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      1 /*
      2  * jdmarker.c
      3  *
      4  * Copyright (C) 1991-1998, Thomas G. Lane.
      5  * This file is part of the Independent JPEG Group's software.
      6  * For conditions of distribution and use, see the accompanying README file.
      7  *
      8  * This file contains routines to decode JPEG datastream markers.
      9  * Most of the complexity arises from our desire to support input
     10  * suspension: if not all of the data for a marker is available,
     11  * we must exit back to the application.  On resumption, we reprocess
     12  * the marker.
     13  */
     14 
     15 #define JPEG_INTERNALS
     16 #include "jinclude.h"
     17 #include "jpeglib.h"
     18 
     19 
     20 typedef enum {			/* JPEG marker codes */
     21   M_SOF0  = 0xc0,
     22   M_SOF1  = 0xc1,
     23   M_SOF2  = 0xc2,
     24   M_SOF3  = 0xc3,
     25 
     26   M_SOF5  = 0xc5,
     27   M_SOF6  = 0xc6,
     28   M_SOF7  = 0xc7,
     29 
     30   M_JPG   = 0xc8,
     31   M_SOF9  = 0xc9,
     32   M_SOF10 = 0xca,
     33   M_SOF11 = 0xcb,
     34 
     35   M_SOF13 = 0xcd,
     36   M_SOF14 = 0xce,
     37   M_SOF15 = 0xcf,
     38 
     39   M_DHT   = 0xc4,
     40 
     41   M_DAC   = 0xcc,
     42 
     43   M_RST0  = 0xd0,
     44   M_RST1  = 0xd1,
     45   M_RST2  = 0xd2,
     46   M_RST3  = 0xd3,
     47   M_RST4  = 0xd4,
     48   M_RST5  = 0xd5,
     49   M_RST6  = 0xd6,
     50   M_RST7  = 0xd7,
     51 
     52   M_SOI   = 0xd8,
     53   M_EOI   = 0xd9,
     54   M_SOS   = 0xda,
     55   M_DQT   = 0xdb,
     56   M_DNL   = 0xdc,
     57   M_DRI   = 0xdd,
     58   M_DHP   = 0xde,
     59   M_EXP   = 0xdf,
     60 
     61   M_APP0  = 0xe0,
     62   M_APP1  = 0xe1,
     63   M_APP2  = 0xe2,
     64   M_APP3  = 0xe3,
     65   M_APP4  = 0xe4,
     66   M_APP5  = 0xe5,
     67   M_APP6  = 0xe6,
     68   M_APP7  = 0xe7,
     69   M_APP8  = 0xe8,
     70   M_APP9  = 0xe9,
     71   M_APP10 = 0xea,
     72   M_APP11 = 0xeb,
     73   M_APP12 = 0xec,
     74   M_APP13 = 0xed,
     75   M_APP14 = 0xee,
     76   M_APP15 = 0xef,
     77 
     78   M_JPG0  = 0xf0,
     79   M_JPG13 = 0xfd,
     80   M_COM   = 0xfe,
     81 
     82   M_TEM   = 0x01,
     83 
     84   M_ERROR = 0x100
     85 } JPEG_MARKER;
     86 
     87 
     88 /* Private state */
     89 
     90 typedef struct {
     91   struct jpeg_marker_reader pub; /* public fields */
     92 
     93   /* Application-overridable marker processing methods */
     94   jpeg_marker_parser_method process_COM;
     95   jpeg_marker_parser_method process_APPn[16];
     96 
     97   /* Limit on marker data length to save for each marker type */
     98   unsigned int length_limit_COM;
     99   unsigned int length_limit_APPn[16];
    100 
    101   /* Status of COM/APPn marker saving */
    102   jpeg_saved_marker_ptr cur_marker;	/* NULL if not processing a marker */
    103   unsigned int bytes_read;		/* data bytes read so far in marker */
    104   /* Note: cur_marker is not linked into marker_list until it's all read. */
    105 } my_marker_reader;
    106 
    107 typedef my_marker_reader * my_marker_ptr;
    108 
    109 
    110 /*
    111  * Macros for fetching data from the data source module.
    112  *
    113  * At all times, cinfo->src->next_input_byte and ->bytes_in_buffer reflect
    114  * the current restart point; we update them only when we have reached a
    115  * suitable place to restart if a suspension occurs.
    116  */
    117 
    118 /* Declare and initialize local copies of input pointer/count */
    119 #define INPUT_VARS(cinfo)  \
    120 	struct jpeg_source_mgr * datasrc = (cinfo)->src;  \
    121 	const JOCTET * next_input_byte = datasrc->next_input_byte;  \
    122 	size_t bytes_in_buffer = datasrc->bytes_in_buffer
    123 
    124 /* Unload the local copies --- do this only at a restart boundary */
    125 #define INPUT_SYNC(cinfo)  \
    126 	( datasrc->next_input_byte = next_input_byte,  \
    127 	  datasrc->bytes_in_buffer = bytes_in_buffer )
    128 
    129 /* Reload the local copies --- used only in MAKE_BYTE_AVAIL */
    130 #define INPUT_RELOAD(cinfo)  \
    131 	( next_input_byte = datasrc->next_input_byte,  \
    132 	  bytes_in_buffer = datasrc->bytes_in_buffer )
    133 
    134 /* Internal macro for INPUT_BYTE and INPUT_2BYTES: make a byte available.
    135  * Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
    136  * but we must reload the local copies after a successful fill.
    137  */
    138 #define MAKE_BYTE_AVAIL(cinfo,action)  \
    139 	if (bytes_in_buffer == 0) {  \
    140 	  if (! (*datasrc->fill_input_buffer) (cinfo))  \
    141 	    { action; }  \
    142 	  INPUT_RELOAD(cinfo);  \
    143 	}
    144 
    145 /* Read a byte into variable V.
    146  * If must suspend, take the specified action (typically "return FALSE").
    147  */
    148 #define INPUT_BYTE(cinfo,V,action)  \
    149 	MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
    150 		  bytes_in_buffer--; \
    151 		  V = GETJOCTET(*next_input_byte++); )
    152 
    153 /* As above, but read two bytes interpreted as an unsigned 16-bit integer.
    154  * V should be declared unsigned int or perhaps INT32.
    155  */
    156 #define INPUT_2BYTES(cinfo,V,action)  \
    157 	MAKESTMT( MAKE_BYTE_AVAIL(cinfo,action); \
    158 		  bytes_in_buffer--; \
    159 		  V = ((unsigned int) GETJOCTET(*next_input_byte++)) << 8; \
    160 		  MAKE_BYTE_AVAIL(cinfo,action); \
    161 		  bytes_in_buffer--; \
    162 		  V += GETJOCTET(*next_input_byte++); )
    163 
    164 
    165 /*
    166  * Routines to process JPEG markers.
    167  *
    168  * Entry condition: JPEG marker itself has been read and its code saved
    169  *   in cinfo->unread_marker; input restart point is just after the marker.
    170  *
    171  * Exit: if return TRUE, have read and processed any parameters, and have
    172  *   updated the restart point to point after the parameters.
    173  *   If return FALSE, was forced to suspend before reaching end of
    174  *   marker parameters; restart point has not been moved.  Same routine
    175  *   will be called again after application supplies more input data.
