blob: db71067f4375f31a3358bbe864ab910107529b99 [file] [log] [blame]
Thomas G. Lanebc79e061995-08-02 00:00:00 +00001/*
2 * jdhuff.h
3 *
DRCa73e8702012-12-31 02:52:30 +00004 * This file was part of the Independent JPEG Group's software:
Thomas G. Lane5ead57a1998-03-27 00:00:00 +00005 * Copyright (C) 1991-1997, Thomas G. Lane.
DRCda13af62014-05-18 17:52:06 +00006 * libjpeg-turbo Modifications:
DRC5a3b4fe2016-01-06 19:17:54 -06007 * Copyright (C) 2010-2011, 2015-2016, D. R. Commander.
Thomas G. Lanebc79e061995-08-02 00:00:00 +00008 * For conditions of distribution and use, see the accompanying README file.
9 *
10 * This file contains declarations for Huffman entropy decoding routines
11 * that are shared between the sequential decoder (jdhuff.c) and the
12 * progressive decoder (jdphuff.c). No other modules need to see these.
13 */
14
DRC5a3b4fe2016-01-06 19:17:54 -060015#include "jconfigint.h"
16
Thomas G. Lanebc79e061995-08-02 00:00:00 +000017
18/* Derived data constructed for each Huffman table */
19
DRCe5eaf372014-05-09 18:00:32 +000020#define HUFF_LOOKAHEAD 8 /* # of bits of lookahead */
Thomas G. Lanebc79e061995-08-02 00:00:00 +000021
22typedef struct {
23 /* Basic tables: (element [0] of each array is unused) */
DRCe5eaf372014-05-09 18:00:32 +000024 INT32 maxcode[18]; /* largest code of length k (-1 if none) */
Thomas G. Lanebc79e061995-08-02 00:00:00 +000025 /* (maxcode[17] is a sentinel to ensure jpeg_huff_decode terminates) */
DRCe5eaf372014-05-09 18:00:32 +000026 INT32 valoffset[18]; /* huffval[] offset for codes of length k */
Thomas G. Lane5ead57a1998-03-27 00:00:00 +000027 /* valoffset[k] = huffval[] index of 1st symbol of code length k, less
28 * the smallest code of length k; so given a code of length k, the
29 * corresponding symbol is huffval[code + valoffset[k]]
30 */
Thomas G. Lanebc79e061995-08-02 00:00:00 +000031
32 /* Link to public Huffman table (needed only in jpeg_huff_decode) */
33 JHUFF_TBL *pub;
34
DRCe2816642009-09-28 00:33:02 +000035 /* Lookahead table: indexed by the next HUFF_LOOKAHEAD bits of
Thomas G. Lanebc79e061995-08-02 00:00:00 +000036 * the input data stream. If the next Huffman code is no more
37 * than HUFF_LOOKAHEAD bits long, we can obtain its length and
DRCe2816642009-09-28 00:33:02 +000038 * the corresponding symbol directly from this tables.
39 *
40 * The lower 8 bits of each table entry contain the number of
41 * bits in the corresponding Huffman code, or HUFF_LOOKAHEAD + 1
42 * if too long. The next 8 bits of each entry contain the
43 * symbol.
Thomas G. Lanebc79e061995-08-02 00:00:00 +000044 */
DRCe2816642009-09-28 00:33:02 +000045 int lookup[1<<HUFF_LOOKAHEAD];
Thomas G. Lanebc79e061995-08-02 00:00:00 +000046} d_derived_tbl;
47
48/* Expand a Huffman table definition into the derived format */
Thomas G. Lane5ead57a1998-03-27 00:00:00 +000049EXTERN(void) jpeg_make_d_derived_tbl
DRCbc56b752014-05-16 10:43:44 +000050 (j_decompress_ptr cinfo, boolean isDC, int tblno,
51 d_derived_tbl ** pdtbl);
Thomas G. Lanebc79e061995-08-02 00:00:00 +000052
53
54/*
55 * Fetching the next N bits from the input stream is a time-critical operation
56 * for the Huffman decoders. We implement it with a combination of inline
57 * macros and out-of-line subroutines. Note that N (the number of bits
58 * demanded at one time) never exceeds 15 for JPEG use.
59 *
60 * We read source bytes into get_buffer and dole out bits as needed.
61 * If get_buffer already contains enough bits, they are fetched in-line
62 * by the macros CHECK_BIT_BUFFER and GET_BITS. When there aren't enough
63 * bits, jpeg_fill_bit_buffer is called; it will attempt to fill get_buffer
64 * as full as possible (not just to the number of bits needed; this
65 * prefetching reduces the overhead cost of calling jpeg_fill_bit_buffer).
66 * Note that jpeg_fill_bit_buffer may return FALSE to indicate suspension.
67 * On TRUE return, jpeg_fill_bit_buffer guarantees that get_buffer contains
68 * at least the requested number of bits --- dummy zeroes are inserted if
69 * necessary.
