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 /*

  * jdmarker.c

  *

  * This file was part of the Independent JPEG Group's software:

  * Copyright (C) 1991-1998, Thomas G. Lane.

  * libjpeg-turbo Modifications:

  * Copyright (C) 2012, D. R. Commander.

  * 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, pi;

   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 < MAX_COMPS_IN_SCAN; i++)

     cinfo->cur_comp_info[i] = NULL;

   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 < MAX_COMPS_IN_SCAN;

 	 ci++, compptr++) {

       if (cc == compptr->component_id && !cinfo->cur_comp_info[ci])

 	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 (pi = 0; pi < i; pi++) {

       if (cinfo->cur_comp_info[pi] == 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);

     MEMZERO(&huffval[count], (256 - count) * SIZEOF(UINT8));

     length -= count;

     if (index & 0x10) {		/* AC table definition */

       index -= 0x10;

       if (index < 0 || index >= NUM_HUFF_TBLS)

         ERREXIT1(cinfo, JERR_DHT_INDEX, index);

       htblptr = &cinfo->ac_huff_tbl_ptrs[index];

     } else {			/* DC table definition */

       if (index < 0 || index >= NUM_HUFF_TBLS)

         ERREXIT1(cinfo, JERR_DHT_INDEX, index);

       htblptr = &cinfo->dc_huff_tbl_ptrs[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);

 }