    176  *
    177  * This approach to suspension assumes that all of a marker's parameters
    178  * can fit into a single input bufferload.  This should hold for "normal"
    179  * markers.  Some COM/APPn markers might have large parameter segments
    180  * that might not fit.  If we are simply dropping such a marker, we use
    181  * skip_input_data to get past it, and thereby put the problem on the
    182  * source manager's shoulders.  If we are saving the marker's contents
    183  * into memory, we use a slightly different convention: when forced to
    184  * suspend, the marker processor updates the restart point to the end of
    185  * what it's consumed (ie, the end of the buffer) before returning FALSE.
    186  * On resumption, cinfo->unread_marker still contains the marker code,
    187  * but the data source will point to the next chunk of marker data.
    188  * The marker processor must retain internal state to deal with this.
    189  *
    190  * Note that we don't bother to avoid duplicate trace messages if a
    191  * suspension occurs within marker parameters.  Other side effects
    192  * require more care.
    193  */
    194 
    195 
    196 LOCAL(boolean)
    197 get_soi (j_decompress_ptr cinfo)
    198 /* Process an SOI marker */
    199 {
    200   int i;
    201 
    202   TRACEMS(cinfo, 1, JTRC_SOI);
    203 
    204   if (cinfo->marker->saw_SOI)
    205     ERREXIT(cinfo, JERR_SOI_DUPLICATE);
    206 
    207   /* Reset all parameters that are defined to be reset by SOI */
    208 
    209   for (i = 0; i < NUM_ARITH_TBLS; i++) {
    210     cinfo->arith_dc_L[i] = 0;
    211     cinfo->arith_dc_U[i] = 1;
    212     cinfo->arith_ac_K[i] = 5;
    213   }
    214   cinfo->restart_interval = 0;
    215 
    216   /* Set initial assumptions for colorspace etc */
    217 
    218   cinfo->jpeg_color_space = JCS_UNKNOWN;
    219   cinfo->CCIR601_sampling = FALSE; /* Assume non-CCIR sampling??? */
    220 
    221   cinfo->saw_JFIF_marker = FALSE;
    222   cinfo->JFIF_major_version = 1; /* set default JFIF APP0 values */
    223   cinfo->JFIF_minor_version = 1;
    224   cinfo->density_unit = 0;
    225   cinfo->X_density = 1;
    226   cinfo->Y_density = 1;
    227   cinfo->saw_Adobe_marker = FALSE;
    228   cinfo->Adobe_transform = 0;
    229 
    230   cinfo->marker->saw_SOI = TRUE;
    231 
    232   return TRUE;
    233 }
    234 
    235 
    236 LOCAL(boolean)
    237 get_sof (j_decompress_ptr cinfo, boolean is_prog, boolean is_arith)
    238 /* Process a SOFn marker */
    239 {
    240   INT32 length;
    241   int c, ci;
    242   jpeg_component_info * compptr;
    243   INPUT_VARS(cinfo);
    244 
    245   cinfo->progressive_mode = is_prog;
    246   cinfo->arith_code = is_arith;
    247 
    248   INPUT_2BYTES(cinfo, length, return FALSE);
    249 
    250   INPUT_BYTE(cinfo, cinfo->data_precision, return FALSE);
    251   INPUT_2BYTES(cinfo, cinfo->image_height, return FALSE);
    252   INPUT_2BYTES(cinfo, cinfo->image_width, return FALSE);
    253   INPUT_BYTE(cinfo, cinfo->num_components, return FALSE);
    254 
    255   length -= 8;
    256 
    257   TRACEMS4(cinfo, 1, JTRC_SOF, cinfo->unread_marker,
    258 	   (int) cinfo->image_width, (int) cinfo->image_height,
    259 	   cinfo->num_components);
    260 
    261   if (cinfo->marker->saw_SOF)
    262     ERREXIT(cinfo, JERR_SOF_DUPLICATE);
    263 
    264   /* We don't support files in which the image height is initially specified */
    265   /* as 0 and is later redefined by DNL.  As long as we have to check that,  */
    266   /* might as well have a general sanity check. */
    267   if (cinfo->image_height <= 0 || cinfo->image_width <= 0
    268       || cinfo->num_components <= 0)
    269     ERREXIT(cinfo, JERR_EMPTY_IMAGE);
    270 
    271   if (length != (cinfo->num_components * 3))
    272     ERREXIT(cinfo, JERR_BAD_LENGTH);
    273 
    274   if (cinfo->comp_info == NULL)	/* do only once, even if suspend */
    275     cinfo->comp_info = (jpeg_component_info *) (*cinfo->mem->alloc_small)
    276 			((j_common_ptr) cinfo, JPOOL_IMAGE,
    277 			 cinfo->num_components * SIZEOF(jpeg_component_info));
    278 
    279   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
    280        ci++, compptr++) {
    281     compptr->component_index = ci;
    282     INPUT_BYTE(cinfo, compptr->component_id, return FALSE);
    283     INPUT_BYTE(cinfo, c, return FALSE);
    284     compptr->h_samp_factor = (c >> 4) & 15;
    285     compptr->v_samp_factor = (c     ) & 15;
    286     INPUT_BYTE(cinfo, compptr->quant_tbl_no, return FALSE);
    287 
    288     TRACEMS4(cinfo, 1, JTRC_SOF_COMPONENT,
    289 	     compptr->component_id, compptr->h_samp_factor,
    290 	     compptr->v_samp_factor, compptr->quant_tbl_no);
    291   }
    292 
    293   cinfo->marker->saw_SOF = TRUE;
    294 
    295   INPUT_SYNC(cinfo);
    296   return TRUE;
    297 }
    298 
    299 
    300 LOCAL(boolean)
    301 get_sos (j_decompress_ptr cinfo)
    302 /* Process a SOS marker */
    303 {
    304   INT32 length;
    305   int i, ci, n, c, cc;
    306   jpeg_component_info * compptr;
    307   INPUT_VARS(cinfo);
    308 
    309   if (! cinfo->marker->saw_SOF)
    310     ERREXIT(cinfo, JERR_SOS_NO_SOF);
    311 
    312   INPUT_2BYTES(cinfo, length, return FALSE);
    313 
    314   INPUT_BYTE(cinfo, n, return FALSE); /* Number of components */
    315 
    316   TRACEMS1(cinfo, 1, JTRC_SOS, n);
    317 
    318   if (length != (n * 2 + 6) || n < 1 || n > MAX_COMPS_IN_SCAN)
    319     ERREXIT(cinfo, JERR_BAD_LENGTH);
    320 
    321   cinfo->comps_in_scan = n;
    322 
    323   /* Collect the component-spec parameters */
    324 
    325   for (i = 0; i < n; i++) {
    326     INPUT_BYTE(cinfo, cc, return FALSE);
    327     INPUT_BYTE(cinfo, c, return FALSE);
    328 
    329     for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
    330 	 ci++, compptr++) {
    331       if (cc == compptr->component_id)
    332 	goto id_found;
    333     }
    334 
    335     ERREXIT1(cinfo, JERR_BAD_COMPONENT_ID, cc);
    336 
    337   id_found:
    338 
    339     cinfo->cur_comp_info[i] = compptr;
    340     compptr->dc_tbl_no = (c >> 4) & 15;
    341     compptr->ac_tbl_no = (c     ) & 15;
    342 
    343     TRACEMS3(cinfo, 1, JTRC_SOS_COMPONENT, cc,
    344 	     compptr->dc_tbl_no, compptr->ac_tbl_no);
    345   }
    346 
    347   /* Collect the additional scan parameters Ss, Se, Ah/Al. */
    348   INPUT_BYTE(cinfo, c, return FALSE);
    349   cinfo->Ss = c;
    350   INPUT_BYTE(cinfo, c, return FALSE);
    351   cinfo->Se = c;
    352   INPUT_BYTE(cinfo, c, return FALSE);
    353   cinfo->Ah = (c >> 4) & 15;
    354   cinfo->Al = (c     ) & 15;
