chromium/third_party/libjpeg_turbo/jdmarker.c

/*
 * jdmarker.c
 *
 * This file was part of the Independent JPEG Group's software:
 * Copyright (C) 1991-1998, Thomas G. Lane.
 * Lossless JPEG Modifications:
 * Copyright (C) 1999, Ken Murchison.
 * libjpeg-turbo Modifications:
 * Copyright (C) 2012, 2015, 2022, 2024, D. R. Commander.
 * For conditions of distribution and use, see the accompanying README.ijg
 * file.
 *
 * This file contains routines to decode JPEG datastream markers.
 * Most of the complexity arises from our desire to support input
 * suspension: if not all of the data for a marker is available,
 * we must exit back to the application.  On resumption, we reprocess
 * the marker.
 */

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


JPEG_MARKER;


/* Private state */

my_marker_reader;

my_marker_ptr;


/*
 * Macros for fetching data from the data source module.
 *
 * At all times, cinfo->src->next_input_byte and ->bytes_in_buffer reflect
 * the current restart point; we update them only when we have reached a
 * suitable place to restart if a suspension occurs.
 */

/* Declare and initialize local copies of input pointer/count */
#define INPUT_VARS(cinfo) …

/* Unload the local copies --- do this only at a restart boundary */
#define INPUT_SYNC(cinfo) …

/* Reload the local copies --- used only in MAKE_BYTE_AVAIL */
#define INPUT_RELOAD(cinfo) …

/* Internal macro for INPUT_BYTE and INPUT_2BYTES: make a byte available.
 * Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
 * but we must reload the local copies after a successful fill.
 */
#define MAKE_BYTE_AVAIL(cinfo, action) …

/* Read a byte into variable V.
 * If must suspend, take the specified action (typically "return FALSE").
 */
#define INPUT_BYTE(cinfo, V, action) …

/* As above, but read two bytes interpreted as an unsigned 16-bit integer.
 * V should be declared unsigned int or perhaps JLONG.
 */
#define INPUT_2BYTES(cinfo, V, action) …


/*
 * Routines to process JPEG markers.
 *
 * Entry condition: JPEG marker itself has been read and its code saved
 *   in cinfo->unread_marker; input restart point is just after the marker.
 *
 * Exit: if return TRUE, have read and processed any parameters, and have
 *   updated the restart point to point after the parameters.
 *   If return FALSE, was forced to suspend before reaching end of
 *   marker parameters; restart point has not been moved.  Same routine
 *   will be called again after application supplies more input data.
 *
 * This approach to suspension assumes that all of a marker's parameters
 * can fit into a single input bufferload.  This should hold for "normal"
 * markers.  Some COM/APPn markers might have large parameter segments
 * that might not fit.  If we are simply dropping such a marker, we use
 * skip_input_data to get past it, and thereby put the problem on the
 * source manager's shoulders.  If we are saving the marker's contents
 * into memory, we use a slightly different convention: when forced to
 * suspend, the marker processor updates the restart point to the end of
 * what it's consumed (ie, the end of the buffer) before returning FALSE.
 * On resumption, cinfo->unread_marker still contains the marker code,
 * but the data source will point to the next chunk of marker data.
 * The marker processor must retain internal state to deal with this.
 *
 * Note that we don't bother to avoid duplicate trace messages if a
 * suspension occurs within marker parameters.  Other side effects
 * require more care.
 */


LOCAL(boolean)
get_soi(j_decompress_ptr cinfo)
/* Process an SOI marker */
{ … }


LOCAL(boolean)
get_sof(j_decompress_ptr cinfo, boolean is_prog, boolean is_arith)
/* Process a SOFn marker */
{ … }


LOCAL(boolean)
get_sos(j_decompress_ptr cinfo)
/* Process a SOS marker */
{ … }


#ifdef D_ARITH_CODING_SUPPORTED

LOCAL(boolean)
get_dac(j_decompress_ptr cinfo)
/* Process a DAC marker */
{
  JLONG length;
  int index, val;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  length -= 2;

  while (length > 0) {
    INPUT_BYTE(cinfo, index, return FALSE);
    INPUT_BYTE(cinfo, val, return FALSE);

    length -= 2;

