1 /*
2  * jcphuff.c
3  *
4  * Copyright (C) 1995-1997, Thomas G. Lane.
5  * This file is part of the Independent JPEG Group's software.
6  * For conditions of distribution and use, see the accompanying README file.
7  *
8  * This file contains Huffman entropy encoding routines for progressive JPEG.
9  *
10  * We do not support output suspension in this module, since the library
11  * currently does not allow multiple-scan files to be written with output
12  * suspension.
13  */
14 
15 #define JPEG_INTERNALS
16 #include "jinclude.h"
17 #include "jpeglib.h"
18 #include "jchuff.h"		/* Declarations shared with jchuff.c */
19 
20 #ifdef C_PROGRESSIVE_SUPPORTED
21 
22 /* Expanded entropy encoder object for progressive Huffman encoding. */
23 
24 typedef struct {
25   struct jpeg_entropy_encoder pub; /* public fields */
26 
27   /* Mode flag: TRUE for optimization, FALSE for actual data output */
28   boolean gather_statistics;
29 
30   /* Bit-level coding status.
31    * next_output_byte/free_in_buffer are local copies of cinfo->dest fields.
32    */
33   JOCTET * next_output_byte;	/* => next byte to write in buffer */
34   size_t free_in_buffer;	/* # of byte spaces remaining in buffer */
35   INT32 put_buffer;		/* current bit-accumulation buffer */
36   int put_bits;			/* # of bits now in it */
37   j_compress_ptr cinfo;		/* link to cinfo (needed for dump_buffer) */
38 
39   /* Coding status for DC components */
40   int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
41 
42   /* Coding status for AC components */
43   int ac_tbl_no;		/* the table number of the single component */
44   unsigned int EOBRUN;		/* run length of EOBs */
45   unsigned int BE;		/* # of buffered correction bits before MCU */
46   char * bit_buffer;		/* buffer for correction bits (1 per char) */
47   /* packing correction bits tightly would save some space but cost time... */
48 
49   unsigned int restarts_to_go;	/* MCUs left in this restart interval */
50   int next_restart_num;		/* next restart number to write (0-7) */
51 
52   /* Pointers to derived tables (these workspaces have image lifespan).
53    * Since any one scan codes only DC or only AC, we only need one set
54    * of tables, not one for DC and one for AC.
55    */
56   c_derived_tbl * derived_tbls[NUM_HUFF_TBLS];
57 
58   /* Statistics tables for optimization; again, one set is enough */
59   long * count_ptrs[NUM_HUFF_TBLS];
60 } phuff_entropy_encoder;
61 
62 typedef phuff_entropy_encoder * phuff_entropy_ptr;
63 
64 /* MAX_CORR_BITS is the number of bits the AC refinement correction-bit
65  * buffer can hold.  Larger sizes may slightly improve compression, but
66  * 1000 is already well into the realm of overkill.
67  * The minimum safe size is 64 bits.
68  */
69 
70 #define MAX_CORR_BITS  1000	/* Max # of correction bits I can buffer */
71 
72 /* IRIGHT_SHIFT is like RIGHT_SHIFT, but works on int rather than INT32.
73  * We assume that int right shift is unsigned if INT32 right shift is,
74  * which should be safe.
75  */
76 
77 #ifdef RIGHT_SHIFT_IS_UNSIGNED
78 #define ISHIFT_TEMPS	int ishift_temp;
79 #define IRIGHT_SHIFT(x,shft)  \
80 	((ishift_temp = (x)) < 0 ? \
81 	 (ishift_temp >> (shft)) | ((~0) << (16-(shft))) : \
82 	 (ishift_temp >> (shft)))
83 #else
84 #define ISHIFT_TEMPS
85 #define IRIGHT_SHIFT(x,shft)	((x) >> (shft))
86 #endif
87 
88 /* Forward declarations */
89 METHODDEF(boolean) encode_mcu_DC_first JPP((j_compress_ptr cinfo,
90 					    JBLOCKROW *MCU_data));
91 METHODDEF(boolean) encode_mcu_AC_first JPP((j_compress_ptr cinfo,
92 					    JBLOCKROW *MCU_data));
93 METHODDEF(boolean) encode_mcu_DC_refine JPP((j_compress_ptr cinfo,
94 					     JBLOCKROW *MCU_data));
95 METHODDEF(boolean) encode_mcu_AC_refine JPP((j_compress_ptr cinfo,
96 					     JBLOCKROW *MCU_data));
97 METHODDEF(void) finish_pass_phuff JPP((j_compress_ptr cinfo));
98 METHODDEF(void) finish_pass_gather_phuff JPP((j_compress_ptr cinfo));
99 
100 
101 /*
102  * Initialize for a Huffman-compressed scan using progressive JPEG.
