1 /* license:BSD-3-Clause
2 * copyright-holders:Aaron Giles
3 ***************************************************************************
7 Static Huffman compression and decompression helpers.
9 ***************************************************************************/
16 #include <libchdr/bitstream.h>
19 /***************************************************************************
21 ***************************************************************************
27 HUFFERR_TOO_MANY_BITS,
29 HUFFERR_INPUT_BUFFER_TOO_SMALL,
30 HUFFERR_OUTPUT_BUFFER_TOO_SMALL,
31 HUFFERR_INTERNAL_INCONSISTENCY,
32 HUFFERR_TOO_MANY_CONTEXTS
35 /***************************************************************************
37 ***************************************************************************
40 typedef uint16_t lookup_value;
42 /* a node in the huffman tree */
45 struct node_t* parent; /* pointer to parent node */
46 uint32_t count; /* number of hits on this node */
47 uint32_t weight; /* assigned weight of this node */
48 uint32_t bits; /* bits used to encode the node */
49 uint8_t numbits; /* number of bits needed for this node */
52 /* ======================> huffman_context_base */
54 /* context class for decoding */
55 struct huffman_decoder
58 uint32_t numcodes; /* number of total codes being processed */
59 uint8_t maxbits; /* maximum bits per code */
60 uint8_t prevdata; /* value of the previous data (for delta-RLE encoding) */
61 int rleremaining; /* number of RLE bytes remaining (for delta-RLE encoding) */
62 lookup_value * lookup; /* pointer to the lookup table */
63 struct node_t * huffnode; /* array of nodes */
64 uint32_t * datahisto; /* histogram of data values */
66 /* array versions of the info we need */
68 node_t* huffnode_array; /* [_NumCodes]; */
69 lookup_value* lookup_array; /* [1 << _MaxBits]; */
73 /* ======================> huffman_decoder */
75 struct huffman_decoder* create_huffman_decoder(int numcodes, int maxbits);
76 void delete_huffman_decoder(struct huffman_decoder* decoder);
78 /* single item operations */
79 uint32_t huffman_decode_one(struct huffman_decoder* decoder, struct bitstream* bitbuf);
81 enum huffman_error huffman_import_tree_rle(struct huffman_decoder* decoder, struct bitstream* bitbuf);
82 enum huffman_error huffman_import_tree_huffman(struct huffman_decoder* decoder, struct bitstream* bitbuf);
84 int huffman_build_tree(struct huffman_decoder* decoder, uint32_t totaldata, uint32_t totalweight);
85 enum huffman_error huffman_assign_canonical_codes(struct huffman_decoder* decoder);
86 enum huffman_error huffman_compute_tree_from_histo(struct huffman_decoder* decoder);
88 void huffman_build_lookup_table(struct huffman_decoder* decoder);