Quake-III-Arena

jdmarker.cpp (30622B)

---

 /*
  * jdmarker.c
  *
  * Copyright (C) 1991-1995, Thomas G. Lane.
  * This file is part of the Independent JPEG Group's software.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains routines to decode JPEG datastream markers.
  * Most of the complexity arises from our desire to support input
  * suspension: if not all of the data for a marker is available,
  * we must exit back to the application.  On resumption, we reprocess
  * the marker.
  */
 
 #define JPEG_INTERNALS
 #include "jinclude.h"
 #include "jpeglib.h"
 
 
 typedef enum {			/* JPEG marker codes */
   M_SOF0  = 0xc0,
   M_SOF1  = 0xc1,
   M_SOF2  = 0xc2,
   M_SOF3  = 0xc3,
   
   M_SOF5  = 0xc5,
   M_SOF6  = 0xc6,
   M_SOF7  = 0xc7,
   
   M_JPG   = 0xc8,
   M_SOF9  = 0xc9,
   M_SOF10 = 0xca,
   M_SOF11 = 0xcb,
   
   M_SOF13 = 0xcd,
   M_SOF14 = 0xce,
   M_SOF15 = 0xcf,
   
   M_DHT   = 0xc4,
   
   M_DAC   = 0xcc,
   
   M_RST0  = 0xd0,
   M_RST1  = 0xd1,
   M_RST2  = 0xd2,
   M_RST3  = 0xd3,
   M_RST4  = 0xd4,
   M_RST5  = 0xd5,
   M_RST6  = 0xd6,
   M_RST7  = 0xd7,
   
   M_SOI   = 0xd8,
   M_EOI   = 0xd9,
   M_SOS   = 0xda,
   M_DQT   = 0xdb,
   M_DNL   = 0xdc,
   M_DRI   = 0xdd,
   M_DHP   = 0xde,
   M_EXP   = 0xdf,
   
   M_APP0  = 0xe0,
   M_APP1  = 0xe1,
   M_APP2  = 0xe2,
   M_APP3  = 0xe3,
   M_APP4  = 0xe4,
   M_APP5  = 0xe5,
   M_APP6  = 0xe6,
   M_APP7  = 0xe7,
   M_APP8  = 0xe8,
   M_APP9  = 0xe9,
   M_APP10 = 0xea,
   M_APP11 = 0xeb,
   M_APP12 = 0xec,
   M_APP13 = 0xed,
   M_APP14 = 0xee,
   M_APP15 = 0xef,
   
   M_JPG0  = 0xf0,
   M_JPG13 = 0xfd,
   M_COM   = 0xfe,
   
   M_TEM   = 0x01,
   
   M_ERROR = 0x100
 } JPEG_MARKER;
 
 
 /*
  * 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 --- seldom used except 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);  \
 	}  \
 	bytes_in_buffer--
 
 /* 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); \
 		  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); \
 		  V = ((unsigned int) GETJOCTET(*next_input_byte++)) << 8; \
 		  MAKE_BYTE_AVAIL(cinfo,action); \
 		  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,
  * but we use skip_input_data to get past those, and thereby put the problem
  * on the source manager's shoulders.
  *
  * 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->density_unit = 0;	/* set default JFIF APP0 values */
   cinfo->X_density = 1;
   cinfo->Y_density = 1;
   cinfo->saw_Adobe_marker = FALSE;
   cinfo->Adobe_transform = 0;
 
   cinfo->marker->saw_SOI = TRUE;
 
   return TRUE;
 }
 
 
 LOCAL boolean
 get_sof (j_decompress_ptr cinfo, boolean is_prog, boolean is_arith)
 /* Process a SOFn marker */
 {
   INT32 length;
   int c, ci;
   jpeg_component_info * compptr;
   INPUT_VARS(cinfo);
 
   cinfo->progressive_mode = is_prog;
   cinfo->arith_code = is_arith;
 
   INPUT_2BYTES(cinfo, length, return FALSE);
 
   INPUT_BYTE(cinfo, cinfo->data_precision, return FALSE);
   INPUT_2BYTES(cinfo, cinfo->image_height, return FALSE);
   INPUT_2BYTES(cinfo, cinfo->image_width, return FALSE);
   INPUT_BYTE(cinfo, cinfo->num_components, return FALSE);
 
   length -= 8;
 
   TRACEMS4(cinfo, 1, JTRC_SOF, cinfo->unread_marker,
 	   (int) cinfo->image_width, (int) cinfo->image_height,
 	   cinfo->num_components);
 
   if (cinfo->marker->saw_SOF)
     ERREXIT(cinfo, JERR_SOF_DUPLICATE);
 