103  */
104 
105 METHODDEF(void)
start_pass_phuff(j_compress_ptr cinfo,boolean gather_statistics)106 start_pass_phuff (j_compress_ptr cinfo, boolean gather_statistics)
107 {
108   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
109   boolean is_DC_band;
110   int ci, tbl;
111   jpeg_component_info * compptr;
112 
113   entropy->cinfo = cinfo;
114   entropy->gather_statistics = gather_statistics;
115 
116   is_DC_band = (cinfo->Ss == 0);
117 
118   /* We assume jcmaster.c already validated the scan parameters. */
119 
120   /* Select execution routines */
121   if (cinfo->Ah == 0) {
122     if (is_DC_band)
123       entropy->pub.encode_mcu = encode_mcu_DC_first;
124     else
125       entropy->pub.encode_mcu = encode_mcu_AC_first;
126   } else {
127     if (is_DC_band)
128       entropy->pub.encode_mcu = encode_mcu_DC_refine;
129     else {
130       entropy->pub.encode_mcu = encode_mcu_AC_refine;
131       /* AC refinement needs a correction bit buffer */
132       if (entropy->bit_buffer == NULL)
133 	entropy->bit_buffer = (char *)
134 	  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
135 				      MAX_CORR_BITS * SIZEOF(char));
136     }
137   }
138   if (gather_statistics)
139     entropy->pub.finish_pass = finish_pass_gather_phuff;
140   else
141     entropy->pub.finish_pass = finish_pass_phuff;
142 
143   /* Only DC coefficients may be interleaved, so cinfo->comps_in_scan = 1
144    * for AC coefficients.
145    */
146   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
147     compptr = cinfo->cur_comp_info[ci];
148     /* Initialize DC predictions to 0 */
149     entropy->last_dc_val[ci] = 0;
150     /* Get table index */
151     if (is_DC_band) {
152       if (cinfo->Ah != 0)	/* DC refinement needs no table */
153 	continue;
154       tbl = compptr->dc_tbl_no;
155     } else {
156       entropy->ac_tbl_no = tbl = compptr->ac_tbl_no;
157     }
158     if (gather_statistics) {
159       /* Check for invalid table index */
160       /* (make_c_derived_tbl does this in the other path) */
161       if (tbl < 0 || tbl >= NUM_HUFF_TBLS)
162         ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
163       /* Allocate and zero the statistics tables */
164       /* Note that jpeg_gen_optimal_table expects 257 entries in each table! */
165       if (entropy->count_ptrs[tbl] == NULL)
166 	entropy->count_ptrs[tbl] = (long *)
167 	  (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
168 				      257 * SIZEOF(long));
169       MEMZERO(entropy->count_ptrs[tbl], 257 * SIZEOF(long));
170     } else {
171       /* Compute derived values for Huffman table */
172       /* We may do this more than once for a table, but it's not expensive */
173       jpeg_make_c_derived_tbl(cinfo, is_DC_band, tbl,
174 			      & entropy->derived_tbls[tbl]);
175     }
176   }
177 
178   /* Initialize AC stuff */
179   entropy->EOBRUN = 0;
180   entropy->BE = 0;
181 
182   /* Initialize bit buffer to empty */
183   entropy->put_buffer = 0;
184   entropy->put_bits = 0;
185 
186   /* Initialize restart stuff */
187   entropy->restarts_to_go = cinfo->restart_interval;
188   entropy->next_restart_num = 0;
189 }
190 
191 
192 /* Outputting bytes to the file.
