// 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);
void delete_huffman_decoder(struct huffman_decoder* decoder);

// 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
