#define JPEG_INTERNALS#include "jpeglib.h"#include "jdhuff.h"		/* Declarations shared with jdphuff.c *//* * Expanded entropy decoder object for Huffman decoding. * * The savable_state subrecord contains fields that change within an MCU, * but must not be updated permanently until we complete the MCU. */typedef struct {  int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */} savable_state;/* This macro is to work around compilers with missing or broken * structure assignment.  You'll need to fix this code if you have * such a compiler and you change MAX_COMPS_IN_SCAN. */#ifndef NO_STRUCT_ASSIGN#define ASSIGN_STATE(dest,src)  ((dest) = (src))#else#if MAX_COMPS_IN_SCAN == 4#define ASSIGN_STATE(dest,src)  \	((dest).last_dc_val[0] = (src).last_dc_val[0], \	 (dest).last_dc_val[1] = (src).last_dc_val[1], \	 (dest).last_dc_val[2] = (src).last_dc_val[2], \	 (dest).last_dc_val[3] = (src).last_dc_val[3])#endif#endiftypedef struct {  struct jpeg_entropy_decoder pub; /* public fields */  /* These fields are loaded into local variables at start of each MCU.   * In case of suspension, we exit WITHOUT updating them.   */  bitread_perm_state bitstate;	/* Bit buffer at start of MCU */  savable_state saved;		/* Other state at start of MCU */  /* These fields are NOT loaded into local working state. */  unsigned int restarts_to_go;	/* MCUs left in this restart interval */  /* Pointers to derived tables (these workspaces have image lifespan) */  d_derived_tbl * dc_derived_tbls[NUM_HUFF_TBLS];  d_derived_tbl * ac_derived_tbls[NUM_HUFF_TBLS];} huff_entropy_decoder;typedef huff_entropy_decoder * huff_entropy_ptr;/* * Initialize for a Huffman-compressed scan. */METHODDEF(void)start_pass_huff_decoder (j_decompress_ptr cinfo){  huff_entropy_ptr entropy = (huff_entropy_ptr) cinfo->entropy;  int ci, dctbl, actbl;  jpeg_component_info * compptr;  /* Check that the scan parameters Ss, Se, Ah/Al are OK for sequential JPEG.   * This ought to be an error condition, but we make it a warning because   * there are some baseline files out there with all zeroes in these bytes.   */  if (cinfo->Ss != 0 || cinfo->Se != DCTSIZE2-1 ||      cinfo->Ah != 0 || cinfo->Al != 0)    WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {    compptr = cinfo->cur_comp_info[ci];    dctbl = compptr->dc_tbl_no;    actbl = compptr->ac_tbl_no;    /* Make sure requested tables are present */    if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS ||	cinfo->dc_huff_tbl_ptrs[dctbl] == NULL)      ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, dctbl);    if (actbl < 0 || actbl >= NUM_HUFF_TBLS ||	cinfo->ac_huff_tbl_ptrs[actbl] == NULL)      ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, actbl);    /* Compute derived values for Huffman tables */    /* We may do this more than once for a table, but it's not expensive */    jpeg_make_d_derived_tbl(cinfo, cinfo->dc_huff_tbl_ptrs[dctbl],			    & entropy->dc_derived_tbls[dctbl]);    jpeg_make_d_derived_tbl(cinfo, cinfo->ac_huff_tbl_ptrs[actbl],			    & entropy->ac_derived_tbls[actbl]);    /* Initialize DC predictions to 0 */    entropy->saved.last_dc_val[ci] = 0;  }  /* Initialize bitread state variables */  entropy->bitstate.bits_left = 0;  entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */  entropy->bitstate.printed_eod = FALSE;  /* Initialize restart counter */  entropy->restarts_to_go = cinfo->restart_interval;}/* * Compute the derived values for a Huffman table. * Note this is also used by jdphuff.c. */GLOBAL(void)jpeg_make_d_derived_tbl (j_decompress_ptr cinfo, JHUFF_TBL * htbl,			 d_derived_tbl ** pdtbl){  d_derived_tbl *dtbl;  int p, i, l, si;  int lookbits, ctr;  char huffsize[257];  unsigned int huffcode[257];  unsigned int code;  /* Allocate a workspace if we haven't already done so. */  if (*pdtbl == NULL)    *pdtbl = (d_derived_tbl *)      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,				  SIZEOF(d_derived_tbl));  dtbl = *pdtbl;  dtbl->pub = htbl;		/* fill in back link */    /* Figure C.1: make table of Huffman code length for each symbol */  /* Note that this is in code-length order. */  p = 0;  for (l = 1; l <= 16; l++) {    for (i = 1; i <= (int) htbl->bits[l]; i++)      huffsize[p++] = (char) l;  }  huffsize[p] = 0;    /* Figure C.2: generate the codes themselves */  /* Note that this is in code-length order. */    code = 0;  si = huffsize[0];  p = 0;  while (huffsize[p]) {    while (((int) huffsize[p]) == si) {      huffcode[p++] = code;      code++;    }    code <<= 1;    si++;  }  /* Figure F.15: generate decoding tables for bit-sequential decoding */  p = 0;  for (l = 1; l <= 16; l++) {    if (htbl->bits[l]) {      dtbl->valptr[l] = p; /* huffval[] index of 1st symbol of code length l */      dtbl->mincode[l] = huffcode[p]; /* minimum code of length l */      p += htbl->bits[l];      dtbl->maxcode[l] = huffcode[p-1]; /* maximum code of length l */    } else {      dtbl->maxcode[l] = -1;	/* -1 if no codes of this length */    }  }  dtbl->maxcode[17] = 0xFFFFFL; /* ensures jpeg_huff_decode terminates */  /* Compute lookahead tables to speed up decoding.   * First we set all the table entries to 0, indicating "too long";   * then we iterate through the Huffman codes that are short enough and   * fill in all the entries that correspond to bit sequences starting   * with that code.   */  MEMZERO(dtbl->look_nbits, SIZEOF(dtbl->look_nbits));  p = 0;  for (l = 1; l <= HUFF_LOOKAHEAD; l++) {    for (i = 1; i <= (int) htbl->bits[l]; i++, p++) {      /* l = current code's length, p = its index in huffcode[] & huffval[]. */      /* Generate left-justified code followed by all possible bit sequences */      lookbits = huffcode[p] << (HUFF_LOOKAHEAD-l);      for (ctr = 1 << (HUFF_LOOKAHEAD-l); ctr > 0; ctr--) {	dtbl->look_nbits[lookbits] = l;	dtbl->look_sym[lookbits] = htbl->huffval[p];	lookbits++;      }    }  }}/* * Out-of-line code for bit fetching (shared with jdphuff.c). * See jdhuff.h for info about usage. * Note: current values of get_buffer and bits_left are passed as parameters, * but are returned in the corresponding fields of the state struct. * * On most machines MIN_GET_BITS should be 25 to allow the full 32-bit width * of get_buffer to be used.  (On machines with wider words, an even larger * buffer could be used.)  However, on some machines 32-bit shifts are * quite slow and take time proportional to the number of places shifted. * (This is true with most PC compilers, for instance.)  In this case it may * be a win to set MIN_GET_BITS to the minimum value of 15.  This reduces the * average shift distance at the cost of more calls to jpeg_fill_bit_buffer. */#ifdef SLOW_SHIFT_32#define MIN_GET_BITS  15	/* minimum allowable value */#else#define MIN_GET_BITS  (BIT_BUF_SIZE-7)#endifGLOBAL(boolean)jpeg_fill_bit_buffer (bitread_working_state * state,		      register bit_buf_type get_buffer, register int bits_left,		      int nbits)/* Load up the bit buffer to a depth of at least nbits */{  /* Copy heavily used state fields into locals (hopefully registers) */  register const JOCTET * next_input_byte = state->next_input_byte;  register size_t bytes_in_buffer = state->bytes_in_buffer;  register int c;  /* Attempt to load at least MIN_GET_BITS bits into get_buffer. */  /* (It is assumed that no request will be for more than that many bits.) */  while (bits_left < MIN_GET_BITS) {    /* Attempt to read a byte */    if (state->unread_marker != 0)      goto no_more_data;	/* can't advance past a marker */    if (bytes_in_buffer == 0) {      if (! (*state->cinfo->src->fill_input_buffer) (state->cinfo))	return FALSE;      next_input_byte = state->cinfo->src->next_input_byte;      bytes_in_buffer = state->cinfo->src->bytes_in_buffer;    }    bytes_in_buffer--;    c = GETJOCTET(*next_input_byte++);    /* If it's 0xFF, check and discard stuffed zero byte */    if (c == 0xFF) {      do {	if (bytes_in_buffer == 0) {	  if (! (*state->cinfo->src->fill_input_buffer) (state->cinfo))	    return FALSE;	  next_input_byte = state->cinfo->src->next_input_byte;	  bytes_in_buffer = state->cinfo->src->bytes_in_buffer;	}	bytes_in_buffer--;	c = GETJOCTET(*next_input_byte++);      } while (c == 0xFF);      if (c == 0) {	/* Found FF/00, which represents an FF data byte */	c = 0xFF;      } else {	/* Oops, it's actually a marker indicating end of compressed data. */	/* Better put it back for use later */	state->unread_marker = c;      no_more_data:	/* There should be enough bits still left in the data segment; */	/* if so, just break out of the outer while loop. */	if (bits_left >= nbits)	  break;	/* Uh-oh.  Report corrupted data to user and stuff zeroes into	 * the data stream, so that we can produce some kind of image.	 * Note that this code will be repeated for each byte demanded	 * for the rest of the segment.  We use a nonvolatile flag to ensure	 * that only one warning message appears.	 */	if (! *(state->printed_eod_ptr)) {	  WARNMS(state->cinfo, JWRN_HIT_MARKER);	  *(state->printed_eod_ptr) = TRUE;	}