    /*
     * jdmarker.c
     *
     * Copyright (C) 1991-1998, Thomas G. Lane.
     * Modified 2009-2019 by Guido Vollbeding.
     * 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_JPG8  = 0xf8,
      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->color_transform = JCT_NONE;
      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_baseline, boolean is_prog,
    	 boolean is_arith)
    /* Process a SOFn marker */
    {
      INT32 length;
      int c, ci, i;
      jpeg_component_info * compptr;
      INPUT_VARS(cinfo);

      cinfo->is_baseline = is_baseline;
      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; ci < cinfo->num_components; ci++) {
        INPUT_BYTE(cinfo, c, return FALSE);
        /* Check to see whether component id has already been seen   */
        /* (in violation of the spec, but unfortunately seen in some */
        /* files).  If so, create "fake" component id equal to the   */
        /* max id seen so far + 1. */
        for (i = 0, compptr = cinfo->comp_info; i < ci; i++, compptr++) {
          if (c == compptr->component_id) {
    	compptr = cinfo->comp_info;
    	c = compptr->component_id;
    	compptr++;
    	for (i = 1; i < ci; i++, compptr++) {
    	  if (compptr->component_id > c) c = compptr->component_id;
    	}
    	c++;
    	break;
          }
        }
        compptr->component_id = c;
        compptr->component_index = ci;
        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 c, ci, i, n;
      jpeg_component_info * compptr;
      INPUT_VARS(cinfo);

      if (! cinfo->marker->saw_SOF)
        ERREXITS(cinfo, JERR_SOF_BEFORE, "SOS");

      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 > MAX_COMPS_IN_SCAN ||
          (n == 0 && !cinfo->progressive_mode))
          /* pseudo SOS marker only allowed in progressive mode */
        ERREXIT(cinfo, JERR_BAD_LENGTH);

      cinfo->comps_in_scan = n;

      /* Collect the component-spec parameters */

      for (i = 0; i < n; i++) {
        INPUT_BYTE(cinfo, c, return FALSE);

        /* Detect the case where component id's are not unique, and, if so, */
        /* create a fake component id using the same logic as in get_sof.   */
        /* Note:  This also ensures that all of the SOF components are      */
        /* referenced in the single scan case, which prevents access to     */
        /* uninitialized memory in later decoding stages. */
        for (ci = 0; ci < i; ci++) {
          if (c == cinfo->cur_comp_info[ci]->component_id) {
    	c = cinfo->cur_comp_info[0]->component_id;
    	for (ci = 1; ci < i; ci++) {
    	  compptr = cinfo->cur_comp_info[ci];
    	  if (compptr->component_id > c) c = compptr->component_id;
    	}
    	c++;
    	break;
          }
        }

        for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
    	 ci++, compptr++) {
          if (c == compptr->component_id)
    	goto id_found;
        }

        ERREXIT1(cinfo, JERR_BAD_COMPONENT_ID, c);

      id_found:

        cinfo->cur_comp_info[i] = compptr;
        INPUT_BYTE(cinfo, c, return FALSE);
        compptr->dc_tbl_no = (c >> 4) & 15;
        compptr->ac_tbl_no = (c     ) & 15;

        TRACEMS3(cinfo, 1, JTRC_SOS_COMPONENT, compptr->component_id,
    	     compptr->dc_tbl_no, compptr->ac_tbl_no);
      }

      /* 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 (non-pseudo) SOS marker */
      if (n) 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));
        if (count > 0)
          MEMCOPY((*htblptr)->huffval, huffval, count * SIZEOF(UINT8));
      }

      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, count, i;
      int n, prec;
      unsigned int tmp;
      JQUANT_TBL *quant_ptr;
      const int *natural_order;
      INPUT_VARS(cinfo);

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

      while (length > 0) {
        length--;
        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];

        if (prec) {
          if (length < DCTSIZE2 * 2) {
    	/* Initialize full table for safety. */
    	for (i = 0; i < DCTSIZE2; i++) {
    	  quant_ptr->quantval[i] = 1;
    	}
    	count = length >> 1;
          } else
    	count = DCTSIZE2;
        } else {
          if (length < DCTSIZE2) {
    	/* Initialize full table for safety. */
    	for (i = 0; i < DCTSIZE2; i++) {
    	  quant_ptr->quantval[i] = 1;
    	}
    	count = length;
          } else
    	count = DCTSIZE2;
        }

        switch ((int) count) {
        case (2*2): natural_order = jpeg_natural_order2; break;
        case (3*3): natural_order = jpeg_natural_order3; break;
        case (4*4): natural_order = jpeg_natural_order4; break;
        case (5*5): natural_order = jpeg_natural_order5; break;
        case (6*6): natural_order = jpeg_natural_order6; break;
        case (7*7): natural_order = jpeg_natural_order7; break;
        default:    natural_order = jpeg_natural_order;
        }

        for (i = 0; i < count; 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[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 -= count;
        if (prec) length -= count;
      }

