Coverage Report

Created: 2024-06-18 06:05

/src/libjpeg-turbo/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, 2015-2020, 2022-2023, 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
#if BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED)
23
#include "jdmainct.h"
24
#include "jdcoefct.h"
25
#else
26
#define JPEG_INTERNALS
27
#include "jpeglib.h"
28
#endif
29
#include "jdmaster.h"
30
#include "jdmerge.h"
31
#include "jdsample.h"
32
#include "jmemsys.h"
33
34
#if BITS_IN_JSAMPLE == 8
35
36
/* Forward declarations */
37
LOCAL(boolean) output_pass_setup(j_decompress_ptr cinfo);
38
39
40
/*
41
 * Decompression initialization.
42
 * jpeg_read_header must be completed before calling this.
43
 *
44
 * If a multipass operating mode was selected, this will do all but the
45
 * last pass, and thus may take a great deal of time.
46
 *
47
 * Returns FALSE if suspended.  The return value need be inspected only if
48
 * a suspending data source is used.
49
 */
50
51
GLOBAL(boolean)
52
jpeg_start_decompress(j_decompress_ptr cinfo)
53
0
{
54
0
  if (cinfo->global_state == DSTATE_READY) {
55
    /* First call: initialize master control, select active modules */
56
0
    jinit_master_decompress(cinfo);
57
0
    if (cinfo->buffered_image) {
58
      /* No more work here; expecting jpeg_start_output next */
59
0
      cinfo->global_state = DSTATE_BUFIMAGE;
60
0
      return TRUE;
61
0
    }
62
0
    cinfo->global_state = DSTATE_PRELOAD;
63
0
  }
64
0
  if (cinfo->global_state == DSTATE_PRELOAD) {
65
    /* If file has multiple scans, absorb them all into the coef buffer */
66
0
    if (cinfo->inputctl->has_multiple_scans) {
67
0
#ifdef D_MULTISCAN_FILES_SUPPORTED
68
0
      for (;;) {
69
0
        int retcode;
70
        /* Call progress monitor hook if present */
71
0
        if (cinfo->progress != NULL)
72
0
          (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
73
        /* Absorb some more input */
74
0
        retcode = (*cinfo->inputctl->consume_input) (cinfo);
75
0
        if (retcode == JPEG_SUSPENDED)
76
0
          return FALSE;
77
0
        if (retcode == JPEG_REACHED_EOI)
78
0
          break;
79
        /* Advance progress counter if appropriate */
80
0
        if (cinfo->progress != NULL &&
81
0
            (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
82
0
          if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
83
            /* jdmaster underestimated number of scans; ratchet up one scan */
84
0
            cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows;
85
0
          }
86
0
        }
87
0
      }
88
#else
89
      ERREXIT(cinfo, JERR_NOT_COMPILED);
90
#endif /* D_MULTISCAN_FILES_SUPPORTED */
91
0
    }
92
0
    cinfo->output_scan_number = cinfo->input_scan_number;
93
0
  } else if (cinfo->global_state != DSTATE_PRESCAN)
94
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
95
  /* Perform any dummy output passes, and set up for the final pass */
96
0
  return output_pass_setup(cinfo);
97
0
}
98
99
100
/*
101
 * Set up for an output pass, and perform any dummy pass(es) needed.
102
 * Common subroutine for jpeg_start_decompress and jpeg_start_output.
103
 * Entry: global_state = DSTATE_PRESCAN only if previously suspended.
104
 * Exit: If done, returns TRUE and sets global_state for proper output mode.
105
 *       If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN.
