62 lines
2.4 KiB
C
62 lines
2.4 KiB
C
#ifndef HISTOY_BUFFER_H
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#define HISTOY_BUFFER_H
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#include "conv_common.h"
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// ring buffer of path histories
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// generates output bits after accumulating sufficient history
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typedef struct {
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// history entries must be at least this old to be decoded
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const uint16_t min_traceback_length;
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// we'll decode entries in bursts. this tells us the length of the burst
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const uint16_t traceback_group_length;
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// we will store a total of cap entries. equal to min_traceback_length +
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// traceback_group_length
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const uint16_t cap;
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// how many states in the shift register? this is one of the dimensions of
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// history table
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const uint16_t num_states;
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// what's the high order bit of the shift register?
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const shift_register_t highbit;
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// history is a compact history representation for every shift register
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// state,
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// one bit per time slice
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uint8_t **history;
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// which slice are we writing next?
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uint16_t index;
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// how many valid entries are there?
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uint16_t len;
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// temporary store of fetched bits
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uint8_t *fetched;
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// how often should we renormalize?
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uint16_t renormalize_interval;
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uint16_t renormalize_counter;
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} history_buffer;
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history_buffer *history_buffer_create(uint16_t min_traceback_length,
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uint16_t traceback_group_length,
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uint16_t renormalize_interval,
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uint16_t num_states,
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shift_register_t highbit);
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void history_buffer_destroy(history_buffer *buf);
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void history_buffer_reset(history_buffer *buf);
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void history_buffer_step(history_buffer *buf);
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uint8_t *history_buffer_get_slice(history_buffer *buf);
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shift_register_t history_buffer_search(history_buffer *buf,
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const distance_t *distances,
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uint16_t search_every);
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void history_buffer_traceback(history_buffer *buf, shift_register_t bestpath,
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uint16_t min_traceback_length,
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bit_writer_t *output);
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void history_buffer_process_skip(history_buffer *buf, distance_t *distances,
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bit_writer_t *output, uint16_t skip);
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void history_buffer_process(history_buffer *buf, distance_t *distances,
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bit_writer_t *output);
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void history_buffer_flush(history_buffer *buf, bit_writer_t *output);
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#endif
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