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, 2015-2018, 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 */
28LOCAL(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
42GLOBAL(boolean)
43jpeg_start_decompress(j_decompress_ptr cinfo)
44{
45 if (cinfo->global_state == DSTATE_READY) {
46 /* First call: initialize master control, select active modules */
47 jinit_master_decompress(cinfo);
48 if (cinfo->buffered_image) {
49 /* No more work here; expecting jpeg_start_output next */
50 cinfo->global_state = DSTATE_BUFIMAGE;
51 return TRUE;
52 }
53 cinfo->global_state = DSTATE_PRELOAD;
54 }
55 if (cinfo->global_state == DSTATE_PRELOAD) {
56 /* If file has multiple scans, absorb them all into the coef buffer */
57 if (cinfo->inputctl->has_multiple_scans) {
58#ifdef D_MULTISCAN_FILES_SUPPORTED
59 for (;;) {
60 int retcode;
61 /* Call progress monitor hook if present */
62 if (cinfo->progress != NULL)
63 (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
64 /* Absorb some more input */
65 retcode = (*cinfo->inputctl->consume_input) (cinfo);
66 if (retcode == JPEG_SUSPENDED)
67 return FALSE;
68 if (retcode == JPEG_REACHED_EOI)
69 break;
70 /* Advance progress counter if appropriate */
71 if (cinfo->progress != NULL &&
72 (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
73 if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
74 /* jdmaster underestimated number of scans; ratchet up one scan */
75 cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows;
76 }
77 }
78 }
79#else
80 ERREXIT(cinfo, JERR_NOT_COMPILED);
81#endif /* D_MULTISCAN_FILES_SUPPORTED */
82 }
83 cinfo->output_scan_number = cinfo->input_scan_number;
84 } else if (cinfo->global_state != DSTATE_PRESCAN)
85 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
86 /* Perform any dummy output passes, and set up for the final pass */
87 return output_pass_setup(cinfo);
88}
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
99LOCAL(boolean)
100output_pass_setup(j_decompress_ptr cinfo)
101{
102 if (cinfo->global_state != DSTATE_PRESCAN) {
103 /* First call: do pass setup */
104 (*cinfo->master->prepare_for_output_pass) (cinfo);
105 cinfo->output_scanline = 0;
106 cinfo->global_state = DSTATE_PRESCAN;
107 }
108 /* Loop over any required dummy passes */
109 while (cinfo->master->is_dummy_pass) {
110#ifdef QUANT_2PASS_SUPPORTED
111 /* Crank through the dummy pass */
112 while (cinfo->output_scanline < cinfo->output_height) {
113 JDIMENSION last_scanline;
114 /* Call progress monitor hook if present */
115 if (cinfo->progress != NULL) {
116 cinfo->progress->pass_counter = (long)cinfo->output_scanline;
117 cinfo->progress->pass_limit = (long)cinfo->output_height;
118 (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
119 }
120 /* Process some data */
121 last_scanline = cinfo->output_scanline;
122 (*cinfo->main->process_data) (cinfo, (JSAMPARRAY)NULL,
123 &cinfo->output_scanline, (JDIMENSION)0);
124 if (cinfo->output_scanline == last_scanline)
125 return FALSE; /* No progress made, must suspend */
126 }
127 /* Finish up dummy pass, and set up for another one */
128 (*cinfo->master->finish_output_pass) (cinfo);
129 (*cinfo->master->prepare_for_output_pass) (cinfo);
130 cinfo->output_scanline = 0;
131#else
132 ERREXIT(cinfo, JERR_NOT_COMPILED);
133#endif /* QUANT_2PASS_SUPPORTED */
134 }
135 /* Ready for application to drive output pass through
136 * jpeg_read_scanlines or jpeg_read_raw_data.
