Coverage Report

Created: 2024-05-04 12:45

/proc/self/cwd/external/libjpeg_turbo/jdmainct.c
Line
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Source (jump to first uncovered line)
1
/*
2
 * jdmainct.c
3
 *
4
 * This file was part of the Independent JPEG Group's software:
5
 * Copyright (C) 1994-1996, Thomas G. Lane.
6
 * libjpeg-turbo Modifications:
7
 * Copyright (C) 2010, 2016, D. R. Commander.
8
 * For conditions of distribution and use, see the accompanying README.ijg
9
 * file.
10
 *
11
 * This file contains the main buffer controller for decompression.
12
 * The main buffer lies between the JPEG decompressor proper and the
13
 * post-processor; it holds downsampled data in the JPEG colorspace.
14
 *
15
 * Note that this code is bypassed in raw-data mode, since the application
16
 * supplies the equivalent of the main buffer in that case.
17
 */
18
19
#include "jinclude.h"
20
#include "jdmainct.h"
21
#include "jconfigint.h"
22
23
24
/*
25
 * In the current system design, the main buffer need never be a full-image
26
 * buffer; any full-height buffers will be found inside the coefficient or
27
 * postprocessing controllers.  Nonetheless, the main controller is not
28
 * trivial.  Its responsibility is to provide context rows for upsampling/
29
 * rescaling, and doing this in an efficient fashion is a bit tricky.
30
 *
31
 * Postprocessor input data is counted in "row groups".  A row group
32
 * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
33
 * sample rows of each component.  (We require DCT_scaled_size values to be
34
 * chosen such that these numbers are integers.  In practice DCT_scaled_size
35
 * values will likely be powers of two, so we actually have the stronger
36
 * condition that DCT_scaled_size / min_DCT_scaled_size is an integer.)
37
 * Upsampling will typically produce max_v_samp_factor pixel rows from each
38
 * row group (times any additional scale factor that the upsampler is
39
 * applying).
40
 *
41
 * The coefficient controller will deliver data to us one iMCU row at a time;
42
 * each iMCU row contains v_samp_factor * DCT_scaled_size sample rows, or
43
 * exactly min_DCT_scaled_size row groups.  (This amount of data corresponds
44
 * to one row of MCUs when the image is fully interleaved.)  Note that the
45
 * number of sample rows varies across components, but the number of row
46
 * groups does not.  Some garbage sample rows may be included in the last iMCU
47
 * row at the bottom of the image.
48
 *
49
 * Depending on the vertical scaling algorithm used, the upsampler may need
50
 * access to the sample row(s) above and below its current input row group.
51
 * The upsampler is required to set need_context_rows TRUE at global selection
52
 * time if so.  When need_context_rows is FALSE, this controller can simply
53
 * obtain one iMCU row at a time from the coefficient controller and dole it
54
 * out as row groups to the postprocessor.
55
 *
56
 * When need_context_rows is TRUE, this controller guarantees that the buffer
57
 * passed to postprocessing contains at least one row group's worth of samples
58
 * above and below the row group(s) being processed.  Note that the context
59
 * rows "above" the first passed row group appear at negative row offsets in
60
 * the passed buffer.  At the top and bottom of the image, the required
61
 * context rows are manufactured by duplicating the first or last real sample
62
 * row; this avoids having special cases in the upsampling inner loops.
63
 *
64
 * The amount of context is fixed at one row group just because that's a
65
 * convenient number for this controller to work with.  The existing
66
 * upsamplers really only need one sample row of context.  An upsampler
67
 * supporting arbitrary output rescaling might wish for more than one row
68
 * group of context when shrinking the image; tough, we don't handle that.
69
 * (This is justified by the assumption that downsizing will be handled mostly
70
 * by adjusting the DCT_scaled_size values, so that the actual scale factor at
71
 * the upsample step needn't be much less than one.)
