File: jdapistd.c

package info (click to toggle)
libjpeg-turbo 1:1.5.1-2
  • links: PTS, VCS
  • area: main
  • in suites: stretch
  • size: 9,068 kB
  • ctags: 6,369
  • sloc: ansic: 43,407; asm: 25,683; sh: 5,436; java: 3,123; makefile: 797; xml: 24
file content (614 lines) | stat: -rw-r--r-- 22,855 bytes parent folder | download | duplicates (11)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
/*
 * jdapistd.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1994-1996, Thomas G. Lane.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2010, 2015-2016, D. R. Commander.
 * Copyright (C) 2015, Google, Inc.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains application interface code for the decompression half
 * of the JPEG library.  These are the "standard" API routines that are
 * used in the normal full-decompression case.  They are not used by a
 * transcoding-only application.  Note that if an application links in
 * jpeg_start_decompress, it will end up linking in the entire decompressor.
 * We thus must separate this file from jdapimin.c to avoid linking the
 * whole decompression library into a transcoder.
 */

#include "jinclude.h"
#include "jdmainct.h"
#include "jdcoefct.h"
#include "jdsample.h"
#include "jmemsys.h"

/* Forward declarations */
LOCAL(boolean) output_pass_setup (j_decompress_ptr cinfo);


/*
 * Decompression initialization.
 * jpeg_read_header must be completed before calling this.
 *
 * If a multipass operating mode was selected, this will do all but the
 * last pass, and thus may take a great deal of time.
 *
 * Returns FALSE if suspended.  The return value need be inspected only if
 * a suspending data source is used.
 */

GLOBAL(boolean)
jpeg_start_decompress (j_decompress_ptr cinfo)
{
  if (cinfo->global_state == DSTATE_READY) {
    /* First call: initialize master control, select active modules */
    jinit_master_decompress(cinfo);
    if (cinfo->buffered_image) {
      /* No more work here; expecting jpeg_start_output next */
      cinfo->global_state = DSTATE_BUFIMAGE;
      return TRUE;
    }
    cinfo->global_state = DSTATE_PRELOAD;
  }
  if (cinfo->global_state == DSTATE_PRELOAD) {
    /* If file has multiple scans, absorb them all into the coef buffer */
    if (cinfo->inputctl->has_multiple_scans) {
#ifdef D_MULTISCAN_FILES_SUPPORTED
      for (;;) {
        int retcode;
        /* Call progress monitor hook if present */
        if (cinfo->progress != NULL)
          (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
        /* Absorb some more input */
        retcode = (*cinfo->inputctl->consume_input) (cinfo);
        if (retcode == JPEG_SUSPENDED)
          return FALSE;
        if (retcode == JPEG_REACHED_EOI)
          break;
        /* Advance progress counter if appropriate */
        if (cinfo->progress != NULL &&
            (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
          if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
            /* jdmaster underestimated number of scans; ratchet up one scan */
            cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
          }
        }
      }
#else
      ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif /* D_MULTISCAN_FILES_SUPPORTED */
    }
    cinfo->output_scan_number = cinfo->input_scan_number;
  } else if (cinfo->global_state != DSTATE_PRESCAN)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  /* Perform any dummy output passes, and set up for the final pass */
  return output_pass_setup(cinfo);
}


/*
 * Set up for an output pass, and perform any dummy pass(es) needed.
 * Common subroutine for jpeg_start_decompress and jpeg_start_output.
 * Entry: global_state = DSTATE_PRESCAN only if previously suspended.
 * Exit: If done, returns TRUE and sets global_state for proper output mode.
 *       If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN.
 */

LOCAL(boolean)
output_pass_setup (j_decompress_ptr cinfo)
{
  if (cinfo->global_state != DSTATE_PRESCAN) {
    /* First call: do pass setup */
    (*cinfo->master->prepare_for_output_pass) (cinfo);
    cinfo->output_scanline = 0;
    cinfo->global_state = DSTATE_PRESCAN;
  }
  /* Loop over any required dummy passes */
  while (cinfo->master->is_dummy_pass) {
#ifdef QUANT_2PASS_SUPPORTED
    /* Crank through the dummy pass */
    while (cinfo->output_scanline < cinfo->output_height) {
      JDIMENSION last_scanline;
      /* Call progress monitor hook if present */
      if (cinfo->progress != NULL) {
        cinfo->progress->pass_counter = (long) cinfo->output_scanline;
        cinfo->progress->pass_limit = (long) cinfo->output_height;
        (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
      }
      /* Process some data */
      last_scanline = cinfo->output_scanline;
      (*cinfo->main->process_data) (cinfo, (JSAMPARRAY) NULL,
                                    &cinfo->output_scanline, (JDIMENSION) 0);
      if (cinfo->output_scanline == last_scanline)
        return FALSE;           /* No progress made, must suspend */
    }
    /* Finish up dummy pass, and set up for another one */
    (*cinfo->master->finish_output_pass) (cinfo);
    (*cinfo->master->prepare_for_output_pass) (cinfo);
    cinfo->output_scanline = 0;
#else
    ERREXIT(cinfo, JERR_NOT_COMPILED);
#endif /* QUANT_2PASS_SUPPORTED */
  }
  /* Ready for application to drive output pass through
   * jpeg_read_scanlines or jpeg_read_raw_data.
   */
  cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING;
  return TRUE;
}