137 */
138 cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING;
139 return TRUE;
140}
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
152GLOBAL(void)
153jpeg_crop_scanline(j_decompress_ptr cinfo, JDIMENSION *xoffset,
154 JDIMENSION *width)
155{
156 int ci, align, orig_downsampled_width;
157 JDIMENSION input_xoffset;
158 boolean reinit_upsampler = FALSE;
159 jpeg_component_info *compptr;
160
161 if (cinfo->global_state != DSTATE_SCANNING || cinfo->output_scanline != 0)
162 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
163
164 if (!xoffset || !width)
165 ERREXIT(cinfo, JERR_BAD_CROP_SPEC);
166
167 /* xoffset and width must fall within the output image dimensions. */
168 if (*width == 0 || *xoffset + *width > cinfo->output_width)
169 ERREXIT(cinfo, JERR_WIDTH_OVERFLOW);
170
171 /* No need to do anything if the caller wants the entire width. */
172 if (*width == cinfo->output_width)
173 return;
174
175 /* Ensuring the proper alignment of xoffset is tricky. At minimum, it
176 * must align with an MCU boundary, because:
177 *
178 * (1) The IDCT is performed in blocks, and it is not feasible to modify
179 * the algorithm so that it can transform partial blocks.
180 * (2) Because of the SIMD extensions, any input buffer passed to the
181 * upsampling and color conversion routines must be aligned to the
182 * SIMD word size (for instance, 128-bit in the case of SSE2.) The
183 * easiest way to accomplish this without copying data is to ensure
184 * that upsampling and color conversion begin at the start of the
185 * first MCU column that will be inverse transformed.
186 *
187 * In practice, we actually impose a stricter alignment requirement. We
188 * require that xoffset be a multiple of the maximum MCU column width of all
189 * of the components (the "iMCU column width.") This is to simplify the
190 * single-pass decompression case, allowing us to use the same MCU column
191 * width for all of the components.
192 */
193 if (cinfo->comps_in_scan == 1 && cinfo->num_components == 1)
194 align = cinfo->_min_DCT_scaled_size;
195 else
196 align = cinfo->_min_DCT_scaled_size * cinfo->max_h_samp_factor;
197
198 /* Adjust xoffset to the nearest iMCU boundary <= the requested value */
199 input_xoffset = *xoffset;
200 *xoffset = (input_xoffset / align) * align;
201
202 /* Adjust the width so that the right edge of the output image is as
203 * requested (only the left edge is altered.) It is important that calling
204 * programs check this value after this function returns, so that they can
205 * allocate an output buffer with the appropriate size.
206 */
207 *width = *width + input_xoffset - *xoffset;
208 cinfo->output_width = *width;
209
210 /* Set the first and last iMCU columns that we must decompress. These values
211 * will be used in single-scan decompressions.
212 */
213 cinfo->master->first_iMCU_col = (JDIMENSION)(long)(*xoffset) / (long)align;
214 cinfo->master->last_iMCU_col =
215 (JDIMENSION)jdiv_round_up((long)(*xoffset + cinfo->output_width),
216 (long)align) - 1;
217
218 for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
219 ci++, compptr++) {
220 int hsf = (cinfo->comps_in_scan == 1 && cinfo->num_components == 1) ?
221 1 : compptr->h_samp_factor;
222
223 /* Set downsampled_width to the new output width. */
224 orig_downsampled_width = compptr->downsampled_width;
225 compptr->downsampled_width =
226 (JDIMENSION)jdiv_round_up((long)(cinfo->output_width *
227 compptr->h_samp_factor),
228 (long)cinfo->max_h_samp_factor);
229 if (compptr->downsampled_width < 2 && orig_downsampled_width >= 2)
230 reinit_upsampler = TRUE;
231
232 /* Set the first and last iMCU columns that we must decompress. These
233 * values will be used in multi-scan decompressions.
