Coverage Report

Created: 2018-09-25 14:53

/src/mozilla-central/media/libjpeg/jdapistd.c
Line
Count
Source (jump to first uncovered line)
1
/*
2
 * jdapistd.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, 2015-2016, D. R. Commander.
8
 * Copyright (C) 2015, Google, Inc.
9
 * For conditions of distribution and use, see the accompanying README.ijg
10
 * file.
11
 *
12
 * This file contains application interface code for the decompression half
13
 * of the JPEG library.  These are the "standard" API routines that are
14
 * used in the normal full-decompression case.  They are not used by a
15
 * transcoding-only application.  Note that if an application links in
16
 * jpeg_start_decompress, it will end up linking in the entire decompressor.
17
 * We thus must separate this file from jdapimin.c to avoid linking the
18
 * whole decompression library into a transcoder.
19
 */
20
21
#include "jinclude.h"
22
#include "jdmainct.h"
23
#include "jdcoefct.h"
24
#include "jdsample.h"
25
#include "jmemsys.h"
26
27
/* Forward declarations */
28
LOCAL(boolean) output_pass_setup (j_decompress_ptr cinfo);
29
30
31
/*
32
 * Decompression initialization.
33
 * jpeg_read_header must be completed before calling this.
34
 *
35
 * If a multipass operating mode was selected, this will do all but the
36
 * last pass, and thus may take a great deal of time.
37
 *
38
 * Returns FALSE if suspended.  The return value need be inspected only if
39
 * a suspending data source is used.
40
 */
41
42
GLOBAL(boolean)
43
jpeg_start_decompress (j_decompress_ptr cinfo)
44
0
{
45
0
  if (cinfo->global_state == DSTATE_READY) {
46
0
    /* First call: initialize master control, select active modules */
47
0
    jinit_master_decompress(cinfo);
48
0
    if (cinfo->buffered_image) {
49
0
      /* No more work here; expecting jpeg_start_output next */
50
0
      cinfo->global_state = DSTATE_BUFIMAGE;
51
0
      return TRUE;
52
0
    }
53
0
    cinfo->global_state = DSTATE_PRELOAD;
54
0
  }
55
0
  if (cinfo->global_state == DSTATE_PRELOAD) {
56
0
    /* If file has multiple scans, absorb them all into the coef buffer */
57
0
    if (cinfo->inputctl->has_multiple_scans) {
58
0
#ifdef D_MULTISCAN_FILES_SUPPORTED
59
0
      for (;;) {
60
0
        int retcode;
61
0
        /* Call progress monitor hook if present */
62
0
        if (cinfo->progress != NULL)
63
0
          (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
64
0
        /* Absorb some more input */
65
0
        retcode = (*cinfo->inputctl->consume_input) (cinfo);
66
0
        if (retcode == JPEG_SUSPENDED)
67
0
          return FALSE;
68
0
        if (retcode == JPEG_REACHED_EOI)
69
0
          break;
70
0
        /* Advance progress counter if appropriate */
71
0
        if (cinfo->progress != NULL &&
72
0
            (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
73
0
          if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
74
0
            /* jdmaster underestimated number of scans; ratchet up one scan */
75
0
            cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
76
0
          }
77
0
        }
78
0
      }
79
#else
80
      ERREXIT(cinfo, JERR_NOT_COMPILED);
81
#endif /* D_MULTISCAN_FILES_SUPPORTED */
82
    }
83
0
    cinfo->output_scan_number = cinfo->input_scan_number;
84
0
  } else if (cinfo->global_state != DSTATE_PRESCAN)
85
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
86
0
  /* Perform any dummy output passes, and set up for the final pass */
87
0
  return output_pass_setup(cinfo);
88
0
}
89
90
91
/*
92
 * Set up for an output pass, and perform any dummy pass(es) needed.
93
 * Common subroutine for jpeg_start_decompress and jpeg_start_output.
94
 * Entry: global_state = DSTATE_PRESCAN only if previously suspended.
