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Annotation of embedaddon/strongswan/src/libstrongswan/plugins/bliss/bliss_huffman_coder.c, revision 1.1.1.1

1.1       misho       1: /*
                      2:  * Copyright (C) 2014 Andreas Steffen
                      3:  * HSR Hochschule fuer Technik Rapperswil
                      4:  *
                      5:  * This program is free software; you can redistribute it and/or modify it
                      6:  * under the terms of the GNU General Public License as published by the
                      7:  * Free Software Foundation; either version 2 of the License, or (at your
                      8:  * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.
                      9:  *
                     10:  * This program is distributed in the hope that it will be useful, but
                     11:  * WITHOUT ANY WARRANTY;https://www.hsr.ch/HSR-intern-Anmeldung.4409.0.html?&no_cache=1 without even the implied warranty of MERCHANTABILITY
                     12:  * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
                     13:  * for more details.
                     14:  */
                     15: 
                     16: #include "bliss_huffman_coder.h"
                     17: 
                     18: typedef struct private_bliss_huffman_coder_t private_bliss_huffman_coder_t;
                     19: 
                     20: /**
                     21:  * Private data structure for bliss_huffman_coder_t object
                     22:  */
                     23: struct private_bliss_huffman_coder_t {
                     24:        /**
                     25:         * Public interface.
                     26:         */
                     27:        bliss_huffman_coder_t public;
                     28: 
                     29:        /**
                     30:         * Bitpacker to write to or read from
                     31:         */
                     32:        bliss_bitpacker_t *packer;
                     33: 
                     34:        /**
                     35:         * Huffman code table to be used
                     36:         */
                     37:        bliss_huffman_code_t *code;
                     38: 
                     39:        /**
                     40:      * Maximum index into tuples table
                     41:         */
                     42:        int index_max;
                     43: 
                     44:        /**
                     45:      * Number of encoded or decoded bits
                     46:         */
                     47:        size_t bits;
                     48: 
                     49: };
                     50: 
                     51: METHOD(bliss_huffman_coder_t, get_bits, size_t,
                     52:        private_bliss_huffman_coder_t *this)
                     53: {
                     54:        return this->bits;
                     55: }
                     56: 
                     57: METHOD(bliss_huffman_coder_t, encode, bool,
                     58:        private_bliss_huffman_coder_t *this, int32_t z1, int16_t z2)
                     59: {
                     60:        uint32_t code;
                     61:        uint16_t bits;
                     62:        int index;
                     63: 
                     64:        index = z1 * (2*this->code->n_z2 - 1) + z2 + this->code->n_z2 - 1;
                     65:        if (index >= this->index_max)
                     66:        {
                     67:                DBG1(DBG_LIB, "index exceeded in Huffman encoding table");
                     68:                return FALSE;
                     69:        }
                     70:        code = this->code->tuples[index].code;
                     71:        bits = this->code->tuples[index].bits;
                     72:        if (!this->packer->write_bits(this->packer, code, bits))
                     73:        {
                     74:                DBG1(DBG_LIB, "bitpacker exceeded its buffer");
                     75:                return FALSE;
                     76:        }
                     77:        this->bits += bits;
                     78: 
                     79:        return TRUE;
                     80: }
                     81: 
                     82: METHOD(bliss_huffman_coder_t, decode, bool,
                     83:        private_bliss_huffman_coder_t *this, int32_t *z1, int16_t *z2)
                     84: {
                     85:        bliss_huffman_code_node_t *node;
                     86:        uint32_t bit;
                     87: 
                     88:        node = this->code->nodes;
                     89:        while (node->tuple == BLISS_HUFFMAN_CODE_NO_TUPLE)
                     90:        {
                     91:                if (node->node_0 == BLISS_HUFFMAN_CODE_NO_NODE ||
                     92:                        node->node_1 == BLISS_HUFFMAN_CODE_NO_NODE)
                     93:                {
                     94:                        DBG1(DBG_LIB, "error in Huffman decoding table");
                     95:                        return FALSE;
                     96:                }
                     97:                if (!this->packer->read_bits(this->packer, &bit, 1))
                     98:                {
                     99:                        DBG1(DBG_LIB, "bitpacker depleted its buffer");
                    100:                        return FALSE;
                    101:                }
                    102:                node = &this->code->nodes[bit ? node->node_1 : node->node_0];
                    103:                this->bits++;
                    104:        }
                    105:        *z1 = node->tuple / (2*this->code->n_z2 - 1);
                    106:        *z2 = node->tuple - (2*this->code->n_z2 - 1) * (*z1) - this->code->n_z2 + 1;
                    107: 
                    108:        return TRUE;
                    109: }
                    110: 
                    111: METHOD(bliss_huffman_coder_t, destroy, void,
                    112:        private_bliss_huffman_coder_t *this)
                    113: {
                    114:        free(this);
                    115: }
                    116: 
                    117: /**
                    118:  * See header.
                    119:  */
                    120: bliss_huffman_coder_t *bliss_huffman_coder_create(bliss_huffman_code_t *code,
                    121:                                                                                                  bliss_bitpacker_t *packer)
                    122: {
                    123:        private_bliss_huffman_coder_t *this;
                    124: 
                    125:        INIT(this,
                    126:                .public = {
                    127:                        .get_bits = _get_bits,
                    128:                        .encode = _encode,
                    129:                        .decode = _decode,
                    130:                        .destroy = _destroy,
                    131:                },
                    132:                .packer = packer,
                    133:                .code = code,
                    134:                .index_max = (2*code->n_z2 - 1) * code->n_z1,
                    135:        );
                    136: 
                    137:        return &this->public;
                    138: }