/*------------------------------------------------------------------------------
 *
 * Copyright (c) 2011-2016, EURid. All rights reserved.
 * The YADIFA TM software product is provided under the BSD 3-clause license:
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions
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 *
 *        * Redistributions of source code must retain the above copyright 
 *          notice, this list of conditions and the following disclaimer.
 *        * 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.
 *        * Neither the name of EURid nor the names of its contributors may 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 HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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 * 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.
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 *------------------------------------------------------------------------------
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/** @defgroup dnsdbcollection Collections used by the database
 *  @ingroup dnsdb
 *  @brief Functions used to hash a dns formatted string
 *
 *  Implements the functions used to hash a dns formatted string.
 *  There functions require the call to an initialization function (hash_init);
 *
 * @{
 */
/*------------------------------------------------------------------------------
 *
 * USE INCLUDES */
#include "dnsdb/dnsdb-config.h"
#include <stdlib.h>
#include <string.h>
#include "dnsdb/hash.h"

#define ZDBHTBL_TAG 0x4c42544842445a

/*
 * [-]
 * [0;9]
 * [a;z]
 *
 * [2D]
 * [30;38]
 * [61;7A]
 *
 */

/**
 *
 * ['0';'9'] + ['A'/'a';'Z'/'z'] + ['-'] = 37
 *
 */

#define ZDB_HASH_TABLE_CHAR_SET_SIZE 37

extern const u32 ZDB_HASH_TABLE[256][ZDB_HASH_TABLE_CHAR_SET_SIZE];

const u32 ZDB_HASH_TABLE_MAP[256];
const u8* WILD_LABEL = (u8*)"\001*";
const hashcode WILD_HASH;


static bool hash_init_done = FALSE;

/** @brief Initializes the hash functions
 *
 *  Initializes the hash function
 */

void
hash_init()
{
    u32 i;

    if(hash_init_done)
    {
        return;
    }

    hash_init_done = TRUE; /* It's not big deal if it's done more
			     * than once.  I will not use a mutex
			     * for this.
			     */

    u32* tmp = (u32*)ZDB_HASH_TABLE_MAP;


    ZEROMEMORY(tmp, sizeof(ZDB_HASH_TABLE_MAP));

    tmp['-'] = 0;

    for(i = '0'; i <= '9'; i++)
    {
        tmp[i] = i - (48 - 1); /* one is taken by '-', '0'=48 */
    }

    for(i = 'A'; i <= 'Z'; i++)
    {
        tmp[i] = i - (65 - 11); /* eleven are taken by '-' and '0' .. '9', 'A'=65 */
    }

    for(i = 'a'; i <= 'z'; i++)
    {
        tmp[i] = i - (97 - 11); /* eleven are taken by '-' and '0' .. '9', 'a'=97 */
    }

    tmp['*'] = 0;

    tmp['_'] = 0;

    hashcode* wild_hashp = (hashcode*) & WILD_HASH;
    *wild_hashp = hash_dnslabel(WILD_LABEL);
}



/** @brief Compute the hash code of a pascal name
 *
 *  Compute the hash code of a pascal name.
 *  The function hash_init() MUST be called once first. (This requirement will be lifted later)
 *  An interesting thing about a dnsname label : it's a pascal string.
 *
 *  @param[in]  pascal_name the name in pascal form
 *
 *  @return the hash code as a 32 bits integer
 */

hashcode
hash_pascalname(const u8* pascal_name)
{
    assert(pascal_name != NULL);

    u32 idx = 1; /* idx points into the HASH_TABLE */

    /* I could initialize it to a hiher value (ie: 255) and
     * decrease it instead of the current behaviour.
     * This would allow to put a cpu-cheap limit on the
     * amount of chars taken in account in the hash computation.
     */
    u32 len = *pascal_name++;

    u32 hash = ZDB_HASH_TABLE[len][0];

    while(len-- > 0)
    {
        hash += ZDB_HASH_TABLE[idx++][ZDB_HASH_TABLE_MAP[*pascal_name++]];
    }

    return hash;
}

/** @brief Compute the hash code of an asciiz name
 *
 *  Compute the hash code of a pascal name from its asciiz form.
 *  The function hash_init() MUST be called once first. (This requirement will be lifted later)
 *
 *  @param[in]  pascal_name the name in asciiz form
 *
 *  @return the hash code as a 32 bits integer
 */

hashcode
hash_asciizname(const char* asciiz_name)
{
    assert(asciiz_name != NULL);

    u32 idx = 1; /* idx points into the HASH_TABLE */

    /* I could initialize it to a hiher value (ie: 255) and
     * decrease it instead of the current behaviour.
     * This would allow to put a cpu-cheap limit on the
     * amount of chars taken in account in the hash computation.
     */
    u32 len = (u32)strlen(asciiz_name);

    u32 hash = ZDB_HASH_TABLE[len][0];

    while(len-- > 0)
    {
        hash += ZDB_HASH_TABLE[idx++][ZDB_HASH_TABLE_MAP[(u8)(*asciiz_name++)]];
    }

    return hash;
}

/** @} */

/*----------------------------------------------------------------------------*/