   /* We don't support files in which the image height is initially specified */
   /* as 0 and is later redefined by DNL.  As long as we have to check that,  */
   /* might as well have a general sanity check. */
   if (cinfo->image_height <= 0 || cinfo->image_width <= 0
       || cinfo->num_components <= 0)
     ERREXIT(cinfo, JERR_EMPTY_IMAGE);
 
   if (length != (cinfo->num_components * 3))
     ERREXIT(cinfo, JERR_BAD_LENGTH);
 
   if (cinfo->comp_info == NULL)	/* do only once, even if suspend */
     cinfo->comp_info = (jpeg_component_info *) (*cinfo->mem->alloc_small)
 			((j_common_ptr) cinfo, JPOOL_IMAGE,
 			 cinfo->num_components * SIZEOF(jpeg_component_info));
   
   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
        ci++, compptr++) {
     compptr->component_index = ci;
     INPUT_BYTE(cinfo, compptr->component_id, return FALSE);
     INPUT_BYTE(cinfo, c, return FALSE);
     compptr->h_samp_factor = (c >> 4) & 15;
     compptr->v_samp_factor = (c     ) & 15;
     INPUT_BYTE(cinfo, compptr->quant_tbl_no, return FALSE);
 
     TRACEMS4(cinfo, 1, JTRC_SOF_COMPONENT,
 	     compptr->component_id, compptr->h_samp_factor,
 	     compptr->v_samp_factor, compptr->quant_tbl_no);
   }
 
   cinfo->marker->saw_SOF = TRUE;
 
   INPUT_SYNC(cinfo);
   return TRUE;
 }
 
 
 LOCAL boolean
 get_sos (j_decompress_ptr cinfo)
 /* Process a SOS marker */
 {
   INT32 length;
   int i, ci, n, c, cc;
   jpeg_component_info * compptr;
   INPUT_VARS(cinfo);
 
   if (! cinfo->marker->saw_SOF)
     ERREXIT(cinfo, JERR_SOS_NO_SOF);
 
   INPUT_2BYTES(cinfo, length, return FALSE);
 
   INPUT_BYTE(cinfo, n, return FALSE); /* Number of components */
 
   if (length != (n * 2 + 6) || n < 1 || n > MAX_COMPS_IN_SCAN)
     ERREXIT(cinfo, JERR_BAD_LENGTH);
 
   TRACEMS1(cinfo, 1, JTRC_SOS, n);
 
   cinfo->comps_in_scan = n;
 
   /* Collect the component-spec parameters */
 
   for (i = 0; i < n; i++) {
     INPUT_BYTE(cinfo, cc, return FALSE);
     INPUT_BYTE(cinfo, c, return FALSE);
     
     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 	 ci++, compptr++) {
       if (cc == compptr->component_id)
 	goto id_found;
     }
 
     ERREXIT1(cinfo, JERR_BAD_COMPONENT_ID, cc);
 
   id_found:
 
     cinfo->cur_comp_info[i] = compptr;
     compptr->dc_tbl_no = (c >> 4) & 15;
     compptr->ac_tbl_no = (c     ) & 15;
     
     TRACEMS3(cinfo, 1, JTRC_SOS_COMPONENT, cc,
 	     compptr->dc_tbl_no, compptr->ac_tbl_no);
   }
 
   /* 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;
 }
 
 
 METHODDEF boolean
 get_app0 (j_decompress_ptr cinfo)
 /* Process an APP0 marker */
 {
 #define JFIF_LEN 14
   INT32 length;
   UINT8 b[JFIF_LEN];
   int buffp;
   INPUT_VARS(cinfo);
 
   INPUT_2BYTES(cinfo, length, return FALSE);
   length -= 2;
 
   /* See if a JFIF APP0 marker is present */
 
   if (length >= JFIF_LEN) {
     for (buffp = 0; buffp < JFIF_LEN; buffp++)
       INPUT_BYTE(cinfo, b[buffp], return FALSE);
     length -= JFIF_LEN;
 
     if (b[0]==0x4A && b[1]==0x46 && b[2]==0x49 && b[3]==0x46 && b[4]==0) {
       /* Found JFIF APP0 marker: 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 (b[5] != 1)
 	WARNMS2(cinfo, JWRN_JFIF_MAJOR, b[5], b[6]);
       else if (b[6] > 2)
 	TRACEMS2(cinfo, 1, JTRC_JFIF_MINOR, b[5], b[6]);
       /* Save info */
       cinfo->saw_JFIF_marker = TRUE;
       cinfo->density_unit = b[7];
       cinfo->X_density = (b[8] << 8) + b[9];
       cinfo->Y_density = (b[10] << 8) + b[11];
       TRACEMS3(cinfo, 1, JTRC_JFIF,
 	       cinfo->X_density, cinfo->Y_density, cinfo->density_unit);
       if (b[12] | b[13])
 	TRACEMS2(cinfo, 1, JTRC_JFIF_THUMBNAIL, b[12], b[13]);
       if (length != ((INT32) b[12] * (INT32) b[13] * (INT32) 3))
 	TRACEMS1(cinfo, 1, JTRC_JFIF_BADTHUMBNAILSIZE, (int) length);
     } else {
       /* Start of APP0 does not match "JFIF" */
       TRACEMS1(cinfo, 1, JTRC_APP0, (int) length + JFIF_LEN);
     }
   } else {
     /* Too short to be JFIF marker */
     TRACEMS1(cinfo, 1, JTRC_APP0, (int) length);
   }
 