    355 
    356   TRACEMS4(cinfo, 1, JTRC_SOS_PARAMS, cinfo->Ss, cinfo->Se,
    357 	   cinfo->Ah, cinfo->Al);
    358 
    359   /* Prepare to scan data & restart markers */
    360   cinfo->marker->next_restart_num = 0;
    361 
    362   /* Count another SOS marker */
    363   cinfo->input_scan_number++;
    364 
    365   INPUT_SYNC(cinfo);
    366   return TRUE;
    367 }
    368 
    369 
    370 #ifdef D_ARITH_CODING_SUPPORTED
    371 
    372 LOCAL(boolean)
    373 get_dac (j_decompress_ptr cinfo)
    374 /* Process a DAC marker */
    375 {
    376   INT32 length;
    377   int index, val;
    378   INPUT_VARS(cinfo);
    379 
    380   INPUT_2BYTES(cinfo, length, return FALSE);
    381   length -= 2;
    382 
    383   while (length > 0) {
    384     INPUT_BYTE(cinfo, index, return FALSE);
    385     INPUT_BYTE(cinfo, val, return FALSE);
    386 
    387     length -= 2;
    388 
    389     TRACEMS2(cinfo, 1, JTRC_DAC, index, val);
    390 
    391     if (index < 0 || index >= (2*NUM_ARITH_TBLS))
    392       ERREXIT1(cinfo, JERR_DAC_INDEX, index);
    393 
    394     if (index >= NUM_ARITH_TBLS) { /* define AC table */
    395       cinfo->arith_ac_K[index-NUM_ARITH_TBLS] = (UINT8) val;
    396     } else {			/* define DC table */
    397       cinfo->arith_dc_L[index] = (UINT8) (val & 0x0F);
    398       cinfo->arith_dc_U[index] = (UINT8) (val >> 4);
    399       if (cinfo->arith_dc_L[index] > cinfo->arith_dc_U[index])
    400 	ERREXIT1(cinfo, JERR_DAC_VALUE, val);
    401     }
    402   }
    403 
    404   if (length != 0)
    405     ERREXIT(cinfo, JERR_BAD_LENGTH);
    406 
    407   INPUT_SYNC(cinfo);
    408   return TRUE;
    409 }
    410 
    411 #else /* ! D_ARITH_CODING_SUPPORTED */
    412 
    413 #define get_dac(cinfo)  skip_variable(cinfo)
    414 
    415 #endif /* D_ARITH_CODING_SUPPORTED */
    416 
    417 
    418 LOCAL(boolean)
    419 get_dht (j_decompress_ptr cinfo)
    420 /* Process a DHT marker */
    421 {
    422   INT32 length;
    423   UINT8 bits[17];
    424   UINT8 huffval[256];
    425   int i, index, count;
    426   JHUFF_TBL **htblptr;
    427   INPUT_VARS(cinfo);
    428 
    429   INPUT_2BYTES(cinfo, length, return FALSE);
    430   length -= 2;
    431 
    432   while (length > 16) {
    433     INPUT_BYTE(cinfo, index, return FALSE);
    434 
    435     TRACEMS1(cinfo, 1, JTRC_DHT, index);
    436 
    437     bits[0] = 0;
    438     count = 0;
    439     for (i = 1; i <= 16; i++) {
    440       INPUT_BYTE(cinfo, bits[i], return FALSE);
    441       count += bits[i];
    442     }
    443 
    444     length -= 1 + 16;
    445 
    446     TRACEMS8(cinfo, 2, JTRC_HUFFBITS,
    447 	     bits[1], bits[2], bits[3], bits[4],
    448 	     bits[5], bits[6], bits[7], bits[8]);
    449     TRACEMS8(cinfo, 2, JTRC_HUFFBITS,
    450 	     bits[9], bits[10], bits[11], bits[12],
    451 	     bits[13], bits[14], bits[15], bits[16]);
    452 
    453     /* Here we just do minimal validation of the counts to avoid walking
    454      * off the end of our table space.  jdhuff.c will check more carefully.
    455      */
    456     if (count > 256 || ((INT32) count) > length)
    457       ERREXIT(cinfo, JERR_BAD_HUFF_TABLE);
    458 
    459     for (i = 0; i < count; i++)
    460       INPUT_BYTE(cinfo, huffval[i], return FALSE);
    461 
    462     length -= count;
    463 
    464     if (index & 0x10) {		/* AC table definition */
    465       index -= 0x10;
    466       htblptr = &cinfo->ac_huff_tbl_ptrs[index];
    467     } else {			/* DC table definition */
    468       htblptr = &cinfo->dc_huff_tbl_ptrs[index];
    469     }
    470 
    471     if (index < 0 || index >= NUM_HUFF_TBLS)
    472       ERREXIT1(cinfo, JERR_DHT_INDEX, index);
    473 
    474     if (*htblptr == NULL)
    475       *htblptr = jpeg_alloc_huff_table((j_common_ptr) cinfo);
    476 
    477     MEMCOPY((*htblptr)->bits, bits, SIZEOF((*htblptr)->bits));
    478     MEMCOPY((*htblptr)->huffval, huffval, SIZEOF((*htblptr)->huffval));
    479   }
    480 
    481   if (length != 0)
    482     ERREXIT(cinfo, JERR_BAD_LENGTH);
    483 
    484   INPUT_SYNC(cinfo);
    485   return TRUE;
    486 }
    487 
    488 
    489 LOCAL(boolean)
    490 get_dqt (j_decompress_ptr cinfo)
    491 /* Process a DQT marker */
    492 {
    493   INT32 length;
    494   int n, i, prec;
    495   unsigned int tmp;
    496   JQUANT_TBL *quant_ptr;
    497   INPUT_VARS(cinfo);
    498 
    499   INPUT_2BYTES(cinfo, length, return FALSE);
    500   length -= 2;
    501 
    502   while (length > 0) {
    503     INPUT_BYTE(cinfo, n, return FALSE);
    504     prec = n >> 4;
    505     n &= 0x0F;
    506 
    507     TRACEMS2(cinfo, 1, JTRC_DQT, n, prec);
    508 
    509     if (n >= NUM_QUANT_TBLS)
    510       ERREXIT1(cinfo, JERR_DQT_INDEX, n);
    511 
    512     if (cinfo->quant_tbl_ptrs[n] == NULL)
    513       cinfo->quant_tbl_ptrs[n] = jpeg_alloc_quant_table((j_common_ptr) cinfo);
    514     quant_ptr = cinfo->quant_tbl_ptrs[n];
    515 
    516     for (i = 0; i < DCTSIZE2; i++) {
    517       if (prec)
    518 	INPUT_2BYTES(cinfo, tmp, return FALSE);
    519       else
    520 	INPUT_BYTE(cinfo, tmp, return FALSE);
    521       /* We convert the zigzag-order table to natural array order. */
    522       quant_ptr->quantval[jpeg_natural_order[i]] = (UINT16) tmp;
    523     }
    524 
    525     if (cinfo->err->trace_level >= 2) {
    526       for (i = 0; i < DCTSIZE2; i += 8) {
    527 	TRACEMS8(cinfo, 2, JTRC_QUANTVALS,
    528 		 quant_ptr->quantval[i],   quant_ptr->quantval[i+1],
    529 		 quant_ptr->quantval[i+2], quant_ptr->quantval[i+3],
    530 		 quant_ptr->quantval[i+4], quant_ptr->quantval[i+5],
    531 		 quant_ptr->quantval[i+6], quant_ptr->quantval[i+7]);
    532       }
    533     }
    534 
    535     length -= DCTSIZE2+1;
    536     if (prec) length -= DCTSIZE2;
    537   }
    538 
    539   if (length != 0)
    540     ERREXIT(cinfo, JERR_BAD_LENGTH);
    541 
    542   INPUT_SYNC(cinfo);
    543   return TRUE;
    544 }
    545 
    546 
    547 LOCAL(boolean)
    548 get_dri (j_decompress_ptr cinfo)
    549 /* Process a DRI marker */
    550 {
    551   INT32 length;
    552   unsigned int tmp;
    553   INPUT_VARS(cinfo);
    554 
    555   INPUT_2BYTES(cinfo, length, return FALSE);
    556 
    557   if (length != 4)
    558     ERREXIT(cinfo, JERR_BAD_LENGTH);
    559 
    560   INPUT_2BYTES(cinfo, tmp, return FALSE);
    561 
    562   TRACEMS1(cinfo, 1, JTRC_DRI, tmp);
    563 
    564   cinfo->restart_interval = tmp;
    565 
    566   INPUT_SYNC(cinfo);
    567   return TRUE;
    568 }
    569 
    570 
    571 /*
    572  * Routines for processing APPn and COM markers.