234 */
235 cinfo->master->first_MCU_col[ci] =
236 (JDIMENSION)(long)(*xoffset * hsf) / (long)align;
237 cinfo->master->last_MCU_col[ci] =
238 (JDIMENSION)jdiv_round_up((long)((*xoffset + cinfo->output_width) * hsf),
239 (long)align) - 1;
240 }
241
242 if (reinit_upsampler) {
243 cinfo->master->jinit_upsampler_no_alloc = TRUE;
244 jinit_upsampler(cinfo);
245 cinfo->master->jinit_upsampler_no_alloc = FALSE;
246 }
247}
248
249
250/*
251 * Read some scanlines of data from the JPEG decompressor.
252 *
253 * The return value will be the number of lines actually read.
254 * This may be less than the number requested in several cases,
255 * including bottom of image, data source suspension, and operating
256 * modes that emit multiple scanlines at a time.
257 *
258 * Note: we warn about excess calls to jpeg_read_scanlines() since
259 * this likely signals an application programmer error. However,
260 * an oversize buffer (max_lines > scanlines remaining) is not an error.
261 */
262
263GLOBAL(JDIMENSION)
264jpeg_read_scanlines(j_decompress_ptr cinfo, JSAMPARRAY scanlines,
265 JDIMENSION max_lines)
266{
267 JDIMENSION row_ctr;
268
269 if (cinfo->global_state != DSTATE_SCANNING)
270 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
271 if (cinfo->output_scanline >= cinfo->output_height) {
272 WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
273 return 0;
274 }
275
276 /* Call progress monitor hook if present */
277 if (cinfo->progress != NULL) {
278 cinfo->progress->pass_counter = (long)cinfo->output_scanline;
279 cinfo->progress->pass_limit = (long)cinfo->output_height;
280 (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
281 }
282
283 /* Process some data */
284 row_ctr = 0;
285 (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines);
286 cinfo->output_scanline += row_ctr;
287 return row_ctr;
288}
289
290
291/* Dummy color convert function used by jpeg_skip_scanlines() */
292LOCAL(void)
293noop_convert(j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
294 JDIMENSION input_row, JSAMPARRAY output_buf, int num_rows)
295{
296}
297
298
299/* Dummy quantize function used by jpeg_skip_scanlines() */
300LOCAL(void)
301noop_quantize(j_decompress_ptr cinfo, JSAMPARRAY input_buf,
302 JSAMPARRAY output_buf, int num_rows)
303{
304}
305
306
307/*
308 * In some cases, it is best to call jpeg_read_scanlines() and discard the
309 * output, rather than skipping the scanlines, because this allows us to
310 * maintain the internal state of the context-based upsampler. In these cases,
311 * we set up and tear down a dummy color converter in order to avoid valgrind
312 * errors and to achieve the best possible performance.
313 */
314
315LOCAL(void)
316read_and_discard_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
317{
318 JDIMENSION n;
319 void (*color_convert) (j_decompress_ptr cinfo, JSAMPIMAGE input_buf,
320 JDIMENSION input_row, JSAMPARRAY output_buf,
321 int num_rows) = NULL;
322 void (*color_quantize) (j_decompress_ptr cinfo, JSAMPARRAY input_buf,
323 JSAMPARRAY output_buf, int num_rows) = NULL;
324
325 if (cinfo->cconvert && cinfo->cconvert->color_convert) {
326 color_convert = cinfo->cconvert->color_convert;
327 cinfo->cconvert->color_convert = noop_convert;
328 }
329
330 if (cinfo->cquantize && cinfo->cquantize->color_quantize) {
331 color_quantize = cinfo->cquantize->color_quantize;
332 cinfo->cquantize->color_quantize = noop_quantize;
333 }
334
335 for (n = 0; n < num_lines; n++)
336 jpeg_read_scanlines(cinfo, NULL, 1);
337
338 if (color_convert)
339 cinfo->cconvert->color_convert = color_convert;
340
341 if (color_quantize)
342 cinfo->cquantize->color_quantize = color_quantize;
343}
344
345
346/*
347 * Called by jpeg_skip_scanlines(). This partially skips a decompress block by
348 * incrementing the rowgroup counter.