106
 */
107
108
LOCAL(boolean)
109
output_pass_setup(j_decompress_ptr cinfo)
110
0
{
111
0
  if (cinfo->global_state != DSTATE_PRESCAN) {
112
    /* First call: do pass setup */
113
0
    (*cinfo->master->prepare_for_output_pass) (cinfo);
114
0
    cinfo->output_scanline = 0;
115
0
    cinfo->global_state = DSTATE_PRESCAN;
116
0
  }
117
  /* Loop over any required dummy passes */
118
0
  while (cinfo->master->is_dummy_pass) {
119
0
#ifdef QUANT_2PASS_SUPPORTED
120
    /* Crank through the dummy pass */
121
0
    while (cinfo->output_scanline < cinfo->output_height) {
122
0
      JDIMENSION last_scanline;
123
      /* Call progress monitor hook if present */
124
0
      if (cinfo->progress != NULL) {
125
0
        cinfo->progress->pass_counter = (long)cinfo->output_scanline;
126
0
        cinfo->progress->pass_limit = (long)cinfo->output_height;
127
0
        (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
128
0
      }
129
      /* Process some data */
130
0
      last_scanline = cinfo->output_scanline;
131
0
#ifdef D_LOSSLESS_SUPPORTED
132
0
      if (cinfo->data_precision == 16)
133
0
        (*cinfo->main->process_data_16) (cinfo, (J16SAMPARRAY)NULL,
134
0
                                         &cinfo->output_scanline,
135
0
                                         (JDIMENSION)0);
136
0
      else
137
0
#endif
138
0
      if (cinfo->data_precision == 12)
139
0
        (*cinfo->main->process_data_12) (cinfo, (J12SAMPARRAY)NULL,
140
0
                                         &cinfo->output_scanline,
141
0
                                         (JDIMENSION)0);
142
0
      else
143
0
        (*cinfo->main->process_data) (cinfo, (JSAMPARRAY)NULL,
144
0
                                      &cinfo->output_scanline, (JDIMENSION)0);
145
0
      if (cinfo->output_scanline == last_scanline)
146
0
        return FALSE;           /* No progress made, must suspend */
147
0
    }
148
    /* Finish up dummy pass, and set up for another one */
149
0
    (*cinfo->master->finish_output_pass) (cinfo);
150
0
    (*cinfo->master->prepare_for_output_pass) (cinfo);
151
0
    cinfo->output_scanline = 0;
152
#else
153
    ERREXIT(cinfo, JERR_NOT_COMPILED);
154
#endif /* QUANT_2PASS_SUPPORTED */
155
0
  }
156
  /* Ready for application to drive output pass through
157
   * _jpeg_read_scanlines or _jpeg_read_raw_data.
158
   */
159
0
  cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING;
160
0
  return TRUE;
161
0
}
162
163
#endif /* BITS_IN_JSAMPLE == 8 */
164
165
166
#if BITS_IN_JSAMPLE != 16
167
168
/*
169
 * Enable partial scanline decompression
170
 *
171
 * Must be called after jpeg_start_decompress() and before any calls to
172
 * _jpeg_read_scanlines() or _jpeg_skip_scanlines().
173
 *
174
 * Refer to libjpeg.txt for more information.
175
 */
176
177
GLOBAL(void)
178
_jpeg_crop_scanline(j_decompress_ptr cinfo, JDIMENSION *xoffset,
179
                    JDIMENSION *width)
180
0
{
181
0
  int ci, align, orig_downsampled_width;
182
0
  JDIMENSION input_xoffset;
183
0
  boolean reinit_upsampler = FALSE;
184
0
  jpeg_component_info *compptr;
185
0
#ifdef UPSAMPLE_MERGING_SUPPORTED
186
0
  my_master_ptr master = (my_master_ptr)cinfo->master;
187
0
#endif
188
189
0
  if (cinfo->data_precision != BITS_IN_JSAMPLE)
190
0
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
191
192
0
  if (cinfo->master->lossless)
193
0
    ERREXIT(cinfo, JERR_NOTIMPL);
194
195
0
  if ((cinfo->global_state != DSTATE_SCANNING &&
196
0
       cinfo->global_state != DSTATE_BUFIMAGE) || cinfo->output_scanline != 0)
197
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
198
199
0
  if (!xoffset || !width)
200
0
    ERREXIT(cinfo, JERR_BAD_CROP_SPEC);
201
202
  /* xoffset and width must fall within the output image dimensions. */
203
0
  if (*width == 0 || *xoffset + *width > cinfo->output_width)
204
0
    ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
205
206
  /* No need to do anything if the caller wants the entire width. */
207
0
  if (*width == cinfo->output_width)
208
0
    return;
209
210
  /* Ensuring the proper alignment of xoffset is tricky.  At minimum, it
211
   * must align with an MCU boundary, because:
212
   *
213
   *   (1) The IDCT is performed in blocks, and it is not feasible to modify
214
   *       the algorithm so that it can transform partial blocks.