    573  * These are either saved in memory or discarded, per application request.
    574  * APP0 and APP14 are specially checked to see if they are
    575  * JFIF and Adobe markers, respectively.
    576  */
    577 
    578 #define APP0_DATA_LEN	14	/* Length of interesting data in APP0 */
    579 #define APP14_DATA_LEN	12	/* Length of interesting data in APP14 */
    580 #define APPN_DATA_LEN	14	/* Must be the largest of the above!! */
    581 
    582 
    583 LOCAL(void)
    584 examine_app0 (j_decompress_ptr cinfo, JOCTET FAR * data,
    585 	      unsigned int datalen, INT32 remaining)
    586 /* Examine first few bytes from an APP0.
    587  * Take appropriate action if it is a JFIF marker.
    588  * datalen is # of bytes at data[], remaining is length of rest of marker data.
    589  */
    590 {
    591   INT32 totallen = (INT32) datalen + remaining;
    592 
    593   if (datalen >= APP0_DATA_LEN &&
    594       GETJOCTET(data[0]) == 0x4A &&
    595       GETJOCTET(data[1]) == 0x46 &&
    596       GETJOCTET(data[2]) == 0x49 &&
    597       GETJOCTET(data[3]) == 0x46 &&
    598       GETJOCTET(data[4]) == 0) {
    599     /* Found JFIF APP0 marker: save info */
    600     cinfo->saw_JFIF_marker = TRUE;
    601     cinfo->JFIF_major_version = GETJOCTET(data[5]);
    602     cinfo->JFIF_minor_version = GETJOCTET(data[6]);
    603     cinfo->density_unit = GETJOCTET(data[7]);
    604     cinfo->X_density = (GETJOCTET(data[8]) << 8) + GETJOCTET(data[9]);
    605     cinfo->Y_density = (GETJOCTET(data[10]) << 8) + GETJOCTET(data[11]);
    606     /* Check version.
    607      * Major version must be 1, anything else signals an incompatible change.
    608      * (We used to treat this as an error, but now it's a nonfatal warning,
    609      * because some bozo at Hijaak couldn't read the spec.)
    610      * Minor version should be 0..2, but process anyway if newer.
    611      */
    612     if (cinfo->JFIF_major_version != 1)
    613       WARNMS2(cinfo, JWRN_JFIF_MAJOR,
    614 	      cinfo->JFIF_major_version, cinfo->JFIF_minor_version);
    615     /* Generate trace messages */
    616     TRACEMS5(cinfo, 1, JTRC_JFIF,
    617 	     cinfo->JFIF_major_version, cinfo->JFIF_minor_version,
    618 	     cinfo->X_density, cinfo->Y_density, cinfo->density_unit);
    619     /* Validate thumbnail dimensions and issue appropriate messages */
    620     if (GETJOCTET(data[12]) | GETJOCTET(data[13]))
    621       TRACEMS2(cinfo, 1, JTRC_JFIF_THUMBNAIL,
    622 	       GETJOCTET(data[12]), GETJOCTET(data[13]));
    623     totallen -= APP0_DATA_LEN;
    624     if (totallen !=
    625 	((INT32)GETJOCTET(data[12]) * (INT32)GETJOCTET(data[13]) * (INT32) 3))
    626       TRACEMS1(cinfo, 1, JTRC_JFIF_BADTHUMBNAILSIZE, (int) totallen);
    627   } else if (datalen >= 6 &&
    628       GETJOCTET(data[0]) == 0x4A &&
    629       GETJOCTET(data[1]) == 0x46 &&
    630       GETJOCTET(data[2]) == 0x58 &&
    631       GETJOCTET(data[3]) == 0x58 &&
    632       GETJOCTET(data[4]) == 0) {
    633     /* Found JFIF "JFXX" extension APP0 marker */
    634     /* The library doesn't actually do anything with these,
    635      * but we try to produce a helpful trace message.
    636      */
    637     switch (GETJOCTET(data[5])) {
    638     case 0x10:
    639       TRACEMS1(cinfo, 1, JTRC_THUMB_JPEG, (int) totallen);
    640       break;
    641     case 0x11:
    642       TRACEMS1(cinfo, 1, JTRC_THUMB_PALETTE, (int) totallen);
    643       break;
    644     case 0x13:
    645       TRACEMS1(cinfo, 1, JTRC_THUMB_RGB, (int) totallen);
    646       break;
    647     default:
    648       TRACEMS2(cinfo, 1, JTRC_JFIF_EXTENSION,
    649 	       GETJOCTET(data[5]), (int) totallen);
    650       break;
    651     }
    652   } else {
    653     /* Start of APP0 does not match "JFIF" or "JFXX", or too short */
    654     TRACEMS1(cinfo, 1, JTRC_APP0, (int) totallen);
    655   }
    656 }
    657 
    658 
    659 LOCAL(void)
    660 examine_app14 (j_decompress_ptr cinfo, JOCTET FAR * data,
    661 	       unsigned int datalen, INT32 remaining)
    662 /* Examine first few bytes from an APP14.
    663  * Take appropriate action if it is an Adobe marker.
    664  * datalen is # of bytes at data[], remaining is length of rest of marker data.