    TRACEMS2(cinfo, 1, JTRC_DAC, index, val);

    if (index < 0 || index >= (2 * NUM_ARITH_TBLS))
      ERREXIT1(cinfo, JERR_DAC_INDEX, index);

    if (index >= NUM_ARITH_TBLS) { /* define AC table */
      cinfo->arith_ac_K[index - NUM_ARITH_TBLS] = (UINT8)val;
    } else {                    /* define DC table */
      cinfo->arith_dc_L[index] = (UINT8)(val & 0x0F);
      cinfo->arith_dc_U[index] = (UINT8)(val >> 4);
      if (cinfo->arith_dc_L[index] > cinfo->arith_dc_U[index])
        ERREXIT1(cinfo, JERR_DAC_VALUE, val);
    }
  }

  if (length != 0)
    ERREXIT(cinfo, JERR_BAD_LENGTH);

  INPUT_SYNC(cinfo);
  return TRUE;
}

#else /* !D_ARITH_CODING_SUPPORTED */

#define get_dac(cinfo) …

#endif /* D_ARITH_CODING_SUPPORTED */


LOCAL(boolean)
get_dht(j_decompress_ptr cinfo)
/* Process a DHT marker */
{ … }


LOCAL(boolean)
get_dqt(j_decompress_ptr cinfo)
/* Process a DQT marker */
{ … }


LOCAL(boolean)
get_dri(j_decompress_ptr cinfo)
/* Process a DRI marker */
{ … }


/*
 * Routines for processing APPn and COM markers.
 * These are either saved in memory or discarded, per application request.
 * APP0 and APP14 are specially checked to see if they are
 * JFIF and Adobe markers, respectively.
 */

#define APP0_DATA_LEN …
#define APP14_DATA_LEN …
#define APPN_DATA_LEN …


LOCAL(void)
examine_app0(j_decompress_ptr cinfo, JOCTET *data, unsigned int datalen,
             JLONG remaining)
/* Examine first few bytes from an APP0.
 * Take appropriate action if it is a JFIF marker.
 * datalen is # of bytes at data[], remaining is length of rest of marker data.
 */
{ … }


LOCAL(void)
examine_app14(j_decompress_ptr cinfo, JOCTET *data, unsigned int datalen,
              JLONG remaining)
/* Examine first few bytes from an APP14.
 * Take appropriate action if it is an Adobe marker.
 * datalen is # of bytes at data[], remaining is length of rest of marker data.
 */
{ … }


METHODDEF(boolean)
get_interesting_appn(j_decompress_ptr cinfo)
/* Process an APP0 or APP14 marker without saving it */
{ … }


#ifdef SAVE_MARKERS_SUPPORTED

METHODDEF(boolean)
save_marker(j_decompress_ptr cinfo)
/* Save an APPn or COM marker into the marker list */
{ … }

#endif /* SAVE_MARKERS_SUPPORTED */


METHODDEF(boolean)
skip_variable(j_decompress_ptr cinfo)
/* Skip over an unknown or uninteresting variable-length marker */
{ … }


/*
 * Find the next JPEG marker, save it in cinfo->unread_marker.
 * Returns FALSE if had to suspend before reaching a marker;
 * in that case cinfo->unread_marker is unchanged.
 *
 * Note that the result might not be a valid marker code,
 * but it will never be 0 or FF.
 */

LOCAL(boolean)
next_marker(j_decompress_ptr cinfo)
{ … }


LOCAL(boolean)
first_marker(j_decompress_ptr cinfo)
/* Like next_marker, but used to obtain the initial SOI marker. */
/* For this marker, we do not allow preceding garbage or fill; otherwise,
 * we might well scan an entire input file before realizing it ain't JPEG.
 * If an application wants to process non-JFIF files, it must seek to the
 * SOI before calling the JPEG library.
 */
{ … }


/*
 * Read markers until SOS or EOI.
 *
 * Returns same codes as are defined for jpeg_consume_input:
 * JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
 */