215
   *   (2) Because of the SIMD extensions, any input buffer passed to the
216
   *       upsampling and color conversion routines must be aligned to the
217
   *       SIMD word size (for instance, 128-bit in the case of SSE2.)  The
218
   *       easiest way to accomplish this without copying data is to ensure
219
   *       that upsampling and color conversion begin at the start of the
220
   *       first MCU column that will be inverse transformed.
221
   *
222
   * In practice, we actually impose a stricter alignment requirement.  We
223
   * require that xoffset be a multiple of the maximum MCU column width of all
224
   * of the components (the "iMCU column width.")  This is to simplify the
225
   * single-pass decompression case, allowing us to use the same MCU column
226
   * width for all of the components.
227
   */
228
0
  if (cinfo->comps_in_scan == 1 && cinfo->num_components == 1)
229
0
    align = cinfo->_min_DCT_scaled_size;
230
0
  else
231
0
    align = cinfo->_min_DCT_scaled_size * cinfo->max_h_samp_factor;
232
233
  /* Adjust xoffset to the nearest iMCU boundary <= the requested value */
234
0
  input_xoffset = *xoffset;
235
0
  *xoffset = (input_xoffset / align) * align;
236
237
  /* Adjust the width so that the right edge of the output image is as
238
   * requested (only the left edge is altered.)  It is important that calling
239
   * programs check this value after this function returns, so that they can
240
   * allocate an output buffer with the appropriate size.
241
   */
242
0
  *width = *width + input_xoffset - *xoffset;
243
0
  cinfo->output_width = *width;
244
0
#ifdef UPSAMPLE_MERGING_SUPPORTED
245
0
  if (master->using_merged_upsample && cinfo->max_v_samp_factor == 2) {
246
0
    my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
247
0
    upsample->out_row_width =
248
0
      cinfo->output_width * cinfo->out_color_components;
249
0
  }
250
0
#endif
251
252
  /* Set the first and last iMCU columns that we must decompress.  These values
253
   * will be used in single-scan decompressions.
254
   */
255
0
  cinfo->master->first_iMCU_col = (JDIMENSION)(long)(*xoffset) / (long)align;
256
0
  cinfo->master->last_iMCU_col =
257
0
    (JDIMENSION)jdiv_round_up((long)(*xoffset + cinfo->output_width),
258
0
                              (long)align) - 1;
259
260
0
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
261
0
       ci++, compptr++) {
262
0
    int hsf = (cinfo->comps_in_scan == 1 && cinfo->num_components == 1) ?
263
0
              1 : compptr->h_samp_factor;
264
265
    /* Set downsampled_width to the new output width. */
266
0
    orig_downsampled_width = compptr->downsampled_width;
267
0
    compptr->downsampled_width =
268
0
      (JDIMENSION)jdiv_round_up((long)cinfo->output_width *
269
0
                                (long)(compptr->h_samp_factor *
270
0
                                       compptr->_DCT_scaled_size),
271
0
                                (long)(cinfo->max_h_samp_factor *
272
0
                                       cinfo->_min_DCT_scaled_size));
273
0
    if (compptr->downsampled_width < 2 && orig_downsampled_width >= 2)
274
0
      reinit_upsampler = TRUE;
275
276
    /* Set the first and last iMCU columns that we must decompress.  These
277
     * values will be used in multi-scan decompressions.
278
     */
279
0
    cinfo->master->first_MCU_col[ci] =
280
0
      (JDIMENSION)(long)(*xoffset * hsf) / (long)align;
281
0
    cinfo->master->last_MCU_col[ci] =
282
0
      (JDIMENSION)jdiv_round_up((long)((*xoffset + cinfo->output_width) * hsf),
283
0
                                (long)align) - 1;
284
0
  }
285
286
0
  if (reinit_upsampler) {
287
0
    cinfo->master->jinit_upsampler_no_alloc = TRUE;
288
0
    _jinit_upsampler(cinfo);
289
0
    cinfo->master->jinit_upsampler_no_alloc = FALSE;
290
0
  }
291
0
}
292
293
#endif /* BITS_IN_JSAMPLE != 16 */
294
295
296
/*
297
 * Read some scanlines of data from the JPEG decompressor.
