root/third_party/libjpeg/jdmarker.c

DEFINITIONS

1. LOCAL
2. LOCAL
3. LOCAL
4. LOCAL
5. LOCAL
6. LOCAL
7. LOCAL
8. LOCAL
9. LOCAL
10. METHODDEF
11. METHODDEF
12. METHODDEF
13. LOCAL
14. LOCAL
15. METHODDEF
16. METHODDEF
17. GLOBAL
18. METHODDEF
19. GLOBAL
20. GLOBAL
21. GLOBAL

/*
 * jdmarker.c
 *
 * Copyright (C) 1991-1998, Thomas G. Lane.
 * This file is part of the Independent JPEG Group's software.
 * For conditions of distribution and use, see the accompanying README 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"


typedef enum {                  /* JPEG marker codes */
  M_SOF0  = 0xc0,
  M_SOF1  = 0xc1,
  M_SOF2  = 0xc2,
  M_SOF3  = 0xc3,
  
  M_SOF5  = 0xc5,
  M_SOF6  = 0xc6,
  M_SOF7  = 0xc7,
  
  M_JPG   = 0xc8,
  M_SOF9  = 0xc9,
  M_SOF10 = 0xca,
  M_SOF11 = 0xcb,
  
  M_SOF13 = 0xcd,
  M_SOF14 = 0xce,
  M_SOF15 = 0xcf,
  
  M_DHT   = 0xc4,
  
  M_DAC   = 0xcc,
  
  M_RST0  = 0xd0,
  M_RST1  = 0xd1,
  M_RST2  = 0xd2,
  M_RST3  = 0xd3,
  M_RST4  = 0xd4,
  M_RST5  = 0xd5,
  M_RST6  = 0xd6,
  M_RST7  = 0xd7,
  
  M_SOI   = 0xd8,
  M_EOI   = 0xd9,
  M_SOS   = 0xda,
  M_DQT   = 0xdb,
  M_DNL   = 0xdc,
  M_DRI   = 0xdd,
  M_DHP   = 0xde,
  M_EXP   = 0xdf,
  
  M_APP0  = 0xe0,
  M_APP1  = 0xe1,
  M_APP2  = 0xe2,
  M_APP3  = 0xe3,
  M_APP4  = 0xe4,
  M_APP5  = 0xe5,
  M_APP6  = 0xe6,
  M_APP7  = 0xe7,
  M_APP8  = 0xe8,
  M_APP9  = 0xe9,
  M_APP10 = 0xea,
  M_APP11 = 0xeb,
  M_APP12 = 0xec,
  M_APP13 = 0xed,
  M_APP14 = 0xee,
  M_APP15 = 0xef,
  
  M_JPG0  = 0xf0,
  M_JPG13 = 0xfd,
  M_COM   = 0xfe,
  
  M_TEM   = 0x01,
  
  M_ERROR = 0x100
} JPEG_MARKER;


/* Private state */

typedef struct {
  struct jpeg_marker_reader pub; /* public fields */

  /* Application-overridable marker processing methods */
  jpeg_marker_parser_method process_COM;
  jpeg_marker_parser_method process_APPn[16];

  /* Limit on marker data length to save for each marker type */
  unsigned int length_limit_COM;
  unsigned int length_limit_APPn[16];

  /* Status of COM/APPn marker saving */
  jpeg_saved_marker_ptr cur_marker;     /* NULL if not processing a marker */
  unsigned int bytes_read;              /* data bytes read so far in marker */
  /* Note: cur_marker is not linked into marker_list until it's all read. */
} my_marker_reader;

typedef 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)  \
        struct jpeg_source_mgr * datasrc = (cinfo)->src;  \
        const JOCTET * next_input_byte = datasrc->next_input_byte;  \
        size_t bytes_in_buffer = datasrc->bytes_in_buffer

/* Unload the local copies --- do this only at a restart boundary */
#define INPUT_SYNC(cinfo)  \
        ( datasrc->next_input_byte = next_input_byte,  \
          datasrc->bytes_in_buffer = bytes_in_buffer )

/* Reload the local copies --- used only in MAKE_BYTE_AVAIL */
#define INPUT_RELOAD(cinfo)  \
        ( next_input_byte = datasrc->next_input_byte,  \
          bytes_in_buffer = datasrc->bytes_in_buffer )

/* 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)  \
        if (bytes_in_buffer == 0) {  \
          if (! (*datasrc->fill_input_buffer) (cinfo))  \
            { action; }  \
          INPUT_RELOAD(cinfo);  \
        }

/* Read a byte into variable V.
 * If must suspend, take the specified action (typically "return FALSE").
 */
#define INPUT_BYTE(cinfo,V,action)  \
        MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
                  bytes_in_buffer--; \
                  V = GETJOCTET(*next_input_byte++); )

/* As above, but read two bytes interpreted as an unsigned 16-bit integer.
 * V should be declared unsigned int or perhaps INT32.
 */
#define INPUT_2BYTES(cinfo,V,action)  \
        MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
                  bytes_in_buffer--; \
                  V = ((unsigned int) GETJOCTET(*next_input_byte++)) << 8; \
                  MAKE_BYTE_AVAIL(cinfo,action); \
                  bytes_in_buffer--; \
                  V += GETJOCTET(*next_input_byte++); )