349 */
350
351LOCAL(void)
352increment_simple_rowgroup_ctr(j_decompress_ptr cinfo, JDIMENSION rows)
353{
354 JDIMENSION rows_left;
355 my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
356
357 /* Increment the counter to the next row group after the skipped rows. */
358 main_ptr->rowgroup_ctr += rows / cinfo->max_v_samp_factor;
359
360 /* Partially skipping a row group would involve modifying the internal state
361 * of the upsampler, so read the remaining rows into a dummy buffer instead.
362 */
363 rows_left = rows % cinfo->max_v_samp_factor;
364 cinfo->output_scanline += rows - rows_left;
365
366 read_and_discard_scanlines(cinfo, rows_left);
367}
368
369/*
370 * Skips some scanlines of data from the JPEG decompressor.
371 *
372 * The return value will be the number of lines actually skipped. If skipping
373 * num_lines would move beyond the end of the image, then the actual number of
374 * lines remaining in the image is returned. Otherwise, the return value will
375 * be equal to num_lines.
376 *
377 * Refer to libjpeg.txt for more information.
378 */
379
380GLOBAL(JDIMENSION)
381jpeg_skip_scanlines(j_decompress_ptr cinfo, JDIMENSION num_lines)
382{
383 my_main_ptr main_ptr = (my_main_ptr)cinfo->main;
384 my_coef_ptr coef = (my_coef_ptr)cinfo->coef;
385 my_upsample_ptr upsample = (my_upsample_ptr)cinfo->upsample;
386 JDIMENSION i, x;
387 int y;
388 JDIMENSION lines_per_iMCU_row, lines_left_in_iMCU_row, lines_after_iMCU_row;
389 JDIMENSION lines_to_skip, lines_to_read;
390
391 if (cinfo->global_state != DSTATE_SCANNING)
392 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
393
394 /* Do not skip past the bottom of the image. */
395 if (cinfo->output_scanline + num_lines >= cinfo->output_height) {
396 cinfo->output_scanline = cinfo->output_height;
397 (*cinfo->inputctl->finish_input_pass) (cinfo);
398 cinfo->inputctl->eoi_reached = TRUE;
399 return cinfo->output_height - cinfo->output_scanline;
400 }
401
402 if (num_lines == 0)
403 return 0;
404
405 lines_per_iMCU_row = cinfo->_min_DCT_scaled_size * cinfo->max_v_samp_factor;
406 lines_left_in_iMCU_row =
407 (lines_per_iMCU_row - (cinfo->output_scanline % lines_per_iMCU_row)) %
408 lines_per_iMCU_row;
409 lines_after_iMCU_row = num_lines - lines_left_in_iMCU_row;
410
411 /* Skip the lines remaining in the current iMCU row. When upsampling
412 * requires context rows, we need the previous and next rows in order to read
413 * the current row. This adds some complexity.
414 */
415 if (cinfo->upsample->need_context_rows) {
416 /* If the skipped lines would not move us past the current iMCU row, we
417 * read the lines and ignore them. There might be a faster way of doing
418 * this, but we are facing increasing complexity for diminishing returns.
419 * The increasing complexity would be a by-product of meddling with the
420 * state machine used to skip context rows. Near the end of an iMCU row,
421 * the next iMCU row may have already been entropy-decoded. In this unique
422 * case, we will read the next iMCU row if we cannot skip past it as well.
423 */
424 if ((num_lines < lines_left_in_iMCU_row + 1) ||
425 (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full &&
426 lines_after_iMCU_row < lines_per_iMCU_row + 1)) {
427 read_and_discard_scanlines(cinfo, num_lines);
428 return num_lines;
429 }
430
431 /* If the next iMCU row has already been entropy-decoded, make sure that
432 * we do not skip too far.