298
 *
299
 * The return value will be the number of lines actually read.
300
 * This may be less than the number requested in several cases,
301
 * including bottom of image, data source suspension, and operating
302
 * modes that emit multiple scanlines at a time.
303
 *
304
 * Note: we warn about excess calls to _jpeg_read_scanlines() since
305
 * this likely signals an application programmer error.  However,
306
 * an oversize buffer (max_lines > scanlines remaining) is not an error.
307
 */
308
309
GLOBAL(JDIMENSION)
310
_jpeg_read_scanlines(j_decompress_ptr cinfo, _JSAMPARRAY scanlines,
311
                     JDIMENSION max_lines)
312
0
{
313
0
#if BITS_IN_JSAMPLE != 16 || defined(D_LOSSLESS_SUPPORTED)
314
0
  JDIMENSION row_ctr;
315
316
0
  if (cinfo->data_precision != BITS_IN_JSAMPLE)
317
0
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
318
319
0
  if (cinfo->global_state != DSTATE_SCANNING)
320
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
321
0
  if (cinfo->output_scanline >= cinfo->output_height) {
322
0
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
323
0
    return 0;
324
0
  }
325
326
  /* Call progress monitor hook if present */
327
0
  if (cinfo->progress != NULL) {
328
0
    cinfo->progress->pass_counter = (long)cinfo->output_scanline;
329
0
    cinfo->progress->pass_limit = (long)cinfo->output_height;
330
0
    (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
331
0
  }
332
333
  /* Process some data */
334
0
  row_ctr = 0;
335
0
  (*cinfo->main->_process_data) (cinfo, scanlines, &row_ctr, max_lines);
336
0
  cinfo->output_scanline += row_ctr;
337
0
  return row_ctr;
338
#else
339
  ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
340
  return 0;
341
#endif
342
0
}
343
344
345
#if BITS_IN_JSAMPLE != 16
346
347
/* Dummy color convert function used by _jpeg_skip_scanlines() */
348
LOCAL(void)
349
noop_convert(j_decompress_ptr cinfo, _JSAMPIMAGE input_buf,
350
             JDIMENSION input_row, _JSAMPARRAY output_buf, int num_rows)
351
0
{
352
0
}
353
354
355
/* Dummy quantize function used by _jpeg_skip_scanlines() */
356
LOCAL(void)
357
noop_quantize(j_decompress_ptr cinfo, _JSAMPARRAY input_buf,
358
              _JSAMPARRAY output_buf, int num_rows)
359
0
{
360
0
}
361
362
363
/*
364
 * In some cases, it is best to call _jpeg_read_scanlines() and discard the
365
 * output, rather than skipping the scanlines, because this allows us to
366
 * maintain the internal state of the context-based upsampler.  In these cases,
367
 * we set up and tear down a dummy color converter in order to avoid valgrind
368
 * errors and to achieve the best possible performance.
369
 */
370
371
LOCAL(void)
372
read_and_discard_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
373
0
{
374
0
  JDIMENSION n;
375
0
#ifdef UPSAMPLE_MERGING_SUPPORTED
376
0
  my_master_ptr master = (my_master_ptr)cinfo->master;
377
0
#endif
378
0
  _JSAMPLE dummy_sample[1] = { 0 };
379
0
  _JSAMPROW dummy_row = dummy_sample;
380
0
  _JSAMPARRAY scanlines = NULL;
381
0
  void (*color_convert) (j_decompress_ptr cinfo, _JSAMPIMAGE input_buf,
382
0
                         JDIMENSION input_row, _JSAMPARRAY output_buf,
383
0
                         int num_rows) = NULL;
384
0
  void (*color_quantize) (j_decompress_ptr cinfo, _JSAMPARRAY input_buf,
385
0
                          _JSAMPARRAY output_buf, int num_rows) = NULL;
386
387
0
  if (cinfo->cconvert && cinfo->cconvert->_color_convert) {
388
0
    color_convert = cinfo->cconvert->_color_convert;
389
0
    cinfo->cconvert->_color_convert = noop_convert;
390
    /* This just prevents UBSan from complaining about adding 0 to a NULL
391
     * pointer.  The pointer isn't actually used.