/*
 * 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 */
{
  int i;
  
  TRACEMS(cinfo, 1, JTRC_SOI);

  if (cinfo->marker->saw_SOI)
    ERREXIT(cinfo, JERR_SOI_DUPLICATE);

  /* Reset all parameters that are defined to be reset by SOI */

  for (i = 0; i < NUM_ARITH_TBLS; i++) {
    cinfo->arith_dc_L[i] = 0;
    cinfo->arith_dc_U[i] = 1;
    cinfo->arith_ac_K[i] = 5;
  }
  cinfo->restart_interval = 0;

  /* Set initial assumptions for colorspace etc */

  cinfo->jpeg_color_space = JCS_UNKNOWN;
  cinfo->CCIR601_sampling = FALSE; /* Assume non-CCIR sampling??? */

  cinfo->saw_JFIF_marker = FALSE;
  cinfo->JFIF_major_version = 1; /* set default JFIF APP0 values */
  cinfo->JFIF_minor_version = 1;
  cinfo->density_unit = 0;
  cinfo->X_density = 1;
  cinfo->Y_density = 1;
  cinfo->saw_Adobe_marker = FALSE;
  cinfo->Adobe_transform = 0;

  cinfo->marker->saw_SOI = TRUE;

  return TRUE;
}


LOCAL(boolean)
get_sof (j_decompress_ptr cinfo, boolean is_prog, boolean is_arith)
/* Process a SOFn marker */
{
  INT32 length;
  int c, ci;
  jpeg_component_info * compptr;
  INPUT_VARS(cinfo);

  cinfo->progressive_mode = is_prog;
  cinfo->arith_code = is_arith;

  INPUT_2BYTES(cinfo, length, return FALSE);

  INPUT_BYTE(cinfo, cinfo->data_precision, return FALSE);
  INPUT_2BYTES(cinfo, cinfo->image_height, return FALSE);
  INPUT_2BYTES(cinfo, cinfo->image_width, return FALSE);
  INPUT_BYTE(cinfo, cinfo->num_components, return FALSE);

  length -= 8;

  TRACEMS4(cinfo, 1, JTRC_SOF, cinfo->unread_marker,
           (int) cinfo->image_width, (int) cinfo->image_height,
           cinfo->num_components);

  if (cinfo->marker->saw_SOF)
    ERREXIT(cinfo, JERR_SOF_DUPLICATE);

  /* We don't support files in which the image height is initially specified */
  /* as 0 and is later redefined by DNL.  As long as we have to check that,  */
  /* might as well have a general sanity check. */
  if (cinfo->image_height <= 0 || cinfo->image_width <= 0
      || cinfo->num_components <= 0)
    ERREXIT(cinfo, JERR_EMPTY_IMAGE);

  if (length != (cinfo->num_components * 3))
    ERREXIT(cinfo, JERR_BAD_LENGTH);

  if (cinfo->comp_info == NULL) /* do only once, even if suspend */
    cinfo->comp_info = (jpeg_component_info *) (*cinfo->mem->alloc_small)
                        ((j_common_ptr) cinfo, JPOOL_IMAGE,
                         cinfo->num_components * SIZEOF(jpeg_component_info));
  
  for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
       ci++, compptr++) {
    compptr->component_index = ci;
    INPUT_BYTE(cinfo, compptr->component_id, return FALSE);
    INPUT_BYTE(cinfo, c, return FALSE);
    compptr->h_samp_factor = (c >> 4) & 15;
    compptr->v_samp_factor = (c     ) & 15;
    INPUT_BYTE(cinfo, compptr->quant_tbl_no, return FALSE);

    TRACEMS4(cinfo, 1, JTRC_SOF_COMPONENT,
             compptr->component_id, compptr->h_samp_factor,
             compptr->v_samp_factor, compptr->quant_tbl_no);
  }

  cinfo->marker->saw_SOF = TRUE;

  INPUT_SYNC(cinfo);
  return TRUE;
}


LOCAL(boolean)
get_sos (j_decompress_ptr cinfo)
/* Process a SOS marker */
{
  INT32 length;
  int i, ci, n, c, cc;
  jpeg_component_info * compptr;
  INPUT_VARS(cinfo);

  if (! cinfo->marker->saw_SOF)
    ERREXIT(cinfo, JERR_SOS_NO_SOF);

  INPUT_2BYTES(cinfo, length, return FALSE);

  INPUT_BYTE(cinfo, n, return FALSE); /* Number of components */

  TRACEMS1(cinfo, 1, JTRC_SOS, n);

  if (length != (n * 2 + 6) || n < 1 || n > MAX_COMPS_IN_SCAN)
    ERREXIT(cinfo, JERR_BAD_LENGTH);

  cinfo->comps_in_scan = n;