433 */
434 if (lines_left_in_iMCU_row <= 1 && main_ptr->buffer_full) {
435 cinfo->output_scanline += lines_left_in_iMCU_row + lines_per_iMCU_row;
436 lines_after_iMCU_row -= lines_per_iMCU_row;
437 } else {
438 cinfo->output_scanline += lines_left_in_iMCU_row;
439 }
440
441 /* If we have just completed the first block, adjust the buffer pointers */
442 if (main_ptr->iMCU_row_ctr == 0 ||
443 (main_ptr->iMCU_row_ctr == 1 && lines_left_in_iMCU_row > 2))
444 set_wraparound_pointers(cinfo);
445 main_ptr->buffer_full = FALSE;
446 main_ptr->rowgroup_ctr = 0;
447 main_ptr->context_state = CTX_PREPARE_FOR_IMCU;
448 upsample->next_row_out = cinfo->max_v_samp_factor;
449 upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
450 }
451
452 /* Skipping is much simpler when context rows are not required. */
453 else {
454 if (num_lines < lines_left_in_iMCU_row) {
455 increment_simple_rowgroup_ctr(cinfo, num_lines);
456 return num_lines;
457 } else {
458 cinfo->output_scanline += lines_left_in_iMCU_row;
459 main_ptr->buffer_full = FALSE;
460 main_ptr->rowgroup_ctr = 0;
461 upsample->next_row_out = cinfo->max_v_samp_factor;
462 upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
463 }
464 }
465
466 /* Calculate how many full iMCU rows we can skip. */
467 if (cinfo->upsample->need_context_rows)
468 lines_to_skip = ((lines_after_iMCU_row - 1) / lines_per_iMCU_row) *
469 lines_per_iMCU_row;
470 else
471 lines_to_skip = (lines_after_iMCU_row / lines_per_iMCU_row) *
472 lines_per_iMCU_row;
473 /* Calculate the number of lines that remain to be skipped after skipping all
474 * of the full iMCU rows that we can. We will not read these lines unless we
475 * have to.
476 */
477 lines_to_read = lines_after_iMCU_row - lines_to_skip;
478
479 /* For images requiring multiple scans (progressive, non-interleaved, etc.),
480 * all of the entropy decoding occurs in jpeg_start_decompress(), assuming
481 * that the input data source is non-suspending. This makes skipping easy.
482 */
483 if (cinfo->inputctl->has_multiple_scans) {
484 if (cinfo->upsample->need_context_rows) {
485 cinfo->output_scanline += lines_to_skip;
486 cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
487 main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row;
488 /* It is complex to properly move to the middle of a context block, so
489 * read the remaining lines instead of skipping them.
490 */
491 read_and_discard_scanlines(cinfo, lines_to_read);
492 } else {
493 cinfo->output_scanline += lines_to_skip;
494 cinfo->output_iMCU_row += lines_to_skip / lines_per_iMCU_row;
495 increment_simple_rowgroup_ctr(cinfo, lines_to_read);
496 }
497 upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
498 return num_lines;
499 }
500
501 /* Skip the iMCU rows that we can safely skip. */
502 for (i = 0; i < lines_to_skip; i += lines_per_iMCU_row) {
503 for (y = 0; y < coef->MCU_rows_per_iMCU_row; y++) {
504 for (x = 0; x < cinfo->MCUs_per_row; x++) {
505 /* Calling decode_mcu() with a NULL pointer causes it to discard the
506 * decoded coefficients. This is ~5% faster for large subsets, but
507 * it's tough to tell a difference for smaller images.
508 */
509 (*cinfo->entropy->decode_mcu) (cinfo, NULL);
510 }
511 }
512 cinfo->input_iMCU_row++;
513 cinfo->output_iMCU_row++;
514 if (cinfo->input_iMCU_row < cinfo->total_iMCU_rows)
515 start_iMCU_row(cinfo);
516 else
517 (*cinfo->inputctl->finish_input_pass) (cinfo);
518 }
519 cinfo->output_scanline += lines_to_skip;
520
521 if (cinfo->upsample->need_context_rows) {
522 /* Context-based upsampling keeps track of iMCU rows. */
523 main_ptr->iMCU_row_ctr += lines_to_skip / lines_per_iMCU_row;
524
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 increment_simple_rowgroup_ctr(cinfo, lines_to_read);
531 }
532
533 /* Since skipping lines involves skipping the upsampling step, the value of
534 * "rows_to_go" will become invalid unless we set it here. NOTE: This is a
535 * bit odd, since "rows_to_go" seems to be redundantly keeping track of
536 * output_scanline.
