1/*
2 * jdtrans.c
3 *
4 * This file was part of the Independent JPEG Group's software:
5 * Copyright (C) 1995-1997, Thomas G. Lane.
6 * It was modified by The libjpeg-turbo Project to include only code relevant
7 * to libjpeg-turbo.
8 * For conditions of distribution and use, see the accompanying README.ijg
9 * file.
10 *
11 * This file contains library routines for transcoding decompression,
12 * that is, reading raw DCT coefficient arrays from an input JPEG file.
13 * The routines in jdapimin.c will also be needed by a transcoder.
14 */
15
16#define JPEG_INTERNALS
17#include "jinclude.h"
18#include "jpeglib.h"
19
20
21/* Forward declarations */
22LOCAL(void) transdecode_master_selection (j_decompress_ptr cinfo);
23
24
25/*
26 * Read the coefficient arrays from a JPEG file.
27 * jpeg_read_header must be completed before calling this.
28 *
29 * The entire image is read into a set of virtual coefficient-block arrays,
30 * one per component.  The return value is a pointer to the array of
31 * virtual-array descriptors.  These can be manipulated directly via the
32 * JPEG memory manager, or handed off to jpeg_write_coefficients().
33 * To release the memory occupied by the virtual arrays, call
34 * jpeg_finish_decompress() when done with the data.
35 *
36 * An alternative usage is to simply obtain access to the coefficient arrays
37 * during a buffered-image-mode decompression operation.  This is allowed
38 * after any jpeg_finish_output() call.  The arrays can be accessed until
39 * jpeg_finish_decompress() is called.  (Note that any call to the library
40 * may reposition the arrays, so don't rely on access_virt_barray() results
41 * to stay valid across library calls.)
42 *
43 * Returns NULL if suspended.  This case need be checked only if
44 * a suspending data source is used.
45 */
46
47GLOBAL(jvirt_barray_ptr *)
48jpeg_read_coefficients (j_decompress_ptr cinfo)
49{
50  if (cinfo->global_state == DSTATE_READY) {
51    /* First call: initialize active modules */
52    transdecode_master_selection(cinfo);
53    cinfo->global_state = DSTATE_RDCOEFS;
54  }
55  if (cinfo->global_state == DSTATE_RDCOEFS) {
56    /* Absorb whole file into the coef buffer */
57    for (;;) {
58      int retcode;
59      /* Call progress monitor hook if present */
60      if (cinfo->progress != NULL)
61        (*cinfo->progress->progress_monitor) ((j_common_ptr) cinfo);
62      /* Absorb some more input */
63      retcode = (*cinfo->inputctl->consume_input) (cinfo);
64      if (retcode == JPEG_SUSPENDED)
65        return NULL;
66      if (retcode == JPEG_REACHED_EOI)
67        break;
68      /* Advance progress counter if appropriate */
69      if (cinfo->progress != NULL &&
70          (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
71        if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
72          /* startup underestimated number of scans; ratchet up one scan */
73          cinfo->progress->pass_limit += (long) cinfo->total_iMCU_rows;
74        }
75      }
76    }
77    /* Set state so that jpeg_finish_decompress does the right thing */
78    cinfo->global_state = DSTATE_STOPPING;
79  }
80  /* At this point we should be in state DSTATE_STOPPING if being used
81   * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
82   * to the coefficients during a full buffered-image-mode decompression.
83   */
84  if ((cinfo->global_state == DSTATE_STOPPING ||
85       cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
86    return cinfo->coef->coef_arrays;
87  }
88  /* Oops, improper usage */
89  ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
90  return NULL;                  /* keep compiler happy */
91}
92
93
94/*
95 * Master selection of decompression modules for transcoding.
96 * This substitutes for jdmaster.c's initialization of the full decompressor.
97 */
98
99LOCAL(void)
100transdecode_master_selection (j_decompress_ptr cinfo)
101{
102  /* This is effectively a buffered-image operation. */
103  cinfo->buffered_image = TRUE;
104
105#if JPEG_LIB_VERSION >= 80
106  /* Compute output image dimensions and related values. */
107  jpeg_core_output_dimensions(cinfo);
108#endif
109
110  /* Entropy decoding: either Huffman or arithmetic coding. */
111  if (cinfo->arith_code) {
112#ifdef D_ARITH_CODING_SUPPORTED
113    jinit_arith_decoder(cinfo);
114#else
115    ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
116#endif
117  } else {
118    if (cinfo->progressive_mode) {
119#ifdef D_PROGRESSIVE_SUPPORTED
120      jinit_phuff_decoder(cinfo);
121#else
122      ERREXIT(cinfo, JERR_NOT_COMPILED);
123#endif
124    } else
125      jinit_huff_decoder(cinfo);
126  }
127
128  /* Always get a full-image coefficient buffer. */
129  jinit_d_coef_controller(cinfo, TRUE);
130
131  /* We can now tell the memory manager to allocate virtual arrays. */
132  (*cinfo->mem->realize_virt_arrays) ((j_common_ptr) cinfo);
133
134  /* Initialize input side of decompressor to consume first scan. */
135  (*cinfo->inputctl->start_input_pass) (cinfo);
136
137  /* Initialize progress monitoring. */
138  if (cinfo->progress != NULL) {
139    int nscans;
140    /* Estimate number of scans to set pass_limit. */
141    if (cinfo->progressive_mode) {
142      /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
143      nscans = 2 + 3 * cinfo->num_components;
144    } else if (cinfo->inputctl->has_multiple_scans) {
145      /* For a nonprogressive multiscan file, estimate 1 scan per component. */
146      nscans = cinfo->num_components;
147    } else {
148      nscans = 1;
149    }
150    cinfo->progress->pass_counter = 0L;
151    cinfo->progress->pass_limit = (long) cinfo->total_iMCU_rows * nscans;
152    cinfo->progress->completed_passes = 0;
153    cinfo->progress->total_passes = 1;
154  }
155}
156