/*

clsync - file tree sync utility based on inotify/kqueue

Copyright (C) 2014 Dmitry Yu Okunev <[email protected]> 0x8E30679C

This program is free software: you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation, either version 3 of the License, or

(at your option) any later version.

This program 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 for more details.

You should have received a copy of the GNU General Public License

along with this program. If not, see <http://www.gnu.org/licenses/>.

*/

#include "common.h"

#include "calc.h"

#include "error.h"

#ifdef HAVE_MHASH

#include <mhash.h>

#endif

#ifndef HAVE_MHASH

/**

* @brief Calculated Adler32 value for char array

*

* @param[in] data Pointer to data

* @param[in] len Length of the data

*

* @retval uint32_t Adler32 value of data

*

*/

// Copied from http://en.wikipedia.org/wiki/Adler-32

uint32_t adler32_calc ( const unsigned char *const data, uint32_t len ) // where data is the location of the data in physical

{

// memory and len is the length of the data in bytes

/*

if (len&3)

warning("len [%i] & 3 == %i != 0. Wrong length (not a multiple of 4).", len, len&3);

*/

debug ( 70, "%p, %i", data, len );

const int MOD_ADLER = 65521;

uint32_t a = 1, b = 0;

uint32_t index;

// Process each byte of the data in order

for ( index = 0; index < len; ++index ) {

debug ( 80, "%5i: %02x %02x %02x", index, data[index], a, b );

a = ( a + data[index] ) % MOD_ADLER;

b = ( b + a ) % MOD_ADLER;

}

return ( b << 16 ) | a;

}

#endif