95
 * Exit: If done, returns TRUE and sets global_state for proper output mode.
96
 *       If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN.
97
 */
98
99
LOCAL(boolean)
100
output_pass_setup (j_decompress_ptr cinfo)
101
0
{
102
0
  if (cinfo->global_state != DSTATE_PRESCAN) {
103
0
    /* First call: do pass setup */
104
0
    (*cinfo->master->prepare_for_output_pass) (cinfo);
105
0
    cinfo->output_scanline = 0;
106
0
    cinfo->global_state = DSTATE_PRESCAN;
107
0
  }
108
0
  /* Loop over any required dummy passes */
109
0
  while (cinfo->master->is_dummy_pass) {
110
0
#ifdef QUANT_2PASS_SUPPORTED
111
0
    /* Crank through the dummy pass */
112
0
    while (cinfo->output_scanline < cinfo->output_height) {
113
0
      JDIMENSION last_scanline;
114
0
      /* Call progress monitor hook if present */
115
0
      if (cinfo->progress != NULL) {
116
0
        cinfo->progress->pass_counter = (long) cinfo->output_scanline;
117
0
        cinfo->progress->pass_limit = (long) cinfo->output_height;
118
0
        (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
119
0
      }
120
0
      /* Process some data */
121
0
      last_scanline = cinfo->output_scanline;
122
0
      (*cinfo->main->process_data) (cinfo, (JSAMPARRAY) NULL,
123
0
                                    &cinfo->output_scanline, (JDIMENSION) 0);
124
0
      if (cinfo->output_scanline == last_scanline)
125
0
        return FALSE;           /* No progress made, must suspend */
126
0
    }
127
0
    /* Finish up dummy pass, and set up for another one */
128
0
    (*cinfo->master->finish_output_pass) (cinfo);
129
0
    (*cinfo->master->prepare_for_output_pass) (cinfo);
130
0
    cinfo->output_scanline = 0;
131
#else
132
    ERREXIT(cinfo, JERR_NOT_COMPILED);
133
#endif /* QUANT_2PASS_SUPPORTED */
134
  }
135
0
  /* Ready for application to drive output pass through
136
0
   * jpeg_read_scanlines or jpeg_read_raw_data.
137
0
   */
138
0
  cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING;
139
0
  return TRUE;
140
0
}
141
142
143
/*
144
 * Enable partial scanline decompression
145
 *
146
 * Must be called after jpeg_start_decompress() and before any calls to
147
 * jpeg_read_scanlines() or jpeg_skip_scanlines().
148
 *
149
 * Refer to libjpeg.txt for more information.
150
 */
151
152
GLOBAL(void)
153
jpeg_crop_scanline (j_decompress_ptr cinfo, JDIMENSION *xoffset,
154
                    JDIMENSION *width)
155
0
{
156
0
  int ci, align, orig_downsampled_width;
157
0
  JDIMENSION input_xoffset;
158
0
  boolean reinit_upsampler = FALSE;
159
0
  jpeg_component_info *compptr;
160
0
161
0
  if (cinfo->global_state != DSTATE_SCANNING || cinfo->output_scanline != 0)
162
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
163
0
164
0
  if (!xoffset || !width)
165
0
    ERREXIT(cinfo, JERR_BAD_CROP_SPEC);
166
0
167
0
  /* xoffset and width must fall within the output image dimensions. */
168
0
  if (*width == 0 || *xoffset + *width > cinfo->output_width)
169
0
    ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
170
0
171
0
  /* No need to do anything if the caller wants the entire width. */
172
0
  if (*width == cinfo->output_width)
173
0
    return;
174
0
175
0
  /* Ensuring the proper alignment of xoffset is tricky.  At minimum, it
176
0
   * must align with an MCU boundary, because:
177
0
   *
178
0
   *   (1) The IDCT is performed in blocks, and it is not feasible to modify
179
0
   *       the algorithm so that it can transform partial blocks.