  /* Collect the component-spec parameters */

  for (i = 0; i < n; i++) {
    INPUT_BYTE(cinfo, cc, return FALSE);
    INPUT_BYTE(cinfo, c, return FALSE);
    
    for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
         ci++, compptr++) {
      if (cc == compptr->component_id)
        goto id_found;
    }

    ERREXIT1(cinfo, JERR_BAD_COMPONENT_ID, cc);

  id_found:

    cinfo->cur_comp_info[i] = compptr;
    compptr->dc_tbl_no = (c >> 4) & 15;
    compptr->ac_tbl_no = (c     ) & 15;
    
    TRACEMS3(cinfo, 1, JTRC_SOS_COMPONENT, cc,
             compptr->dc_tbl_no, compptr->ac_tbl_no);

    /* This CSi (cc) should differ from the previous CSi */
    for (ci = 0; ci < i; ci++) {
      if (cinfo->cur_comp_info[ci] == compptr)
        ERREXIT1(cinfo, JERR_BAD_COMPONENT_ID, cc);
    }
  }

  /* Collect the additional scan parameters Ss, Se, Ah/Al. */
  INPUT_BYTE(cinfo, c, return FALSE);
  cinfo->Ss = c;
  INPUT_BYTE(cinfo, c, return FALSE);
  cinfo->Se = c;
  INPUT_BYTE(cinfo, c, return FALSE);
  cinfo->Ah = (c >> 4) & 15;
  cinfo->Al = (c     ) & 15;

  TRACEMS4(cinfo, 1, JTRC_SOS_PARAMS, cinfo->Ss, cinfo->Se,
           cinfo->Ah, cinfo->Al);

  /* Prepare to scan data & restart markers */
  cinfo->marker->next_restart_num = 0;

  /* Count another SOS marker */
  cinfo->input_scan_number++;

  INPUT_SYNC(cinfo);
  return TRUE;
}


#ifdef D_ARITH_CODING_SUPPORTED

LOCAL(boolean)
get_dac (j_decompress_ptr cinfo)
/* Process a DAC marker */
{
  INT32 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)  skip_variable(cinfo)

#endif /* D_ARITH_CODING_SUPPORTED */


LOCAL(boolean)
get_dht (j_decompress_ptr cinfo)
/* Process a DHT marker */
{
  INT32 length;
  UINT8 bits[17];
  UINT8 huffval[256];
  int i, index, count;
  JHUFF_TBL **htblptr;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  length -= 2;
  
  while (length > 16) {
    INPUT_BYTE(cinfo, index, return FALSE);

    TRACEMS1(cinfo, 1, JTRC_DHT, index);
      
    bits[0] = 0;
    count = 0;
    for (i = 1; i <= 16; i++) {
      INPUT_BYTE(cinfo, bits[i], return FALSE);
      count += bits[i];
    }

    length -= 1 + 16;

    TRACEMS8(cinfo, 2, JTRC_HUFFBITS,
             bits[1], bits[2], bits[3], bits[4],
             bits[5], bits[6], bits[7], bits[8]);
    TRACEMS8(cinfo, 2, JTRC_HUFFBITS,
             bits[9], bits[10], bits[11], bits[12],
             bits[13], bits[14], bits[15], bits[16]);

    /* Here we just do minimal validation of the counts to avoid walking
     * off the end of our table space.  jdhuff.c will check more carefully.
     */
    if (count > 256 || ((INT32) count) > length)
      ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);

    for (i = 0; i < count; i++)
      INPUT_BYTE(cinfo, huffval[i], return FALSE);

    length -= count;

    if (index & 0x10) {         /* AC table definition */
      index -= 0x10;
      htblptr = &cinfo->ac_huff_tbl_ptrs[index];
    } else {                    /* DC table definition */
      htblptr = &cinfo->dc_huff_tbl_ptrs[index];
    }

    if (index < 0 || index >= NUM_HUFF_TBLS)
      ERREXIT1(cinfo, JERR_DHT_INDEX, index);

    if (*htblptr == NULL)
      *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
  
    MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));
    MEMCOPY((*htblptr)->huffval, huffval, SIZEOF((*htblptr)->huffval));
  }

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

  INPUT_SYNC(cinfo);
  return TRUE;
}


LOCAL(boolean)
get_dqt (j_decompress_ptr cinfo)
/* Process a DQT marker */
{
  INT32 length;
  int n, i, prec;
  unsigned int tmp;
  JQUANT_TBL *quant_ptr;
  INPUT_VARS(cinfo);

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

  while (length > 0) {
    INPUT_BYTE(cinfo, n, return FALSE);
    prec = n >> 4;
    n &= 0x0F;

