AppPkg/Applications/Python/Python-2.7.10: Initial Checkin part 2/5.

[mirror_edk2.git] / AppPkg / Applications / Python / Python-2.7.10 / Modules / zlib / adler32.c

/* adler32.c -- compute the Adler-32 checksum of a data stream\r
 * Copyright (C) 1995-2011 Mark Adler\r
 * For conditions of distribution and use, see copyright notice in zlib.h\r
 */\r
\r
/* @(#) $Id$ */\r
\r
#include "zutil.h"\r
\r
#define local static\r
\r
local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2));\r
\r
#define BASE 65521      /* largest prime smaller than 65536 */\r
#define NMAX 5552\r
/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */\r
\r
#define DO1(buf,i)  {adler += (buf)[i]; sum2 += adler;}\r
#define DO2(buf,i)  DO1(buf,i); DO1(buf,i+1);\r
#define DO4(buf,i)  DO2(buf,i); DO2(buf,i+2);\r
#define DO8(buf,i)  DO4(buf,i); DO4(buf,i+4);\r
#define DO16(buf)   DO8(buf,0); DO8(buf,8);\r
\r
/* use NO_DIVIDE if your processor does not do division in hardware --\r
   try it both ways to see which is faster */\r
#ifdef NO_DIVIDE\r
/* note that this assumes BASE is 65521, where 65536 % 65521 == 15\r
   (thank you to John Reiser for pointing this out) */\r
#  define CHOP(a) \\r
    do { \\r
        unsigned long tmp = a >> 16; \\r
        a &= 0xffffUL; \\r
        a += (tmp << 4) - tmp; \\r
    } while (0)\r
#  define MOD28(a) \\r
    do { \\r
        CHOP(a); \\r
        if (a >= BASE) a -= BASE; \\r
    } while (0)\r
#  define MOD(a) \\r
    do { \\r
        CHOP(a); \\r
        MOD28(a); \\r
    } while (0)\r
#  define MOD63(a) \\r
    do { /* this assumes a is not negative */ \\r
        z_off64_t tmp = a >> 32; \\r
        a &= 0xffffffffL; \\r
        a += (tmp << 8) - (tmp << 5) + tmp; \\r
        tmp = a >> 16; \\r
        a &= 0xffffL; \\r
        a += (tmp << 4) - tmp; \\r
        tmp = a >> 16; \\r
        a &= 0xffffL; \\r
        a += (tmp << 4) - tmp; \\r
        if (a >= BASE) a -= BASE; \\r
    } while (0)\r
#else\r
#  define MOD(a) a %= BASE\r
#  define MOD28(a) a %= BASE\r
#  define MOD63(a) a %= BASE\r
#endif\r
\r
/* ========================================================================= */\r
uLong ZEXPORT adler32(adler, buf, len)\r
    uLong adler;\r
    const Bytef *buf;\r
    uInt len;\r
{\r
    unsigned long sum2;\r
    unsigned n;\r
\r
    /* split Adler-32 into component sums */\r
    sum2 = (adler >> 16) & 0xffff;\r
    adler &= 0xffff;\r
\r
    /* in case user likes doing a byte at a time, keep it fast */\r
    if (len == 1) {\r
        adler += buf[0];\r
        if (adler >= BASE)\r
            adler -= BASE;\r
        sum2 += adler;\r
        if (sum2 >= BASE)\r
            sum2 -= BASE;\r
        return adler | (sum2 << 16);\r
    }\r
\r
    /* initial Adler-32 value (deferred check for len == 1 speed) */\r
    if (buf == Z_NULL)\r
        return 1L;\r
\r
    /* in case short lengths are provided, keep it somewhat fast */\r
    if (len < 16) {\r
        while (len--) {\r
            adler += *buf++;\r
            sum2 += adler;\r
        }\r
        if (adler >= BASE)\r
            adler -= BASE;\r
        MOD28(sum2);            /* only added so many BASE's */\r
        return adler | (sum2 << 16);\r
    }\r
\r
    /* do length NMAX blocks -- requires just one modulo operation */\r
    while (len >= NMAX) {\r
        len -= NMAX;\r
        n = NMAX / 16;          /* NMAX is divisible by 16 */\r
        do {\r
            DO16(buf);          /* 16 sums unrolled */\r
            buf += 16;\r
        } while (--n);\r
        MOD(adler);\r
        MOD(sum2);\r
    }\r
\r
    /* do remaining bytes (less than NMAX, still just one modulo) */\r
    if (len) {                  /* avoid modulos if none remaining */\r
        while (len >= 16) {\r
            len -= 16;\r
            DO16(buf);\r
            buf += 16;\r
        }\r
        while (len--) {\r
            adler += *buf++;\r
            sum2 += adler;\r
        }\r
        MOD(adler);\r
        MOD(sum2);\r
    }\r
\r
    /* return recombined sums */\r
    return adler | (sum2 << 16);\r
}\r
\r
/* ========================================================================= */\r
local uLong adler32_combine_(adler1, adler2, len2)\r
    uLong adler1;\r
    uLong adler2;\r
    z_off64_t len2;\r
{\r
    unsigned long sum1;\r
    unsigned long sum2;\r
    unsigned rem;\r
\r
    /* for negative len, return invalid adler32 as a clue for debugging */\r
    if (len2 < 0)\r
        return 0xffffffffUL;\r
\r
    /* the derivation of this formula is left as an exercise for the reader */\r
    MOD63(len2);                /* assumes len2 >= 0 */\r
    rem = (unsigned)len2;\r
    sum1 = adler1 & 0xffff;\r
    sum2 = rem * sum1;\r
    MOD(sum2);\r
    sum1 += (adler2 & 0xffff) + BASE - 1;\r
    sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;\r
    if (sum1 >= BASE) sum1 -= BASE;\r
    if (sum1 >= BASE) sum1 -= BASE;\r
    if (sum2 >= (BASE << 1)) sum2 -= (BASE << 1);\r
    if (sum2 >= BASE) sum2 -= BASE;\r
    return sum1 | (sum2 << 16);\r
}\r
\r
/* ========================================================================= */\r
uLong ZEXPORT adler32_combine(adler1, adler2, len2)\r
    uLong adler1;\r
    uLong adler2;\r
    z_off_t len2;\r
{\r
    return adler32_combine_(adler1, adler2, len2);\r
}\r
\r
uLong ZEXPORT adler32_combine64(adler1, adler2, len2)\r
    uLong adler1;\r
    uLong adler2;\r
    z_off64_t len2;\r
{\r
    return adler32_combine_(adler1, adler2, len2);\r
}\r