180
0
   *   (2) Because of the SIMD extensions, any input buffer passed to the
181
0
   *       upsampling and color conversion routines must be aligned to the
182
0
   *       SIMD word size (for instance, 128-bit in the case of SSE2.)  The
183
0
   *       easiest way to accomplish this without copying data is to ensure
184
0
   *       that upsampling and color conversion begin at the start of the
185
0
   *       first MCU column that will be inverse transformed.
186
0
   *
187
0
   * In practice, we actually impose a stricter alignment requirement.  We
188
0
   * require that xoffset be a multiple of the maximum MCU column width of all
189
0
   * of the components (the "iMCU column width.")  This is to simplify the
190
0
   * single-pass decompression case, allowing us to use the same MCU column
191
0
   * width for all of the components.
192
0
   */
193
0
  align = cinfo->_min_DCT_scaled_size * cinfo->max_h_samp_factor;
194
0
195
0
  /* Adjust xoffset to the nearest iMCU boundary <= the requested value */
196
0
  input_xoffset = *xoffset;
197
0
  *xoffset = (input_xoffset / align) * align;
198
0
199
0
  /* Adjust the width so that the right edge of the output image is as
200
0
   * requested (only the left edge is altered.)  It is important that calling
201
0
   * programs check this value after this function returns, so that they can
202
0
   * allocate an output buffer with the appropriate size.
203
0
   */
204
0
  *width = *width + input_xoffset - *xoffset;
205
0
  cinfo->output_width = *width;
206
0
207
0
  /* Set the first and last iMCU columns that we must decompress.  These values
208
0
   * will be used in single-scan decompressions.
209
0
   */
210
0
  cinfo->master->first_iMCU_col =
211
0
    (JDIMENSION) (long) (*xoffset) / (long) align;
212
0
  cinfo->master->last_iMCU_col =
213
0
    (JDIMENSION) jdiv_round_up((long) (*xoffset + cinfo->output_width),
214
0
                               (long) align) - 1;
215
0
216
0
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
217
0
       ci++, compptr++) {
218
0
    /* Set downsampled_width to the new output width. */
219
0
    orig_downsampled_width = compptr->downsampled_width;
220
0
    compptr->downsampled_width =
221
0
      (JDIMENSION) jdiv_round_up((long) (cinfo->output_width *
222
0
                                         compptr->h_samp_factor),
223
0
                                 (long) cinfo->max_h_samp_factor);
224
0
    if (compptr->downsampled_width < 2 && orig_downsampled_width >= 2)
225
0
      reinit_upsampler = TRUE;
226
0
227
0
    /* Set the first and last iMCU columns that we must decompress.  These
228
0
     * values will be used in multi-scan decompressions.
229
0
     */
230
0
    cinfo->master->first_MCU_col[ci] =
231
0
      (JDIMENSION) (long) (*xoffset * compptr->h_samp_factor) /
232
0
                   (long) align;
233
0
    cinfo->master->last_MCU_col[ci] =
234
0
      (JDIMENSION) jdiv_round_up((long) ((*xoffset + cinfo->output_width) *
235
0
                                         compptr->h_samp_factor),
236
0
                                 (long) align) - 1;
237
0
  }
238
0
239
0
  if (reinit_upsampler) {
240
0
    cinfo->master->jinit_upsampler_no_alloc = TRUE;
241
0
    jinit_upsampler(cinfo);
242
0
    cinfo->master->jinit_upsampler_no_alloc = FALSE;
243
0
  }
244
0
}
245
246
247
/*
248
 * Read some scanlines of data from the JPEG decompressor.
249
 *
250
 * The return value will be the number of lines actually read.
251
 * This may be less than the number requested in several cases,
252
 * including bottom of image, data source suspension, and operating
253
 * modes that emit multiple scanlines at a time.
254
 *
255
 * Note: we warn about excess calls to jpeg_read_scanlines() since
256
 * this likely signals an application programmer error.  However,
257
 * an oversize buffer (max_lines > scanlines remaining) is not an error.
