libjpeg update

git-svn-id: http://svn.miranda-ng.org/main/trunk@5843 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c

1 files changed, 782 insertions, 776 deletions

diff --git a/plugins/AdvaImg/src/LibJPEG/jdarith.c b/plugins/AdvaImg/src/LibJPEG/jdarith.c
index 092f8af5fe..5cd294260d 100644
--- a/plugins/AdvaImg/src/LibJPEG/jdarith.c
+++ b/plugins/AdvaImg/src/LibJPEG/jdarith.c
@@ -1,776 +1,782 @@
-/*
- * jdarith.c
- *
- * Developed 1997-2011 by Guido Vollbeding.
- * 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 portable arithmetic entropy decoding routines for JPEG
- * (implementing the ISO/IEC IS 10918-1 and CCITT Recommendation ITU-T T.81).
- *
- * Both sequential and progressive modes are supported in this single module.
- *
- * Suspension is not currently supported in this module.
- */
-
-#define JPEG_INTERNALS
-#include "jinclude.h"
-#include "jpeglib.h"
-
-
-/* Expanded entropy decoder object for arithmetic decoding. */
-
-typedef struct {
-  struct jpeg_entropy_decoder pub; /* public fields */
-
-  INT32 c;       /* C register, base of coding interval + input bit buffer */
-  INT32 a;               /* A register, normalized size of coding interval */
-  int ct;     /* bit shift counter, # of bits left in bit buffer part of C */
-                                                         /* init: ct = -16 */
-                                                         /* run: ct = 0..7 */
-                                                         /* error: ct = -1 */
-  int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */
-  int dc_context[MAX_COMPS_IN_SCAN]; /* context index for DC conditioning */
-
-  unsigned int restarts_to_go;	/* MCUs left in this restart interval */
-
-  /* Pointers to statistics areas (these workspaces have image lifespan) */
-  unsigned char * dc_stats[NUM_ARITH_TBLS];
-  unsigned char * ac_stats[NUM_ARITH_TBLS];
-
-  /* Statistics bin for coding with fixed probability 0.5 */
-  unsigned char fixed_bin[4];
-} arith_entropy_decoder;
-
-typedef arith_entropy_decoder * arith_entropy_ptr;
-
-/* The following two definitions specify the allocation chunk size
- * for the statistics area.
- * According to sections F.1.4.4.1.3 and F.1.4.4.2, we need at least
- * 49 statistics bins for DC, and 245 statistics bins for AC coding.
- *
- * We use a compact representation with 1 byte per statistics bin,
- * thus the numbers directly represent byte sizes.
- * This 1 byte per statistics bin contains the meaning of the MPS
- * (more probable symbol) in the highest bit (mask 0x80), and the
- * index into the probability estimation state machine table
- * in the lower bits (mask 0x7F).
- */
-
-#define DC_STAT_BINS 64
-#define AC_STAT_BINS 256
-
-
-LOCAL(int)
-get_byte (j_decompress_ptr cinfo)
-/* Read next input byte; we do not support suspension in this module. */
-{
-  struct jpeg_source_mgr * src = cinfo->src;
-
-  if (src->bytes_in_buffer == 0)
-    if (! (*src->fill_input_buffer) (cinfo))
-      ERREXIT(cinfo, JERR_CANT_SUSPEND);
-  src->bytes_in_buffer--;
-  return GETJOCTET(*src->next_input_byte++);
-}
-
-
-/*
- * The core arithmetic decoding routine (common in JPEG and JBIG).
- * This needs to go as fast as possible.
- * Machine-dependent optimization facilities
- * are not utilized in this portable implementation.
- * However, this code should be fairly efficient and
- * may be a good base for further optimizations anyway.
- *
- * Return value is 0 or 1 (binary decision).
- *
- * Note: I've changed the handling of the code base & bit
- * buffer register C compared to other implementations
- * based on the standards layout & procedures.
- * While it also contains both the actual base of the
- * coding interval (16 bits) and the next-bits buffer,
- * the cut-point between these two parts is floating
- * (instead of fixed) with the bit shift counter CT.
- * Thus, we also need only one (variable instead of
- * fixed size) shift for the LPS/MPS decision, and
- * we can get away with any renormalization update
- * of C (except for new data insertion, of course).
- *
- * I've also introduced a new scheme for accessing
- * the probability estimation state machine table,
- * derived from Markus Kuhn's JBIG implementation.
- */
-
-LOCAL(int)
-arith_decode (j_decompress_ptr cinfo, unsigned char *st)
-{
-  register arith_entropy_ptr e = (arith_entropy_ptr) cinfo->entropy;
-  register unsigned char nl, nm;
-  register INT32 qe, temp;
-  register int sv, data;
-
-  /* Renormalization & data input per section D.2.6 */
-  while (e->a < 0x8000L) {
-    if (--e->ct < 0) {
-      /* Need to fetch next data byte */
-      if (cinfo->unread_marker)
-	data = 0;		/* stuff zero data */
-      else {
-	data = get_byte(cinfo);	/* read next input byte */