    665  */
    666 {
    667   unsigned int version, flags0, flags1, transform;
    668 
    669   if (datalen >= APP14_DATA_LEN &&
    670       GETJOCTET(data[0]) == 0x41 &&
    671       GETJOCTET(data[1]) == 0x64 &&
    672       GETJOCTET(data[2]) == 0x6F &&
    673       GETJOCTET(data[3]) == 0x62 &&
    674       GETJOCTET(data[4]) == 0x65) {
    675     /* Found Adobe APP14 marker */
    676     version = (GETJOCTET(data[5]) << 8) + GETJOCTET(data[6]);
    677     flags0 = (GETJOCTET(data[7]) << 8) + GETJOCTET(data[8]);
    678     flags1 = (GETJOCTET(data[9]) << 8) + GETJOCTET(data[10]);
    679     transform = GETJOCTET(data[11]);
    680     TRACEMS4(cinfo, 1, JTRC_ADOBE, version, flags0, flags1, transform);
    681     cinfo->saw_Adobe_marker = TRUE;
    682     cinfo->Adobe_transform = (UINT8) transform;
    683   } else {
    684     /* Start of APP14 does not match "Adobe", or too short */
    685     TRACEMS1(cinfo, 1, JTRC_APP14, (int) (datalen + remaining));
    686   }
    687 }
    688 
    689 
    690 METHODDEF(boolean)
    691 get_interesting_appn (j_decompress_ptr cinfo)
    692 /* Process an APP0 or APP14 marker without saving it */
    693 {
    694   INT32 length;
    695   JOCTET b[APPN_DATA_LEN];
    696   unsigned int i, numtoread;
    697   INPUT_VARS(cinfo);
    698 
    699   INPUT_2BYTES(cinfo, length, return FALSE);
    700   length -= 2;
    701 
    702   /* get the interesting part of the marker data */
    703   if (length >= APPN_DATA_LEN)
    704     numtoread = APPN_DATA_LEN;
    705   else if (length > 0)
    706     numtoread = (unsigned int) length;
    707   else
    708     numtoread = 0;
    709   for (i = 0; i < numtoread; i++)
    710     INPUT_BYTE(cinfo, b[i], return FALSE);
    711   length -= numtoread;
    712 
    713   /* process it */
    714   switch (cinfo->unread_marker) {
    715   case M_APP0:
    716     examine_app0(cinfo, (JOCTET FAR *) b, numtoread, length);
    717     break;
    718   case M_APP14:
    719     examine_app14(cinfo, (JOCTET FAR *) b, numtoread, length);
    720     break;
    721   default:
    722     /* can't get here unless jpeg_save_markers chooses wrong processor */
    723     ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker);
    724     break;
    725   }
    726 
    727   /* skip any remaining data -- could be lots */
    728   INPUT_SYNC(cinfo);
    729   if (length > 0)
    730     (*cinfo->src->skip_input_data) (cinfo, (long) length);
    731 
    732   return TRUE;
    733 }
    734 
    735 
    736 #ifdef SAVE_MARKERS_SUPPORTED
    737 
    738 METHODDEF(boolean)
    739 save_marker (j_decompress_ptr cinfo)
    740 /* Save an APPn or COM marker into the marker list */
    741 {
    742   my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
    743   jpeg_saved_marker_ptr cur_marker = marker->cur_marker;
    744   unsigned int bytes_read, data_length;
    745   JOCTET FAR * data;
    746   INT32 length = 0;
    747   INPUT_VARS(cinfo);
    748 
    749   if (cur_marker == NULL) {
    750     /* begin reading a marker */
    751     INPUT_2BYTES(cinfo, length, return FALSE);
    752     length -= 2;
    753     if (length >= 0) {		/* watch out for bogus length word */
    754       /* figure out how much we want to save */
    755       unsigned int limit;
    756       if (cinfo->unread_marker == (int) M_COM)
    757 	limit = marker->length_limit_COM;
    758       else
    759 	limit = marker->length_limit_APPn[cinfo->unread_marker - (int) M_APP0];
    760       if ((unsigned int) length < limit)
    761 	limit = (unsigned int) length;
    762       /* allocate and initialize the marker item */
    763       cur_marker = (jpeg_saved_marker_ptr)
    764 	(*cinfo->mem->alloc_large) ((j_common_ptr) cinfo, JPOOL_IMAGE,
    765 				    SIZEOF(struct jpeg_marker_struct) + limit);
    766       cur_marker->next = NULL;
    767       cur_marker->marker = (UINT8) cinfo->unread_marker;
    768       cur_marker->original_length = (unsigned int) length;
    769       cur_marker->data_length = limit;
    770       /* data area is just beyond the jpeg_marker_struct */
    771       data = cur_marker->data = (JOCTET FAR *) (cur_marker + 1);
    772       marker->cur_marker = cur_marker;
    773       marker->bytes_read = 0;
    774       bytes_read = 0;
    775       data_length = limit;
    776     } else {
    777       /* deal with bogus length word */
    778       bytes_read = data_length = 0;
    779       data = NULL;
    780     }
    781   } else {
    782     /* resume reading a marker */
    783     bytes_read = marker->bytes_read;
    784     data_length = cur_marker->data_length;
    785     data = cur_marker->data + bytes_read;
    786   }
    787 
    788   while (bytes_read < data_length) {
    789     INPUT_SYNC(cinfo);		/* move the restart point to here */
    790     marker->bytes_read = bytes_read;
    791     /* If there's not at least one byte in buffer, suspend */
    792     MAKE_BYTE_AVAIL(cinfo, return FALSE);
    793     /* Copy bytes with reasonable rapidity */
    794     while (bytes_read < data_length && bytes_in_buffer > 0) {
    795       *data++ = *next_input_byte++;
    796       bytes_in_buffer--;
    797       bytes_read++;
    798     }
    799   }
    800 
    801   /* Done reading what we want to read */
    802   if (cur_marker != NULL) {	/* will be NULL if bogus length word */
    803     /* Add new marker to end of list */
    804     if (cinfo->marker_list == NULL) {
    805       cinfo->marker_list = cur_marker;
    806     } else {
    807       jpeg_saved_marker_ptr prev = cinfo->marker_list;
    808       while (prev->next != NULL)
    809 	prev = prev->next;
    810       prev->next = cur_marker;
    811     }
    812     /* Reset pointer & calc remaining data length */
    813     data = cur_marker->data;
    814     length = cur_marker->original_length - data_length;
    815   }
    816   /* Reset to initial state for next marker */
    817   marker->cur_marker = NULL;
    818 
    819   /* Process the marker if interesting; else just make a generic trace msg */
    820   switch (cinfo->unread_marker) {
    821   case M_APP0:
    822     examine_app0(cinfo, data, data_length, length);
    823     break;
    824   case M_APP14:
    825     examine_app14(cinfo, data, data_length, length);
    826     break;
    827   default:
    828     TRACEMS2(cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker,
    829 	     (int) (data_length + length));
    830     break;
    831   }
    832 
    833   /* skip any remaining data -- could be lots */
    834   INPUT_SYNC(cinfo);		/* do before skip_input_data */
    835   if (length > 0)
    836     (*cinfo->src->skip_input_data) (cinfo, (long) length);
    837 
    838   return TRUE;
    839 }
    840 
    841 #endif /* SAVE_MARKERS_SUPPORTED */
    842 
    843 
    844 METHODDEF(boolean)
    845 skip_variable (j_decompress_ptr cinfo)
    846 /* Skip over an unknown or uninteresting variable-length marker */
    847 {
    848   INT32 length;
    849   INPUT_VARS(cinfo);
    850 
    851   INPUT_2BYTES(cinfo, length, return FALSE);
    852   length -= 2;
    853 
    854   TRACEMS2(cinfo, 1, JTRC_MISC_MARKER, cinfo->unread_marker, (int) length);
    855 
    856   INPUT_SYNC(cinfo);		/* do before skip_input_data */
    857   if (length > 0)
    858     (*cinfo->src->skip_input_data) (cinfo, (long) length);
    859 
    860   return TRUE;
    861 }
    862 
    863 
    864 /*
    865  * Find the next JPEG marker, save it in cinfo->unread_marker.
    866  * Returns FALSE if had to suspend before reaching a marker;
    867  * in that case cinfo->unread_marker is unchanged.
    868  *
    869  * Note that the result might not be a valid marker code,
    870  * but it will never be 0 or FF.