193  * NB: these must be called only when actually outputting,
194  * that is, entropy->gather_statistics == FALSE.
195  */
196 
197 /* Emit a byte */
198 #define emit_byte(entropy,val)  \
199 	{ *(entropy)->next_output_byte++ = (JOCTET) (val);  \
200 	  if (--(entropy)->free_in_buffer == 0)  \
201 	    dump_buffer(entropy); }
202 
203 
204 LOCAL(void)
dump_buffer(phuff_entropy_ptr entropy)205 dump_buffer (phuff_entropy_ptr entropy)
206 /* Empty the output buffer; we do not support suspension in this module. */
207 {
208   struct jpeg_destination_mgr * dest = entropy->cinfo->dest;
209 
210   if (! (*dest->empty_output_buffer) (entropy->cinfo))
211     ERREXIT(entropy->cinfo, JERR_CANT_SUSPEND);
212   /* After a successful buffer dump, must reset buffer pointers */
213   entropy->next_output_byte = dest->next_output_byte;
214   entropy->free_in_buffer = dest->free_in_buffer;
215 }
216 
217 
218 /* Outputting bits to the file */
219 
220 /* Only the right 24 bits of put_buffer are used; the valid bits are
221  * left-justified in this part.  At most 16 bits can be passed to emit_bits
222  * in one call, and we never retain more than 7 bits in put_buffer
223  * between calls, so 24 bits are sufficient.
224  */
225 
226 INLINE
LOCAL(void)227 LOCAL(void)
228 emit_bits (phuff_entropy_ptr entropy, unsigned int code, int size)
229 /* Emit some bits, unless we are in gather mode */
230 {
231   /* This routine is heavily used, so it's worth coding tightly. */
232   register INT32 put_buffer = (INT32) code;
233   register int put_bits = entropy->put_bits;
234 
235   /* if size is 0, caller used an invalid Huffman table entry */
236   if (size == 0)
237     ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
238 
239   if (entropy->gather_statistics)
240     return;			/* do nothing if we're only getting stats */
241 
242   put_buffer &= (((INT32) 1)<<size) - 1; /* mask off any extra bits in code */
243 
244   put_bits += size;		/* new number of bits in buffer */
245 
246   put_buffer <<= 24 - put_bits; /* align incoming bits */
247 
248   put_buffer |= entropy->put_buffer; /* and merge with old buffer contents */
249 
250   while (put_bits >= 8) {
251     int c = (int) ((put_buffer >> 16) & 0xFF);
252 
253     emit_byte(entropy, c);
254     if (c == 0xFF) {		/* need to stuff a zero byte? */
255       emit_byte(entropy, 0);
256     }
257     put_buffer <<= 8;
258     put_bits -= 8;
259   }
260 
261   entropy->put_buffer = put_buffer; /* update variables */
262   entropy->put_bits = put_bits;
263 }
264 
265 
266 LOCAL(void)
flush_bits(phuff_entropy_ptr entropy)267 flush_bits (phuff_entropy_ptr entropy)
268 {
269   emit_bits(entropy, 0x7F, 7); /* fill any partial byte with ones */
270   entropy->put_buffer = 0;     /* and reset bit-buffer to empty */
271   entropy->put_bits = 0;
272 }
273 
274 
275 /*
276  * Emit (or just count) a Huffman symbol.
277  */
278 
279 INLINE
LOCAL(void)280 LOCAL(void)
281 emit_symbol (phuff_entropy_ptr entropy, int tbl_no, int symbol)
282 {
283   if (entropy->gather_statistics)
284     entropy->count_ptrs[tbl_no][symbol]++;
285   else {
286     c_derived_tbl * tbl = entropy->derived_tbls[tbl_no];
287     emit_bits(entropy, tbl->ehufco[symbol], tbl->ehufsi[symbol]);
288   }
289 }
290 
291 
292 /*
293  * Emit bits from a correction bit buffer.