70 */
71
DRC3ebcc322015-05-15 19:09:44 +000072#if !defined(_WIN32) && !defined(SIZEOF_SIZE_T)
73#error Cannot determine word size
74#endif
75
76#if SIZEOF_SIZE_T==8 || defined(_WIN64)
DRC021da082009-09-28 08:19:40 +000077
DRCe5eaf372014-05-09 18:00:32 +000078typedef size_t bit_buf_type; /* type of bit-extraction buffer */
79#define BIT_BUF_SIZE 64 /* size of buffer in bits */
DRC021da082009-09-28 08:19:40 +000080
81#else
82
DRCe5eaf372014-05-09 18:00:32 +000083typedef INT32 bit_buf_type; /* type of bit-extraction buffer */
84#define BIT_BUF_SIZE 32 /* size of buffer in bits */
DRC021da082009-09-28 08:19:40 +000085
86#endif
Thomas G. Lanebc79e061995-08-02 00:00:00 +000087
88/* If long is > 32 bits on your machine, and shifting/masking longs is
89 * reasonably fast, making bit_buf_type be long and setting BIT_BUF_SIZE
Thomas G. Lane5ead57a1998-03-27 00:00:00 +000090 * appropriately should be a win. Unfortunately we can't define the size
91 * with something like #define BIT_BUF_SIZE (sizeof(bit_buf_type)*8)
Thomas G. Lanebc79e061995-08-02 00:00:00 +000092 * because not all machines measure sizeof in 8-bit bytes.
93 */
94
DRCe5eaf372014-05-09 18:00:32 +000095typedef struct { /* Bitreading state saved across MCUs */
96 bit_buf_type get_buffer; /* current bit-extraction buffer */
97 int bits_left; /* # of unused bits in it */
Thomas G. Lanebc79e061995-08-02 00:00:00 +000098} bitread_perm_state;
99
DRCe5eaf372014-05-09 18:00:32 +0000100typedef struct { /* Bitreading working state within an MCU */
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000101 /* Current data source location */
102 /* We need a copy, rather than munging the original, in case of suspension */
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000103 const JOCTET * next_input_byte; /* => next byte to read from source */
DRCe5eaf372014-05-09 18:00:32 +0000104 size_t bytes_in_buffer; /* # of bytes remaining in source buffer */
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000105 /* Bit input buffer --- note these values are kept in register variables,
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000106 * not in this struct, inside the inner loops.
107 */
DRCe5eaf372014-05-09 18:00:32 +0000108 bit_buf_type get_buffer; /* current bit-extraction buffer */
109 int bits_left; /* # of unused bits in it */
Thomas G. Lane5ead57a1998-03-27 00:00:00 +0000110 /* Pointer needed by jpeg_fill_bit_buffer. */
DRCe5eaf372014-05-09 18:00:32 +0000111 j_decompress_ptr cinfo; /* back link to decompress master record */
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000112} bitread_working_state;
113
114/* Macros to declare and load/save bitread local variables. */
115#define BITREAD_STATE_VARS \
DRCe5eaf372014-05-09 18:00:32 +0000116 register bit_buf_type get_buffer; \
117 register int bits_left; \
118 bitread_working_state br_state
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000119
120#define BITREAD_LOAD_STATE(cinfop,permstate) \
DRCe5eaf372014-05-09 18:00:32 +0000121 br_state.cinfo = cinfop; \
122 br_state.next_input_byte = cinfop->src->next_input_byte; \
123 br_state.bytes_in_buffer = cinfop->src->bytes_in_buffer; \
124 get_buffer = permstate.get_buffer; \
125 bits_left = permstate.bits_left;
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000126
127#define BITREAD_SAVE_STATE(cinfop,permstate) \
DRCe5eaf372014-05-09 18:00:32 +0000128 cinfop->src->next_input_byte = br_state.next_input_byte; \
129 cinfop->src->bytes_in_buffer = br_state.bytes_in_buffer; \
130 permstate.get_buffer = get_buffer; \
131 permstate.bits_left = bits_left
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000132
133/*
134 * These macros provide the in-line portion of bit fetching.
135 * Use CHECK_BIT_BUFFER to ensure there are N bits in get_buffer
136 * before using GET_BITS, PEEK_BITS, or DROP_BITS.
137 * The variables get_buffer and bits_left are assumed to be locals,
138 * but the state struct might not be (jpeg_huff_decode needs this).
DRCe5eaf372014-05-09 18:00:32 +0000139 * CHECK_BIT_BUFFER(state,n,action);
140 * Ensure there are N bits in get_buffer; if suspend, take action.
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000141 * val = GET_BITS(n);
DRCe5eaf372014-05-09 18:00:32 +0000142 * Fetch next N bits.
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000143 * val = PEEK_BITS(n);
DRCe5eaf372014-05-09 18:00:32 +0000144 * Fetch next N bits without removing them from the buffer.
145 * DROP_BITS(n);
146 * Discard next N bits.
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000147 * The value N should be a simple variable, not an expression, because it
148 * is evaluated multiple times.
