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https://github.com/ekeeke/Genesis-Plus-GX.git
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89 lines
2.9 KiB
C
89 lines
2.9 KiB
C
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// license:BSD-3-Clause
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// copyright-holders:Aaron Giles
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/***************************************************************************
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huffman.h
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Static Huffman compression and decompression helpers.
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***************************************************************************/
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#pragma once
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#ifndef __HUFFMAN_H__
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#define __HUFFMAN_H__
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#include "bitstream.h"
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//**************************************************************************
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// CONSTANTS
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//**************************************************************************
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enum huffman_error
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{
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HUFFERR_NONE = 0,
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HUFFERR_TOO_MANY_BITS,
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HUFFERR_INVALID_DATA,
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HUFFERR_INPUT_BUFFER_TOO_SMALL,
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HUFFERR_OUTPUT_BUFFER_TOO_SMALL,
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HUFFERR_INTERNAL_INCONSISTENCY,
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HUFFERR_TOO_MANY_CONTEXTS
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};
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//**************************************************************************
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// TYPE DEFINITIONS
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//**************************************************************************
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typedef uint16_t lookup_value;
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// a node in the huffman tree
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struct node_t
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{
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struct node_t* parent; // pointer to parent node
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uint32_t count; // number of hits on this node
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uint32_t weight; // assigned weight of this node
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uint32_t bits; // bits used to encode the node
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uint8_t numbits; // number of bits needed for this node
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};
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// ======================> huffman_context_base
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// context class for decoding
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struct huffman_decoder
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{
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// internal state
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uint32_t numcodes; // number of total codes being processed
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uint8_t maxbits; // maximum bits per code
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uint8_t prevdata; // value of the previous data (for delta-RLE encoding)
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int rleremaining; // number of RLE bytes remaining (for delta-RLE encoding)
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lookup_value * lookup; // pointer to the lookup table
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struct node_t * huffnode; // array of nodes
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uint32_t * datahisto; // histogram of data values
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// array versions of the info we need
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//node_t* huffnode_array; //[_NumCodes];
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//lookup_value* lookup_array; //[1 << _MaxBits];
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};
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// ======================> huffman_decoder
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struct huffman_decoder* create_huffman_decoder(int numcodes, int maxbits);
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void delete_huffman_decoder(struct huffman_decoder* decoder);
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// single item operations
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uint32_t huffman_decode_one(struct huffman_decoder* decoder, struct bitstream* bitbuf);
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enum huffman_error huffman_import_tree_rle(struct huffman_decoder* decoder, struct bitstream* bitbuf);
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enum huffman_error huffman_import_tree_huffman(struct huffman_decoder* decoder, struct bitstream* bitbuf);
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int huffman_build_tree(struct huffman_decoder* decoder, uint32_t totaldata, uint32_t totalweight);
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enum huffman_error huffman_assign_canonical_codes(struct huffman_decoder* decoder);
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enum huffman_error huffman_compute_tree_from_histo(struct huffman_decoder* decoder);
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void huffman_build_lookup_table(struct huffman_decoder* decoder);
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#endif
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