/*
 * Enable partial scanline decompression
 *
 * Must be called after jpeg_start_decompress() and before any calls to
 * jpeg_read_scanlines() or jpeg_skip_scanlines().
 *
 * Refer to libjpeg.txt for more information.
 */

GLOBAL(void)
jpeg_crop_scanline (j_decompress_ptr cinfo, JDIMENSION *xoffset,
                    JDIMENSION *width)
{
  int ci, align, orig_downsampled_width;
  JDIMENSION input_xoffset;
  boolean reinit_upsampler = FALSE;
  jpeg_component_info *compptr;

  if (cinfo->global_state != DSTATE_SCANNING || cinfo->output_scanline != 0)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  if (!xoffset || !width)
    ERREXIT(cinfo, JERR_BAD_CROP_SPEC);

  /* xoffset and width must fall within the output image dimensions. */
  if (*width == 0 || *xoffset + *width > cinfo->output_width)
    ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);

  /* No need to do anything if the caller wants the entire width. */
  if (*width == cinfo->output_width)
    return;

  /* Ensuring the proper alignment of xoffset is tricky.  At minimum, it
   * must align with an MCU boundary, because:
   *
   *   (1) The IDCT is performed in blocks, and it is not feasible to modify
   *       the algorithm so that it can transform partial blocks.
   *   (2) Because of the SIMD extensions, any input buffer passed to the
   *       upsampling and color conversion routines must be aligned to the
   *       SIMD word size (for instance, 128-bit in the case of SSE2.)  The
   *       easiest way to accomplish this without copying data is to ensure
   *       that upsampling and color conversion begin at the start of the
   *       first MCU column that will be inverse transformed.
   *
   * In practice, we actually impose a stricter alignment requirement.  We
   * require that xoffset be a multiple of the maximum MCU column width of all
   * of the components (the "iMCU column width.")  This is to simplify the
   * single-pass decompression case, allowing us to use the same MCU column
   * width for all of the components.
   */
  align = cinfo->_min_DCT_scaled_size * cinfo->max_h_samp_factor;

  /* Adjust xoffset to the nearest iMCU boundary <= the requested value */
  input_xoffset = *xoffset;
  *xoffset = (input_xoffset / align) * align;

  /* Adjust the width so that the right edge of the output image is as
   * requested (only the left edge is altered.)  It is important that calling
   * programs check this value after this function returns, so that they can
   * allocate an output buffer with the appropriate size.
   */
  *width = *width + input_xoffset - *xoffset;
  cinfo->output_width = *width;

  /* Set the first and last iMCU columns that we must decompress.  These values
   * will be used in single-scan decompressions.
   */
  cinfo->master->first_iMCU_col =
    (JDIMENSION) (long) (*xoffset) / (long) align;
  cinfo->master->last_iMCU_col =
    (JDIMENSION) jdiv_round_up((long) (*xoffset + cinfo->output_width),
                               (long) align) - 1;

  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    /* Set downsampled_width to the new output width. */
    orig_downsampled_width = compptr->downsampled_width;
    compptr->downsampled_width =
      (JDIMENSION) jdiv_round_up((long) (cinfo->output_width *
                                         compptr->h_samp_factor),
                                 (long) cinfo->max_h_samp_factor);
    if (compptr->downsampled_width < 2 && orig_downsampled_width >= 2)
      reinit_upsampler = TRUE;

    /* Set the first and last iMCU columns that we must decompress.  These
     * values will be used in multi-scan decompressions.
     */
    cinfo->master->first_MCU_col[ci] =
      (JDIMENSION) (long) (*xoffset * compptr->h_samp_factor) /
                   (long) align;
    cinfo->master->last_MCU_col[ci] =
      (JDIMENSION) jdiv_round_up((long) ((*xoffset + cinfo->output_width) *
                                         compptr->h_samp_factor),
                                 (long) align) - 1;
  }

  if (reinit_upsampler) {
    cinfo->master->jinit_upsampler_no_alloc = TRUE;
    jinit_upsampler(cinfo);
    cinfo->master->jinit_upsampler_no_alloc = FALSE;
  }
}