294  */
295 
296 LOCAL(void)
emit_buffered_bits(phuff_entropy_ptr entropy,char * bufstart,unsigned int nbits)297 emit_buffered_bits (phuff_entropy_ptr entropy, char * bufstart,
298 		    unsigned int nbits)
299 {
300   if (entropy->gather_statistics)
301     return;			/* no real work */
302 
303   while (nbits > 0) {
304     emit_bits(entropy, (unsigned int) (*bufstart), 1);
305     bufstart++;
306     nbits--;
307   }
308 }
309 
310 
311 /*
312  * Emit any pending EOBRUN symbol.
313  */
314 
315 LOCAL(void)
emit_eobrun(phuff_entropy_ptr entropy)316 emit_eobrun (phuff_entropy_ptr entropy)
317 {
318   register int temp, nbits;
319 
320   if (entropy->EOBRUN > 0) {	/* if there is any pending EOBRUN */
321     temp = entropy->EOBRUN;
322     nbits = 0;
323     while ((temp >>= 1))
324       nbits++;
325     /* safety check: shouldn't happen given limited correction-bit buffer */
326     if (nbits > 14)
327       ERREXIT(entropy->cinfo, JERR_HUFF_MISSING_CODE);
328 
329     emit_symbol(entropy, entropy->ac_tbl_no, nbits << 4);
330     if (nbits)
331       emit_bits(entropy, entropy->EOBRUN, nbits);
332 
333     entropy->EOBRUN = 0;
334 
335     /* Emit any buffered correction bits */
336     emit_buffered_bits(entropy, entropy->bit_buffer, entropy->BE);
337     entropy->BE = 0;
338   }
339 }
340 
341 
342 /*
343  * Emit a restart marker & resynchronize predictions.
344  */
345 
346 LOCAL(void)
emit_restart(phuff_entropy_ptr entropy,int restart_num)347 emit_restart (phuff_entropy_ptr entropy, int restart_num)
348 {
349   int ci;
350 
351   emit_eobrun(entropy);
352 
353   if (! entropy->gather_statistics) {
354     flush_bits(entropy);
355     emit_byte(entropy, 0xFF);
356     emit_byte(entropy, JPEG_RST0 + restart_num);
357   }
358 
359   if (entropy->cinfo->Ss == 0) {
360     /* Re-initialize DC predictions to 0 */
361     for (ci = 0; ci < entropy->cinfo->comps_in_scan; ci++)
362       entropy->last_dc_val[ci] = 0;
363   } else {
364     /* Re-initialize all AC-related fields to 0 */
365     entropy->EOBRUN = 0;
366     entropy->BE = 0;
367   }
368 }
369 
370 
371 /*
372  * MCU encoding for DC initial scan (either spectral selection,
373  * or first pass of successive approximation).
374  */
375 
376 METHODDEF(boolean)
encode_mcu_DC_first(j_compress_ptr cinfo,JBLOCKROW * MCU_data)377 encode_mcu_DC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
378 {
379   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
380   register int temp, temp2;
381   register int nbits;
382   int blkn, ci;
383   int Al = cinfo->Al;
384   JBLOCKROW block;
385   jpeg_component_info * compptr;
386   ISHIFT_TEMPS
387 
388   entropy->next_output_byte = cinfo->dest->next_output_byte;
389   entropy->free_in_buffer = cinfo->dest->free_in_buffer;
390 
391   /* Emit restart marker if needed */
392   if (cinfo->restart_interval)
393     if (entropy->restarts_to_go == 0)
394       emit_restart(entropy, entropy->next_restart_num);
395 
396   /* Encode the MCU data blocks */
397   for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
398     block = MCU_data[blkn];
399     ci = cinfo->MCU_membership[blkn];
400     compptr = cinfo->cur_comp_info[ci];
401 
402     /* Compute the DC value after the required point transform by Al.
403      * This is simply an arithmetic right shift.