72
 *
73
 * To provide the desired context, we have to retain the last two row groups
74
 * of one iMCU row while reading in the next iMCU row.  (The last row group
75
 * can't be processed until we have another row group for its below-context,
76
 * and so we have to save the next-to-last group too for its above-context.)
77
 * We could do this most simply by copying data around in our buffer, but
78
 * that'd be very slow.  We can avoid copying any data by creating a rather
79
 * strange pointer structure.  Here's how it works.  We allocate a workspace
80
 * consisting of M+2 row groups (where M = min_DCT_scaled_size is the number
81
 * of row groups per iMCU row).  We create two sets of redundant pointers to
82
 * the workspace.  Labeling the physical row groups 0 to M+1, the synthesized
83
 * pointer lists look like this:
84
 *                   M+1                          M-1
85
 * master pointer --> 0         master pointer --> 0
86
 *                    1                            1
87
 *                   ...                          ...
88
 *                   M-3                          M-3
89
 *                   M-2                           M
90
 *                   M-1                          M+1
91
 *                    M                           M-2
92
 *                   M+1                          M-1
93
 *                    0                            0
94
 * We read alternate iMCU rows using each master pointer; thus the last two
95
 * row groups of the previous iMCU row remain un-overwritten in the workspace.
96
 * The pointer lists are set up so that the required context rows appear to
97
 * be adjacent to the proper places when we pass the pointer lists to the
98
 * upsampler.
99
 *
100
 * The above pictures describe the normal state of the pointer lists.
101
 * At top and bottom of the image, we diddle the pointer lists to duplicate
102
 * the first or last sample row as necessary (this is cheaper than copying
103
 * sample rows around).
104
 *
105
 * This scheme breaks down if M < 2, ie, min_DCT_scaled_size is 1.  In that
106
 * situation each iMCU row provides only one row group so the buffering logic
107
 * must be different (eg, we must read two iMCU rows before we can emit the
108
 * first row group).  For now, we simply do not support providing context
109
 * rows when min_DCT_scaled_size is 1.  That combination seems unlikely to
110
 * be worth providing --- if someone wants a 1/8th-size preview, they probably
111
 * want it quick and dirty, so a context-free upsampler is sufficient.
112
 */
113
114
115
/* Forward declarations */
116
METHODDEF(void) process_data_simple_main(j_decompress_ptr cinfo,
117
                                         JSAMPARRAY output_buf,
118
                                         JDIMENSION *out_row_ctr,
119
                                         JDIMENSION out_rows_avail);
120
METHODDEF(void) process_data_context_main(j_decompress_ptr cinfo,
121
                                          JSAMPARRAY output_buf,
122
                                          JDIMENSION *out_row_ctr,
123
                                          JDIMENSION out_rows_avail);
124
#ifdef QUANT_2PASS_SUPPORTED
125
METHODDEF(void) process_data_crank_post(j_decompress_ptr cinfo,
126
                                        JSAMPARRAY output_buf,
127
                                        JDIMENSION *out_row_ctr,
128
                                        JDIMENSION out_rows_avail);
129
#endif
130
131
132
LOCAL(void)
133
alloc_funny_pointers(j_decompress_ptr cinfo)
134
/* Allocate space for the funny pointer lists.
135
 * This is done only once, not once per pass.
136
 */
137
19
{
138
19
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
139
19
  int ci, rgroup;
140
19
  int M = cinfo->_min_DCT_scaled_size;
141
19
  jpeg_component_info *compptr;
142
19
  JSAMPARRAY xbuf;
143
144
  /* Get top-level space for component array pointers.
145
   * We alloc both arrays with one call to save a few cycles.
146
   */
147
19
  main_ptr->xbuffer[0] = (JSAMPIMAGE)
148
19
    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
149
19
                                cinfo->num_components * 2 * sizeof(JSAMPARRAY));
150
19
  main_ptr->xbuffer[1] = main_ptr->xbuffer[0] + cinfo->num_components;
151
152
76
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
153
57
       ci++, compptr++) {
154
57
    rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
155
57
      cinfo->_min_DCT_scaled_size; /* height of a row group of component */
156
    /* Get space for pointer lists --- M+4 row groups in each list.