392
     */
393
0
    scanlines = &dummy_row;
394
0
  }
395
396
0
  if (cinfo->cquantize && cinfo->cquantize->_color_quantize) {
397
0
    color_quantize = cinfo->cquantize->_color_quantize;
398
0
    cinfo->cquantize->_color_quantize = noop_quantize;
399
0
  }
400
401
0
#ifdef UPSAMPLE_MERGING_SUPPORTED
402
0
  if (master->using_merged_upsample && cinfo->max_v_samp_factor == 2) {
403
0
    my_merged_upsample_ptr upsample = (my_merged_upsample_ptr)cinfo->upsample;
404
0
    scanlines = &upsample->spare_row;
405
0
  }
406
0
#endif
407
408
0
  for (n = 0; n < num_lines; n++)
409
0
    _jpeg_read_scanlines(cinfo, scanlines, 1);
410
411
0
  if (color_convert)
412
0
    cinfo->cconvert->_color_convert = color_convert;
413
414
0
  if (color_quantize)
415
0
    cinfo->cquantize->_color_quantize = color_quantize;
416
0
}
417
418
419
/*
420
 * Called by _jpeg_skip_scanlines().  This partially skips a decompress block
421
 * by incrementing the rowgroup counter.
422
 */
423
424
LOCAL(void)
425
increment_simple_rowgroup_ctr(j_decompress_ptr cinfo, JDIMENSION rows)
426
0
{
427
0
  JDIMENSION rows_left;
428
0
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
429
0
  my_master_ptr master = (my_master_ptr)cinfo->master;
430
431
0
  if (master->using_merged_upsample && cinfo->max_v_samp_factor == 2) {
432
0
    read_and_discard_scanlines(cinfo, rows);
433
0
    return;
434
0
  }
435
436
  /* Increment the counter to the next row group after the skipped rows. */
437
0
  main_ptr->rowgroup_ctr += rows / cinfo->max_v_samp_factor;
438
439
  /* Partially skipping a row group would involve modifying the internal state
440
   * of the upsampler, so read the remaining rows into a dummy buffer instead.
441
   */
442
0
  rows_left = rows % cinfo->max_v_samp_factor;
443
0
  cinfo->output_scanline += rows - rows_left;
444
445
0
  read_and_discard_scanlines(cinfo, rows_left);
446
0
}
447
448
/*
449
 * Skips some scanlines of data from the JPEG decompressor.
450
 *
451
 * The return value will be the number of lines actually skipped.  If skipping
452
 * num_lines would move beyond the end of the image, then the actual number of
453
 * lines remaining in the image is returned.  Otherwise, the return value will
454
 * be equal to num_lines.
455
 *
456
 * Refer to libjpeg.txt for more information.