    TRACEMS2(cinfo, 1, JTRC_DQT, n, prec);

    if (n >= NUM_QUANT_TBLS)
      ERREXIT1(cinfo, JERR_DQT_INDEX, n);
      
    if (cinfo->quant_tbl_ptrs[n] == NULL)
      cinfo->quant_tbl_ptrs[n] = jpeg_alloc_quant_table((j_common_ptr) cinfo);
    quant_ptr = cinfo->quant_tbl_ptrs[n];

    for (i = 0; i < DCTSIZE2; i++) {
      if (prec)
        INPUT_2BYTES(cinfo, tmp, return FALSE);
      else
        INPUT_BYTE(cinfo, tmp, return FALSE);
      /* We convert the zigzag-order table to natural array order. */
      quant_ptr->quantval[jpeg_natural_order[i]] = (UINT16) tmp;
    }

    if (cinfo->err->trace_level >= 2) {
      for (i = 0; i < DCTSIZE2; i += 8) {
        TRACEMS8(cinfo, 2, JTRC_QUANTVALS,
                 quant_ptr->quantval[i],   quant_ptr->quantval[i+1],
                 quant_ptr->quantval[i+2], quant_ptr->quantval[i+3],
                 quant_ptr->quantval[i+4], quant_ptr->quantval[i+5],
                 quant_ptr->quantval[i+6], quant_ptr->quantval[i+7]);
      }
    }

    length -= DCTSIZE2+1;
    if (prec) length -= DCTSIZE2;
  }

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

  INPUT_SYNC(cinfo);
  return TRUE;
}


LOCAL(boolean)
get_dri (j_decompress_ptr cinfo)
/* Process a DRI marker */
{
  INT32 length;
  unsigned int tmp;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  
  if (length != 4)
    ERREXIT(cinfo, JERR_BAD_LENGTH);

  INPUT_2BYTES(cinfo, tmp, return FALSE);

  TRACEMS1(cinfo, 1, JTRC_DRI, tmp);

  cinfo->restart_interval = tmp;

  INPUT_SYNC(cinfo);
  return TRUE;
}


/*
 * 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   14      /* Length of interesting data in APP0 */
#define APP14_DATA_LEN  12      /* Length of interesting data in APP14 */
#define APPN_DATA_LEN   14      /* Must be the largest of the above!! */


LOCAL(void)
examine_app0 (j_decompress_ptr cinfo, JOCTET FAR * data,
              unsigned int datalen, INT32 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.
 */
{
  INT32 totallen = (INT32) datalen + remaining;

  if (datalen >= APP0_DATA_LEN &&
      GETJOCTET(data[0]) == 0x4A &&
      GETJOCTET(data[1]) == 0x46 &&
      GETJOCTET(data[2]) == 0x49 &&
      GETJOCTET(data[3]) == 0x46 &&
      GETJOCTET(data[4]) == 0) {
    /* Found JFIF APP0 marker: save info */
    cinfo->saw_JFIF_marker = TRUE;
    cinfo->JFIF_major_version = GETJOCTET(data[5]);
    cinfo->JFIF_minor_version = GETJOCTET(data[6]);
    cinfo->density_unit = GETJOCTET(data[7]);
    cinfo->X_density = (GETJOCTET(data[8]) << 8) + GETJOCTET(data[9]);
    cinfo->Y_density = (GETJOCTET(data[10]) << 8) + GETJOCTET(data[11]);
    /* Check version.
     * Major version must be 1, anything else signals an incompatible change.
     * (We used to treat this as an error, but now it's a nonfatal warning,
     * because some bozo at Hijaak couldn't read the spec.)
     * Minor version should be 0..2, but process anyway if newer.
     */
    if (cinfo->JFIF_major_version != 1)
      WARNMS2(cinfo, JWRN_JFIF_MAJOR,
              cinfo->JFIF_major_version, cinfo->JFIF_minor_version);
    /* Generate trace messages */
    TRACEMS5(cinfo, 1, JTRC_JFIF,
             cinfo->JFIF_major_version, cinfo->JFIF_minor_version,
             cinfo->X_density, cinfo->Y_density, cinfo->density_unit);
    /* Validate thumbnail dimensions and issue appropriate messages */
    if (GETJOCTET(data[12]) | GETJOCTET(data[13]))
      TRACEMS2(cinfo, 1, JTRC_JFIF_THUMBNAIL,
               GETJOCTET(data[12]), GETJOCTET(data[13]));
    totallen -= APP0_DATA_LEN;
    if (totallen !=
        ((INT32)GETJOCTET(data[12]) * (INT32)GETJOCTET(data[13]) * (INT32) 3))
      TRACEMS1(cinfo, 1, JTRC_JFIF_BADTHUMBNAILSIZE, (int) totallen);
  } else if (datalen >= 6 &&
      GETJOCTET(data[0]) == 0x4A &&
      GETJOCTET(data[1]) == 0x46 &&
      GETJOCTET(data[2]) == 0x58 &&
      GETJOCTET(data[3]) == 0x58 &&
      GETJOCTET(data[4]) == 0) {
    /* Found JFIF "JFXX" extension APP0 marker */
    /* The library doesn't actually do anything with these,
     * but we try to produce a helpful trace message.
     */
    switch (GETJOCTET(data[5])) {
    case 0x10:
      TRACEMS1(cinfo, 1, JTRC_THUMB_JPEG, (int) totallen);
      break;
    case 0x11:
      TRACEMS1(cinfo, 1, JTRC_THUMB_PALETTE, (int) totallen);
      break;
    case 0x13:
      TRACEMS1(cinfo, 1, JTRC_THUMB_RGB, (int) totallen);
      break;
    default:
      TRACEMS2(cinfo, 1, JTRC_JFIF_EXTENSION,
               GETJOCTET(data[5]), (int) totallen);
      break;
    }
  } else {
    /* Start of APP0 does not match "JFIF" or "JFXX", or too short */
    TRACEMS1(cinfo, 1, JTRC_APP0, (int) totallen);
  }
}