404      */
405     temp2 = IRIGHT_SHIFT((int) ((*block)[0]), Al);
406 
407     /* DC differences are figured on the point-transformed values. */
408     temp = temp2 - entropy->last_dc_val[ci];
409     entropy->last_dc_val[ci] = temp2;
410 
411     /* Encode the DC coefficient difference per section G.1.2.1 */
412     temp2 = temp;
413     if (temp < 0) {
414       temp = -temp;		/* temp is abs value of input */
415       /* For a negative input, want temp2 = bitwise complement of abs(input) */
416       /* This code assumes we are on a two's complement machine */
417       temp2--;
418     }
419 
420     /* Find the number of bits needed for the magnitude of the coefficient */
421     nbits = 0;
422     while (temp) {
423       nbits++;
424       temp >>= 1;
425     }
426     /* Check for out-of-range coefficient values.
427      * Since we're encoding a difference, the range limit is twice as much.
428      */
429     if (nbits > MAX_COEF_BITS+1)
430       ERREXIT(cinfo, JERR_BAD_DCT_COEF);
431 
432     /* Count/emit the Huffman-coded symbol for the number of bits */
433     emit_symbol(entropy, compptr->dc_tbl_no, nbits);
434 
435     /* Emit that number of bits of the value, if positive, */
436     /* or the complement of its magnitude, if negative. */
437     if (nbits)			/* emit_bits rejects calls with size 0 */
438       emit_bits(entropy, (unsigned int) temp2, nbits);
439   }
440 
441   cinfo->dest->next_output_byte = entropy->next_output_byte;
442   cinfo->dest->free_in_buffer = entropy->free_in_buffer;
443 
444   /* Update restart-interval state too */
445   if (cinfo->restart_interval) {
446     if (entropy->restarts_to_go == 0) {
447       entropy->restarts_to_go = cinfo->restart_interval;
448       entropy->next_restart_num++;
449       entropy->next_restart_num &= 7;
450     }
451     entropy->restarts_to_go--;
452   }
453 
454   return TRUE;
455 }
456 
457 
458 /*
459  * MCU encoding for AC initial scan (either spectral selection,
460  * or first pass of successive approximation).
461  */
462 
463 METHODDEF(boolean)
encode_mcu_AC_first(j_compress_ptr cinfo,JBLOCKROW * MCU_data)464 encode_mcu_AC_first (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
465 {
466   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
467   register int temp, temp2;
468   register int nbits;
469   register int r, k;
470   int Se = cinfo->Se;
471   int Al = cinfo->Al;
472   JBLOCKROW block;
473 
474   entropy->next_output_byte = cinfo->dest->next_output_byte;
475   entropy->free_in_buffer = cinfo->dest->free_in_buffer;
476 
477   /* Emit restart marker if needed */
478   if (cinfo->restart_interval)
479     if (entropy->restarts_to_go == 0)
480       emit_restart(entropy, entropy->next_restart_num);
481 
482   /* Encode the MCU data block */
483   block = MCU_data[0];
484 
485   /* Encode the AC coefficients per section G.1.2.2, fig. G.3 */
486 
487   r = 0;			/* r = run length of zeros */
488 
489   for (k = cinfo->Ss; k <= Se; k++) {
490     if ((temp = (*block)[jpeg_natural_order[k]]) == 0) {
491       r++;
492       continue;
493     }
494     /* We must apply the point transform by Al.  For AC coefficients this
495      * is an integer division with rounding towards 0.  To do this portably
496      * in C, we shift after obtaining the absolute value; so the code is
497      * interwoven with finding the abs value (temp) and output bits (temp2).
