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