LOCAL(void)
examine_app14 (j_decompress_ptr cinfo, JOCTET FAR * data,
               unsigned int datalen, INT32 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.
 */
{
  unsigned int version, flags0, flags1, transform;

  if (datalen >= APP14_DATA_LEN &&
      GETJOCTET(data[0]) == 0x41 &&
      GETJOCTET(data[1]) == 0x64 &&
      GETJOCTET(data[2]) == 0x6F &&
      GETJOCTET(data[3]) == 0x62 &&
      GETJOCTET(data[4]) == 0x65) {
    /* Found Adobe APP14 marker */
    version = (GETJOCTET(data[5]) << 8) + GETJOCTET(data[6]);
    flags0 = (GETJOCTET(data[7]) << 8) + GETJOCTET(data[8]);
    flags1 = (GETJOCTET(data[9]) << 8) + GETJOCTET(data[10]);
    transform = GETJOCTET(data[11]);
    TRACEMS4(cinfo, 1, JTRC_ADOBE, version, flags0, flags1, transform);
    cinfo->saw_Adobe_marker = TRUE;
    cinfo->Adobe_transform = (UINT8) transform;
  } else {
    /* Start of APP14 does not match "Adobe", or too short */
    TRACEMS1(cinfo, 1, JTRC_APP14, (int) (datalen + remaining));
  }
}


METHODDEF(boolean)
get_interesting_appn (j_decompress_ptr cinfo)
/* Process an APP0 or APP14 marker without saving it */
{
  INT32 length;
  JOCTET b[APPN_DATA_LEN];
  unsigned int i, numtoread;
  INPUT_VARS(cinfo);

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

  /* get the interesting part of the marker data */
  if (length >= APPN_DATA_LEN)
    numtoread = APPN_DATA_LEN;
  else if (length > 0)
    numtoread = (unsigned int) length;
  else
    numtoread = 0;
  for (i = 0; i < numtoread; i++)
    INPUT_BYTE(cinfo, b[i], return FALSE);
  length -= numtoread;

  /* process it */
  switch (cinfo->unread_marker) {
  case M_APP0:
    examine_app0(cinfo, (JOCTET FAR *) b, numtoread, length);
    break;
  case M_APP14:
    examine_app14(cinfo, (JOCTET FAR *) b, numtoread, length);
    break;
  default:
    /* can't get here unless jpeg_save_markers chooses wrong processor */
    ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker);
    break;
  }

  /* skip any remaining data -- could be lots */
  INPUT_SYNC(cinfo);
  if (length > 0)
    (*cinfo->src->skip_input_data) (cinfo, (long) length);

  return TRUE;
}


#ifdef SAVE_MARKERS_SUPPORTED

METHODDEF(boolean)
save_marker (j_decompress_ptr cinfo)
/* Save an APPn or COM marker into the marker list */
{
  my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
  jpeg_saved_marker_ptr cur_marker = marker->cur_marker;
  unsigned int bytes_read, data_length;
  JOCTET FAR * data;
  INT32 length = 0;
  INPUT_VARS(cinfo);

  if (cur_marker == NULL) {
    /* begin reading a marker */
    INPUT_2BYTES(cinfo, length, return FALSE);
    length -= 2;
    if (length >= 0) {          /* watch out for bogus length word */
      /* figure out how much we want to save */
      unsigned int limit;
      if (cinfo->unread_marker == (int) M_COM)
        limit = marker->length_limit_COM;
      else
        limit = marker->length_limit_APPn[cinfo->unread_marker - (int) M_APP0];
      if ((unsigned int) length < limit)
        limit = (unsigned int) length;
      /* allocate and initialize the marker item */
      cur_marker = (jpeg_saved_marker_ptr)
        (*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
                                    SIZEOF(struct jpeg_marker_struct) + limit);
      cur_marker->next = NULL;
      cur_marker->marker = (UINT8) cinfo->unread_marker;
      cur_marker->original_length = (unsigned int) length;
      cur_marker->data_length = limit;
      /* data area is just beyond the jpeg_marker_struct */
      data = cur_marker->data = (JOCTET FAR *) (cur_marker + 1);
      marker->cur_marker = cur_marker;
      marker->bytes_read = 0;
      bytes_read = 0;
      data_length = limit;
    } else {
      /* deal with bogus length word */
      bytes_read = data_length = 0;
      data = NULL;
    }
  } else {
    /* resume reading a marker */
    bytes_read = marker->bytes_read;
    data_length = cur_marker->data_length;
    data = cur_marker->data + bytes_read;
  }

  while (bytes_read < data_length) {
    INPUT_SYNC(cinfo);          /* move the restart point to here */
    marker->bytes_read = bytes_read;
    /* If there's not at least one byte in buffer, suspend */
    MAKE_BYTE_AVAIL(cinfo, return FALSE);
    /* Copy bytes with reasonable rapidity */
    while (bytes_read < data_length && bytes_in_buffer > 0) {
      *data++ = *next_input_byte++;
      bytes_in_buffer--;
      bytes_read++;
    }
  }