537 */
538 upsample->rows_to_go = cinfo->output_height - cinfo->output_scanline;
539
540 /* Always skip the requested number of lines. */
541 return num_lines;
542}
543
544/*
545 * Alternate entry point to read raw data.
546 * Processes exactly one iMCU row per call, unless suspended.
547 */
548
549GLOBAL(JDIMENSION)
550jpeg_read_raw_data(j_decompress_ptr cinfo, JSAMPIMAGE data,
551 JDIMENSION max_lines)
552{
553 JDIMENSION lines_per_iMCU_row;
554
555 if (cinfo->global_state != DSTATE_RAW_OK)
556 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
557 if (cinfo->output_scanline >= cinfo->output_height) {
558 WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
559 return 0;
560 }
561
562 /* Call progress monitor hook if present */
563 if (cinfo->progress != NULL) {
564 cinfo->progress->pass_counter = (long)cinfo->output_scanline;
565 cinfo->progress->pass_limit = (long)cinfo->output_height;
566 (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
567 }
568
569 /* Verify that at least one iMCU row can be returned. */
570 lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->_min_DCT_scaled_size;
571 if (max_lines < lines_per_iMCU_row)
572 ERREXIT(cinfo, JERR_BUFFER_SIZE);
573
574 /* Decompress directly into user's buffer. */
575 if (!(*cinfo->coef->decompress_data) (cinfo, data))
576 return 0; /* suspension forced, can do nothing more */
577
578 /* OK, we processed one iMCU row. */
579 cinfo->output_scanline += lines_per_iMCU_row;
580 return lines_per_iMCU_row;
581}
582
583
584/* Additional entry points for buffered-image mode. */
585
586#ifdef D_MULTISCAN_FILES_SUPPORTED
587
588/*
589 * Initialize for an output pass in buffered-image mode.
590 */
591
592GLOBAL(boolean)
593jpeg_start_output(j_decompress_ptr cinfo, int scan_number)
594{
595 if (cinfo->global_state != DSTATE_BUFIMAGE &&
596 cinfo->global_state != DSTATE_PRESCAN)
597 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
598 /* Limit scan number to valid range */
599 if (scan_number <= 0)
600 scan_number = 1;
601 if (cinfo->inputctl->eoi_reached && scan_number > cinfo->input_scan_number)
602 scan_number = cinfo->input_scan_number;
603 cinfo->output_scan_number = scan_number;
604 /* Perform any dummy output passes, and set up for the real pass */
605 return output_pass_setup(cinfo);
606}
607
608
609/*
610 * Finish up after an output pass in buffered-image mode.
611 *
612 * Returns FALSE if suspended. The return value need be inspected only if
613 * a suspending data source is used.
614 */
615
616GLOBAL(boolean)
617jpeg_finish_output(j_decompress_ptr cinfo)
618{
619 if ((cinfo->global_state == DSTATE_SCANNING ||
620 cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) {
621 /* Terminate this pass. */
622 /* We do not require the whole pass to have been completed. */
623 (*cinfo->master->finish_output_pass) (cinfo);
624 cinfo->global_state = DSTATE_BUFPOST;
625 } else if (cinfo->global_state != DSTATE_BUFPOST) {
626 /* BUFPOST = repeat call after a suspension, anything else is error */
627 ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
628 }
629 /* Read markers looking for SOS or EOI */
630 while (cinfo->input_scan_number <= cinfo->output_scan_number &&
631 !cinfo->inputctl->eoi_reached) {
632 if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
633 return FALSE; /* Suspend, come back later */
634 }
635 cinfo->global_state = DSTATE_BUFIMAGE;
636 return TRUE;
637}
638
639#endif /* D_MULTISCAN_FILES_SUPPORTED */
640