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