457
 */
458
459
GLOBAL(JDIMENSION)
460
_jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
461
0
{
462
0
  my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
463
0
  my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
464
0
  my_master_ptr master = (my_master_ptr)cinfo->master;
465
0
  my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
466
0
  JDIMENSION i, x;
467
0
  int y;
468
0
  JDIMENSION lines_per_iMCU_row, lines_left_in_iMCU_row, lines_after_iMCU_row;
469
0
  JDIMENSION lines_to_skip, lines_to_read;
470
471
0
  if (cinfo->data_precision != BITS_IN_JSAMPLE)
472
0
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
473
474
0
  if (cinfo->master->lossless)
475
0
    ERREXIT(cinfo, JERR_NOTIMPL);
476
477
  /* Two-pass color quantization is not supported. */
478
0
  if (cinfo->quantize_colors && cinfo->two_pass_quantize)
479
0
    ERREXIT(cinfo, JERR_NOTIMPL);
480
481
0
  if (cinfo->global_state != DSTATE_SCANNING)
482
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
483
484
  /* Do not skip past the bottom of the image. */
485
0
  if (cinfo->output_scanline + num_lines >= cinfo->output_height) {
486
0
    num_lines = cinfo->output_height - cinfo->output_scanline;
487
0
    cinfo->output_scanline = cinfo->output_height;
488
0
    (*cinfo->inputctl->finish_input_pass) (cinfo);
489
0
    cinfo->inputctl->eoi_reached = TRUE;
490
0
    return num_lines;
491
0
  }
492
493
0
  if (num_lines == 0)
494
0
    return 0;
495
496
0
  lines_per_iMCU_row = cinfo->_min_DCT_scaled_size * cinfo->max_v_samp_factor;
497
0
  lines_left_in_iMCU_row =
498
0
    (lines_per_iMCU_row - (cinfo->output_scanline % lines_per_iMCU_row)) %
499
0
    lines_per_iMCU_row;
500
0
  lines_after_iMCU_row = num_lines - lines_left_in_iMCU_row;
501
502
  /* Skip the lines remaining in the current iMCU row.  When upsampling
503
   * requires context rows, we need the previous and next rows in order to read
504
   * the current row.  This adds some complexity.
505
   */
506
0
  if (cinfo->upsample->need_context_rows) {
507
    /* If the skipped lines would not move us past the current iMCU row, we
508
     * read the lines and ignore them.  There might be a faster way of doing
509
     * this, but we are facing increasing complexity for diminishing returns.
510
     * The increasing complexity would be a by-product of meddling with the
511
     * state machine used to skip context rows.  Near the end of an iMCU row,
512
     * the next iMCU row may have already been entropy-decoded.  In this unique
513
     * case, we will read the next iMCU row if we cannot skip past it as well.
514
     */
515
0
    if ((num_lines < lines_left_in_iMCU_row + 1) ||
516
0
        (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full &&
517
0
         lines_after_iMCU_row < lines_per_iMCU_row + 1)) {
518
0
      read_and_discard_scanlines(cinfo, num_lines);
519
0
      return num_lines;
520
0
    }
521
522
    /* If the next iMCU row has already been entropy-decoded, make sure that
523
     * we do not skip too far.
524
     */
525
0
    if (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full) {
526
0
      cinfo->output_scanline += lines_left_in_iMCU_row + lines_per_iMCU_row;
527
0
      lines_after_iMCU_row -= lines_per_iMCU_row;
528
0
    } else {
529
0
      cinfo->output_scanline += lines_left_in_iMCU_row;
530
0
    }
531
532
    /* If we have just completed the first block, adjust the buffer pointers */
533
0
    if (main_ptr->iMCU_row_ctr == 0 ||
534
0
        (main_ptr->iMCU_row_ctr == 1 && lines_left_in_iMCU_row > 2))
535
0
      set_wraparound_pointers(cinfo);
536
0
    main_ptr->buffer_full = FALSE;
537
0
    main_ptr->rowgroup_ctr = 0;
538
0
    main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
539
0
    if (!master->using_merged_upsample) {
540
0
      upsample->next_row_out = cinfo->max_v_samp_factor;
541
0
      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
542
0
    }
543
0
  }
544
545
  /* Skipping is much simpler when context rows are not required. */
546
0
  else {
547
0
    if (num_lines < lines_left_in_iMCU_row) {
548
0
      increment_simple_rowgroup_ctr(cinfo, num_lines);
549
0
      return num_lines;
550
0
    } else {
551
0
      cinfo->output_scanline += lines_left_in_iMCU_row;
552
0
      main_ptr->buffer_full = FALSE;
553
0
      main_ptr->rowgroup_ctr = 0;
554
0
      if (!master->using_merged_upsample) {
555
0
        upsample->next_row_out = cinfo->max_v_samp_factor;
556
0
        upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
557
0
      }
558
0
    }
559
0
  }
560
561
  /* Calculate how many full iMCU rows we can skip. */
562
0
  if (cinfo->upsample->need_context_rows)
563
0
    lines_to_skip = ((lines_after_iMCU_row - 1) / lines_per_iMCU_row) *
564
0
                    lines_per_iMCU_row;
565
0
  else
566
0
    lines_to_skip = (lines_after_iMCU_row / lines_per_iMCU_row) *
567
0
                    lines_per_iMCU_row;
568
  /* Calculate the number of lines that remain to be skipped after skipping all
569
   * of the full iMCU rows that we can.  We will not read these lines unless we
570
   * have to.
