/* Portions Copyright (c) 2007-2009 Nokia Corporation and/or its subsidiary(-ies).

  * All rights reserved.

  */

 /* adler32.cpp -- compute the Adler-32 checksum of a data stream

  * Copyright (C) 1995-2004 Mark Adler

  * For conditions of distribution and use, see copyright notice in zlib.h

  */

 /* @(#) $Id$ */

 #define ZLIB_INTERNAL

 #include "libzcore.h"

 #define BASE 65521UL    /* 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 */

 #ifdef NO_DIVIDE

 #  define MOD(a) \

     do { \

         if (a >= (BASE << 16)) a -= (BASE << 16); \

         if (a >= (BASE << 15)) a -= (BASE << 15); \

         if (a >= (BASE << 14)) a -= (BASE << 14); \

         if (a >= (BASE << 13)) a -= (BASE << 13); \

         if (a >= (BASE << 12)) a -= (BASE << 12); \

         if (a >= (BASE << 11)) a -= (BASE << 11); \

         if (a >= (BASE << 10)) a -= (BASE << 10); \

         if (a >= (BASE << 9)) a -= (BASE << 9); \

         if (a >= (BASE << 8)) a -= (BASE << 8); \

         if (a >= (BASE << 7)) a -= (BASE << 7); \

         if (a >= (BASE << 6)) a -= (BASE << 6); \

         if (a >= (BASE << 5)) a -= (BASE << 5); \

         if (a >= (BASE << 4)) a -= (BASE << 4); \

         if (a >= (BASE << 3)) a -= (BASE << 3); \

         if (a >= (BASE << 2)) a -= (BASE << 2); \

         if (a >= (BASE << 1)) a -= (BASE << 1); \

         if (a >= BASE) a -= BASE; \

     } while (0)

 #  define MOD4(a) \

     do { \

         if (a >= (BASE << 4)) a -= (BASE << 4); \

         if (a >= (BASE << 3)) a -= (BASE << 3); \

         if (a >= (BASE << 2)) a -= (BASE << 2); \

         if (a >= (BASE << 1)) a -= (BASE << 1); \

         if (a >= BASE) a -= BASE; \

     } while (0)

 #else

 #  define MOD(a) a %= BASE

 #  define MOD4(a) a %= BASE

 #endif

 /* ========================================================================= */

 #ifdef __SYMBIAN32__

 EXPORT_C uLong  adler32_r(uLong adler,const Bytef *  buf,uInt len)

 #else

 uLong ZEXPORT adler32(adler, buf, len)

     uLong adler;

     const Bytef *buf;

     uInt len;

 #endif /* __SYMBIAN32__ */

 {

     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;

         MOD4(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);

 }

 /* ========================================================================= */

 #ifdef __SYMBIAN32__

 EXPORT_C uLong adler32_combine_r(uLong adler1, uLong adler2, z_off_t len2)

 #else

 uLong ZEXPORT adler32_combine(adler1, adler2, len2)

     uLong adler1;

     uLong adler2;

     z_off_t len2;

 #endif /* __SYMBIAN32__ */

 {

     unsigned long sum1;

     unsigned long sum2;

     unsigned rem;

     /* the derivation of this formula is left as an exercise for the reader */

     rem = (unsigned)(len2 % BASE);

     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);

 }