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Diffstat (limited to 'src/liblzma/lzma/lzma_literal.h')
-rw-r--r-- | src/liblzma/lzma/lzma_literal.h | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/src/liblzma/lzma/lzma_literal.h b/src/liblzma/lzma/lzma_literal.h new file mode 100644 index 00000000..174f5ed4 --- /dev/null +++ b/src/liblzma/lzma/lzma_literal.h @@ -0,0 +1,74 @@ +/////////////////////////////////////////////////////////////////////////////// +// +/// \file lzma_literal.h +/// \brief Literal Coder +/// +/// This is used as is by both LZMA encoder and 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_LITERAL_H +#define LZMA_LITERAL_H + +#include "common.h" + +// We need typedef of `probability'. +#include "range_common.h" + + +/// Each literal coder is divided in three sections: +/// - 0x001-0x0FF: Without match byte +/// - 0x101-0x1FF: With match byte; match bit is 0 +/// - 0x201-0x2FF: With match byte; match bit is 1 +#define LIT_SIZE 0x300 + +/// Calculate how many states are needed. Each state has +/// LIT_SIZE `probability' variables. +#define literal_states(literal_context_bits, literal_pos_bits) \ + (1U << ((literal_context_bits) + (literal_pos_bits))) + +/// Locate the literal coder for the next literal byte. The choice depends on +/// - the lowest literal_pos_bits bits of the position of the current +/// byte; and +/// - the highest literal_context_bits bits of the previous byte. +#define literal_get_subcoder(literal_coder, pos, prev_byte) \ + (literal_coder)->coders[(((pos) & (literal_coder)->literal_pos_mask) \ + << (literal_coder)->literal_context_bits) \ + + ((prev_byte) >> (8 - (literal_coder)->literal_context_bits))] + + +typedef struct { + uint32_t literal_context_bits; + uint32_t literal_pos_bits; + + /// literal_pos_mask is always (1 << literal_pos_bits) - 1. + uint32_t literal_pos_mask; + + /// There are (1 << (literal_pos_bits + literal_context_bits)) + /// literal coders. + probability coders[][LIT_SIZE]; + +} lzma_literal_coder; + + +extern lzma_ret lzma_literal_init( + lzma_literal_coder **coder, lzma_allocator *allocator, + uint32_t literal_context_bits, uint32_t literal_pos_bits); + +extern void lzma_literal_end( + lzma_literal_coder **coder, lzma_allocator *allocator); + +#endif |