jpc_mqdec.h
1 /*
2  * Copyright (c) 1999-2000 Image Power, Inc. and the University of
3  * British Columbia.
4  * Copyright (c) 2001-2003 Michael David Adams.
5  * All rights reserved.
6  */
7 
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62  */
63 
64 /*
65  * MQ Arithmetic Decoder
66  *
67  * $Id$
68  */
69 
70 #ifndef JPC_MQDEC_H
71 #define JPC_MQDEC_H
72 
73 /******************************************************************************\
74 * Includes.
75 \******************************************************************************/
76 
77 #include "jasper/jas_types.h"
78 #include "jasper/jas_stream.h"
79 
80 #include "jpc_mqcod.h"
81 
82 /******************************************************************************\
83 * Types.
84 \******************************************************************************/
85 
86 /* MQ arithmetic decoder. */
87 
88 typedef struct {
89 
90  /* The C register. */
91  uint_fast32_t creg;
92 
93  /* The A register. */
94  uint_fast32_t areg;
95 
96  /* The CT register. */
97  uint_fast32_t ctreg;
98 
99  /* The current context. */
100  jpc_mqstate_t **curctx;
101 
102  /* The per-context information. */
103  jpc_mqstate_t **ctxs;
104 
105  /* The maximum number of contexts. */
106  int maxctxs;
107 
108  /* The stream from which to read data. */
109  jas_stream_t *in;
110 
111  /* The last character read. */
112  jas_uchar inbuffer;
113 
114  /* The EOF indicator. */
115  int eof;
116 
117 } jpc_mqdec_t;
118 
119 /******************************************************************************\
120 * Functions/macros for construction and destruction.
121 \******************************************************************************/
122 
123 /* Create a MQ decoder. */
124 jpc_mqdec_t *jpc_mqdec_create(int maxctxs, jas_stream_t *in);
125 
126 /* Destroy a MQ decoder. */
127 void jpc_mqdec_destroy(jpc_mqdec_t *dec);
128 
129 /******************************************************************************\
130 * Functions/macros for initialization.
131 \******************************************************************************/
132 
133 /* Set the input stream associated with a MQ decoder. */
134 void jpc_mqdec_setinput(jpc_mqdec_t *dec, jas_stream_t *in);
135 
136 /* Initialize a MQ decoder. */
137 void jpc_mqdec_init(jpc_mqdec_t *dec);
138 
139 /******************************************************************************\
140 * Functions/macros for manipulating contexts.
141 \******************************************************************************/
142 
143 /* Set the current context for a MQ decoder. */
144 #define jpc_mqdec_setcurctx(dec, ctxno) \
145  ((mqdec)->curctx = &(mqdec)->ctxs[ctxno]);
146 
147 /* Set the state information for a particular context of a MQ decoder. */
148 void jpc_mqdec_setctx(jpc_mqdec_t *dec, int ctxno, jpc_mqctx_t *ctx);
149 
150 /* Set the state information for all contexts of a MQ decoder. */
151 void jpc_mqdec_setctxs(jpc_mqdec_t *dec, int numctxs, jpc_mqctx_t *ctxs);
152 
153 /******************************************************************************\
154 * Functions/macros for decoding bits.
155 \******************************************************************************/
156 
157 /* Decode a symbol. */
158 #if !defined(DEBUG)
159 #define jpc_mqdec_getbit(dec) \
160  jpc_mqdec_getbit_macro(dec)
161 #else
162 #define jpc_mqdec_getbit(dec) \
163  jpc_mqdec_getbit_func(dec)
164 #endif
165 
166 /* Decode a symbol (assuming an unskewed probability distribution). */
167 #if !defined(DEBUG)
168 #define jpc_mqdec_getbitnoskew(dec) \
169  jpc_mqdec_getbit_macro(dec)
170 #else
171 #define jpc_mqdec_getbitnoskew(dec) \
172  jpc_mqdec_getbit_func(dec)
173 #endif
174 
175 /******************************************************************************\
176 * Functions/macros for debugging.
