE; |
| return sum1 | (sum2 << 16); |
| } |
| |
| /* ========================================================================= */ |
| uLong ZEXPORT adler32_combine(adler1, adler2, len2) |
| uLong adler1; |
| uLong adler2; |
| z_off_t len2; |
| { |
| return adler32_combine_(adler1, adler2, len2); |
| } |
| |
| uLong ZEXPORT adler32_combine64(adler1, adler2, len2) |
| uLong adler1; |
| uLong adler2; |
| z_off64_t len2; |
| { |
| return adler32_combine_(adler1, adler2, len2); |
| } |