157
     * We alloc both pointer lists with one call to save a few cycles.
158
     */
159
57
    xbuf = (JSAMPARRAY)
160
57
      (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
161
57
                                  2 * (rgroup * (M + 4)) * sizeof(JSAMPROW));
162
57
    xbuf += rgroup;             /* want one row group at negative offsets */
163
57
    main_ptr->xbuffer[0][ci] = xbuf;
164
57
    xbuf += rgroup * (M + 4);
165
57
    main_ptr->xbuffer[1][ci] = xbuf;
166
57
  }
167
19
}
168
169
170
LOCAL(void)
171
make_funny_pointers(j_decompress_ptr cinfo)
172
/* Create the funny pointer lists discussed in the comments above.
173
 * The actual workspace is already allocated (in main_ptr->buffer),
174
 * and the space for the pointer lists is allocated too.
175
 * This routine just fills in the curiously ordered lists.
176
 * This will be repeated at the beginning of each pass.
177
 */
178
4
{
179
4
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
180
4
  int ci, i, rgroup;
181
4
  int M = cinfo->_min_DCT_scaled_size;
182
4
  jpeg_component_info *compptr;
183
4
  JSAMPARRAY buf, xbuf0, xbuf1;
184
185
16
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
186
12
       ci++, compptr++) {
187
12
    rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
188
12
      cinfo->_min_DCT_scaled_size; /* height of a row group of component */
189
12
    xbuf0 = main_ptr->xbuffer[0][ci];
190
12
    xbuf1 = main_ptr->xbuffer[1][ci];
191
    /* First copy the workspace pointers as-is */
192
12
    buf = main_ptr->buffer[ci];
193
172
    for (i = 0; i < rgroup * (M + 2); i++) {
194
160
      xbuf0[i] = xbuf1[i] = buf[i];
195
160
    }
196
    /* In the second list, put the last four row groups in swapped order */
197
44
    for (i = 0; i < rgroup * 2; i++) {
198
32
      xbuf1[rgroup * (M - 2) + i] = buf[rgroup * M + i];
199
32
      xbuf1[rgroup * M + i] = buf[rgroup * (M - 2) + i];
200
32
    }
201
    /* The wraparound pointers at top and bottom will be filled later
202
     * (see set_wraparound_pointers, below).  Initially we want the "above"
203
     * pointers to duplicate the first actual data line.  This only needs
204
     * to happen in xbuffer[0].
205
     */
206
28
    for (i = 0; i < rgroup; i++) {
207
16
      xbuf0[i - rgroup] = xbuf0[0];
208
16
    }
209
12
  }
210
4
}
211
212
213
LOCAL(void)
214
set_bottom_pointers(j_decompress_ptr cinfo)
215
/* Change the pointer lists to duplicate the last sample row at the bottom
216
 * of the image.  whichptr indicates which xbuffer holds the final iMCU row.
217
 * Also sets rowgroups_avail to indicate number of nondummy row groups in row.
218
 */
219
3
{
220
3
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
221
3
  int ci, i, rgroup, iMCUheight, rows_left;
222
3
  jpeg_component_info *compptr;
223
3
  JSAMPARRAY xbuf;
224
225
12
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
226
9
       ci++, compptr++) {
227
    /* Count sample rows in one iMCU row and in one row group */
228
9
    iMCUheight = compptr->v_samp_factor * compptr->_DCT_scaled_size;
229
9
    rgroup = iMCUheight / cinfo->_min_DCT_scaled_size;
230
    /* Count nondummy sample rows remaining for this component */
231
9
    rows_left = (int)(compptr->downsampled_height % (JDIMENSION)iMCUheight);
232
9
    if (rows_left == 0) rows_left = iMCUheight;
233
    /* Count nondummy row groups.  Should get same answer for each component,
234
     * so we need only do it once.
