sample11.c

/*
 * Copyright (c) 2010, Paul Hsieh (superfasthash)
 *
 * All rights reserved.  Redistribution and use in source and binary forms,
 * with or without modification, are permitted provided that the following
 * conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * 3. Neither my name, Paul Hsieh, nor the names of any other contributors to
 *    the code use may not be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
 * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 */

#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>

uint32_t hash(const char * data, int len);
uint32_t hash_inc(const char * data, int len, uint32_t hash);

#undef get16bits
#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
    || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
#define get16bits(d) (*((const uint16_t *) (d)))
#endif

#if !defined (get16bits)
#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
        +(uint32_t)(((const uint8_t *)(d))[0]) )
#endif

uint32_t hash(const char * data, int len)
{
    return hash_inc(data, len, (uint32_t) len);
}

uint32_t hash_inc(const char * data, int len, uint32_t hash)
{
    uint32_t tmp;
    int rem;

    if (len <= 0 || data == NULL) return 0;

    rem = len & 3;
    len >>= 2;

    /* Main loop */
    for (;len > 0; len--) {
        hash  += get16bits (data);
        tmp    = (get16bits (data+2) << 11) ^ hash;
        hash   = (hash << 16) ^ tmp;
        data  += 2*sizeof (uint16_t);
        hash  += hash >> 11;
    }

    /* Handle end cases */
    switch (rem) {
        case 3: hash += get16bits (data);
                hash ^= hash << 16;
                hash ^= data[sizeof (uint16_t)] << 18;
                hash += hash >> 11;
                break;
        case 2: hash += get16bits (data);
                hash ^= hash << 11;
                hash += hash >> 17;
                break;
        case 1: hash += *data;
                hash ^= hash << 10;
                hash += hash >> 1;
    }

    /* Force "avalanching" of final 127 bits */
    hash ^= hash << 3;
    hash += hash >> 5;
    hash ^= hash << 4;
    hash += hash >> 17;
    hash ^= hash << 25;
    hash += hash >> 6;

    return hash;
}


uint32_t SECRET(unsigned long input) {
  return hash((const char*)&input, sizeof(input));
}

int main(int argc, char **argv) {
    if (argc < 2) {
        printf("Call this program with 1 arguments\n");
        return 1;
    }

    unsigned long input = strtoul(argv[1], 0, 10);
    unsigned long output = SECRET(input);

    printf("%lu\n", output);

    return 0;
}