/*
 * 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 );
}