    871  */
    872 
    873 LOCAL(boolean)
    874 next_marker (j_decompress_ptr cinfo)
    875 {
    876   int c;
    877   INPUT_VARS(cinfo);
    878 
    879   for (;;) {
    880     INPUT_BYTE(cinfo, c, return FALSE);
    881     /* Skip any non-FF bytes.
    882      * This may look a bit inefficient, but it will not occur in a valid file.
    883      * We sync after each discarded byte so that a suspending data source
    884      * can discard the byte from its buffer.
    885      */
    886     while (c != 0xFF) {
    887       cinfo->marker->discarded_bytes++;
    888       INPUT_SYNC(cinfo);
    889       INPUT_BYTE(cinfo, c, return FALSE);
    890     }
    891     /* This loop swallows any duplicate FF bytes.  Extra FFs are legal as
    892      * pad bytes, so don't count them in discarded_bytes.  We assume there
    893      * will not be so many consecutive FF bytes as to overflow a suspending
    894      * data source's input buffer.
    895      */
    896     do {
    897       INPUT_BYTE(cinfo, c, return FALSE);
    898     } while (c == 0xFF);
    899     if (c != 0)
    900       break;			/* found a valid marker, exit loop */
    901     /* Reach here if we found a stuffed-zero data sequence (FF/00).
    902      * Discard it and loop back to try again.
    903      */
    904     cinfo->marker->discarded_bytes += 2;
    905     INPUT_SYNC(cinfo);
    906   }
    907 
    908   if (cinfo->marker->discarded_bytes != 0) {
    909     WARNMS2(cinfo, JWRN_EXTRANEOUS_DATA, cinfo->marker->discarded_bytes, c);
    910     cinfo->marker->discarded_bytes = 0;
    911   }
    912 
    913   cinfo->unread_marker = c;
    914 
    915   INPUT_SYNC(cinfo);
    916   return TRUE;
    917 }
    918 
    919 
    920 LOCAL(boolean)
    921 first_marker (j_decompress_ptr cinfo)
    922 /* Like next_marker, but used to obtain the initial SOI marker. */
    923 /* For this marker, we do not allow preceding garbage or fill; otherwise,
    924  * we might well scan an entire input file before realizing it ain't JPEG.
    925  * If an application wants to process non-JFIF files, it must seek to the
    926  * SOI before calling the JPEG library.
    927  */
    928 {
    929   int c, c2;
    930   INPUT_VARS(cinfo);
    931 
    932   INPUT_BYTE(cinfo, c, return FALSE);
    933   INPUT_BYTE(cinfo, c2, return FALSE);
    934   if (c != 0xFF || c2 != (int) M_SOI)
    935     ERREXIT2(cinfo, JERR_NO_SOI, c, c2);
    936 
    937   cinfo->unread_marker = c2;
    938 
    939   INPUT_SYNC(cinfo);
    940   return TRUE;
    941 }
    942 
    943 
    944 /*
    945  * Read markers until SOS or EOI.
    946  *
    947  * Returns same codes as are defined for jpeg_consume_input:
    948  * JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
    949  */
    950 
    951 METHODDEF(int)
    952 read_markers (j_decompress_ptr cinfo)
    953 {
    954   /* Outer loop repeats once for each marker. */
    955   for (;;) {
    956     /* Collect the marker proper, unless we already did. */
    957     /* NB: first_marker() enforces the requirement that SOI appear first. */
    958     if (cinfo->unread_marker == 0) {
    959       if (! cinfo->marker->saw_SOI) {
    960 	if (! first_marker(cinfo))
    961 	  return JPEG_SUSPENDED;
    962       } else {
    963 	if (! next_marker(cinfo))
    964 	  return JPEG_SUSPENDED;
    965       }
    966     }
    967 
    968     /*
    969      * Save the position of the fist marker after SOF.
    970      */
    971     if (cinfo->marker->current_sos_marker_position == -1)
    972       cinfo->marker->current_sos_marker_position =
    973           jget_input_stream_position(cinfo) - 2;
    974 
    975     /* At this point cinfo->unread_marker contains the marker code and the
    976      * input point is just past the marker proper, but before any parameters.
    977      * A suspension will cause us to return with this state still true.
    978      */
    979     switch (cinfo->unread_marker) {
    980     case M_SOI:
    981       if (! get_soi(cinfo))
    982 	return JPEG_SUSPENDED;
    983       break;
    984 
    985     case M_SOF0:		/* Baseline */
    986     case M_SOF1:		/* Extended sequential, Huffman */
    987       if (! get_sof(cinfo, FALSE, FALSE))
    988 	return JPEG_SUSPENDED;
    989       break;
    990 
    991     case M_SOF2:		/* Progressive, Huffman */
    992       cinfo->marker->current_sos_marker_position = -1;
    993       if (! get_sof(cinfo, TRUE, FALSE))
    994 	return JPEG_SUSPENDED;
    995       break;
    996 
    997     case M_SOF9:		/* Extended sequential, arithmetic */
    998       if (! get_sof(cinfo, FALSE, TRUE))
    999 	return JPEG_SUSPENDED;
   1000       break;
   1001 
   1002     case M_SOF10:		/* Progressive, arithmetic */
   1003       if (! get_sof(cinfo, TRUE, TRUE))
   1004 	return JPEG_SUSPENDED;
   1005       break;
   1006 
   1007     /* Currently unsupported SOFn types */
   1008     case M_SOF3:		/* Lossless, Huffman */
   1009     case M_SOF5:		/* Differential sequential, Huffman */
   1010     case M_SOF6:		/* Differential progressive, Huffman */
   1011     case M_SOF7:		/* Differential lossless, Huffman */
   1012     case M_JPG:			/* Reserved for JPEG extensions */
   1013     case M_SOF11:		/* Lossless, arithmetic */
   1014     case M_SOF13:		/* Differential sequential, arithmetic */
   1015     case M_SOF14:		/* Differential progressive, arithmetic */
   1016     case M_SOF15:		/* Differential lossless, arithmetic */
   1017       ERREXIT1(cinfo, JERR_SOF_UNSUPPORTED, cinfo->unread_marker);
   1018       break;
   1019 
   1020     case M_SOS:
   1021       if (! get_sos(cinfo))
   1022 	return JPEG_SUSPENDED;
   1023       cinfo->unread_marker = 0;	/* processed the marker */
   1024       return JPEG_REACHED_SOS;
   1025 
   1026     case M_EOI:
   1027       TRACEMS(cinfo, 1, JTRC_EOI);
   1028       cinfo->unread_marker = 0;	/* processed the marker */
   1029       return JPEG_REACHED_EOI;
   1030 
   1031     case M_DAC:
   1032       if (! get_dac(cinfo))
   1033 	return JPEG_SUSPENDED;
   1034       break;
   1035 
   1036     case M_DHT:
   1037       if (! get_dht(cinfo))
   1038 	return JPEG_SUSPENDED;
   1039       break;
   1040 
   1041     case M_DQT:
   1042       if (! get_dqt(cinfo))
   1043 	return JPEG_SUSPENDED;
   1044       break;
   1045 
   1046     case M_DRI:
   1047       if (! get_dri(cinfo))
   1048 	return JPEG_SUSPENDED;
   1049       break;
   1050 
   1051     case M_APP0:
   1052     case M_APP1:
   1053     case M_APP2:
   1054     case M_APP3:
   1055     case M_APP4:
   1056     case M_APP5:
   1057     case M_APP6:
   1058     case M_APP7:
   1059     case M_APP8:
   1060     case M_APP9:
   1061     case M_APP10:
   1062     case M_APP11:
   1063     case M_APP12:
   1064     case M_APP13:
   1065     case M_APP14:
   1066     case M_APP15:
   1067       if (! (*((my_marker_ptr) cinfo->marker)->process_APPn[
   1068 		cinfo->unread_marker - (int) M_APP0]) (cinfo))
   1069 	return JPEG_SUSPENDED;
   1070       break;
   1071 
   1072     case M_COM:
   1073       if (! (*((my_marker_ptr) cinfo->marker)->process_COM) (cinfo))
   1074 	return JPEG_SUSPENDED;
   1075       break;
   1076 
   1077     case M_RST0:		/* these are all parameterless */
   1078     case M_RST1:
   1079     case M_RST2:
   1080     case M_RST3:
   1081     case M_RST4:
   1082     case M_RST5:
   1083     case M_RST6:
   1084     case M_RST7:
   1085     case M_TEM:
   1086       TRACEMS1(cinfo, 1, JTRC_PARMLESS_MARKER, cinfo->unread_marker);
   1087       break;
   1088 
   1089     case M_DNL:			/* Ignore DNL ... perhaps the wrong thing */
   1090       if (! skip_variable(cinfo))
   1091 	return JPEG_SUSPENDED;
   1092       break;
   1093 
   1094     default:			/* must be DHP, EXP, JPGn, or RESn */
   1095       /* For now, we treat the reserved markers as fatal errors since they are
   1096        * likely to be used to signal incompatible JPEG Part 3 extensions.