498      */
499     if (temp < 0) {
500       temp = -temp;		/* temp is abs value of input */
501       temp >>= Al;		/* apply the point transform */
502       /* For a negative coef, want temp2 = bitwise complement of abs(coef) */
503       temp2 = ~temp;
504     } else {
505       temp >>= Al;		/* apply the point transform */
506       temp2 = temp;
507     }
508     /* Watch out for case that nonzero coef is zero after point transform */
509     if (temp == 0) {
510       r++;
511       continue;
512     }
513 
514     /* Emit any pending EOBRUN */
515     if (entropy->EOBRUN > 0)
516       emit_eobrun(entropy);
517     /* if run length > 15, must emit special run-length-16 codes (0xF0) */
518     while (r > 15) {
519       emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
520       r -= 16;
521     }
522 
523     /* Find the number of bits needed for the magnitude of the coefficient */
524     nbits = 1;			/* there must be at least one 1 bit */
525     while ((temp >>= 1))
526       nbits++;
527     /* Check for out-of-range coefficient values */
528     if (nbits > MAX_COEF_BITS)
529       ERREXIT(cinfo, JERR_BAD_DCT_COEF);
530 
531     /* Count/emit Huffman symbol for run length / number of bits */
532     emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + nbits);
533 
534     /* Emit that number of bits of the value, if positive, */
535     /* or the complement of its magnitude, if negative. */
536     emit_bits(entropy, (unsigned int) temp2, nbits);
537 
538     r = 0;			/* reset zero run length */
539   }
540 
541   if (r > 0) {			/* If there are trailing zeroes, */
542     entropy->EOBRUN++;		/* count an EOB */
543     if (entropy->EOBRUN == 0x7FFF)
544       emit_eobrun(entropy);	/* force it out to avoid overflow */
545   }
546 
547   cinfo->dest->next_output_byte = entropy->next_output_byte;
548   cinfo->dest->free_in_buffer = entropy->free_in_buffer;
549 
550   /* Update restart-interval state too */
551   if (cinfo->restart_interval) {
552     if (entropy->restarts_to_go == 0) {
553       entropy->restarts_to_go = cinfo->restart_interval;
554       entropy->next_restart_num++;
555       entropy->next_restart_num &= 7;
556     }
557     entropy->restarts_to_go--;
558   }
559 
560   return TRUE;
561 }
562 
563 
564 /*
565  * MCU encoding for DC successive approximation refinement scan.
566  * Note: we assume such scans can be multi-component, although the spec
567  * is not very clear on the point.
568  */
569 
570 METHODDEF(boolean)
encode_mcu_DC_refine(j_compress_ptr cinfo,JBLOCKROW * MCU_data)571 encode_mcu_DC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
572 {
573   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
574   register int temp;
575   int blkn;
576   int Al = cinfo->Al;
577   JBLOCKROW block;
578 
579   entropy->next_output_byte = cinfo->dest->next_output_byte;
580   entropy->free_in_buffer = cinfo->dest->free_in_buffer;
581 
582   /* Emit restart marker if needed */
583   if (cinfo->restart_interval)
584     if (entropy->restarts_to_go == 0)
585       emit_restart(entropy, entropy->next_restart_num);
586 
587   /* Encode the MCU data blocks */
588   for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
589     block = MCU_data[blkn];
590 
591     /* We simply emit the Al'th bit of the DC coefficient value. */
592     temp = (*block)[0];
593     emit_bits(entropy, (unsigned int) (temp >> Al), 1);
594   }
595 
596   cinfo->dest->next_output_byte = entropy->next_output_byte;
597   cinfo->dest->free_in_buffer = entropy->free_in_buffer;
598 
599   /* Update restart-interval state too */
600   if (cinfo->restart_interval) {
601     if (entropy->restarts_to_go == 0) {
602       entropy->restarts_to_go = cinfo->restart_interval;
603       entropy->next_restart_num++;
604       entropy->next_restart_num &= 7;
605     }
606     entropy->restarts_to_go--;
607   }
608 
609   return TRUE;
610 }
611 
612 
613 /*
614  * MCU encoding for AC successive approximation refinement scan.