      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;
    }

    LOCAL(boolean)
    get_lse (j_decompress_ptr cinfo)
    /* Process an LSE marker */
    {
      INT32 length;
      unsigned int tmp;
      int cid;
      INPUT_VARS(cinfo);

      if (! cinfo->marker->saw_SOF)
        ERREXITS(cinfo, JERR_SOF_BEFORE, "LSE");

      if (cinfo->num_components < 3) goto bad;

      INPUT_2BYTES(cinfo, length, return FALSE);

      if (length != 24)
        ERREXIT(cinfo, JERR_BAD_LENGTH);

      INPUT_BYTE(cinfo, tmp, return FALSE);
      if (tmp != 0x0D)	/* ID inverse transform specification */
        ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker);
      INPUT_2BYTES(cinfo, tmp, return FALSE);
      if (tmp != MAXJSAMPLE) goto bad;		/* MAXTRANS */
      INPUT_BYTE(cinfo, tmp, return FALSE);
      if (tmp != 3) goto bad;			/* Nt=3 */
      INPUT_BYTE(cinfo, cid, return FALSE);
      if (cid != cinfo->comp_info[1].component_id) goto bad;
      INPUT_BYTE(cinfo, cid, return FALSE);
      if (cid != cinfo->comp_info[0].component_id) goto bad;
      INPUT_BYTE(cinfo, cid, return FALSE);
      if (cid != cinfo->comp_info[2].component_id) goto bad;
      INPUT_BYTE(cinfo, tmp, return FALSE);
      if (tmp != 0x80) goto bad;		/* F1: CENTER1=1, NORM1=0 */
      INPUT_2BYTES(cinfo, tmp, return FALSE);
      if (tmp != 0) goto bad;			/* A(1,1)=0 */
      INPUT_2BYTES(cinfo, tmp, return FALSE);
      if (tmp != 0) goto bad;			/* A(1,2)=0 */
      INPUT_BYTE(cinfo, tmp, return FALSE);
      if (tmp != 0) goto bad;		/* F2: CENTER2=0, NORM2=0 */
      INPUT_2BYTES(cinfo, tmp, return FALSE);
      if (tmp != 1) goto bad;			/* A(2,1)=1 */
      INPUT_2BYTES(cinfo, tmp, return FALSE);
      if (tmp != 0) goto bad;			/* A(2,2)=0 */
      INPUT_BYTE(cinfo, tmp, return FALSE);
      if (tmp != 0) goto bad;		/* F3: CENTER3=0, NORM3=0 */
      INPUT_2BYTES(cinfo, tmp, return FALSE);
      if (tmp != 1) goto bad;			/* A(3,1)=1 */
      INPUT_2BYTES(cinfo, tmp, return FALSE);
      if (tmp != 0) {				/* A(3,2)=0 */
        bad:
        ERREXIT(cinfo, JERR_CONVERSION_NOTIMPL);
      }

      /* OK, valid transform that we can handle. */
      cinfo->color_transform = JCT_SUBTRACT_GREEN;

      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 or 2, 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 && cinfo->JFIF_major_version != 2)
          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);
        }
      } 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);
      }

      /* 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));
      }

      /* 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.
     *
     * Note: This function may return a pseudo SOS marker (with zero
     * component number) for treat by input controller's consume_input.
     * consume_input itself should filter out (skip) the pseudo marker
     * after processing for the caller.
     */

    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 */
          if (! get_sof(cinfo, TRUE, FALSE, FALSE))
    	return JPEG_SUSPENDED;
          break;

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

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

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

        case M_SOF10:		/* Progressive, arithmetic */
          if (! get_sof(cinfo, FALSE, 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_JPG8:
          if (! get_lse(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);
        }
        /* 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 = &marker->pub;
      /* 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);
    }