235
     */
236
9
    if (ci == 0) {
237
3
      main_ptr->rowgroups_avail = (JDIMENSION)((rows_left - 1) / rgroup + 1);
238
3
    }
239
    /* Duplicate the last real sample row rgroup*2 times; this pads out the
240
     * last partial rowgroup and ensures at least one full rowgroup of context.
241
     */
242
9
    xbuf = main_ptr->xbuffer[main_ptr->whichptr][ci];
243
33
    for (i = 0; i < rgroup * 2; i++) {
244
24
      xbuf[rows_left + i] = xbuf[rows_left - 1];
245
24
    }
246
9
  }
247
3
}
248
249
250
/*
251
 * Initialize for a processing pass.
252
 */
253
254
METHODDEF(void)
255
start_pass_main(j_decompress_ptr cinfo, J_BUF_MODE pass_mode)
256
34
{
257
34
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
258
259
34
  switch (pass_mode) {
260
34
  case JBUF_PASS_THRU:
261
34
    if (cinfo->upsample->need_context_rows) {
262
4
      main_ptr->pub.process_data = process_data_context_main;
263
4
      make_funny_pointers(cinfo); /* Create the xbuffer[] lists */
264
4
      main_ptr->whichptr = 0;   /* Read first iMCU row into xbuffer[0] */
265
4
      main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
266
4
      main_ptr->iMCU_row_ctr = 0;
267
30
    } else {
268
      /* Simple case with no context needed */
269
30
      main_ptr->pub.process_data = process_data_simple_main;
270
30
    }
271
34
    main_ptr->buffer_full = FALSE;      /* Mark buffer empty */
272
34
    main_ptr->rowgroup_ctr = 0;
273
34
    break;
274
0
#ifdef QUANT_2PASS_SUPPORTED
275
0
  case JBUF_CRANK_DEST:
276
    /* For last pass of 2-pass quantization, just crank the postprocessor */
277
0
    main_ptr->pub.process_data = process_data_crank_post;
278
0
    break;
279
0
#endif
280
0
  default:
281
0
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
282
0
    break;
283
34
  }
284
34
}
285
286
287
/*
288
 * Process some data.
289
 * This handles the simple case where no context is required.
290
 */
291
292
METHODDEF(void)
293
process_data_simple_main(j_decompress_ptr cinfo, JSAMPARRAY output_buf,
294
                         JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
295
73.7k
{
296
73.7k
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
297
73.7k
  JDIMENSION rowgroups_avail;
298
299
  /* Read input data if we haven't filled the main buffer yet */
300
73.7k
  if (!main_ptr->buffer_full) {
301
8.78k
    if (!(*cinfo->coef->decompress_data) (cinfo, main_ptr->buffer))
302
10
      return;                   /* suspension forced, can do nothing more */
303
8.77k
    main_ptr->buffer_full = TRUE;       /* OK, we have an iMCU row to work with */
304
8.77k
  }
305
306
  /* There are always min_DCT_scaled_size row groups in an iMCU row. */
307
73.7k
  rowgroups_avail = (JDIMENSION)cinfo->_min_DCT_scaled_size;
308
  /* Note: at the bottom of the image, we may pass extra garbage row groups
309
   * to the postprocessor.  The postprocessor has to check for bottom
310
   * of image anyway (at row resolution), so no point in us doing it too.
311
   */
312
313
  /* Feed the postprocessor */
314
73.7k
  (*cinfo->post->post_process_data) (cinfo, main_ptr->buffer,
315
73.7k
                                     &main_ptr->rowgroup_ctr, rowgroups_avail,
316
73.7k
                                     output_buf, out_row_ctr, out_rows_avail);
317
318
  /* Has postprocessor consumed all the data yet? If so, mark buffer empty */
319
73.7k
  if (main_ptr->rowgroup_ctr >= rowgroups_avail) {
320
8.76k
    main_ptr->buffer_full = FALSE;
321
8.76k
    main_ptr->rowgroup_ctr = 0;
322
8.76k
  }
323
73.7k
}
324
325
326
/*
327
 * Process some data.