/*
 * Read some scanlines of data from the JPEG decompressor.
 *
 * The return value will be the number of lines actually read.
 * This may be less than the number requested in several cases,
 * including bottom of image, data source suspension, and operating
 * modes that emit multiple scanlines at a time.
 *
 * Note: we warn about excess calls to jpeg_read_scanlines() since
 * this likely signals an application programmer error.  However,
 * an oversize buffer (max_lines > scanlines remaining) is not an error.
 */

GLOBAL(JDIMENSION)
jpeg_read_scanlines (j_decompress_ptr cinfo, JSAMPARRAY scanlines,
                     JDIMENSION max_lines)
{
  JDIMENSION row_ctr;

  if (cinfo->global_state != DSTATE_SCANNING)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  if (cinfo->output_scanline >= cinfo->output_height) {
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
    return 0;
  }

  /* Call progress monitor hook if present */
  if (cinfo->progress != NULL) {
    cinfo->progress->pass_counter = (long) cinfo->output_scanline;
    cinfo->progress->pass_limit = (long) cinfo->output_height;
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
  }

  /* Process some data */
  row_ctr = 0;
  (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines);
  cinfo->output_scanline += row_ctr;
  return row_ctr;
}


/* Dummy color convert function used by jpeg_skip_scanlines() */
LOCAL(void)
noop_convert (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
              JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
{
}


/*
 * In some cases, it is best to call jpeg_read_scanlines() and discard the
 * output, rather than skipping the scanlines, because this allows us to
 * maintain the internal state of the context-based upsampler.  In these cases,
 * we set up and tear down a dummy color converter in order to avoid valgrind
 * errors and to achieve the best possible performance.
 */

LOCAL(void)
read_and_discard_scanlines (j_decompress_ptr cinfo, JDIMENSION num_lines)
{
  JDIMENSION n;
  void (*color_convert) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
                         JDIMENSION input_row, JSAMPARRAY output_buf,
                         int num_rows);

  color_convert = cinfo->cconvert->color_convert;
  cinfo->cconvert->color_convert = noop_convert;

  for (n = 0; n < num_lines; n++)
    jpeg_read_scanlines(cinfo, NULL, 1);

  cinfo->cconvert->color_convert = color_convert;
}


/*
 * Called by jpeg_skip_scanlines().  This partially skips a decompress block by
 * incrementing the rowgroup counter.
 */

LOCAL(void)
increment_simple_rowgroup_ctr (j_decompress_ptr cinfo, JDIMENSION rows)
{
  JDIMENSION rows_left;
  my_main_ptr main_ptr = (my_main_ptr) cinfo->main;

  /* Increment the counter to the next row group after the skipped rows. */
  main_ptr->rowgroup_ctr += rows / cinfo->max_v_samp_factor;

  /* Partially skipping a row group would involve modifying the internal state
   * of the upsampler, so read the remaining rows into a dummy buffer instead.
   */
  rows_left = rows % cinfo->max_v_samp_factor;
  cinfo->output_scanline += rows - rows_left;

  read_and_discard_scanlines(cinfo, rows_left);
}

/*
 * Skips some scanlines of data from the JPEG decompressor.
 *
 * The return value will be the number of lines actually skipped.  If skipping
 * num_lines would move beyond the end of the image, then the actual number of
 * lines remaining in the image is returned.  Otherwise, the return value will
 * be equal to num_lines.
 *
 * Refer to libjpeg.txt for more information.
 */

GLOBAL(JDIMENSION)
jpeg_skip_scanlines (j_decompress_ptr cinfo, JDIMENSION num_lines)
{
  my_main_ptr main_ptr = (my_main_ptr) cinfo->main;
  my_coef_ptr coef = (my_coef_ptr) cinfo->coef;
  my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
  JDIMENSION i, x;
  int y;
  JDIMENSION lines_per_iMCU_row, lines_left_in_iMCU_row, lines_after_iMCU_row;
  JDIMENSION lines_to_skip, lines_to_read;

  if (cinfo->global_state != DSTATE_SCANNING)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);