   INPUT_SYNC(cinfo);
   if (length > 0)		/* skip any remaining data -- could be lots */
     (*cinfo->src->skip_input_data) (cinfo, (long) length);
 
   return TRUE;
 }
 
 
 METHODDEF boolean
 get_app14 (j_decompress_ptr cinfo)
 /* Process an APP14 marker */
 {
 #define ADOBE_LEN 12
   INT32 length;
   UINT8 b[ADOBE_LEN];
   int buffp;
   unsigned int version, flags0, flags1, transform;
   INPUT_VARS(cinfo);
 
   INPUT_2BYTES(cinfo, length, return FALSE);
   length -= 2;
 
   /* See if an Adobe APP14 marker is present */
 
   if (length >= ADOBE_LEN) {
     for (buffp = 0; buffp < ADOBE_LEN; buffp++)
       INPUT_BYTE(cinfo, b[buffp], return FALSE);
     length -= ADOBE_LEN;
 
     if (b[0]==0x41 && b[1]==0x64 && b[2]==0x6F && b[3]==0x62 && b[4]==0x65) {
       /* Found Adobe APP14 marker */
       version = (b[5] << 8) + b[6];
       flags0 = (b[7] << 8) + b[8];
       flags1 = (b[9] << 8) + b[10];
       transform = b[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" */
       TRACEMS1(cinfo, 1, JTRC_APP14, (int) length + ADOBE_LEN);
     }
   } else {
     /* Too short to be Adobe marker */
     TRACEMS1(cinfo, 1, JTRC_APP14, (int) length);
   }
 
   INPUT_SYNC(cinfo);
   if (length > 0)		/* skip any remaining data -- could be lots */
     (*cinfo->src->skip_input_data) (cinfo, (long) length);
 
   return TRUE;
 }
 
 
 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);
     }
   }
 
   INPUT_SYNC(cinfo);
   return TRUE;
 }
 
 
 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 > 0) {
     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]);
 
     if (count > 256 || ((INT32) count) > length)
       ERREXIT(cinfo, JERR_DHT_COUNTS);
 
     for (i = 0; i < count; i++)
       INPUT_BYTE(cinfo, huffval[i], return FALSE);
 
     length -= count;
 
     if (index & 0x10) {		/* AC table definition */
       index -= 0x10;
       htblptr = &cinfo->ac_huff_tbl_ptrs[index];
     } else {			/* DC table definition */
       htblptr = &cinfo->dc_huff_tbl_ptrs[index];
     }
 
     if (index < 0 || index >= NUM_HUFF_TBLS)
       ERREXIT1(cinfo, JERR_DHT_INDEX, index);
 
     if (*htblptr == NULL)
       *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
   
     MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));
     MEMCOPY((*htblptr)->huffval, huffval, SIZEOF((*htblptr)->huffval));
   }
 
   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);
       quant_ptr->quantval[i] = (UINT16) tmp;
     }
 
     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;
   }
 
   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;
 }
 
 
 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);
   
   TRACEMS2(cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker, (int) length);
 
   INPUT_SYNC(cinfo);		/* do before skip_input_data */
   (*cinfo->src->skip_input_data) (cinfo, (long) length - 2L);
 
   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 (! (*cinfo->marker->process_APPn[cinfo->unread_marker - (int) M_APP0]) (cinfo))
 	return JPEG_SUSPENDED;
       break;
       
     case M_COM:
       if (! (*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, 2, 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)
 {
   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 */
   cinfo->marker->saw_SOI = FALSE;	/* set internal state too */
   cinfo->marker->saw_SOF = FALSE;
   cinfo->marker->discarded_bytes = 0;
 }
 
 
 /*
  * 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)
 {
   int i;
 
   /* Create subobject in permanent pool */
   cinfo->marker = (struct jpeg_marker_reader *)
     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
 				SIZEOF(struct jpeg_marker_reader));
   /* Initialize method pointers */
   cinfo->marker->reset_marker_reader = reset_marker_reader;
   cinfo->marker->read_markers = read_markers;
   cinfo->marker->read_restart_marker = read_restart_marker;
   cinfo->marker->process_COM = skip_variable;
   for (i = 0; i < 16; i++)
     cinfo->marker->process_APPn[i] = skip_variable;
   cinfo->marker->process_APPn[0] = get_app0;
   cinfo->marker->process_APPn[14] = get_app14;
   /* Reset marker processing state */
   reset_marker_reader(cinfo);
 }