METHODDEF(int)
read_markers(j_decompress_ptr cinfo)
{ … }


/*
 * Read a restart marker, which is expected to appear next in the datastream;
 * if the marker is not there, take appropriate recovery action.
 * Returns FALSE if suspension is required.
 *
 * This is called by the entropy decoder after it has read an appropriate
 * number of MCUs.  cinfo->unread_marker may be nonzero if the entropy decoder
 * has already read a marker from the data source.  Under normal conditions
 * cinfo->unread_marker will be reset to 0 before returning; if not reset,
 * it holds a marker which the decoder will be unable to read past.
 */

METHODDEF(boolean)
read_restart_marker(j_decompress_ptr cinfo)
{ … }


/*
 * This is the default resync_to_restart method for data source managers
 * to use if they don't have any better approach.  Some data source managers
 * may be able to back up, or may have additional knowledge about the data
 * which permits a more intelligent recovery strategy; such managers would
 * presumably supply their own resync method.
 *
 * read_restart_marker calls resync_to_restart if it finds a marker other than
 * the restart marker it was expecting.  (This code is *not* used unless
 * a nonzero restart interval has been declared.)  cinfo->unread_marker is
 * the marker code actually found (might be anything, except 0 or FF).
 * The desired restart marker number (0..7) is passed as a parameter.
 * This routine is supposed to apply whatever error recovery strategy seems
 * appropriate in order to position the input stream to the next data segment.
 * Note that cinfo->unread_marker is treated as a marker appearing before
 * the current data-source input point; usually it should be reset to zero
 * before returning.
 * Returns FALSE if suspension is required.
 *
 * This implementation is substantially constrained by wanting to treat the
 * input as a data stream; this means we can't back up.  Therefore, we have
 * only the following actions to work with:
 *   1. Simply discard the marker and let the entropy decoder resume at next
 *      byte of file.
 *   2. Read forward until we find another marker, discarding intervening
 *      data.  (In theory we could look ahead within the current bufferload,
 *      without having to discard data if we don't find the desired marker.
 *      This idea is not implemented here, in part because it makes behavior
 *      dependent on buffer size and chance buffer-boundary positions.)
 *   3. Leave the marker unread (by failing to zero cinfo->unread_marker).
 *      This will cause the entropy decoder to process an empty data segment,
 *      inserting dummy zeroes, and then we will reprocess the marker.
 *
 * #2 is appropriate if we think the desired marker lies ahead, while #3 is
 * appropriate if the found marker is a future restart marker (indicating
 * that we have missed the desired restart marker, probably because it got
 * corrupted).
 * We apply #2 or #3 if the found marker is a restart marker no more than
 * two counts behind or ahead of the expected one.  We also apply #2 if the
 * found marker is not a legal JPEG marker code (it's certainly bogus data).
 * If the found marker is a restart marker more than 2 counts away, we do #1
 * (too much risk that the marker is erroneous; with luck we will be able to
 * resync at some future point).
 * For any valid non-restart JPEG marker, we apply #3.  This keeps us from
 * overrunning the end of a scan.  An implementation limited to single-scan
 * files might find it better to apply #2 for markers other than EOI, since
 * any other marker would have to be bogus data in that case.
 */

GLOBAL(boolean)
jpeg_resync_to_restart(j_decompress_ptr cinfo, int desired)
{ … }


/*
 * Reset marker processing state to begin a fresh datastream.
 */

METHODDEF(void)
reset_marker_reader(j_decompress_ptr cinfo)
{ … }


/*
 * Initialize the marker reader module.
 * This is called only once, when the decompression object is created.
 */

GLOBAL(void)
jinit_marker_reader(j_decompress_ptr cinfo)
{ … }


/*
 * Control saving of COM and APPn markers into marker_list.
 */

#ifdef SAVE_MARKERS_SUPPORTED

GLOBAL(void)
jpeg_save_markers(j_decompress_ptr cinfo, int marker_code,
                  unsigned int length_limit)
{ … }

#endif /* SAVE_MARKERS_SUPPORTED */


/*
 * Install a special processing method for COM or APPn markers.
 */

GLOBAL(void)
jpeg_set_marker_processor(j_decompress_ptr cinfo, int marker_code,
                          jpeg_marker_parser_method routine)
{ … }