   1097        * Once the JPEG 3 version-number marker is well defined, this code
   1098        * ought to change!
   1099        */
   1100       ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, cinfo->unread_marker);
   1101       break;
   1102     }
   1103     /* Successfully processed marker, so reset state variable */
   1104     cinfo->unread_marker = 0;
   1105   } /* end loop */
   1106 }
   1107 
   1108 
   1109 /*
   1110  * Read a restart marker, which is expected to appear next in the datastream;
   1111  * if the marker is not there, take appropriate recovery action.
   1112  * Returns FALSE if suspension is required.
   1113  *
   1114  * This is called by the entropy decoder after it has read an appropriate
   1115  * number of MCUs.  cinfo->unread_marker may be nonzero if the entropy decoder
   1116  * has already read a marker from the data source.  Under normal conditions
   1117  * cinfo->unread_marker will be reset to 0 before returning; if not reset,
   1118  * it holds a marker which the decoder will be unable to read past.
   1119  */
   1120 
   1121 METHODDEF(boolean)
   1122 read_restart_marker (j_decompress_ptr cinfo)
   1123 {
   1124   /* Obtain a marker unless we already did. */
   1125   /* Note that next_marker will complain if it skips any data. */
   1126   if (cinfo->unread_marker == 0) {
   1127     if (! next_marker(cinfo))
   1128       return FALSE;
   1129   }
   1130 
   1131   if (cinfo->unread_marker ==
   1132       ((int) M_RST0 + cinfo->marker->next_restart_num)) {
   1133     /* Normal case --- swallow the marker and let entropy decoder continue */
   1134     TRACEMS1(cinfo, 3, JTRC_RST, cinfo->marker->next_restart_num);
   1135     cinfo->unread_marker = 0;
   1136   } else {
   1137     /* Uh-oh, the restart markers have been messed up. */
   1138     /* Let the data source manager determine how to resync. */
   1139     if (! (*cinfo->src->resync_to_restart) (cinfo,
   1140 					    cinfo->marker->next_restart_num))
   1141       return FALSE;
   1142   }
   1143 
   1144   /* Update next-restart state */
   1145   cinfo->marker->next_restart_num = (cinfo->marker->next_restart_num + 1) & 7;
   1146 
   1147   return TRUE;
   1148 }
   1149 
   1150 
   1151 /*
   1152  * This is the default resync_to_restart method for data source managers
   1153  * to use if they don't have any better approach.  Some data source managers
   1154  * may be able to back up, or may have additional knowledge about the data
   1155  * which permits a more intelligent recovery strategy; such managers would
   1156  * presumably supply their own resync method.
   1157  *
   1158  * read_restart_marker calls resync_to_restart if it finds a marker other than
   1159  * the restart marker it was expecting.  (This code is *not* used unless
   1160  * a nonzero restart interval has been declared.)  cinfo->unread_marker is
   1161  * the marker code actually found (might be anything, except 0 or FF).
   1162  * The desired restart marker number (0..7) is passed as a parameter.
   1163  * This routine is supposed to apply whatever error recovery strategy seems
   1164  * appropriate in order to position the input stream to the next data segment.
   1165  * Note that cinfo->unread_marker is treated as a marker appearing before
   1166  * the current data-source input point; usually it should be reset to zero
   1167  * before returning.
   1168  * Returns FALSE if suspension is required.
   1169  *
   1170  * This implementation is substantially constrained by wanting to treat the
   1171  * input as a data stream; this means we can't back up.  Therefore, we have
   1172  * only the following actions to work with:
   1173  *   1. Simply discard the marker and let the entropy decoder resume at next
   1174  *      byte of file.
   1175  *   2. Read forward until we find another marker, discarding intervening
   1176  *      data.  (In theory we could look ahead within the current bufferload,
   1177  *      without having to discard data if we don't find the desired marker.
   1178  *      This idea is not implemented here, in part because it makes behavior
   1179  *      dependent on buffer size and chance buffer-boundary positions.)
   1180  *   3. Leave the marker unread (by failing to zero cinfo->unread_marker).
   1181  *      This will cause the entropy decoder to process an empty data segment,
   1182  *      inserting dummy zeroes, and then we will reprocess the marker.
   1183  *
   1184  * #2 is appropriate if we think the desired marker lies ahead, while #3 is
   1185  * appropriate if the found marker is a future restart marker (indicating
   1186  * that we have missed the desired restart marker, probably because it got
   1187  * corrupted).
   1188  * We apply #2 or #3 if the found marker is a restart marker no more than
   1189  * two counts behind or ahead of the expected one.  We also apply #2 if the
   1190  * found marker is not a legal JPEG marker code (it's certainly bogus data).
   1191  * If the found marker is a restart marker more than 2 counts away, we do #1
   1192  * (too much risk that the marker is erroneous; with luck we will be able to
   1193  * resync at some future point).
   1194  * For any valid non-restart JPEG marker, we apply #3.  This keeps us from
   1195  * overrunning the end of a scan.  An implementation limited to single-scan
   1196  * files might find it better to apply #2 for markers other than EOI, since
   1197  * any other marker would have to be bogus data in that case.
   1198  */
   1199 
   1200 GLOBAL(boolean)
   1201 jpeg_resync_to_restart (j_decompress_ptr cinfo, int desired)
   1202 {
   1203   int marker = cinfo->unread_marker;
   1204   int action = 1;
   1205 
   1206   /* Always put up a warning. */
   1207   WARNMS2(cinfo, JWRN_MUST_RESYNC, marker, desired);
   1208 
   1209   /* Outer loop handles repeated decision after scanning forward. */
   1210   for (;;) {
   1211     if (marker < (int) M_SOF0)
   1212       action = 2;		/* invalid marker */
   1213     else if (marker < (int) M_RST0 || marker > (int) M_RST7)
   1214       action = 3;		/* valid non-restart marker */
   1215     else {
   1216       if (marker == ((int) M_RST0 + ((desired+1) & 7)) ||
   1217 	  marker == ((int) M_RST0 + ((desired+2) & 7)))
   1218 	action = 3;		/* one of the next two expected restarts */
   1219       else if (marker == ((int) M_RST0 + ((desired-1) & 7)) ||
   1220 	       marker == ((int) M_RST0 + ((desired-2) & 7)))
   1221 	action = 2;		/* a prior restart, so advance */
   1222       else
   1223 	action = 1;		/* desired restart or too far away */
   1224     }
   1225     TRACEMS2(cinfo, 4, JTRC_RECOVERY_ACTION, marker, action);
   1226     switch (action) {
   1227     case 1:
   1228       /* Discard marker and let entropy decoder resume processing. */
   1229       cinfo->unread_marker = 0;
   1230       return TRUE;
   1231     case 2:
   1232       /* Scan to the next marker, and repeat the decision loop. */
   1233       if (! next_marker(cinfo))
   1234 	return FALSE;
   1235       marker = cinfo->unread_marker;
   1236       break;
   1237     case 3:
   1238       /* Return without advancing past this marker. */
   1239       /* Entropy decoder will be forced to process an empty segment. */
   1240       return TRUE;
   1241     }
   1242   } /* end loop */
   1243 }
   1244 
   1245 /*
   1246  * Get the position for all SOS markers in the image.