  /* Done reading what we want to read */
  if (cur_marker != NULL) {     /* will be NULL if bogus length word */
    /* Add new marker to end of list */
    if (cinfo->marker_list == NULL) {
      cinfo->marker_list = cur_marker;
    } else {
      jpeg_saved_marker_ptr prev = cinfo->marker_list;
      while (prev->next != NULL)
        prev = prev->next;
      prev->next = cur_marker;
    }
    /* Reset pointer & calc remaining data length */
    data = cur_marker->data;
    length = cur_marker->original_length - data_length;
  }
  /* Reset to initial state for next marker */
  marker->cur_marker = NULL;

  /* Process the marker if interesting; else just make a generic trace msg */
  switch (cinfo->unread_marker) {
  case M_APP0:
    examine_app0(cinfo, data, data_length, length);
    break;
  case M_APP14:
    examine_app14(cinfo, data, data_length, length);
    break;
  default:
    TRACEMS2(cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker,
             (int) (data_length + length));
    break;
  }

  /* skip any remaining data -- could be lots */
  INPUT_SYNC(cinfo);            /* do before skip_input_data */
  if (length > 0)
    (*cinfo->src->skip_input_data) (cinfo, (long) length);

  return TRUE;
}

#endif /* SAVE_MARKERS_SUPPORTED */


METHODDEF(boolean)
skip_variable (j_decompress_ptr cinfo)
/* Skip over an unknown or uninteresting variable-length marker */
{
  INT32 length;
  INPUT_VARS(cinfo);

  INPUT_2BYTES(cinfo, length, return FALSE);
  length -= 2;
  
  TRACEMS2(cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker, (int) length);

  INPUT_SYNC(cinfo);            /* do before skip_input_data */
  if (length > 0)
    (*cinfo->src->skip_input_data) (cinfo, (long) length);

  return TRUE;
}


/*
 * 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)
{
  int c;
  INPUT_VARS(cinfo);

  for (;;) {
    INPUT_BYTE(cinfo, c, return FALSE);
    /* Skip any non-FF bytes.
     * This may look a bit inefficient, but it will not occur in a valid file.
     * We sync after each discarded byte so that a suspending data source
     * can discard the byte from its buffer.
     */
    while (c != 0xFF) {
      cinfo->marker->discarded_bytes++;
      INPUT_SYNC(cinfo);
      INPUT_BYTE(cinfo, c, return FALSE);
    }
    /* This loop swallows any duplicate FF bytes.  Extra FFs are legal as
     * pad bytes, so don't count them in discarded_bytes.  We assume there
     * will not be so many consecutive FF bytes as to overflow a suspending
     * data source's input buffer.
     */
    do {
      INPUT_BYTE(cinfo, c, return FALSE);
    } while (c == 0xFF);
    if (c != 0)
      break;                    /* found a valid marker, exit loop */
    /* Reach here if we found a stuffed-zero data sequence (FF/00).
     * Discard it and loop back to try again.
     */
    cinfo->marker->discarded_bytes += 2;
    INPUT_SYNC(cinfo);
  }

  if (cinfo->marker->discarded_bytes != 0) {
    WARNMS2(cinfo, JWRN_EXTRANEOUS_DATA, cinfo->marker->discarded_bytes, c);
    cinfo->marker->discarded_bytes = 0;
  }

  cinfo->unread_marker = c;

  INPUT_SYNC(cinfo);
  return TRUE;
}


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.
 */
{
  int c, c2;
  INPUT_VARS(cinfo);

  INPUT_BYTE(cinfo, c, return FALSE);
  INPUT_BYTE(cinfo, c2, return FALSE);
  if (c != 0xFF || c2 != (int) M_SOI)
    ERREXIT2(cinfo, JERR_NO_SOI, c, c2);

  cinfo->unread_marker = c2;

  INPUT_SYNC(cinfo);
  return TRUE;
}


/*
 * 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)
{
  /* Outer loop repeats once for each marker. */
  for (;;) {
    /* Collect the marker proper, unless we already did. */
    /* NB: first_marker() enforces the requirement that SOI appear first. */
    if (cinfo->unread_marker == 0) {
      if (! cinfo->marker->saw_SOI) {
        if (! first_marker(cinfo))
          return JPEG_SUSPENDED;
      } else {
        if (! next_marker(cinfo))
          return JPEG_SUSPENDED;
      }
    }
    /* At this point cinfo->unread_marker contains the marker code and the
     * input point is just past the marker proper, but before any parameters.
     * A suspension will cause us to return with this state still true.
     */
    switch (cinfo->unread_marker) {
    case M_SOI:
      if (! get_soi(cinfo))
        return JPEG_SUSPENDED;
      break;

    case M_SOF0:                /* Baseline */
    case M_SOF1:                /* Extended sequential, Huffman */
      if (! get_sof(cinfo, FALSE, FALSE))
        return JPEG_SUSPENDED;
      break;

    case M_SOF2:                /* Progressive, Huffman */
      if (! get_sof(cinfo, TRUE, FALSE))
        return JPEG_SUSPENDED;
      break;

    case M_SOF9:                /* Extended sequential, arithmetic */
      if (! get_sof(cinfo, FALSE, TRUE))
        return JPEG_SUSPENDED;
      break;

    case M_SOF10:               /* Progressive, arithmetic */
      if (! get_sof(cinfo, TRUE, TRUE))
        return JPEG_SUSPENDED;
      break;

