/*
  * 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>
  */
 
 #ifndef AVCODEC_DIRAC_ARITH_H
 #define AVCODEC_DIRAC_ARITH_H
 
 #include "bytestream.h"
 #include "get_bits.h"
 
 enum dirac_arith_contexts {
     CTX_ZPZN_F1,
     CTX_ZPNN_F1,
     CTX_NPZN_F1,
     CTX_NPNN_F1,
     CTX_ZP_F2,
     CTX_ZP_F3,
     CTX_ZP_F4,
     CTX_ZP_F5,
     CTX_ZP_F6,
     CTX_NP_F2,
     CTX_NP_F3,
     CTX_NP_F4,
     CTX_NP_F5,
     CTX_NP_F6,
     CTX_COEFF_DATA,
     CTX_SIGN_NEG,
     CTX_SIGN_ZERO,
     CTX_SIGN_POS,
     CTX_ZERO_BLOCK,
     CTX_DELTA_Q_F,
     CTX_DELTA_Q_DATA,
     CTX_DELTA_Q_SIGN,
 
     DIRAC_CTX_COUNT
 };
 
 // Dirac resets the arith decoder between decoding various types of data,
 // so many contexts are never used simultaneously. Thus, we can reduce
 // the number of contexts needed by reusing them.
 #define CTX_SB_F1        CTX_ZP_F5
 #define CTX_SB_DATA      0
 #define CTX_PMODE_REF1   0
 #define CTX_PMODE_REF2   1
 #define CTX_GLOBAL_BLOCK 2
 #define CTX_MV_F1        CTX_ZP_F2
 #define CTX_MV_DATA      0
 #define CTX_DC_F1        CTX_ZP_F5
 #define CTX_DC_DATA      0
 
 typedef struct {
     unsigned low;
     uint16_t range;
     int16_t  counter;
 
     const uint8_t *bytestream;
     const uint8_t *bytestream_end;
 
     uint16_t contexts[DIRAC_CTX_COUNT];
 } DiracArith;
 
 extern const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT];
 extern const uint16_t ff_dirac_prob[256];
 extern int16_t ff_dirac_prob_branchless[256][2];
 
 static inline void renorm(DiracArith *c)
 {
 #if HAVE_FAST_CLZ
     int shift = 14 - av_log2_16bit(c->range-1) + ((c->range-1)>>15);
 
     c->low    <<= shift;
     c->range  <<= shift;
     c->counter += shift;
 #else
     while (c->range <= 0x4000) {
         c->low   <<= 1;
         c->range <<= 1;
         c->counter++;
     }
 #endif
 }
 
 static inline void refill(DiracArith *c)
 {
     int counter = c->counter;
 
     if (counter >= 0) {
         int new = bytestream_get_be16(&c->bytestream);
 
         // the spec defines overread bits to be 1, and streams rely on this
         if (c->bytestream > c->bytestream_end) {
             new |= 0xff;
             if (c->bytestream > c->bytestream_end+1)
                 new |= 0xff00;
 
             c->bytestream = c->bytestream_end;
         }
 
         c->low += new << counter;
         counter -= 16;
     }
     c->counter = counter;
 }
 
 static inline int dirac_get_arith_bit(DiracArith *c, int ctx)
 {
     int prob_zero = c->contexts[ctx];
     int range_times_prob, bit;
     unsigned low = c->low;
     int    range = c->range;
 
     range_times_prob = (c->range * prob_zero) >> 16;
 

 #if HAVE_FAST_CMOV && HAVE_INLINE_ASM

     low   -= range_times_prob << 16;
     range -= range_times_prob;
     bit = 0;
     __asm__(
         "cmpl   %5, %4 \n\t"
         "setae  %b0    \n\t"
         "cmovb  %3, %2 \n\t"
         "cmovb  %5, %1 \n\t"
         : "+q"(bit), "+r"(range), "+r"(low)
         : "r"(c->low), "r"(c->low>>16),
           "r"(range_times_prob)
     );
 #else
     bit = (low >> 16) >= range_times_prob;
     if (bit) {
         low   -= range_times_prob << 16;
         range -= range_times_prob;
     } else {
         range  = range_times_prob;
     }
 #endif
 
     c->contexts[ctx] += ff_dirac_prob_branchless[prob_zero>>8][bit];
     c->low   = low;
     c->range = range;
 
     renorm(c);
     refill(c);
     return bit;
 }
 
 static inline int dirac_get_arith_uint(DiracArith *c, int follow_ctx, int data_ctx)
 {
     int ret = 1;
     while (!dirac_get_arith_bit(c, follow_ctx)) {
         ret <<= 1;
         ret += dirac_get_arith_bit(c, data_ctx);
         follow_ctx = ff_dirac_next_ctx[follow_ctx];
     }
     return ret-1;
 }
 
 static inline int dirac_get_arith_int(DiracArith *c, int follow_ctx, int data_ctx)
 {
     int ret = dirac_get_arith_uint(c, follow_ctx, data_ctx);
     if (ret && dirac_get_arith_bit(c, data_ctx+1))
         ret = -ret;
     return ret;
 }
 
 void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length);
 
 #endif /* AVCODEC_DIRAC_ARITH_H */