   1247  */
   1248 
   1249 METHODDEF(void)
   1250 get_sos_marker_position(j_decompress_ptr cinfo, huffman_index *index)
   1251 {
   1252   unsigned char *head;
   1253   int count = 0;
   1254   int retcode = JPEG_REACHED_SOS;
   1255 
   1256   while (cinfo->src->bytes_in_buffer > 0) {
   1257     if (retcode == JPEG_REACHED_SOS) {
   1258       jpeg_configure_huffman_index_scan(cinfo, index, count++,
   1259               cinfo->marker->current_sos_marker_position);
   1260       // Skips scan content to the next non-RST JPEG marker.
   1261       while(next_marker(cinfo) &&
   1262               cinfo->unread_marker >= M_RST0 && cinfo->unread_marker <= M_RST7)
   1263           ;
   1264       cinfo->marker->current_sos_marker_position =
   1265         jget_input_stream_position(cinfo) - 2;
   1266       retcode = read_markers(cinfo);
   1267     } else {
   1268       break;
   1269     }
   1270   }
   1271 }
   1272 
   1273 /*
   1274  * Reset marker processing state to begin a fresh datastream.
   1275  */
   1276 
   1277 METHODDEF(void)
   1278 reset_marker_reader (j_decompress_ptr cinfo)
   1279 {
   1280   my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
   1281 
   1282   cinfo->comp_info = NULL;		/* until allocated by get_sof */
   1283   cinfo->input_scan_number = 0;		/* no SOS seen yet */
   1284   cinfo->unread_marker = 0;		/* no pending marker */
   1285   marker->pub.saw_SOI = FALSE;		/* set internal state too */
   1286   marker->pub.saw_SOF = FALSE;
   1287   marker->pub.discarded_bytes = 0;
   1288   marker->cur_marker = NULL;
   1289 }
   1290 
   1291 
   1292 /*
   1293  * Initialize the marker reader module.
   1294  * This is called only once, when the decompression object is created.
   1295  */
   1296 
   1297 GLOBAL(void)
   1298 jinit_marker_reader (j_decompress_ptr cinfo)
   1299 {
   1300   my_marker_ptr marker;
   1301   int i;
   1302 
   1303   /* Create subobject in permanent pool */
   1304   marker = (my_marker_ptr)
   1305     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
   1306 				SIZEOF(my_marker_reader));
   1307   cinfo->marker = (struct jpeg_marker_reader *) marker;
   1308   /* Initialize public method pointers */
   1309   marker->pub.reset_marker_reader = reset_marker_reader;
   1310   marker->pub.read_markers = read_markers;
   1311   marker->pub.read_restart_marker = read_restart_marker;
   1312   marker->pub.get_sos_marker_position = get_sos_marker_position;
   1313   /* Initialize COM/APPn processing.
   1314    * By default, we examine and then discard APP0 and APP14,
   1315    * but simply discard COM and all other APPn.
   1316    */
   1317   marker->process_COM = skip_variable;
   1318   marker->length_limit_COM = 0;
   1319   for (i = 0; i < 16; i++) {
   1320     marker->process_APPn[i] = skip_variable;
   1321     marker->length_limit_APPn[i] = 0;
   1322   }
   1323   marker->process_APPn[0] = get_interesting_appn;
   1324   marker->process_APPn[14] = get_interesting_appn;
   1325   /* Reset marker processing state */
   1326   reset_marker_reader(cinfo);
   1327 }
   1328 
   1329 
   1330 /*
   1331  * Control saving of COM and APPn markers into marker_list.
   1332  */
   1333 
   1334 #ifdef SAVE_MARKERS_SUPPORTED
   1335 
   1336 GLOBAL(void)
   1337 jpeg_save_markers (j_decompress_ptr cinfo, int marker_code,
   1338 		   unsigned int length_limit)
   1339 {
   1340   my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
   1341   long maxlength;
   1342   jpeg_marker_parser_method processor;
   1343 
   1344   /* Length limit mustn't be larger than what we can allocate
   1345    * (should only be a concern in a 16-bit environment).
   1346    */
   1347   maxlength = cinfo->mem->max_alloc_chunk - SIZEOF(struct jpeg_marker_struct);
   1348   if (((long) length_limit) > maxlength)
   1349     length_limit = (unsigned int) maxlength;
   1350 
   1351   /* Choose processor routine to use.
   1352    * APP0/APP14 have special requirements.
   1353    */
   1354   if (length_limit) {
   1355     processor = save_marker;
   1356     /* If saving APP0/APP14, save at least enough for our internal use. */
   1357     if (marker_code == (int) M_APP0 && length_limit < APP0_DATA_LEN)
   1358       length_limit = APP0_DATA_LEN;
   1359     else if (marker_code == (int) M_APP14 && length_limit < APP14_DATA_LEN)
   1360       length_limit = APP14_DATA_LEN;
   1361   } else {
   1362     processor = skip_variable;
   1363     /* If discarding APP0/APP14, use our regular on-the-fly processor. */
   1364     if (marker_code == (int) M_APP0 || marker_code == (int) M_APP14)
   1365       processor = get_interesting_appn;
   1366   }
   1367 
   1368   if (marker_code == (int) M_COM) {
   1369     marker->process_COM = processor;
   1370     marker->length_limit_COM = length_limit;
   1371   } else if (marker_code >= (int) M_APP0 && marker_code <= (int) M_APP15) {
   1372     marker->process_APPn[marker_code - (int) M_APP0] = processor;
   1373     marker->length_limit_APPn[marker_code - (int) M_APP0] = length_limit;
   1374   } else
   1375     ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, marker_code);
   1376 }
   1377 
   1378 #endif /* SAVE_MARKERS_SUPPORTED */
   1379 
   1380 
   1381 /*
   1382  * Install a special processing method for COM or APPn markers.
   1383  */
   1384 
   1385 GLOBAL(void)
   1386 jpeg_set_marker_processor (j_decompress_ptr cinfo, int marker_code,
   1387 			   jpeg_marker_parser_method routine)
   1388 {
   1389   my_marker_ptr marker = (my_marker_ptr) cinfo->marker;
   1390 
   1391   if (marker_code == (int) M_COM)
   1392     marker->process_COM = routine;
   1393   else if (marker_code >= (int) M_APP0 && marker_code <= (int) M_APP15)
   1394     marker->process_APPn[marker_code - (int) M_APP0] = routine;
   1395   else
   1396     ERREXIT1(cinfo, JERR_UNKNOWN_MARKER, marker_code);
   1397 }
   1398