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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 */
28 LOCAL(boolean) output_pass_setup(j_decompress_ptr cinfo);
29 
30 
31 /*
32  * Decompression initialization.
33  * jpeg_read_header must be completed before calling this.
34  *
35  * If a multipass operating mode was selected, this will do all but the
36  * last pass, and thus may take a great deal of time.
37  *
38  * Returns FALSE if suspended.  The return value need be inspected only if
39  * a suspending data source is used.
40  */
41 
42 GLOBAL(boolean)
jpeg_start_decompress(j_decompress_ptr cinfo)43 jpeg_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 
99 LOCAL(boolean)
output_pass_setup(j_decompress_ptr cinfo)100 output_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 
152 GLOBAL(void)
jpeg_crop_scanline(j_decompress_ptr cinfo,JDIMENSION * xoffset,JDIMENSION * width)153 jpeg_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 
263 GLOBAL(JDIMENSION)
jpeg_read_scanlines(j_decompress_ptr cinfo,JSAMPARRAY scanlines,JDIMENSION max_lines)264 jpeg_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() */
292 LOCAL(void)
noop_convert(j_decompress_ptr cinfo,JSAMPIMAGE input_buf,JDIMENSION input_row,JSAMPARRAY output_buf,int num_rows)293 noop_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() */
300 LOCAL(void)
noop_quantize(j_decompress_ptr cinfo,JSAMPARRAY input_buf,JSAMPARRAY output_buf,int num_rows)301 noop_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 
315 LOCAL(void)
read_and_discard_scanlines(j_decompress_ptr cinfo,JDIMENSION num_lines)316 read_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 
351 LOCAL(void)
increment_simple_rowgroup_ctr(j_decompress_ptr cinfo,JDIMENSION rows)352 increment_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 
380 GLOBAL(JDIMENSION)
jpeg_skip_scanlines(j_decompress_ptr cinfo,JDIMENSION num_lines)381 jpeg_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 
549 GLOBAL(JDIMENSION)
jpeg_read_raw_data(j_decompress_ptr cinfo,JSAMPIMAGE data,JDIMENSION max_lines)550 jpeg_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 
592 GLOBAL(boolean)
jpeg_start_output(j_decompress_ptr cinfo,int scan_number)593 jpeg_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 
616 GLOBAL(boolean)
jpeg_finish_output(j_decompress_ptr cinfo)617 jpeg_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