328
 * This handles the case where context rows must be provided.
329
 */
330
331
METHODDEF(void)
332
process_data_context_main(j_decompress_ptr cinfo, JSAMPARRAY output_buf,
333
                          JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
334
10.9k
{
335
10.9k
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
336
337
  /* Read input data if we haven't filled the main buffer yet */
338
10.9k
  if (!main_ptr->buffer_full) {
339
687
    if (!(*cinfo->coef->decompress_data) (cinfo,
340
687
                                          main_ptr->xbuffer[main_ptr->whichptr]))
341
1
      return;                   /* suspension forced, can do nothing more */
342
686
    main_ptr->buffer_full = TRUE;       /* OK, we have an iMCU row to work with */
343
686
    main_ptr->iMCU_row_ctr++;   /* count rows received */
344
686
  }
345
346
  /* Postprocessor typically will not swallow all the input data it is handed
347
   * in one call (due to filling the output buffer first).  Must be prepared
348
   * to exit and restart.  This switch lets us keep track of how far we got.
349
   * Note that each case falls through to the next on successful completion.
350
   */
351
10.9k
  switch (main_ptr->context_state) {
352
1.36k
  case CTX_POSTPONED_ROW:
353
    /* Call postprocessor using previously set pointers for postponed row */
354
1.36k
    (*cinfo->post->post_process_data) (cinfo,
355
1.36k
                                       main_ptr->xbuffer[main_ptr->whichptr],
356
1.36k
                                       &main_ptr->rowgroup_ctr,
357
1.36k
                                       main_ptr->rowgroups_avail, output_buf,
358
1.36k
                                       out_row_ctr, out_rows_avail);
359
1.36k
    if (main_ptr->rowgroup_ctr < main_ptr->rowgroups_avail)
360
682
      return;                   /* Need to suspend */
361
682
    main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
362
682
    if (*out_row_ctr >= out_rows_avail)
363
682
      return;                   /* Postprocessor exactly filled output buf */
364
    FALLTHROUGH                 /*FALLTHROUGH*/
365
686
  case CTX_PREPARE_FOR_IMCU:
366
    /* Prepare to process first M-1 row groups of this iMCU row */
367
686
    main_ptr->rowgroup_ctr = 0;
368
686
    main_ptr->rowgroups_avail = (JDIMENSION)(cinfo->_min_DCT_scaled_size - 1);
369
    /* Check for bottom of image: if so, tweak pointers to "duplicate"
370
     * the last sample row, and adjust rowgroups_avail to ignore padding rows.
371
     */
372
686
    if (main_ptr->iMCU_row_ctr == cinfo->total_iMCU_rows)
373
3
      set_bottom_pointers(cinfo);
374
686
    main_ptr->context_state = CTX_PROCESS_IMCU;
375
    FALLTHROUGH                 /*FALLTHROUGH*/
376
9.61k
  case CTX_PROCESS_IMCU:
377
    /* Call postprocessor using previously set pointers */
378
9.61k
    (*cinfo->post->post_process_data) (cinfo,
379
9.61k
                                       main_ptr->xbuffer[main_ptr->whichptr],
380
9.61k
                                       &main_ptr->rowgroup_ctr,
381
9.61k
                                       main_ptr->rowgroups_avail, output_buf,
382
9.61k
                                       out_row_ctr, out_rows_avail);
383
9.61k
    if (main_ptr->rowgroup_ctr < main_ptr->rowgroups_avail)
384
8.92k
      return;                   /* Need to suspend */
385
    /* After the first iMCU, change wraparound pointers to normal state */
386
686
    if (main_ptr->iMCU_row_ctr == 1)
387
4
      set_wraparound_pointers(cinfo);
388
    /* Prepare to load new iMCU row using other xbuffer list */
389
686
    main_ptr->whichptr ^= 1;    /* 0=>1 or 1=>0 */
390
686
    main_ptr->buffer_full = FALSE;
391
    /* Still need to process last row group of this iMCU row, */
392
    /* which is saved at index M+1 of the other xbuffer */
393
686
    main_ptr->rowgroup_ctr = (JDIMENSION)(cinfo->_min_DCT_scaled_size + 1);
394
686
    main_ptr->rowgroups_avail = (JDIMENSION)(cinfo->_min_DCT_scaled_size + 2);
395
686
    main_ptr->context_state = CTX_POSTPONED_ROW;
396
10.9k
  }
397
10.9k
}
398
399
400
/*
401
 * Process some data.
