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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
//node_t* huffnode_array; //[_NumCodes];
//lookup_value* lookup_array; //[1 << _MaxBits];
};
// ======================> 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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