/* Chrysalide - Outil d'analyse de fichiers binaires
 * pearson.c - implémentaton du calcul rapide d'empreintes de chaînes
 *
 * Copyright (C) 2021 Cyrille Bagard
 *
 *  This file is part of Chrysalide.
 *
 *  Chrysalide 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.
 *
 *  Chrysalide 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 Chrysalide.  If not, see <http://www.gnu.org/licenses/>.
 */


#include "pearson.h"


#include <stddef.h>



/* Permutations proposées */
static const char _pearson_permutations[256] = {

      1,  87,  49,  12, 176, 178, 102, 166, 121, 193,   6,  84, 249, 230,  44, 163,
     14, 197, 213, 181, 161,  85, 218,  80,  64, 239,  24, 226, 236, 142,  38, 200,
    110, 177, 104, 103, 141, 253, 255,  50,  77, 101,  81,  18,  45,  96,  31, 222,
     25, 107, 190,  70,  86, 237, 240,  34,  72, 242,  20, 214, 244, 227, 149, 235,
     97, 234,  57,  22,  60, 250,  82, 175, 208,   5, 127, 199, 111,  62, 135, 248,
    174, 169, 211,  58,  66, 154, 106, 195, 245, 171,  17, 187, 182, 179,   0, 243,
    132,  56, 148,  75, 128, 133, 158, 100, 130, 126,  91,  13, 153, 246, 216, 219,
    119,  68, 223,  78,  83,  88, 201,  99, 122,  11,  92,  32, 136, 114,  52,  10,
    138,  30,  48, 183, 156,  35,  61,  26, 143,  74, 251,  94, 129, 162,  63, 152,
    170,   7, 115, 167, 241, 206,   3, 150,  55,  59, 151, 220,  90,  53,  23, 131,
    125, 173,  15, 238,  79,  95,  89,  16, 105, 137, 225, 224, 217, 160,  37, 123,
    118,  73,   2, 157,  46, 116,   9, 145, 134, 228, 207, 212, 202, 215,  69, 229,
     27, 188,  67, 124, 168, 252,  42,   4,  29, 108,  21, 247,  19, 205,  39, 203,
    233,  40, 186, 147, 198, 192, 155,  33, 164, 191,  98, 204, 165, 180, 117,  76,
    140,  36, 210, 172,  41,  54, 159,   8, 185, 232, 113, 196, 231,  47, 146, 120,
     51,  65,  28, 144, 254, 221,  93, 189, 194, 139, 112,  43,  71, 109, 184, 209

};



/******************************************************************************
*                                                                             *
*  Paramètres  : -                                                            *
*                                                                             *
*  Description : Fournit les permutations par défaut par Pearson.             *
*                                                                             *
*  Retour      : Table de valeurs utilisées par défaut.                       *
*                                                                             *
*  Remarques   : -                                                            *
*                                                                             *
******************************************************************************/

const char *get_pearson_permutations(void)
{
    const char *result;                     /* Table à renvoyer            */

    result = _pearson_permutations;

    return result;

}


/******************************************************************************
*                                                                             *
*  Paramètres  : str = chaîne de caractères à traiter.                        *
*                table = permutations à employer, NULL pour celles par défaut.*
*                                                                             *
*  Description : Détermine l'empreinte Pearson d'une chaîne de caractères.    *
*                                                                             *
*  Retour      : Valeur calculée.                                             *
*                                                                             *
*  Remarques   : -                                                            *
*                                                                             *
******************************************************************************/

uint8_t pearson_hash(const char *str, const char *table)
{
    uint8_t result;                         /* Valeur à retourner          */
    unsigned char *iter;                    /* Boucle de parcours          */

    if (table == NULL)
        table = _pearson_permutations;

    result = 0;

    for (iter = (unsigned char *)str; *iter; iter++)
        result = table[result ^ (*iter)];

    return result;

}