571
   */
572
0
  lines_to_read = lines_after_iMCU_row - lines_to_skip;
573
574
  /* For images requiring multiple scans (progressive, non-interleaved, etc.),
575
   * all of the entropy decoding occurs in jpeg_start_decompress(), assuming
576
   * that the input data source is non-suspending.  This makes skipping easy.
577
   */
578
0
  if (cinfo->inputctl->has_multiple_scans || cinfo->buffered_image) {
579
0
    if (cinfo->upsample->need_context_rows) {
580
0
      cinfo->output_scanline += lines_to_skip;
581
0
      cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
582
0
      main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row;
583
      /* It is complex to properly move to the middle of a context block, so
584
       * read the remaining lines instead of skipping them.
585
       */
586
0
      read_and_discard_scanlines(cinfo, lines_to_read);
587
0
    } else {
588
0
      cinfo->output_scanline += lines_to_skip;
589
0
      cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
590
0
      increment_simple_rowgroup_ctr(cinfo, lines_to_read);
591
0
    }
592
0
    if (!master->using_merged_upsample)
593
0
      upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
594
0
    return num_lines;
595
0
  }
596
597
  /* Skip the iMCU rows that we can safely skip. */
598
0
  for (i = 0; i < lines_to_skip; i += lines_per_iMCU_row) {
599
0
    for (y = 0; y < coef->MCU_rows_per_iMCU_row; y++) {
600
0
      for (x = 0; x < cinfo->MCUs_per_row; x++) {
601
        /* Calling decode_mcu() with a NULL pointer causes it to discard the
602
         * decoded coefficients.  This is ~5% faster for large subsets, but
603
         * it's tough to tell a difference for smaller images.
604
         */
605
0
        if (!cinfo->entropy->insufficient_data)
606
0
          cinfo->master->last_good_iMCU_row = cinfo->input_iMCU_row;
607
0
        (*cinfo->entropy->decode_mcu) (cinfo, NULL);
608
0
      }
609
0
    }
610
0
    cinfo->input_iMCU_row++;
611
0
    cinfo->output_iMCU_row++;
612
0
    if (cinfo->input_iMCU_row < cinfo->total_iMCU_rows)
613
0
      start_iMCU_row(cinfo);
614
0
    else
615
0
      (*cinfo->inputctl->finish_input_pass) (cinfo);
616
0
  }
617
0
  cinfo->output_scanline += lines_to_skip;
618
619
0
  if (cinfo->upsample->need_context_rows) {
620
    /* Context-based upsampling keeps track of iMCU rows. */
621
0
    main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row;
622
623
    /* It is complex to properly move to the middle of a context block, so
624
     * read the remaining lines instead of skipping them.
625
     */
626
0
    read_and_discard_scanlines(cinfo, lines_to_read);
627
0
  } else {
628
0
    increment_simple_rowgroup_ctr(cinfo, lines_to_read);
629
0
  }
630
631
  /* Since skipping lines involves skipping the upsampling step, the value of
632
   * "rows_to_go" will become invalid unless we set it here.  NOTE: This is a
633
   * bit odd, since "rows_to_go" seems to be redundantly keeping track of
634
   * output_scanline.
635
   */
636
0
  if (!master->using_merged_upsample)
637
0
    upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
638
639
  /* Always skip the requested number of lines. */
640
0
  return num_lines;
641
0
}
642
643
/*
644
 * Alternate entry point to read raw data.
645
 * Processes exactly one iMCU row per call, unless suspended.