258
 */
259
260
GLOBAL(JDIMENSION)
261
jpeg_read_scanlines (j_decompress_ptr cinfo, JSAMPARRAY scanlines,
262
                     JDIMENSION max_lines)
263
0
{
264
0
  JDIMENSION row_ctr;
265
0
266
0
  if (cinfo->global_state != DSTATE_SCANNING)
267
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
268
0
  if (cinfo->output_scanline >= cinfo->output_height) {
269
0
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
270
0
    return 0;
271
0
  }
272
0
273
0
  /* Call progress monitor hook if present */
274
0
  if (cinfo->progress != NULL) {
275
0
    cinfo->progress->pass_counter = (long) cinfo->output_scanline;
276
0
    cinfo->progress->pass_limit = (long) cinfo->output_height;
277
0
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
278
0
  }
279
0
280
0
  /* Process some data */
281
0
  row_ctr = 0;
282
0
  (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines);
283
0
  cinfo->output_scanline += row_ctr;
284
0
  return row_ctr;
285
0
}
286
287
288
/* Dummy color convert function used by jpeg_skip_scanlines() */
289
LOCAL(void)
290
noop_convert (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
291
              JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
292
0
{
293
0
}
294
295
296
/*
297
 * In some cases, it is best to call jpeg_read_scanlines() and discard the
298
 * output, rather than skipping the scanlines, because this allows us to
299
 * maintain the internal state of the context-based upsampler.  In these cases,
300
 * we set up and tear down a dummy color converter in order to avoid valgrind
301
 * errors and to achieve the best possible performance.
302
 */
303
304
LOCAL(void)
305
read_and_discard_scanlines (j_decompress_ptr cinfo, JDIMENSION num_lines)
306
0
{
307
0
  JDIMENSION n;
308
0
  void (*color_convert) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
309
0
                         JDIMENSION input_row, JSAMPARRAY output_buf,
310
0
                         int num_rows);
311
0
312
0
  color_convert = cinfo->cconvert->color_convert;
313
0
  cinfo->cconvert->color_convert = noop_convert;
314
0
315
0
  for (n = 0; n < num_lines; n++)
316
0
    jpeg_read_scanlines(cinfo, NULL, 1);
317
0
318
0
  cinfo->cconvert->color_convert = color_convert;
319
0
}
320
321
322
/*
323
 * Called by jpeg_skip_scanlines().  This partially skips a decompress block by
324
 * incrementing the rowgroup counter.
325
 */
326
327
LOCAL(void)
328
increment_simple_rowgroup_ctr (j_decompress_ptr cinfo, JDIMENSION rows)
329
0
{
330
0
  JDIMENSION rows_left;
331
0
  my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
332
0
333
0
  /* Increment the counter to the next row group after the skipped rows. */
334
0
  main_ptr->rowgroup_ctr += rows / cinfo->max_v_samp_factor;
335
0
336
0
  /* Partially skipping a row group would involve modifying the internal state
337
0
   * of the upsampler, so read the remaining rows into a dummy buffer instead.
338
0
   */
339
0
  rows_left = rows % cinfo->max_v_samp_factor;
340
0
  cinfo->output_scanline += rows - rows_left;
341
0
342
0
  read_and_discard_scanlines(cinfo, rows_left);
343
0
}
344
345
/*
346
 * Skips some scanlines of data from the JPEG decompressor.
347
 *
348
 * The return value will be the number of lines actually skipped.  If skipping
349
 * num_lines would move beyond the end of the image, then the actual number of
350
 * lines remaining in the image is returned.  Otherwise, the return value will
351
 * be equal to num_lines.
352
 *
353
 * Refer to libjpeg.txt for more information.
