veclavtlica
56 lines
1.9 KiB
C
56 lines
1.9 KiB
C
#ifndef COM_LZW_H
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#define COM_LZW_H
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#include <stdbool.h>
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#include <stdint.h>
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/* Alphabet table for use in LZW algorithms */
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struct com_lzw_table {
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/* table_size indexed entry is reserved for clear code */
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/* table_size+1 indexed entry is reserved for terminator */
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struct com_lzw_table_entry *table;
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uint32_t init_size; /* Alphabet size, table clear is done over it */
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uint32_t size;
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uint32_t cap;
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bool continuous; /* If true, first order search is simple indexing, where
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codepoint = index, up to table_init_size */
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};
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struct com_lzw_table_entry {
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uint16_t child_chain; /* Start of linked list inside table, or 0 if none */
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uint16_t next_child; /* Index of next child, or 0 if none */
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char code; /* Single byte, children bytes are appended to it */
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};
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/* Returns table that is optimized for continuous range of codepoints */
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/* Useful for binary compression, such as .GIF and .SAM formats */
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struct com_lzw_table com_lzw_continous_table(uint8_t codepoints);
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/* Returns table with alphabet inferred from the incoming data */
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/* Useful for alphanumeric compression, where not all codepoints are in use */
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/* TODO: Sort table by frequency? */
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struct com_lzw_table com_lzw_infer_table(const char *datain, uint32_t sizein);
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/* Each bit corresponds to a byte value, position-wise */
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struct com_lzw_encoded_alphabet {
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uint64_t b0;
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uint64_t b1;
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uint64_t b2;
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uint64_t b3;
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};
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struct com_lzw_encoded_alphabet
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com_lzw_encode_alphabet(const struct com_lzw_table *table);
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struct com_lzw_table
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com_lzw_decode_table(struct com_lzw_encoded_alphabet alphabet);
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/* Return table to its original form */
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void com_lzw_clear_table(struct com_lzw_table *table);
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void com_lzw_free_table(struct com_lzw_table *table);
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bool com_lzw_compress(const struct com_lzw_table *table, const char *datain,
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uint32_t sizein, char **dataout, uint32_t *sizeout);
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#endif
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