    /* Currently unsupported SOFn types */
    case M_SOF3:                /* Lossless, Huffman */
    case M_SOF5:                /* Differential sequential, Huffman */
    case M_SOF6:                /* Differential progressive, Huffman */
    case M_SOF7:                /* Differential lossless, Huffman */
    case M_JPG:                 /* Reserved for JPEG extensions */
    case M_SOF11:               /* Lossless, arithmetic */
    case M_SOF13:               /* Differential sequential, arithmetic */
    case M_SOF14:               /* Differential progressive, arithmetic */
    case M_SOF15:               /* Differential lossless, arithmetic */
      ERREXIT1(cinfo, JERR_SOF_UNSUPPORTED, cinfo->unread_marker);
      break;

    case M_SOS:
      if (! get_sos(cinfo))
        return JPEG_SUSPENDED;
      cinfo->unread_marker = 0; /* processed the marker */
      return JPEG_REACHED_SOS;
    
    case M_EOI:
      TRACEMS(cinfo, 1, JTRC_EOI);
      cinfo->unread_marker = 0; /* processed the marker */
      return JPEG_REACHED_EOI;
      
    case M_DAC:
      if (! get_dac(cinfo))
        return JPEG_SUSPENDED;
      break;
      
    case M_DHT:
      if (! get_dht(cinfo))
        return JPEG_SUSPENDED;
      break;
      
    case M_DQT:
      if (! get_dqt(cinfo))
        return JPEG_SUSPENDED;
      break;
      
    case M_DRI:
      if (! get_dri(cinfo))
        return JPEG_SUSPENDED;
      break;
      
    case M_APP0:
    case M_APP1:
    case M_APP2:
    case M_APP3:
    case M_APP4:
    case M_APP5:
    case M_APP6:
    case M_APP7:
    case M_APP8:
    case M_APP9:
    case M_APP10:
    case M_APP11:
    case M_APP12:
    case M_APP13:
    case M_APP14:
    case M_APP15:
      if (! (*((my_marker_ptr) cinfo->marker)->process_APPn[
                cinfo->unread_marker - (int) M_APP0]) (cinfo))
        return JPEG_SUSPENDED;
      break;
      
    case M_COM:
      if (! (*((my_marker_ptr) cinfo->marker)->process_COM) (cinfo))
        return JPEG_SUSPENDED;
      break;

    case M_RST0:                /* these are all parameterless */
    case M_RST1:
    case M_RST2:
    case M_RST3:
    case M_RST4:
    case M_RST5:
    case M_RST6:
    case M_RST7:
    case M_TEM:
      TRACEMS1(cinfo, 1, JTRC_PARMLESS_MARKER, cinfo->unread_marker);
      break;

    case M_DNL:                 /* Ignore DNL ... perhaps the wrong thing */
      if (! skip_variable(cinfo))
        return JPEG_SUSPENDED;
      break;

    default:                    /* must be DHP, EXP, JPGn, or RESn */
      /* For now, we treat the reserved markers as fatal errors since they are
       * likely to be used to signal incompatible JPEG Part 3 extensions.
       * Once the JPEG 3 version-number marker is well defined, this code
       * ought to change!
       */
      ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker);
      break;
    }
    /* Successfully processed marker, so reset state variable */
    cinfo->unread_marker = 0;
  } /* end loop */
}


/*
 * 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)
{
  /* Obtain a marker unless we already did. */
  /* Note that next_marker will complain if it skips any data. */
  if (cinfo->unread_marker == 0) {
    if (! next_marker(cinfo))
      return FALSE;
  }

  if (cinfo->unread_marker ==
      ((int) M_RST0 + cinfo->marker->next_restart_num)) {
    /* Normal case --- swallow the marker and let entropy decoder continue */
    TRACEMS1(cinfo, 3, JTRC_RST, cinfo->marker->next_restart_num);
    cinfo->unread_marker = 0;
  } else {
    /* Uh-oh, the restart markers have been messed up. */
    /* Let the data source manager determine how to resync. */
    if (! (*cinfo->src->resync_to_restart) (cinfo,
                                            cinfo->marker->next_restart_num))
      return FALSE;
  }

  /* Update next-restart state */
  cinfo->marker->next_restart_num = (cinfo->marker->next_restart_num + 1) & 7;

  return TRUE;
}


/*
 * 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)
{
  int marker = cinfo->unread_marker;
  int action = 1;
  