354
 */
355
356
GLOBAL(JDIMENSION)
357
jpeg_skip_scanlines (j_decompress_ptr cinfo, JDIMENSION num_lines)
358
0
{
359
0
  my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
360
0
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
361
0
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
362
0
  JDIMENSION i, x;
363
0
  int y;
364
0
  JDIMENSION lines_per_iMCU_row, lines_left_in_iMCU_row, lines_after_iMCU_row;
365
0
  JDIMENSION lines_to_skip, lines_to_read;
366
0
367
0
  if (cinfo->global_state != DSTATE_SCANNING)
368
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
369
0
370
0
  /* Do not skip past the bottom of the image. */
371
0
  if (cinfo->output_scanline + num_lines >= cinfo->output_height) {
372
0
    cinfo->output_scanline = cinfo->output_height;
373
0
    return cinfo->output_height - cinfo->output_scanline;
374
0
  }
375
0
376
0
  if (num_lines == 0)
377
0
    return 0;
378
0
379
0
  lines_per_iMCU_row = cinfo->_min_DCT_scaled_size * cinfo->max_v_samp_factor;
380
0
  lines_left_in_iMCU_row =
381
0
    (lines_per_iMCU_row - (cinfo->output_scanline % lines_per_iMCU_row)) %
382
0
    lines_per_iMCU_row;
383
0
  lines_after_iMCU_row = num_lines - lines_left_in_iMCU_row;
384
0
385
0
  /* Skip the lines remaining in the current iMCU row.  When upsampling
386
0
   * requires context rows, we need the previous and next rows in order to read
387
0
   * the current row.  This adds some complexity.
388
0
   */
389
0
  if (cinfo->upsample->need_context_rows) {
390
0
    /* If the skipped lines would not move us past the current iMCU row, we
391
0
     * read the lines and ignore them.  There might be a faster way of doing
392
0
     * this, but we are facing increasing complexity for diminishing returns.
393
0
     * The increasing complexity would be a by-product of meddling with the
394
0
     * state machine used to skip context rows.  Near the end of an iMCU row,
395
0
     * the next iMCU row may have already been entropy-decoded.  In this unique
396
0
     * case, we will read the next iMCU row if we cannot skip past it as well.
397
0
     */
398
0
    if ((num_lines < lines_left_in_iMCU_row + 1) ||
399
0
        (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full &&
400
0
         lines_after_iMCU_row < lines_per_iMCU_row + 1)) {
401
0
      read_and_discard_scanlines(cinfo, num_lines);
402
0
      return num_lines;
403
0
    }
404
0
405
0
    /* If the next iMCU row has already been entropy-decoded, make sure that
406
0
     * we do not skip too far.
407
0
     */
408
0
    if (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full) {
409
0
      cinfo->output_scanline += lines_left_in_iMCU_row + lines_per_iMCU_row;
410
0
      lines_after_iMCU_row -= lines_per_iMCU_row;
411
0
    } else {
412
0
      cinfo->output_scanline += lines_left_in_iMCU_row;
413
0
    }
414
0
415
0
    /* If we have just completed the first block, adjust the buffer pointers */
416
0
    if (main_ptr->iMCU_row_ctr == 0 ||
417
0
        (main_ptr->iMCU_row_ctr == 1 && lines_left_in_iMCU_row > 2))
418
0
      set_wraparound_pointers(cinfo);
419
0
    main_ptr->buffer_full = FALSE;
420
0
    main_ptr->rowgroup_ctr = 0;
421
0
    main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
422
0
    upsample->next_row_out = cinfo->max_v_samp_factor;
423
0
    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
424
0
  }
425
0
426
0
  /* Skipping is much simpler when context rows are not required. */
427
0
  else {
428
0
    if (num_lines < lines_left_in_iMCU_row) {
429
0
      increment_simple_rowgroup_ctr(cinfo, num_lines);
430
0
      return num_lines;
431
0
    } else {
432
0
      cinfo->output_scanline += lines_left_in_iMCU_row;
433
0
      main_ptr->buffer_full = FALSE;
434
0
      main_ptr->rowgroup_ctr = 0;
435
0
      upsample->next_row_out = cinfo->max_v_samp_factor;
436
0
      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
437
0
    }
438
0
  }
439
0
440
0
  /* Calculate how many full iMCU rows we can skip. */
441
0
  if (cinfo->upsample->need_context_rows)
442
0
    lines_to_skip = ((lines_after_iMCU_row - 1) / lines_per_iMCU_row) *
443
0
                    lines_per_iMCU_row;
444
0
  else
445
0
    lines_to_skip = (lines_after_iMCU_row / lines_per_iMCU_row) *
446
0
                    lines_per_iMCU_row;
447
0
  /* Calculate the number of lines that remain to be skipped after skipping all
448
0
   * of the full iMCU rows that we can.  We will not read these lines unless we
449
0
   * have to.