177 \******************************************************************************/
178 
179 /* Dump the MQ decoder state for debugging. */
180 void jpc_mqdec_dump(jpc_mqdec_t *dec, FILE *out);
181 
182 /******************************************************************************\
183 * EVERYTHING BELOW THIS POINT IS IMPLEMENTATION SPECIFIC AND NOT PART OF THE
184 * APPLICATION INTERFACE. DO NOT RELY ON ANY OF THE INTERNAL FUNCTIONS/MACROS
185 * GIVEN BELOW.
186 \******************************************************************************/
187 
188 #define jpc_mqdec_getbit_macro(dec) \
189  ((((dec)->areg -= (*(dec)->curctx)->qeval), \
190  (dec)->creg >> 16 >= (*(dec)->curctx)->qeval) ? \
191  ((((dec)->creg -= (*(dec)->curctx)->qeval << 16), \
192  (dec)->areg & 0x8000) ? (*(dec)->curctx)->mps : \
193  jpc_mqdec_mpsexchrenormd(dec)) : \
194  jpc_mqdec_lpsexchrenormd(dec))
195 
196 #define jpc_mqdec_mpsexchange(areg, delta, curctx, bit) \
197 { \
198  if ((areg) < (delta)) { \
199  register jpc_mqstate_t *state = *(curctx); \
200  /* LPS decoded. */ \
201  (bit) = state->mps ^ 1; \
202  *(curctx) = state->nlps; \
203  } else { \
204  register jpc_mqstate_t *state = *(curctx); \
205  /* MPS decoded. */ \
206  (bit) = state->mps; \
207  *(curctx) = state->nmps; \
208  } \
209 }
210 
211 #define jpc_mqdec_lpsexchange(areg, delta, curctx, bit) \
212 { \
213  if ((areg) >= (delta)) { \
214  register jpc_mqstate_t *state = *(curctx); \
215  (areg) = (delta); \
216  (bit) = state->mps ^ 1; \
217  *(curctx) = state->nlps; \
218  } else { \
219  register jpc_mqstate_t *state = *(curctx); \
220  (areg) = (delta); \
221  (bit) = state->mps; \
222  *(curctx) = state->nmps; \
223  } \
224 }
225 
226 #define jpc_mqdec_renormd(areg, creg, ctreg, in, eof, inbuf) \
227 { \
228  do { \
229  if (!(ctreg)) { \
230  jpc_mqdec_bytein2(creg, ctreg, in, eof, inbuf); \
231  } \
232  (areg) <<= 1; \
233  (creg) <<= 1; \
234  --(ctreg); \
235  } while (!((areg) & 0x8000)); \
236 }
237 
238 #define jpc_mqdec_bytein2(creg, ctreg, in, eof, inbuf) \
239 { \
240  int c; \
241  unsigned char prevbuf; \
242  if (!(eof)) { \
243  if ((c = jas_stream_getc(in)) == EOF) { \
244  (eof) = 1; \
245  c = 0xff; \
246  } \
247  prevbuf = (inbuf); \
248  (inbuf) = c; \
249  if (prevbuf == 0xff) { \
250  if (c > 0x8f) { \
251  (creg) += 0xff00; \
252  (ctreg) = 8; \
253  } else { \
254  (creg) += c << 9; \
255  (ctreg) = 7; \
256  } \
257  } else { \
258  (creg) += c << 8; \
259  (ctreg) = 8; \
260  } \
261  } else { \
262  (creg) += 0xff00; \
263  (ctreg) = 8; \
264  } \
265 }
266 
267 int jpc_mqdec_getbit_func(jpc_mqdec_t *dec);
268 int jpc_mqdec_mpsexchrenormd(jpc_mqdec_t *dec);
269 int jpc_mqdec_lpsexchrenormd(jpc_mqdec_t *dec);
270 
271 #endif