  /* Do not skip past the bottom of the image. */
  if (cinfo->output_scanline + num_lines >= cinfo->output_height) {
    cinfo->output_scanline = cinfo->output_height;
    return cinfo->output_height - cinfo->output_scanline;
  }

  if (num_lines == 0)
    return 0;

  lines_per_iMCU_row = cinfo->_min_DCT_scaled_size * cinfo->max_v_samp_factor;
  lines_left_in_iMCU_row =
    (lines_per_iMCU_row - (cinfo->output_scanline % lines_per_iMCU_row)) %
    lines_per_iMCU_row;
  lines_after_iMCU_row = num_lines - lines_left_in_iMCU_row;

  /* Skip the lines remaining in the current iMCU row.  When upsampling
   * requires context rows, we need the previous and next rows in order to read
   * the current row.  This adds some complexity.
   */
  if (cinfo->upsample->need_context_rows) {
    /* If the skipped lines would not move us past the current iMCU row, we
     * read the lines and ignore them.  There might be a faster way of doing
     * this, but we are facing increasing complexity for diminishing returns.
     * The increasing complexity would be a by-product of meddling with the
     * state machine used to skip context rows.  Near the end of an iMCU row,
     * the next iMCU row may have already been entropy-decoded.  In this unique
     * case, we will read the next iMCU row if we cannot skip past it as well.
     */
    if ((num_lines < lines_left_in_iMCU_row + 1) ||
        (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full &&
         lines_after_iMCU_row < lines_per_iMCU_row + 1)) {
      read_and_discard_scanlines(cinfo, num_lines);
      return num_lines;
    }

    /* If the next iMCU row has already been entropy-decoded, make sure that
     * we do not skip too far.
     */
    if (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full) {
      cinfo->output_scanline += lines_left_in_iMCU_row + lines_per_iMCU_row;
      lines_after_iMCU_row -= lines_per_iMCU_row;
    } else {
      cinfo->output_scanline += lines_left_in_iMCU_row;
    }

    /* If we have just completed the first block, adjust the buffer pointers */
    if (main_ptr->iMCU_row_ctr == 0 ||
        (main_ptr->iMCU_row_ctr == 1 && lines_left_in_iMCU_row > 2))
      set_wraparound_pointers(cinfo);
    main_ptr->buffer_full = FALSE;
    main_ptr->rowgroup_ctr = 0;
    main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
    upsample->next_row_out = cinfo->max_v_samp_factor;
    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
  }

  /* Skipping is much simpler when context rows are not required. */
  else {
    if (num_lines < lines_left_in_iMCU_row) {
      increment_simple_rowgroup_ctr(cinfo, num_lines);
      return num_lines;
    } else {
      cinfo->output_scanline += lines_left_in_iMCU_row;
      main_ptr->buffer_full = FALSE;
      main_ptr->rowgroup_ctr = 0;
      upsample->next_row_out = cinfo->max_v_samp_factor;
      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
    }
  }

  /* Calculate how many full iMCU rows we can skip. */
  if (cinfo->upsample->need_context_rows)
    lines_to_skip = ((lines_after_iMCU_row - 1) / lines_per_iMCU_row) *
                    lines_per_iMCU_row;
  else
    lines_to_skip = (lines_after_iMCU_row / lines_per_iMCU_row) *
                    lines_per_iMCU_row;
  /* Calculate the number of lines that remain to be skipped after skipping all
   * of the full iMCU rows that we can.  We will not read these lines unless we
   * have to.
   */
  lines_to_read = lines_after_iMCU_row - lines_to_skip;

  /* For images requiring multiple scans (progressive, non-interleaved, etc.),
   * all of the entropy decoding occurs in jpeg_start_decompress(), assuming
   * that the input data source is non-suspending.  This makes skipping easy.
   */
  if (cinfo->inputctl->has_multiple_scans) {
    if (cinfo->upsample->need_context_rows) {
      cinfo->output_scanline += lines_to_skip;
      cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
      main_ptr->iMCU_row_ctr += lines_after_iMCU_row / lines_per_iMCU_row;
      /* It is complex to properly move to the middle of a context block, so
       * read the remaining lines instead of skipping them.
       */
      read_and_discard_scanlines(cinfo, lines_to_read);
    } else {
      cinfo->output_scanline += lines_to_skip;
      cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
      increment_simple_rowgroup_ctr(cinfo, lines_to_read);
    }
    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
    return num_lines;
  }