450
0
   */
451
0
  lines_to_read = lines_after_iMCU_row - lines_to_skip;
452
0
453
0
  /* For images requiring multiple scans (progressive, non-interleaved, etc.),
454
0
   * all of the entropy decoding occurs in jpeg_start_decompress(), assuming
455
0
   * that the input data source is non-suspending.  This makes skipping easy.
456
0
   */
457
0
  if (cinfo->inputctl->has_multiple_scans) {
458
0
    if (cinfo->upsample->need_context_rows) {
459
0
      cinfo->output_scanline += lines_to_skip;
460
0
      cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
461
0
      main_ptr->iMCU_row_ctr += lines_after_iMCU_row / lines_per_iMCU_row;
462
0
      /* It is complex to properly move to the middle of a context block, so
463
0
       * read the remaining lines instead of skipping them.
464
0
       */
465
0
      read_and_discard_scanlines(cinfo, lines_to_read);
466
0
    } else {
467
0
      cinfo->output_scanline += lines_to_skip;
468
0
      cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
469
0
      increment_simple_rowgroup_ctr(cinfo, lines_to_read);
470
0
    }
471
0
    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
472
0
    return num_lines;
473
0
  }
474
0
475
0
  /* Skip the iMCU rows that we can safely skip. */
476
0
  for (i = 0; i < lines_to_skip; i += lines_per_iMCU_row) {
477
0
    for (y = 0; y < coef->MCU_rows_per_iMCU_row; y++) {
478
0
      for (x = 0; x < cinfo->MCUs_per_row; x++) {
479
0
        /* Calling decode_mcu() with a NULL pointer causes it to discard the
480
0
         * decoded coefficients.  This is ~5% faster for large subsets, but
481
0
         * it's tough to tell a difference for smaller images.
482
0
         */
483
0
        (*cinfo->entropy->decode_mcu) (cinfo, NULL);
484
0
      }
485
0
    }
486
0
    cinfo->input_iMCU_row++;
487
0
    cinfo->output_iMCU_row++;
488
0
    if (cinfo->input_iMCU_row < cinfo->total_iMCU_rows)
489
0
      start_iMCU_row(cinfo);
490
0
    else
491
0
      (*cinfo->inputctl->finish_input_pass) (cinfo);
492
0
  }
493
0
  cinfo->output_scanline += lines_to_skip;
494
0
495
0
  if (cinfo->upsample->need_context_rows) {
496
0
    /* Context-based upsampling keeps track of iMCU rows. */
497
0
    main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row;
498
0
499
0
    /* It is complex to properly move to the middle of a context block, so
500
0
     * read the remaining lines instead of skipping them.
501
0
     */
502
0
    read_and_discard_scanlines(cinfo, lines_to_read);
503
0
  } else {
504
0
    increment_simple_rowgroup_ctr(cinfo, lines_to_read);
505
0
  }
506
0
507
0
  /* Since skipping lines involves skipping the upsampling step, the value of
508
0
   * "rows_to_go" will become invalid unless we set it here.  NOTE: This is a
509
0
   * bit odd, since "rows_to_go" seems to be redundantly keeping track of
510
0
   * output_scanline.
511
0
   */
512
0
  upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
513
0
514
0
  /* Always skip the requested number of lines. */
515
0
  return num_lines;
516
0
}
517
518
/*
519
 * Alternate entry point to read raw data.