402
 * Final pass of two-pass quantization: just call the postprocessor.
403
 * Source data will be the postprocessor controller's internal buffer.
404
 */
405
406
#ifdef QUANT_2PASS_SUPPORTED
407
408
METHODDEF(void)
409
process_data_crank_post(j_decompress_ptr cinfo, JSAMPARRAY output_buf,
410
                        JDIMENSION *out_row_ctr, JDIMENSION out_rows_avail)
411
0
{
412
0
  (*cinfo->post->post_process_data) (cinfo, (JSAMPIMAGE)NULL,
413
0
                                     (JDIMENSION *)NULL, (JDIMENSION)0,
414
0
                                     output_buf, out_row_ctr, out_rows_avail);
415
0
}
416
417
#endif /* QUANT_2PASS_SUPPORTED */
418
419
420
/*
421
 * Initialize main buffer controller.
422
 */
423
424
GLOBAL(void)
425
jinit_d_main_controller(j_decompress_ptr cinfo, boolean need_full_buffer)
426
124
{
427
124
  my_main_ptr main_ptr;
428
124
  int ci, rgroup, ngroups;
429
124
  jpeg_component_info *compptr;
430
431
124
  main_ptr = (my_main_ptr)
432
124
    (*cinfo->mem->alloc_small) ((j_common_ptr)cinfo, JPOOL_IMAGE,
433
124
                                sizeof(my_main_controller));
434
124
  cinfo->main = (struct jpeg_d_main_controller *)main_ptr;
435
124
  main_ptr->pub.start_pass = start_pass_main;
436
437
124
  if (need_full_buffer)         /* shouldn't happen */
438
0
    ERREXIT(cinfo, JERR_BAD_BUFFER_MODE);
439
440
  /* Allocate the workspace.
441
   * ngroups is the number of row groups we need.
442
   */
443
124
  if (cinfo->upsample->need_context_rows) {
444
19
    if (cinfo->_min_DCT_scaled_size < 2) /* unsupported, see comments above */
445
0
      ERREXIT(cinfo, JERR_NOTIMPL);
446
19
    alloc_funny_pointers(cinfo); /* Alloc space for xbuffer[] lists */
447
19
    ngroups = cinfo->_min_DCT_scaled_size + 2;
448
105
  } else {
449
105
    ngroups = cinfo->_min_DCT_scaled_size;
450
105
  }
451
452
459
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
453
335
       ci++, compptr++) {
454
335
    rgroup = (compptr->v_samp_factor * compptr->_DCT_scaled_size) /
455
335
      cinfo->_min_DCT_scaled_size; /* height of a row group of component */
456
335
    main_ptr->buffer[ci] = (*cinfo->mem->alloc_sarray)
457
335
                        ((j_common_ptr)cinfo, JPOOL_IMAGE,
458
335
                         compptr->width_in_blocks * compptr->_DCT_scaled_size,
459
335
                         (JDIMENSION)(rgroup * ngroups));
460
335
  }
461
124
}