ffmpeg/libavcodec/mlp.c

   1 /*
   2  * MLP codec common code
   3  * Copyright (c) 2007-2008 Ian Caulfield
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 #include <stdint.h>
  23
  24 #include "libavutil/crc.h"
  25 #include "libavutil/intreadwrite.h"
  26 #include "mlp.h"
  27
  28 const uint8_t ff_mlp_huffman_tables[3][18][2] = {
  29     {    /* Huffman table 0, -7 - +10 */
  30         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  31         {0x04, 3}, {0x05, 3}, {0x06, 3}, {0x07, 3},
  32         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  33     }, { /* Huffman table 1, -7 - +8 */
  34         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  35         {0x02, 2}, {0x03, 2},
  36         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  37     }, { /* Huffman table 2, -7 - +7 */
  38         {0x01, 9}, {0x01, 8}, {0x01, 7}, {0x01, 6}, {0x01, 5}, {0x01, 4}, {0x01, 3},
  39         {0x01, 1},
  40         {0x03, 3}, {0x05, 4}, {0x09, 5}, {0x11, 6}, {0x21, 7}, {0x41, 8}, {0x81, 9},
  41     }
  42 };
  43
  44 static int crc_init = 0;
  45 #if CONFIG_SMALL
  46 #define CRC_TABLE_SIZE 257
  47 #else
  48 #define CRC_TABLE_SIZE 1024
  49 #endif
  50 static AVCRC crc_63[CRC_TABLE_SIZE];
  51 static AVCRC crc_1D[CRC_TABLE_SIZE];
  52 static AVCRC crc_2D[CRC_TABLE_SIZE];
  53
  54 av_cold void ff_mlp_init_crc(void)
  55 {
  56     if (!crc_init) {
  57         av_crc_init(crc_63, 0,  8,   0x63, sizeof(crc_63));
  58         av_crc_init(crc_1D, 0,  8,   0x1D, sizeof(crc_1D));
  59         av_crc_init(crc_2D, 0, 16, 0x002D, sizeof(crc_2D));
  60         crc_init = 1;
  61     }
  62 }
  63
  64 uint16_t ff_mlp_checksum16(const uint8_t *buf, unsigned int buf_size)
  65 {
  66     uint16_t crc;
  67
  68     crc = av_crc(crc_2D, 0, buf, buf_size - 2);
  69     crc ^= AV_RL16(buf + buf_size - 2);
  70     return crc;
  71 }
  72
  73 uint8_t ff_mlp_checksum8(const uint8_t *buf, unsigned int buf_size)
  74 {
  75     uint8_t checksum = av_crc(crc_63, 0x3c, buf, buf_size - 1); // crc_63[0xa2] == 0x3c
  76     checksum ^= buf[buf_size-1];
  77     return checksum;
  78 }
  79
  80 uint8_t ff_mlp_restart_checksum(const uint8_t *buf, unsigned int bit_size)
  81 {
  82     int i;
  83     int num_bytes = (bit_size + 2) / 8;
  84
  85     int crc = crc_1D[buf[0] & 0x3f];
  86     crc = av_crc(crc_1D, crc, buf + 1, num_bytes - 2);
  87     crc ^= buf[num_bytes - 1];
  88
  89     for (i = 0; i < ((bit_size + 2) & 7); i++) {
  90         crc <<= 1;
  91         if (crc & 0x100)
  92             crc ^= 0x11D;
  93         crc ^= (buf[num_bytes] >> (7 - i)) & 1;
  94     }
  95
  96     return crc;
  97 }
  98
  99 uint8_t ff_mlp_calculate_parity(const uint8_t *buf, unsigned int buf_size)
 100 {
 101     uint32_t scratch = 0;
 102     const uint8_t *buf_end = buf + buf_size;
 103
 104     for (; ((intptr_t) buf & 3) && buf < buf_end; buf++)
 105         scratch ^= *buf;
 106     for (; buf < buf_end - 3; buf += 4)
 107         scratch ^= *((const uint32_t*)buf);
 108
 109     scratch = xor_32_to_8(scratch);
 110
 111     for (; buf < buf_end; buf++)
 112         scratch ^= *buf;
 113
 114     return scratch;
 115 }