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Diffstat (limited to 'src/liblzma/rangecoder/range_decoder.h')
| -rw-r--r-- | src/liblzma/rangecoder/range_decoder.h | 189 |
1 files changed, 189 insertions, 0 deletions
diff --git a/src/liblzma/rangecoder/range_decoder.h b/src/liblzma/rangecoder/range_decoder.h new file mode 100644 index 00000000..0583faaf --- /dev/null +++ b/src/liblzma/rangecoder/range_decoder.h @@ -0,0 +1,189 @@ +/////////////////////////////////////////////////////////////////////////////// +// +/// \file range_decoder.h +/// \brief Range Decoder +// +// Copyright (C) 1999-2006 Igor Pavlov +// Copyright (C) 2007 Lasse Collin +// +// This library 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. +// +// This library 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. +// +/////////////////////////////////////////////////////////////////////////////// + +#ifndef LZMA_RANGE_DECODER_H +#define LZMA_RANGE_DECODER_H + +#include "range_common.h" + + +typedef struct { + uint32_t range; + uint32_t code; +} lzma_range_decoder; + + +/// Makes local copies of range decoder variables. +#define rc_to_local(rc) \ + uint32_t rc_range = (rc).range; \ + uint32_t rc_code = (rc).code; \ + uint32_t rc_bound + +/// Stores the local copes back to the range decoder structure. +#define rc_from_local(rc) \ +do {\ + (rc).range = rc_range; \ + (rc).code = rc_code; \ +} while (0) + +/// Resets the range decoder structure. +#define rc_reset(rc) \ +do { \ + (rc).range = UINT32_MAX; \ + (rc).code = 0; \ +} while (0) + + +// All of the macros in this file expect the following variables being defined: +// - uint32_t rc_range; +// - uint32_t rc_code; +// - uint32_t rc_bound; // Temporary variable +// - uint8_t *in; +// - size_t in_pos_local; // Local alias for *in_pos + + +////////////////// +// Buffer "I/O" // +////////////////// + +// Read the next byte of compressed data from buffer_in, if needed. +#define rc_normalize() \ +do { \ + if (rc_range < TOP_VALUE) { \ + rc_range <<= SHIFT_BITS; \ + rc_code = (rc_code << SHIFT_BITS) | in[in_pos_local++]; \ + } \ +} while (0) + + +////////////////// +// Bit decoding // +////////////////// + +// Range decoder's DecodeBit() is splitted into three macros: +// if_bit_0(prob) { +// update_bit_0(prob) +// ... +// } else { +// update_bit_1(prob) +// ... +// } + +#define if_bit_0(prob) \ + rc_normalize(); \ + rc_bound = (rc_range >> BIT_MODEL_TOTAL_BITS) * (prob); \ + if (rc_code < rc_bound) + + +#define update_bit_0(prob) \ +do { \ + rc_range = rc_bound; \ + prob += (BIT_MODEL_TOTAL - (prob)) >> MOVE_BITS; \ +} while (0) + + +#define update_bit_1(prob) \ +do { \ + rc_range -= rc_bound; \ + rc_code -= rc_bound; \ + prob -= (prob) >> MOVE_BITS; \ +} while (0) + + +// Dummy versions don't update prob. +#define update_bit_0_dummy() \ + rc_range = rc_bound + + +#define update_bit_1_dummy() \ +do { \ + rc_range -= rc_bound; \ + rc_code -= rc_bound; \ +} while (0) + + +/////////////////////// +// Bit tree decoding // +/////////////////////// + +#define bittree_decode(target, probs, bit_levels) \ +do { \ + uint32_t model_index = 1; \ + for (uint32_t bit_index = (bit_levels); bit_index != 0; --bit_index) { \ + if_bit_0((probs)[model_index]) { \ + update_bit_0((probs)[model_index]); \ + model_index <<= 1; \ + } else { \ + update_bit_1((probs)[model_index]); \ + model_index = (model_index << 1) | 1; \ + } \ + } \ + target += model_index - (1 << bit_levels); \ +} while (0) + + +#define bittree_reverse_decode(target, probs, bit_levels) \ +do { \ + uint32_t model_index = 1; \ + for (uint32_t bit_index = 0; bit_index < bit_levels; ++bit_index) { \ + if_bit_0((probs)[model_index]) { \ + update_bit_0((probs)[model_index]); \ + model_index <<= 1; \ + } else { \ + update_bit_1((probs)[model_index]); \ + model_index = (model_index << 1) | 1; \ + target += 1 << bit_index; \ + } \ + } \ +} while (0) + + +// Dummy versions don't update prob. +#define bittree_decode_dummy(target, probs, bit_levels) \ +do { \ + uint32_t model_index = 1; \ + for (uint32_t bit_index = (bit_levels); bit_index != 0; --bit_index) { \ + if_bit_0((probs)[model_index]) { \ + update_bit_0_dummy(); \ + model_index <<= 1; \ + } else { \ + update_bit_1_dummy(); \ + model_index = (model_index << 1) | 1; \ + } \ + } \ + target += model_index - (1 << bit_levels); \ +} while (0) + + +#define bittree_reverse_decode_dummy(probs, bit_levels) \ +do { \ + uint32_t model_index = 1; \ + for (uint32_t bit_index = 0; bit_index < bit_levels; ++bit_index) { \ + if_bit_0((probs)[model_index]) { \ + update_bit_0_dummy(); \ + model_index <<= 1; \ + } else { \ + update_bit_1_dummy(); \ + model_index = (model_index << 1) | 1; \ + } \ + } \ +} while (0) + +#endif |