jdapistd.c revision 5996a25e2f50d20d6a8f09830724035b49c3927b 
1/*
2 * jdapistd.c
3 *
4 * Copyright (C) 1994-1996, Thomas G. Lane.
5 * This file is part of the Independent JPEG Group's software.
6 * For conditions of distribution and use, see the accompanying README file.
7 *
8 * This file contains application interface code for the decompression half
9 * of the JPEG library.  These are the "standard" API routines that are
10 * used in the normal full-decompression case.  They are not used by a
11 * transcoding-only application.  Note that if an application links in
12 * jpeg_start_decompress, it will end up linking in the entire decompressor.
13 * We thus must separate this file from jdapimin.c to avoid linking the
14 * whole decompression library into a transcoder.
15 */
16
17#define JPEG_INTERNALS
18#include "jinclude.h"
19#include "jpeglib.h"
20
21
22/* Forward declarations */
23LOCAL(boolean) output_pass_setup JPP((j_decompress_ptr cinfo));
24
25
26/*
27 * Decompression initialization.
28 * jpeg_read_header must be completed before calling this.
29 *
30 * If a multipass operating mode was selected, this will do all but the
31 * last pass, and thus may take a great deal of time.
32 *
33 * Returns FALSE if suspended.  The return value need be inspected only if
34 * a suspending data source is used.
35 */
36
37GLOBAL(boolean)
38jpeg_start_decompress (j_decompress_ptr cinfo)
39{
40  if (cinfo->global_state == DSTATE_READY) {
41    /* First call: initialize master control, select active modules */
42    jinit_master_decompress(cinfo);
43    if (cinfo->buffered_image) {
44      /* No more work here; expecting jpeg_start_output next */
45      cinfo->global_state = DSTATE_BUFIMAGE;
46      return TRUE;
47    }
48    cinfo->global_state = DSTATE_PRELOAD;
49  }
50  if (cinfo->global_state == DSTATE_PRELOAD) {
51    /* If file has multiple scans, absorb them all into the coef buffer */
52    if (cinfo->inputctl->has_multiple_scans) {
53#ifdef D_MULTISCAN_FILES_SUPPORTED
54      for (;;) {
55	int retcode;
56	/* Call progress monitor hook if present */
57	if (cinfo->progress != NULL)
58	  (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
59	/* Absorb some more input */
60	retcode = (*cinfo->inputctl->consume_input) (cinfo);
61	if (retcode == JPEG_SUSPENDED)
62	  return FALSE;
63	if (retcode == JPEG_REACHED_EOI)
64	  break;
65	/* Advance progress counter if appropriate */
66	if (cinfo->progress != NULL &&
67	    (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
68	  if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
69	    /* jdmaster underestimated number of scans; ratchet up one scan */
70	    cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
71	  }
72	}
73      }
74#else
75      ERREXIT(cinfo, JERR_NOT_COMPILED);
76#endif /* D_MULTISCAN_FILES_SUPPORTED */
77    }
78    cinfo->output_scan_number = cinfo->input_scan_number;
79  } else if (cinfo->global_state != DSTATE_PRESCAN)
80    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
81  /* Perform any dummy output passes, and set up for the final pass */
82  return output_pass_setup(cinfo);
83}
84
85
86/*
87 * Set up for an output pass, and perform any dummy pass(es) needed.
88 * Common subroutine for jpeg_start_decompress and jpeg_start_output.
89 * Entry: global_state = DSTATE_PRESCAN only if previously suspended.
90 * Exit: If done, returns TRUE and sets global_state for proper output mode.
91 *       If suspended, returns FALSE and sets global_state = DSTATE_PRESCAN.
92 */
93
94LOCAL(boolean)
95output_pass_setup (j_decompress_ptr cinfo)
96{
97  if (cinfo->global_state != DSTATE_PRESCAN) {
98    /* First call: do pass setup */
99    (*cinfo->master->prepare_for_output_pass) (cinfo);
100    cinfo->output_scanline = 0;
101    cinfo->global_state = DSTATE_PRESCAN;
102  }
103  /* Loop over any required dummy passes */
104  while (cinfo->master->is_dummy_pass) {
105#ifdef QUANT_2PASS_SUPPORTED
106    /* Crank through the dummy pass */
107    while (cinfo->output_scanline < cinfo->output_height) {
108      JDIMENSION last_scanline;
109      /* Call progress monitor hook if present */
110      if (cinfo->progress != NULL) {
111	cinfo->progress->pass_counter = (long) cinfo->output_scanline;
112	cinfo->progress->pass_limit = (long) cinfo->output_height;
113	(*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
114      }
115      /* Process some data */
116      last_scanline = cinfo->output_scanline;
117      (*cinfo->main->process_data) (cinfo, (JSAMPARRAY) NULL,
118				    &cinfo->output_scanline, (JDIMENSION) 0);
119      if (cinfo->output_scanline == last_scanline)
120	return FALSE;		/* No progress made, must suspend */
121    }
122    /* Finish up dummy pass, and set up for another one */
123    (*cinfo->master->finish_output_pass) (cinfo);
124    (*cinfo->master->prepare_for_output_pass) (cinfo);
125    cinfo->output_scanline = 0;
126#else
127    ERREXIT(cinfo, JERR_NOT_COMPILED);
128#endif /* QUANT_2PASS_SUPPORTED */
129  }
130  /* Ready for application to drive output pass through
131   * jpeg_read_scanlines or jpeg_read_raw_data.