615  */
616 
617 METHODDEF(boolean)
encode_mcu_AC_refine(j_compress_ptr cinfo,JBLOCKROW * MCU_data)618 encode_mcu_AC_refine (j_compress_ptr cinfo, JBLOCKROW *MCU_data)
619 {
620   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
621   register int temp;
622   register int r, k;
623   int EOB;
624   char *BR_buffer;
625   unsigned int BR;
626   int Se = cinfo->Se;
627   int Al = cinfo->Al;
628   JBLOCKROW block;
629   int absvalues[DCTSIZE2];
630 
631   entropy->next_output_byte = cinfo->dest->next_output_byte;
632   entropy->free_in_buffer = cinfo->dest->free_in_buffer;
633 
634   /* Emit restart marker if needed */
635   if (cinfo->restart_interval)
636     if (entropy->restarts_to_go == 0)
637       emit_restart(entropy, entropy->next_restart_num);
638 
639   /* Encode the MCU data block */
640   block = MCU_data[0];
641 
642   /* It is convenient to make a pre-pass to determine the transformed
643    * coefficients' absolute values and the EOB position.
644    */
645   EOB = 0;
646   for (k = cinfo->Ss; k <= Se; k++) {
647     temp = (*block)[jpeg_natural_order[k]];
648     /* We must apply the point transform by Al.  For AC coefficients this
649      * is an integer division with rounding towards 0.  To do this portably
650      * in C, we shift after obtaining the absolute value.
651      */
652     if (temp < 0)
653       temp = -temp;		/* temp is abs value of input */
654     temp >>= Al;		/* apply the point transform */
655     absvalues[k] = temp;	/* save abs value for main pass */
656     if (temp == 1)
657       EOB = k;			/* EOB = index of last newly-nonzero coef */
658   }
659 
660   /* Encode the AC coefficients per section G.1.2.3, fig. G.7 */
661 
662   r = 0;			/* r = run length of zeros */
663   BR = 0;			/* BR = count of buffered bits added now */
664   BR_buffer = entropy->bit_buffer + entropy->BE; /* Append bits to buffer */
665 
666   for (k = cinfo->Ss; k <= Se; k++) {
667     if ((temp = absvalues[k]) == 0) {
668       r++;
669       continue;
670     }
671 
672     /* Emit any required ZRLs, but not if they can be folded into EOB */
673     while (r > 15 && k <= EOB) {
674       /* emit any pending EOBRUN and the BE correction bits */
675       emit_eobrun(entropy);
676       /* Emit ZRL */
677       emit_symbol(entropy, entropy->ac_tbl_no, 0xF0);
678       r -= 16;
679       /* Emit buffered correction bits that must be associated with ZRL */
680       emit_buffered_bits(entropy, BR_buffer, BR);
681       BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
682       BR = 0;
683     }
684 
685     /* If the coef was previously nonzero, it only needs a correction bit.
686      * NOTE: a straight translation of the spec's figure G.7 would suggest
687      * that we also need to test r > 15.  But if r > 15, we can only get here
688      * if k > EOB, which implies that this coefficient is not 1.
689      */
690     if (temp > 1) {
691       /* The correction bit is the next bit of the absolute value. */
692       BR_buffer[BR++] = (char) (temp & 1);
693       continue;
694     }
695 
696     /* Emit any pending EOBRUN and the BE correction bits */
697     emit_eobrun(entropy);
698 
699     /* Count/emit Huffman symbol for run length / number of bits */
700     emit_symbol(entropy, entropy->ac_tbl_no, (r << 4) + 1);
701 
702     /* Emit output bit for newly-nonzero coef */
703     temp = ((*block)[jpeg_natural_order[k]] < 0) ? 0 : 1;
704     emit_bits(entropy, (unsigned int) temp, 1);
705 
706     /* Emit buffered correction bits that must be associated with this code */
707     emit_buffered_bits(entropy, BR_buffer, BR);
708     BR_buffer = entropy->bit_buffer; /* BE bits are gone now */
709     BR = 0;
710     r = 0;			/* reset zero run length */
711   }
712 
713   if (r > 0 || BR > 0) {	/* If there are trailing zeroes, */
714     entropy->EOBRUN++;		/* count an EOB */
715     entropy->BE += BR;		/* concat my correction bits to older ones */
716     /* We force out the EOB if we risk either:
717      * 1. overflow of the EOB counter;
718      * 2. overflow of the correction bit buffer during the next MCU.
