hash_xor.c

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/**
 * \addtogroup hash
 * @{
 */

/**
 * \defgroup hash_xor 'Hashing' implementation using the XOR function
 *
 * @{
 */

/**
 * \file
 * \brief Implementation of the hashing interface based on the XOR function
 * \author Wolf-Bastian Poettner <poettner@ibr.cs.tu-bs.de>
 */

#include <stdio.h>
#include <string.h> // memcpy

#include "hash.h"

void hash_xor_init() {
}

uint32_t hash_xor_buffer(uint8_t * buffer, uint16_t length)
{
        int i;
        int limit = (length / 4) * 4;
        uint32_t hash = 0;

        for( i=0; i < limit; i = i + 4) {
                uint32_t * value = (uint32_t* ) &buffer[i];
                hash ^= *value;
        }

        if( limit < length ) {
                uint32_t remainder = 0;
                memcpy(&remainder, &buffer[limit], length - limit);
                hash ^= remainder;
        }

        return hash;
}

uint32_t hash_xor_convenience(uint32_t one, uint32_t two, uint32_t three, uint32_t four, uint32_t five)
{
        uint8_t buffer[20];

        memcpy(buffer + 0, &one, sizeof(uint32_t));
        memcpy(buffer + 4, &two, sizeof(uint32_t));
        memcpy(buffer + 8, &three, sizeof(uint32_t));
        memcpy(buffer + 12, &four, sizeof(uint32_t));
        memcpy(buffer + 16, &five, sizeof(uint32_t));

        return hash_xor_buffer(buffer, 16);
}

uint32_t hash_xor_convenience_ptr(uint32_t * one, uint32_t * two, uint32_t * three, uint32_t * four, uint32_t * five)
{
        uint8_t buffer[20];

        memcpy(buffer + 0, one, sizeof(uint32_t));
        memcpy(buffer + 4, two, sizeof(uint32_t));
        memcpy(buffer + 8, three, sizeof(uint32_t));
        memcpy(buffer + 12, four, sizeof(uint32_t));
        memcpy(buffer + 16, five, sizeof(uint32_t));

        return hash_xor_buffer(buffer, 16);
}

const struct hash_driver hash_xor = {
        "XOR",
        hash_xor_init,
        hash_xor_convenience,
        hash_xor_convenience_ptr,
        hash_xor_buffer,
};

/** @} */
/** @} */