520
 * Processes exactly one iMCU row per call, unless suspended.
521
 */
522
523
GLOBAL(JDIMENSION)
524
jpeg_read_raw_data (j_decompress_ptr cinfo, JSAMPIMAGE data,
525
                    JDIMENSION max_lines)
526
0
{
527
0
  JDIMENSION lines_per_iMCU_row;
528
0
529
0
  if (cinfo->global_state != DSTATE_RAW_OK)
530
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
531
0
  if (cinfo->output_scanline >= cinfo->output_height) {
532
0
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
533
0
    return 0;
534
0
  }
535
0
536
0
  /* Call progress monitor hook if present */
537
0
  if (cinfo->progress != NULL) {
538
0
    cinfo->progress->pass_counter = (long) cinfo->output_scanline;
539
0
    cinfo->progress->pass_limit = (long) cinfo->output_height;
540
0
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
541
0
  }
542
0
543
0
  /* Verify that at least one iMCU row can be returned. */
544
0
  lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size;
545
0
  if (max_lines < lines_per_iMCU_row)
546
0
    ERREXIT(cinfo, JERR_BUFFER_SIZE);
547
0
548
0
  /* Decompress directly into user's buffer. */
549
0
  if (! (*cinfo->coef->decompress_data) (cinfo, data))
550
0
    return 0;                   /* suspension forced, can do nothing more */
551
0
552
0
  /* OK, we processed one iMCU row. */
553
0
  cinfo->output_scanline += lines_per_iMCU_row;
554
0
  return lines_per_iMCU_row;
555
0
}
556
557
558
/* Additional entry points for buffered-image mode. */
559
560
#ifdef D_MULTISCAN_FILES_SUPPORTED
561
562
/*
563
 * Initialize for an output pass in buffered-image mode.
564
 */
565
566
GLOBAL(boolean)
567
jpeg_start_output (j_decompress_ptr cinfo, int scan_number)
568
0
{
569
0
  if (cinfo->global_state != DSTATE_BUFIMAGE &&
570
0
      cinfo->global_state != DSTATE_PRESCAN)
571
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
572
0
  /* Limit scan number to valid range */
573
0
  if (scan_number <= 0)
574
0
    scan_number = 1;
575
0
  if (cinfo->inputctl->eoi_reached &&
576
0
      scan_number > cinfo->input_scan_number)
577
0
    scan_number = cinfo->input_scan_number;
578
0
  cinfo->output_scan_number = scan_number;
579
0
  /* Perform any dummy output passes, and set up for the real pass */
580
0
  return output_pass_setup(cinfo);
581
0
}
582
583
584
/*
585
 * Finish up after an output pass in buffered-image mode.
586
 *
587
 * Returns FALSE if suspended.  The return value need be inspected only if
588
 * a suspending data source is used.
589
 */
590
591
GLOBAL(boolean)
592
jpeg_finish_output (j_decompress_ptr cinfo)
593
0
{
594
0
  if ((cinfo->global_state == DSTATE_SCANNING ||
595
0
       cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) {
596
0
    /* Terminate this pass. */
597
0
    /* We do not require the whole pass to have been completed. */
598
0
    (*cinfo->master->finish_output_pass) (cinfo);
599
0
    cinfo->global_state = DSTATE_BUFPOST;
600
0
  } else if (cinfo->global_state != DSTATE_BUFPOST) {
601
0
    /* BUFPOST = repeat call after a suspension, anything else is error */
602
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
603
0
  }
604
0
  /* Read markers looking for SOS or EOI */
605
0
  while (cinfo->input_scan_number <= cinfo->output_scan_number &&
606
0
         ! cinfo->inputctl->eoi_reached) {
607
0
    if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
608
0
      return FALSE;             /* Suspend, come back later */
609
0
  }
610
0
  cinfo->global_state = DSTATE_BUFIMAGE;
611
0
  return TRUE;
612
0
}
613
614
#endif /* D_MULTISCAN_FILES_SUPPORTED */