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Diffstat (limited to 'converter/other/fiasco/lib/arith.h')
| -rw-r--r-- | converter/other/fiasco/lib/arith.h | 122 |
1 files changed, 122 insertions, 0 deletions
diff --git a/converter/other/fiasco/lib/arith.h b/converter/other/fiasco/lib/arith.h new file mode 100644 index 00000000..744eb9d7 --- /dev/null +++ b/converter/other/fiasco/lib/arith.h @@ -0,0 +1,122 @@ +/* + * arith.h + * + * This file is part of FIASCO («F»ractal «I»mage «A»nd «S»equence «CO»dec) + * Copyright (C) 1994-2000 Ullrich Hafner <hafner@bigfoot.de> + */ + +/* + * $Date: 2000/06/14 20:49:37 $ + * $Author: hafner $ + * $Revision: 5.1 $ + * $State: Exp $ + */ + +#ifndef _ARITH_H +#define _ARITH_H + +#include "types.h" +#include "bit-io.h" + +typedef struct model +{ + unsigned symbols; /* number of symbols in the alphabet */ + unsigned scale; /* if totals > scale rescale totals */ + unsigned order; /* order of the probability model */ + unsigned *context; /* context of the model */ + unsigned *totals; /* the totals */ +} model_t; + +typedef struct arith +{ + u_word_t low; /* start of the current code range */ + u_word_t high; /* end of the current code range */ + u_word_t underflow; /* number of underflow bits pending */ + u_word_t code; /* the present input code value */ + bitfile_t *file; /* I/O stream */ +} arith_t; + +enum interval {LOW = 0x0000, FIRST_QUARTER = 0x4000, HALF = 0x8000, + THIRD_QUARTER = 0xc000, HIGH = 0xffff}; + +arith_t * +alloc_encoder (bitfile_t *file); +void +free_encoder (arith_t *arith); +real_t +encode_symbol (unsigned symbol, arith_t *arith, model_t *model); +void +encode_array (bitfile_t *output, const unsigned *data, const unsigned *context, + const unsigned *c_symbols, unsigned n_context, unsigned n_data, + unsigned scaling); +arith_t * +alloc_decoder (bitfile_t *input); +void +free_decoder (arith_t *arith); +unsigned +decode_symbol (arith_t *arith, model_t *model); +unsigned * +decode_array (bitfile_t *input, const unsigned *context, + const unsigned *c_symbols, unsigned n_context, + unsigned n_data, unsigned scaling); +model_t * +alloc_model (unsigned m, unsigned scale, unsigned n, unsigned *totals); +void +free_model (model_t *model); + +#define RESCALE_INPUT_INTERVAL for (;;) \ + if ((high >= HALF) && (low < HALF) && \ + ((low & FIRST_QUARTER) != FIRST_QUARTER \ + || (high & FIRST_QUARTER) != 0)) \ + { \ + break; \ + } \ + else if ((high < HALF) || (low >= HALF)) \ + { \ + low <<= 1; \ + high <<= 1; \ + high |= 1; \ + code <<= 1; \ + code += get_bit (input); \ + } \ + else \ + { \ + code ^= FIRST_QUARTER; \ + low &= FIRST_QUARTER - 1; \ + low <<= 1; \ + high <<= 1; \ + high |= HALF + 1; \ + code <<= 1; \ + code += get_bit (input); \ + } + +#define RESCALE_OUTPUT_INTERVAL for (;;) \ + { \ + if (high < HALF) \ + { \ + put_bit (output, 0); \ + for (; underflow; underflow--) \ + put_bit (output, 1); \ + } \ + else if (low >= HALF) \ + { \ + put_bit (output, 1); \ + for (; underflow; underflow--) \ + put_bit (output, 0); \ + } \ + else if (high < THIRD_QUARTER && \ + low >= FIRST_QUARTER) \ + { \ + underflow++; \ + high |= FIRST_QUARTER; \ + low &= FIRST_QUARTER - 1; \ + } \ + else \ + break; \ + high <<= 1; \ + high |= 1; \ + low <<= 1; \ + } + +#endif /* not _ARITH_H */ + |