646
 */
647
648
GLOBAL(JDIMENSION)
649
_jpeg_read_raw_data(j_decompress_ptr cinfo, _JSAMPIMAGE data,
650
                    JDIMENSION max_lines)
651
0
{
652
0
  JDIMENSION lines_per_iMCU_row;
653
654
0
  if (cinfo->data_precision != BITS_IN_JSAMPLE)
655
0
    ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
656
657
0
  if (cinfo->master->lossless)
658
0
    ERREXIT(cinfo, JERR_NOTIMPL);
659
660
0
  if (cinfo->global_state != DSTATE_RAW_OK)
661
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
662
0
  if (cinfo->output_scanline >= cinfo->output_height) {
663
0
    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
664
0
    return 0;
665
0
  }
666
667
  /* Call progress monitor hook if present */
668
0
  if (cinfo->progress != NULL) {
669
0
    cinfo->progress->pass_counter = (long)cinfo->output_scanline;
670
0
    cinfo->progress->pass_limit = (long)cinfo->output_height;
671
0
    (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
672
0
  }
673
674
  /* Verify that at least one iMCU row can be returned. */
675
0
  lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size;
676
0
  if (max_lines < lines_per_iMCU_row)
677
0
    ERREXIT(cinfo, JERR_BUFFER_SIZE);
678
679
  /* Decompress directly into user's buffer. */
680
0
  if (!(*cinfo->coef->_decompress_data) (cinfo, data))
681
0
    return 0;                   /* suspension forced, can do nothing more */
682
683
  /* OK, we processed one iMCU row. */
684
0
  cinfo->output_scanline += lines_per_iMCU_row;
685
0
  return lines_per_iMCU_row;
686
0
}
687
688
#endif /* BITS_IN_JSAMPLE != 16 */
689
690
691
#if BITS_IN_JSAMPLE == 8
692
693
/* Additional entry points for buffered-image mode. */
694
695
#ifdef D_MULTISCAN_FILES_SUPPORTED
696
697
/*
698
 * Initialize for an output pass in buffered-image mode.
699
 */
700
701
GLOBAL(boolean)
702
jpeg_start_output(j_decompress_ptr cinfo, int scan_number)
703
0
{
704
0
  if (cinfo->global_state != DSTATE_BUFIMAGE &&
705
0
      cinfo->global_state != DSTATE_PRESCAN)
706
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
707
  /* Limit scan number to valid range */
708
0
  if (scan_number <= 0)
709
0
    scan_number = 1;
710
0
  if (cinfo->inputctl->eoi_reached && scan_number > cinfo->input_scan_number)
711
0
    scan_number = cinfo->input_scan_number;
712
0
  cinfo->output_scan_number = scan_number;
713
  /* Perform any dummy output passes, and set up for the real pass */
714
0
  return output_pass_setup(cinfo);
715
0
}
716
717
718
/*
719
 * Finish up after an output pass in buffered-image mode.
720
 *
721
 * Returns FALSE if suspended.  The return value need be inspected only if
722
 * a suspending data source is used.
723
 */
724
725
GLOBAL(boolean)
726
jpeg_finish_output(j_decompress_ptr cinfo)
727
0
{
728
0
  if ((cinfo->global_state == DSTATE_SCANNING ||
729
0
       cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) {
730
    /* Terminate this pass. */
731
    /* We do not require the whole pass to have been completed. */
732
0
    (*cinfo->master->finish_output_pass) (cinfo);
733
0
    cinfo->global_state = DSTATE_BUFPOST;
734
0
  } else if (cinfo->global_state != DSTATE_BUFPOST) {
735
    /* BUFPOST = repeat call after a suspension, anything else is error */
736
0
    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
737
0
  }
738
  /* Read markers looking for SOS or EOI */
739
0
  while (cinfo->input_scan_number <= cinfo->output_scan_number &&
740
0
         !cinfo->inputctl->eoi_reached) {
741
0
    if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
742
0
      return FALSE;             /* Suspend, come back later */
743
0
  }
744
0
  cinfo->global_state = DSTATE_BUFIMAGE;
745
0
  return TRUE;
746
0
}
747
748
#endif /* D_MULTISCAN_FILES_SUPPORTED */
749
750
#endif /* BITS_IN_JSAMPLE == 8 */