/*
  * Copyright (C) 2007 Marco Gerards <marco@gnu.org>
  * Copyright (C) 2009 David Conrad
  *
  * This file is part of FFmpeg.
  *
  * FFmpeg is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2.1 of the License, or (at your option) any later version.
  *
  * FFmpeg 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
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with FFmpeg; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
 /**

  * @file

  * Arithmetic decoder for Dirac
  * @author Marco Gerards <marco@gnu.org>
  */
 
 #include "dirac_arith.h"
 

 const uint16_t ff_dirac_prob[256] = {
     0,    2,    5,    8,    11,   15,   20,   24,
     29,   35,   41,   47,   53,   60,   67,   74,
     82,   89,   97,   106,  114,  123,  132,  141,
     150,  160,  170,  180,  190,  201,  211,  222,
     233,  244,  256,  267,  279,  291,  303,  315,
     327,  340,  353,  366,  379,  392,  405,  419,
     433,  447,  461,  475,  489,  504,  518,  533,
     548,  563,  578,  593,  609,  624,  640,  656,
     672,  688,  705,  721,  738,  754,  771,  788,
     805,  822,  840,  857,  875,  892,  910,  928,
     946,  964,  983,  1001, 1020, 1038, 1057, 1076,
     1095, 1114, 1133, 1153, 1172, 1192, 1211, 1231,
     1251, 1271, 1291, 1311, 1332, 1352, 1373, 1393,
     1414, 1435, 1456, 1477, 1498, 1520, 1541, 1562,
     1584, 1606, 1628, 1649, 1671, 1694, 1716, 1738,
     1760, 1783, 1806, 1828, 1851, 1874, 1897, 1920,
     1935, 1942, 1949, 1955, 1961, 1968, 1974, 1980,
     1985, 1991, 1996, 2001, 2006, 2011, 2016, 2021,
     2025, 2029, 2033, 2037, 2040, 2044, 2047, 2050,
     2053, 2056, 2058, 2061, 2063, 2065, 2066, 2068,
     2069, 2070, 2071, 2072, 2072, 2072, 2072, 2072,
     2072, 2071, 2070, 2069, 2068, 2066, 2065, 2063,
     2060, 2058, 2055, 2052, 2049, 2045, 2042, 2038,
     2033, 2029, 2024, 2019, 2013, 2008, 2002, 1996,
     1989, 1982, 1975, 1968, 1960, 1952, 1943, 1934,
     1925, 1916, 1906, 1896, 1885, 1874, 1863, 1851,
     1839, 1827, 1814, 1800, 1786, 1772, 1757, 1742,
     1727, 1710, 1694, 1676, 1659, 1640, 1622, 1602,
     1582, 1561, 1540, 1518, 1495, 1471, 1447, 1422,
     1396, 1369, 1341, 1312, 1282, 1251, 1219, 1186,
     1151, 1114, 1077, 1037, 995,  952,  906,  857,
     805,  750,  690,  625,  553,  471,  376,  255
 };
 
 const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT] = {
     [CTX_ZPZN_F1]   = CTX_ZP_F2,
     [CTX_ZPNN_F1]   = CTX_ZP_F2,
     [CTX_ZP_F2]     = CTX_ZP_F3,
     [CTX_ZP_F3]     = CTX_ZP_F4,
     [CTX_ZP_F4]     = CTX_ZP_F5,
     [CTX_ZP_F5]     = CTX_ZP_F6,
     [CTX_ZP_F6]     = CTX_ZP_F6,
     [CTX_NPZN_F1]   = CTX_NP_F2,
     [CTX_NPNN_F1]   = CTX_NP_F2,
     [CTX_NP_F2]     = CTX_NP_F3,
     [CTX_NP_F3]     = CTX_NP_F4,
     [CTX_NP_F4]     = CTX_NP_F5,
     [CTX_NP_F5]     = CTX_NP_F6,
     [CTX_NP_F6]     = CTX_NP_F6,
     [CTX_DELTA_Q_F] = CTX_DELTA_Q_F,
 };
 
 int16_t ff_dirac_prob_branchless[256][2];
 
 void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length)
 {
     int i;
     align_get_bits(gb);
 
     length = FFMIN(length, get_bits_left(gb)/8);
 
     c->bytestream     = gb->buffer + get_bits_count(gb)/8;
     c->bytestream_end = c->bytestream + length;
     skip_bits_long(gb, length*8);
 
     c->low = 0;
     for (i = 0; i < 4; i++) {
         c->low <<= 8;
         if (c->bytestream < c->bytestream_end)
             c->low |= *c->bytestream++;
         else
             c->low |= 0xff;
     }
 
     c->counter = -16;
     c->range   = 0xffff;
 
     for (i = 0; i < 256; i++) {
         ff_dirac_prob_branchless[i][0] =  ff_dirac_prob[255-i];
         ff_dirac_prob_branchless[i][1] = -ff_dirac_prob[i];
     }
 
     for (i = 0; i < DIRAC_CTX_COUNT; i++)
         c->contexts[i] = 0x8000;
 }