  /* Always put up a warning. */
  WARNMS2(cinfo, JWRN_MUST_RESYNC, marker, desired);
  
  /* Outer loop handles repeated decision after scanning forward. */
  for (;;) {
    if (marker < (int) M_SOF0)
      action = 2;               /* invalid marker */
    else if (marker < (int) M_RST0 || marker > (int) M_RST7)
      action = 3;               /* valid non-restart marker */
    else {
      if (marker == ((int) M_RST0 + ((desired+1) & 7)) ||
          marker == ((int) M_RST0 + ((desired+2) & 7)))
        action = 3;             /* one of the next two expected restarts */
      else if (marker == ((int) M_RST0 + ((desired-1) & 7)) ||
               marker == ((int) M_RST0 + ((desired-2) & 7)))
        action = 2;             /* a prior restart, so advance */
      else
        action = 1;             /* desired restart or too far away */
    }
    TRACEMS2(cinfo, 4, JTRC_RECOVERY_ACTION, marker, action);
    switch (action) {
    case 1:
      /* Discard marker and let entropy decoder resume processing. */
      cinfo->unread_marker = 0;
      return TRUE;
    case 2:
      /* Scan to the next marker, and repeat the decision loop. */
      if (! next_marker(cinfo))
        return FALSE;
      marker = cinfo->unread_marker;
      break;
    case 3:
      /* Return without advancing past this marker. */
      /* Entropy decoder will be forced to process an empty segment. */
      return TRUE;
    }
  } /* end loop */
}


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

METHODDEF(void)
reset_marker_reader (j_decompress_ptr cinfo)
{
  my_marker_ptr marker = (my_marker_ptr) cinfo->marker;

  cinfo->comp_info = NULL;              /* until allocated by get_sof */
  cinfo->input_scan_number = 0;         /* no SOS seen yet */
  cinfo->unread_marker = 0;             /* no pending marker */
  marker->pub.saw_SOI = FALSE;          /* set internal state too */
  marker->pub.saw_SOF = FALSE;
  marker->pub.discarded_bytes = 0;
  marker->cur_marker = NULL;
}


/*
 * 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)
{
  my_marker_ptr marker;
  int i;

  /* Create subobject in permanent pool */
  marker = (my_marker_ptr)
    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
                                SIZEOF(my_marker_reader));
  cinfo->marker = (struct jpeg_marker_reader *) marker;
  /* Initialize public method pointers */
  marker->pub.reset_marker_reader = reset_marker_reader;
  marker->pub.read_markers = read_markers;
  marker->pub.read_restart_marker = read_restart_marker;
  /* Initialize COM/APPn processing.
   * By default, we examine and then discard APP0 and APP14,
   * but simply discard COM and all other APPn.
   */
  marker->process_COM = skip_variable;
  marker->length_limit_COM = 0;
  for (i = 0; i < 16; i++) {
    marker->process_APPn[i] = skip_variable;
    marker->length_limit_APPn[i] = 0;
  }
  marker->process_APPn[0] = get_interesting_appn;
  marker->process_APPn[14] = get_interesting_appn;
  /* Reset marker processing state */
  reset_marker_reader(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)
{
  my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
  long maxlength;
  jpeg_marker_parser_method processor;

  /* Length limit mustn't be larger than what we can allocate
   * (should only be a concern in a 16-bit environment).
   */
  maxlength = cinfo->mem->max_alloc_chunk - SIZEOF(struct jpeg_marker_struct);
  if (((long) length_limit) > maxlength)
    length_limit = (unsigned int) maxlength;

  /* Choose processor routine to use.
   * APP0/APP14 have special requirements.
   */
  if (length_limit) {
    processor = save_marker;
    /* If saving APP0/APP14, save at least enough for our internal use. */
    if (marker_code == (int) M_APP0 && length_limit < APP0_DATA_LEN)
      length_limit = APP0_DATA_LEN;
    else if (marker_code == (int) M_APP14 && length_limit < APP14_DATA_LEN)
      length_limit = APP14_DATA_LEN;
  } else {
    processor = skip_variable;
    /* If discarding APP0/APP14, use our regular on-the-fly processor. */
    if (marker_code == (int) M_APP0 || marker_code == (int) M_APP14)
      processor = get_interesting_appn;
  }

  if (marker_code == (int) M_COM) {
    marker->process_COM = processor;
    marker->length_limit_COM = length_limit;
  } else if (marker_code >= (int) M_APP0 && marker_code <= (int) M_APP15) {
    marker->process_APPn[marker_code - (int) M_APP0] = processor;
    marker->length_limit_APPn[marker_code - (int) M_APP0] = length_limit;
  } else
    ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, marker_code);
}

#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)
{
  my_marker_ptr marker = (my_marker_ptr) cinfo->marker;

  if (marker_code == (int) M_COM)
    marker->process_COM = routine;
  else if (marker_code >= (int) M_APP0 && marker_code <= (int) M_APP15)
    marker->process_APPn[marker_code - (int) M_APP0] = routine;
  else
    ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, marker_code);
}