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 * libjpeg-turbo Modifications:
7 * Copyright (C) 2020, D. R. Commander.
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#include "jpegcomp.h"
20
21
22/* Forward declarations */
23LOCAL(void) transdecode_master_selection(j_decompress_ptr cinfo);
24
25
26/*
27 * Read the coefficient arrays from a JPEG file.
28 * jpeg_read_header must be completed before calling this.
29 *
30 * The entire image is read into a set of virtual coefficient-block arrays,
31 * one per component.  The return value is a pointer to the array of
32 * virtual-array descriptors.  These can be manipulated directly via the
33 * JPEG memory manager, or handed off to jpeg_write_coefficients().
34 * To release the memory occupied by the virtual arrays, call
35 * jpeg_finish_decompress() when done with the data.
36 *
37 * An alternative usage is to simply obtain access to the coefficient arrays
38 * during a buffered-image-mode decompression operation.  This is allowed
39 * after any jpeg_finish_output() call.  The arrays can be accessed until
40 * jpeg_finish_decompress() is called.  (Note that any call to the library
41 * may reposition the arrays, so don't rely on access_virt_barray() results
42 * to stay valid across library calls.)
43 *
44 * Returns NULL if suspended.  This case need be checked only if
45 * a suspending data source is used.
46 */
47
48GLOBAL(jvirt_barray_ptr *)
49jpeg_read_coefficients(j_decompress_ptr cinfo)
50{
51  if (cinfo->global_state == DSTATE_READY) {
52    /* First call: initialize active modules */
53    transdecode_master_selection(cinfo);
54    cinfo->global_state = DSTATE_RDCOEFS;
55  }
56  if (cinfo->global_state == DSTATE_RDCOEFS) {
57    /* Absorb whole file into the coef buffer */
58    for (;;) {
59      int retcode;
60      /* Call progress monitor hook if present */
61      if (cinfo->progress != NULL)
62        (*cinfo->progress->progress_monitor) ((j_common_ptr)cinfo);
63      /* Absorb some more input */
64      retcode = (*cinfo->inputctl->consume_input) (cinfo);
65      if (retcode == JPEG_SUSPENDED)
66        return NULL;
67      if (retcode == JPEG_REACHED_EOI)
68        break;
69      /* Advance progress counter if appropriate */
70      if (cinfo->progress != NULL &&
71          (retcode == JPEG_ROW_COMPLETED || retcode == JPEG_REACHED_SOS)) {
72        if (++cinfo->progress->pass_counter >= cinfo->progress->pass_limit) {
73          /* startup underestimated number of scans; ratchet up one scan */
74          cinfo->progress->pass_limit += (long)cinfo->total_iMCU_rows;
75        }
76      }
77    }
78    /* Set state so that jpeg_finish_decompress does the right thing */
79    cinfo->global_state = DSTATE_STOPPING;
80  }
81  /* At this point we should be in state DSTATE_STOPPING if being used
82   * standalone, or in state DSTATE_BUFIMAGE if being invoked to get access
83   * to the coefficients during a full buffered-image-mode decompression.
84   */
85  if ((cinfo->global_state == DSTATE_STOPPING ||
86       cinfo->global_state == DSTATE_BUFIMAGE) && cinfo->buffered_image) {
87    return cinfo->coef->coef_arrays;
88  }
89  /* Oops, improper usage */
90  ERREXIT1(cinfo, JERR_BAD_STATE, cinfo->global_state);
91  return NULL;                  /* keep compiler happy */
92}
93
94
95/*
96 * Master selection of decompression modules for transcoding.
97 * This substitutes for jdmaster.c's initialization of the full decompressor.
98 */
99
100LOCAL(void)
101transdecode_master_selection(j_decompress_ptr cinfo)
102{
103  /* This is effectively a buffered-image operation. */
104  cinfo->buffered_image = TRUE;
105
106#if JPEG_LIB_VERSION >= 80
107  /* Compute output image dimensions and related values. */
108  jpeg_core_output_dimensions(cinfo);
109#endif
110
111  /* Entropy decoding: either Huffman or arithmetic coding. */
112  if (cinfo->arith_code) {
113#ifdef D_ARITH_CODING_SUPPORTED
114    jinit_arith_decoder(cinfo);
115#else
116    ERREXIT(cinfo, JERR_ARITH_NOTIMPL);
117#endif
118  } else {
119    if (cinfo->progressive_mode) {
120#ifdef D_PROGRESSIVE_SUPPORTED
121      jinit_phuff_decoder(cinfo);
122#else
123      ERREXIT(cinfo, JERR_NOT_COMPILED);
124#endif
125    } else
126      jinit_huff_decoder(cinfo);
127  }
128
129  /* Always get a full-image coefficient buffer. */
130  jinit_d_coef_controller(cinfo, TRUE);
131
132  /* We can now tell the memory manager to allocate virtual arrays. */
133  (*cinfo->mem->realize_virt_arrays) ((j_common_ptr)cinfo);
134
135  /* Initialize input side of decompressor to consume first scan. */
136  (*cinfo->inputctl->start_input_pass) (cinfo);
137
138  /* Initialize progress monitoring. */
139  if (cinfo->progress != NULL) {
140    int nscans;
141    /* Estimate number of scans to set pass_limit. */
142    if (cinfo->progressive_mode) {
143      /* Arbitrarily estimate 2 interleaved DC scans + 3 AC scans/component. */
144      nscans = 2 + 3 * cinfo->num_components;
145    } else if (cinfo->inputctl->has_multiple_scans) {
146      /* For a nonprogressive multiscan file, estimate 1 scan per component. */
147      nscans = cinfo->num_components;
148    } else {
149      nscans = 1;
150    }
151    cinfo->progress->pass_counter = 0L;
152    cinfo->progress->pass_limit = (long)cinfo->total_iMCU_rows * nscans;
153    cinfo->progress->completed_passes = 0;
154    cinfo->progress->total_passes = 1;
155  }
156}
157