132   */
133  cinfo->global_state = cinfo->raw_data_out ? DSTATE_RAW_OK : DSTATE_SCANNING;
134  return TRUE;
135}
136
137
138/*
139 * Read some scanlines of data from the JPEG decompressor.
140 *
141 * The return value will be the number of lines actually read.
142 * This may be less than the number requested in several cases,
143 * including bottom of image, data source suspension, and operating
144 * modes that emit multiple scanlines at a time.
145 *
146 * Note: we warn about excess calls to jpeg_read_scanlines() since
147 * this likely signals an application programmer error.  However,
148 * an oversize buffer (max_lines > scanlines remaining) is not an error.
149 */
150
151GLOBAL(JDIMENSION)
152jpeg_read_scanlines (j_decompress_ptr cinfo, JSAMPARRAY scanlines,
153		     JDIMENSION max_lines)
154{
155  JDIMENSION row_ctr;
156
157  if (cinfo->global_state != DSTATE_SCANNING)
158    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
159  if (cinfo->output_scanline >= cinfo->output_height) {
160    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
161    return 0;
162  }
163
164  /* Call progress monitor hook if present */
165  if (cinfo->progress != NULL) {
166    cinfo->progress->pass_counter = (long) cinfo->output_scanline;
167    cinfo->progress->pass_limit = (long) cinfo->output_height;
168    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
169  }
170
171  /* Process some data */
172  row_ctr = 0;
173  (*cinfo->main->process_data) (cinfo, scanlines, &row_ctr, max_lines);
174  cinfo->output_scanline += row_ctr;
175  return row_ctr;
176}
177
178
179/*
180 * Alternate entry point to read raw data.
181 * Processes exactly one iMCU row per call, unless suspended.
182 */
183
184GLOBAL(JDIMENSION)
185jpeg_read_raw_data (j_decompress_ptr cinfo, JSAMPIMAGE data,
186		    JDIMENSION max_lines)
187{
188  JDIMENSION lines_per_iMCU_row;
189
190  if (cinfo->global_state != DSTATE_RAW_OK)
191    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
192  if (cinfo->output_scanline >= cinfo->output_height) {
193    WARNMS(cinfo, JWRN_TOO_MUCH_DATA);
194    return 0;
195  }
196
197  /* Call progress monitor hook if present */
198  if (cinfo->progress != NULL) {
199    cinfo->progress->pass_counter = (long) cinfo->output_scanline;
200    cinfo->progress->pass_limit = (long) cinfo->output_height;
201    (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
202  }
203
204  /* Verify that at least one iMCU row can be returned. */
205  lines_per_iMCU_row = cinfo->max_v_samp_factor * cinfo->min_DCT_v_scaled_size;
206  if (max_lines < lines_per_iMCU_row)
207    ERREXIT(cinfo, JERR_BUFFER_SIZE);
208
209  /* Decompress directly into user's buffer. */
210  if (! (*cinfo->coef->decompress_data) (cinfo, data))
211    return 0;			/* suspension forced, can do nothing more */
212
213  /* OK, we processed one iMCU row. */
214  cinfo->output_scanline += lines_per_iMCU_row;
215  return lines_per_iMCU_row;
216}
217
218
219/* Additional entry points for buffered-image mode. */
220
221#ifdef D_MULTISCAN_FILES_SUPPORTED
222
223/*
224 * Initialize for an output pass in buffered-image mode.
225 */
226
227GLOBAL(boolean)
228jpeg_start_output (j_decompress_ptr cinfo, int scan_number)
229{
230  if (cinfo->global_state != DSTATE_BUFIMAGE &&
231      cinfo->global_state != DSTATE_PRESCAN)
232    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
233  /* Limit scan number to valid range */
234  if (scan_number <= 0)
235    scan_number = 1;
236  if (cinfo->inputctl->eoi_reached &&
237      scan_number > cinfo->input_scan_number)
238    scan_number = cinfo->input_scan_number;
239  cinfo->output_scan_number = scan_number;
240  /* Perform any dummy output passes, and set up for the real pass */
241  return output_pass_setup(cinfo);
242}
243
244
245/*
246 * Finish up after an output pass in buffered-image mode.
247 *
248 * Returns FALSE if suspended.  The return value need be inspected only if
249 * a suspending data source is used.
250 */
251
252GLOBAL(boolean)
253jpeg_finish_output (j_decompress_ptr cinfo)
254{
255  if ((cinfo->global_state == DSTATE_SCANNING ||
256       cinfo->global_state == DSTATE_RAW_OK) && cinfo->buffered_image) {
257    /* Terminate this pass. */
258    /* We do not require the whole pass to have been completed. */
259    (*cinfo->master->finish_output_pass) (cinfo);
260    cinfo->global_state = DSTATE_BUFPOST;
261  } else if (cinfo->global_state != DSTATE_BUFPOST) {
262    /* BUFPOST = repeat call after a suspension, anything else is error */
263    ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
264  }
265  /* Read markers looking for SOS or EOI */
266  while (cinfo->input_scan_number <= cinfo->output_scan_number &&
267	 ! cinfo->inputctl->eoi_reached) {
268    if ((*cinfo->inputctl->consume_input) (cinfo) == JPEG_SUSPENDED)
269      return FALSE;		/* Suspend, come back later */
270  }
271  cinfo->global_state = DSTATE_BUFIMAGE;
272  return TRUE;
273}
274
275#endif /* D_MULTISCAN_FILES_SUPPORTED */
276