  /* Skip the iMCU rows that we can safely skip. */
  for (i = 0; i < lines_to_skip; i += lines_per_iMCU_row) {
    for (y = 0; y < coef->MCU_rows_per_iMCU_row; y++) {
      for (x = 0; x < cinfo->MCUs_per_row; x++) {
        /* Calling decode_mcu() with a NULL pointer causes it to discard the
         * decoded coefficients.  This is ~5% faster for large subsets, but
         * it's tough to tell a difference for smaller images.
         */
        (*cinfo->entropy->decode_mcu) (cinfo, NULL);
      }
    }
    cinfo->input_iMCU_row++;
    cinfo->output_iMCU_row++;
    if (cinfo->input_iMCU_row < cinfo->total_iMCU_rows)
      start_iMCU_row(cinfo);
    else
      (*cinfo->inputctl->finish_input_pass) (cinfo);
  }
  cinfo->output_scanline += lines_to_skip;

  if (cinfo->upsample->need_context_rows) {
    /* Context-based upsampling keeps track of iMCU rows. */
    main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row;

    /* It is complex to properly move to the middle of a context block, so
     * read the remaining lines instead of skipping them.
     */
    read_and_discard_scanlines(cinfo, lines_to_read);
  } else {
    increment_simple_rowgroup_ctr(cinfo, lines_to_read);
  }

  /* Since skipping lines involves skipping the upsampling step, the value of
   * "rows_to_go" will become invalid unless we set it here.  NOTE: This is a
   * bit odd, since "rows_to_go" seems to be redundantly keeping track of
   * output_scanline.
   */
  upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;

  /* Always skip the requested number of lines. */
  return num_lines;
}

/*
 * Alternate entry point to read raw data.
 * Processes exactly one iMCU row per call, unless suspended.
 */

GLOBAL(JDIMENSION)
jpeg_read_raw_data (j_decompress_ptr cinfo, JSAMPIMAGE data,
                    JDIMENSION max_lines)
{
  JDIMENSION lines_per_iMCU_row;

  if (cinfo->global_state != DSTATE_RAW_OK)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  if (cinfo->output_scanline >= cinfo->output_height) {
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
    return 0;
  }

  /* Call progress monitor hook if present */
  if (cinfo->progress != NULL) {
    cinfo->progress->pass_counter = (long) cinfo->output_scanline;
    cinfo->progress->pass_limit = (long) cinfo->output_height;
    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
  }

  /* Verify that at least one iMCU row can be returned. */
  lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size;
  if (max_lines < lines_per_iMCU_row)
    ERREXIT(cinfo, JERR_BUFFER_SIZE);

  /* Decompress directly into user's buffer. */
  if (! (*cinfo->coef->decompress_data) (cinfo, data))
    return 0;                   /* suspension forced, can do nothing more */

  /* OK, we processed one iMCU row. */
  cinfo->output_scanline += lines_per_iMCU_row;
  return lines_per_iMCU_row;
}


/* Additional entry points for buffered-image mode. */

#ifdef D_MULTISCAN_FILES_SUPPORTED

/*
 * Initialize for an output pass in buffered-image mode.
 */

GLOBAL(boolean)
jpeg_start_output (j_decompress_ptr cinfo, int scan_number)
{
  if (cinfo->global_state != DSTATE_BUFIMAGE &&
      cinfo->global_state != DSTATE_PRESCAN)
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  /* Limit scan number to valid range */
  if (scan_number <= 0)
    scan_number = 1;
  if (cinfo->inputctl->eoi_reached &&
      scan_number > cinfo->input_scan_number)
    scan_number = cinfo->input_scan_number;
  cinfo->output_scan_number = scan_number;
  /* Perform any dummy output passes, and set up for the real pass */
  return output_pass_setup(cinfo);
}


/*
 * Finish up after an output pass in buffered-image mode.
 *
 * Returns FALSE if suspended.  The return value need be inspected only if
 * a suspending data source is used.
 */

GLOBAL(boolean)
jpeg_finish_output (j_decompress_ptr cinfo)
{
  if ((cinfo->global_state == DSTATE_SCANNING ||
       cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) {
    /* Terminate this pass. */
    /* We do not require the whole pass to have been completed. */
    (*cinfo->master->finish_output_pass) (cinfo);
    cinfo->global_state = DSTATE_BUFPOST;
  } else if (cinfo->global_state != DSTATE_BUFPOST) {
    /* BUFPOST = repeat call after a suspension, anything else is error */
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
  }
  /* Read markers looking for SOS or EOI */
  while (cinfo->input_scan_number <= cinfo->output_scan_number &&
         ! cinfo->inputctl->eoi_reached) {
    if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
      return FALSE;             /* Suspend, come back later */
  }
  cinfo->global_state = DSTATE_BUFIMAGE;
  return TRUE;
}

#endif /* D_MULTISCAN_FILES_SUPPORTED */