149 */
150
151#define CHECK_BIT_BUFFER(state,nbits,action) \
DRCe5eaf372014-05-09 18:00:32 +0000152 { if (bits_left < (nbits)) { \
153 if (! jpeg_fill_bit_buffer(&(state),get_buffer,bits_left,nbits)) \
154 { action; } \
155 get_buffer = (state).get_buffer; bits_left = (state).bits_left; } }
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000156
157#define GET_BITS(nbits) \
DRCe5eaf372014-05-09 18:00:32 +0000158 (((int) (get_buffer >> (bits_left -= (nbits)))) & ((1<<(nbits))-1))
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000159
160#define PEEK_BITS(nbits) \
DRCe5eaf372014-05-09 18:00:32 +0000161 (((int) (get_buffer >> (bits_left - (nbits)))) & ((1<<(nbits))-1))
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000162
163#define DROP_BITS(nbits) \
DRCe5eaf372014-05-09 18:00:32 +0000164 (bits_left -= (nbits))
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000165
166/* Load up the bit buffer to a depth of at least nbits */
Thomas G. Lane489583f1996-02-07 00:00:00 +0000167EXTERN(boolean) jpeg_fill_bit_buffer
DRCbc56b752014-05-16 10:43:44 +0000168 (bitread_working_state * state, register bit_buf_type get_buffer,
169 register int bits_left, int nbits);
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000170
171
172/*
173 * Code for extracting next Huffman-coded symbol from input bit stream.
174 * Again, this is time-critical and we make the main paths be macros.
175 *
176 * We use a lookahead table to process codes of up to HUFF_LOOKAHEAD bits
177 * without looping. Usually, more than 95% of the Huffman codes will be 8
178 * or fewer bits long. The few overlength codes are handled with a loop,
179 * which need not be inline code.
180 *
181 * Notes about the HUFF_DECODE macro:
182 * 1. Near the end of the data segment, we may fail to get enough bits
183 * for a lookahead. In that case, we do it the hard way.
184 * 2. If the lookahead table contains no entry, the next code must be
185 * more than HUFF_LOOKAHEAD bits long.
186 * 3. jpeg_huff_decode returns -1 if forced to suspend.
187 */
188
189#define HUFF_DECODE(result,state,htbl,failaction,slowlabel) \
190{ register int nb, look; \
191 if (bits_left < HUFF_LOOKAHEAD) { \
192 if (! jpeg_fill_bit_buffer(&state,get_buffer,bits_left, 0)) {failaction;} \
193 get_buffer = state.get_buffer; bits_left = state.bits_left; \
194 if (bits_left < HUFF_LOOKAHEAD) { \
195 nb = 1; goto slowlabel; \
196 } \
197 } \
198 look = PEEK_BITS(HUFF_LOOKAHEAD); \
DRCe2816642009-09-28 00:33:02 +0000199 if ((nb = (htbl->lookup[look] >> HUFF_LOOKAHEAD)) <= HUFF_LOOKAHEAD) { \
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000200 DROP_BITS(nb); \
DRCe2816642009-09-28 00:33:02 +0000201 result = htbl->lookup[look] & ((1 << HUFF_LOOKAHEAD) - 1); \
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000202 } else { \
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000203slowlabel: \
204 if ((result=jpeg_huff_decode(&state,get_buffer,bits_left,htbl,nb)) < 0) \
DRCe5eaf372014-05-09 18:00:32 +0000205 { failaction; } \
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000206 get_buffer = state.get_buffer; bits_left = state.bits_left; \
207 } \
208}
209
DRCbc515802011-04-18 06:52:07 +0000210#define HUFF_DECODE_FAST(s,nb,htbl) \
211 FILL_BIT_BUFFER_FAST; \
212 s = PEEK_BITS(HUFF_LOOKAHEAD); \
213 s = htbl->lookup[s]; \
214 nb = s >> HUFF_LOOKAHEAD; \
215 /* Pre-execute the common case of nb <= HUFF_LOOKAHEAD */ \
216 DROP_BITS(nb); \
217 s = s & ((1 << HUFF_LOOKAHEAD) - 1); \
218 if (nb > HUFF_LOOKAHEAD) { \
219 /* Equivalent of jpeg_huff_decode() */ \
220 /* Don't use GET_BITS() here because we don't want to modify bits_left */ \
221 s = (get_buffer >> bits_left) & ((1 << (nb)) - 1); \
222 while (s > htbl->maxcode[nb]) { \
223 s <<= 1; \
224 s |= GET_BITS(1); \
225 nb++; \
226 } \
227 s = htbl->pub->huffval[ (int) (s + htbl->valoffset[nb]) & 0xFF ]; \
228 }
229
Thomas G. Lanebc79e061995-08-02 00:00:00 +0000230/* Out-of-line case for Huffman code fetching */
Thomas G. Lane489583f1996-02-07 00:00:00 +0000231EXTERN(int) jpeg_huff_decode
DRCbc56b752014-05-16 10:43:44 +0000232 (bitread_working_state * state, register bit_buf_type get_buffer,
233 register int bits_left, d_derived_tbl * htbl, int min_bits);