719      */
720     if (entropy->EOBRUN == 0x7FFF || entropy->BE > (MAX_CORR_BITS-DCTSIZE2+1))
721       emit_eobrun(entropy);
722   }
723 
724   cinfo->dest->next_output_byte = entropy->next_output_byte;
725   cinfo->dest->free_in_buffer = entropy->free_in_buffer;
726 
727   /* Update restart-interval state too */
728   if (cinfo->restart_interval) {
729     if (entropy->restarts_to_go == 0) {
730       entropy->restarts_to_go = cinfo->restart_interval;
731       entropy->next_restart_num++;
732       entropy->next_restart_num &= 7;
733     }
734     entropy->restarts_to_go--;
735   }
736 
737   return TRUE;
738 }
739 
740 
741 /*
742  * Finish up at the end of a Huffman-compressed progressive scan.
743  */
744 
745 METHODDEF(void)
finish_pass_phuff(j_compress_ptr cinfo)746 finish_pass_phuff (j_compress_ptr cinfo)
747 {
748   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
749 
750   entropy->next_output_byte = cinfo->dest->next_output_byte;
751   entropy->free_in_buffer = cinfo->dest->free_in_buffer;
752 
753   /* Flush out any buffered data */
754   emit_eobrun(entropy);
755   flush_bits(entropy);
756 
757   cinfo->dest->next_output_byte = entropy->next_output_byte;
758   cinfo->dest->free_in_buffer = entropy->free_in_buffer;
759 }
760 
761 
762 /*
763  * Finish up a statistics-gathering pass and create the new Huffman tables.
764  */
765 
766 METHODDEF(void)
finish_pass_gather_phuff(j_compress_ptr cinfo)767 finish_pass_gather_phuff (j_compress_ptr cinfo)
768 {
769   phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;
770   boolean is_DC_band;
771   int ci, tbl;
772   jpeg_component_info * compptr;
773   JHUFF_TBL **htblptr;
774   boolean did[NUM_HUFF_TBLS];
775 
776   /* Flush out buffered data (all we care about is counting the EOB symbol) */
777   emit_eobrun(entropy);
778 
779   is_DC_band = (cinfo->Ss == 0);
780 
781   /* It's important not to apply jpeg_gen_optimal_table more than once
782    * per table, because it clobbers the input frequency counts!
783    */
784   MEMZERO(did, SIZEOF(did));
785 
786   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
787     compptr = cinfo->cur_comp_info[ci];
788     if (is_DC_band) {
789       if (cinfo->Ah != 0)	/* DC refinement needs no table */
790 	continue;
791       tbl = compptr->dc_tbl_no;
792     } else {
793       tbl = compptr->ac_tbl_no;
794     }
795     if (! did[tbl]) {
796       if (is_DC_band)
797         htblptr = & cinfo->dc_huff_tbl_ptrs[tbl];
798       else
799         htblptr = & cinfo->ac_huff_tbl_ptrs[tbl];
800       if (*htblptr == NULL)
801         *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
802       jpeg_gen_optimal_table(cinfo, *htblptr, entropy->count_ptrs[tbl]);
803       did[tbl] = TRUE;
804     }
805   }
806 }
807 
808 
809 /*
810  * Module initialization routine for progressive Huffman entropy encoding.
811  */
812 
813 GLOBAL(void)
jinit_phuff_encoder(j_compress_ptr cinfo)814 jinit_phuff_encoder (j_compress_ptr cinfo)
815 {
816   phuff_entropy_ptr entropy;
817   int i;
818 
819   entropy = (phuff_entropy_ptr)
820     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
821 				SIZEOF(phuff_entropy_encoder));
822   cinfo->entropy = (struct jpeg_entropy_encoder *) entropy;
823   entropy->pub.start_pass = start_pass_phuff;
824 
825   /* Mark tables unallocated */
826   for (i = 0; i < NUM_HUFF_TBLS; i++) {
827     entropy->derived_tbls[i] = NULL;
828     entropy->count_ptrs[i] = NULL;
829   }
830   entropy->bit_buffer = NULL;	/* needed only in AC refinement scan */
831 }
832 
833 #endif /* C_PROGRESSIVE_SUPPORTED */
834