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authorLasse Collin <lasse.collin@tukaani.org>2007-12-09 00:42:33 +0200
committerLasse Collin <lasse.collin@tukaani.org>2007-12-09 00:42:33 +0200
commit5d018dc03549c1ee4958364712fb0c94e1bf2741 (patch)
tree1b211911fb33fddb3f04b77f99e81df23623ffc4 /src/liblzma/rangecoder/range_decoder.h
downloadxz-5d018dc03549c1ee4958364712fb0c94e1bf2741.tar.xz
Imported to git.
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diff --git a/src/liblzma/rangecoder/range_decoder.h b/src/liblzma/rangecoder/range_decoder.h
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+///////////////////////////////////////////////////////////////////////////////
+//
+/// \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