-	if (data == 0xFF) {	/* zero stuff or marker code */
-	  do data = get_byte(cinfo);
-	  while (data == 0xFF);	/* swallow extra 0xFF bytes */
-	  if (data == 0)
-	    data = 0xFF;	/* discard stuffed zero byte */
-	  else {
-	    /* Note: Different from the Huffman decoder, hitting
-	     * a marker while processing the compressed data
-	     * segment is legal in arithmetic coding.
-	     * The convention is to supply zero data
-	     * then until decoding is complete.
-	     */
-	    cinfo->unread_marker = data;
-	    data = 0;
-	  }
-	}
-      }
-      e->c = (e->c << 8) | data; /* insert data into C register */
-      if ((e->ct += 8) < 0)	 /* update bit shift counter */
-	/* Need more initial bytes */
-	if (++e->ct == 0)
-	  /* Got 2 initial bytes -> re-init A and exit loop */
-	  e->a = 0x8000L; /* => e->a = 0x10000L after loop exit */
-    }
-    e->a <<= 1;
-  }
-
-  /* Fetch values from our compact representation of Table D.3(D.2):
-   * Qe values and probability estimation state machine
-   */
-  sv = *st;
-  qe = jpeg_aritab[sv & 0x7F];	/* => Qe_Value */
-  nl = qe & 0xFF; qe >>= 8;	/* Next_Index_LPS + Switch_MPS */
-  nm = qe & 0xFF; qe >>= 8;	/* Next_Index_MPS */
-
-  /* Decode & estimation procedures per sections D.2.4 & D.2.5 */
-  temp = e->a - qe;
-  e->a = temp;
-  temp <<= e->ct;
-  if (e->c >= temp) {
-    e->c -= temp;
-    /* Conditional LPS (less probable symbol) exchange */
-    if (e->a < qe) {
-      e->a = qe;
-      *st = (sv & 0x80) ^ nm;	/* Estimate_after_MPS */
-    } else {
-      e->a = qe;
-      *st = (sv & 0x80) ^ nl;	/* Estimate_after_LPS */
-      sv ^= 0x80;		/* Exchange LPS/MPS */
-    }
-  } else if (e->a < 0x8000L) {
-    /* Conditional MPS (more probable symbol) exchange */
-    if (e->a < qe) {
-      *st = (sv & 0x80) ^ nl;	/* Estimate_after_LPS */
-      sv ^= 0x80;		/* Exchange LPS/MPS */
-    } else {
-      *st = (sv & 0x80) ^ nm;	/* Estimate_after_MPS */
-    }
-  }
-
-  return sv >> 7;
-}
-
-
-/*
- * Check for a restart marker & resynchronize decoder.
- */
-
-LOCAL(void)
-process_restart (j_decompress_ptr cinfo)
-{
-  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
-  int ci;
-  jpeg_component_info * compptr;
-
-  /* Advance past the RSTn marker */
-  if (! (*cinfo->marker->read_restart_marker) (cinfo))
-    ERREXIT(cinfo, JERR_CANT_SUSPEND);
-
-  /* Re-initialize statistics areas */
-  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
-    compptr = cinfo->cur_comp_info[ci];
-    if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) {
-      MEMZERO(entropy->dc_stats[compptr->dc_tbl_no], DC_STAT_BINS);
-      /* Reset DC predictions to 0 */
-      entropy->last_dc_val[ci] = 0;
-      entropy->dc_context[ci] = 0;
-    }
-    if ((! cinfo->progressive_mode && cinfo->lim_Se) ||
-	(cinfo->progressive_mode && cinfo->Ss)) {
-      MEMZERO(entropy->ac_stats[compptr->ac_tbl_no], AC_STAT_BINS);
-    }
-  }
-
-  /* Reset arithmetic decoding variables */
-  entropy->c = 0;
-  entropy->a = 0;
-  entropy->ct = -16;	/* force reading 2 initial bytes to fill C */
-
-  /* Reset restart counter */
-  entropy->restarts_to_go = cinfo->restart_interval;
-}
-
-
-/*
- * Arithmetic MCU decoding.
- * Each of these routines decodes and returns one MCU's worth of
- * arithmetic-compressed coefficients.
- * The coefficients are reordered from zigzag order into natural array order,
- * but are not dequantized.
- *
- * The i'th block of the MCU is stored into the block pointed to by
- * MCU_data[i].  WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.
- */
-
-/*
- * MCU decoding for DC initial scan (either spectral selection,
- * or first pass of successive approximation).
- */
-
-METHODDEF(boolean)
-decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
-  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
-  JBLOCKROW block;
-  unsigned char *st;
-  int blkn, ci, tbl, sign;
-  int v, m;
-
-  /* Process restart marker if needed */
-  if (cinfo->restart_interval) {
-    if (entropy->restarts_to_go == 0)
-      process_restart(cinfo);
-    entropy->restarts_to_go--;
-  }
-
-  if (entropy->ct == -1) return TRUE;	/* if error do nothing */
-
-  /* Outer loop handles each block in the MCU */
-
-  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
-    block = MCU_data[blkn];
-    ci = cinfo->MCU_membership[blkn];
-    tbl = cinfo->cur_comp_info[ci]->dc_tbl_no;
-
-    /* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */
-
-    /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
-    st = entropy->dc_stats[tbl] + entropy->dc_context[ci];
-
-    /* Figure F.19: Decode_DC_DIFF */
-    if (arith_decode(cinfo, st) == 0)
-      entropy->dc_context[ci] = 0;
-    else {
-      /* Figure F.21: Decoding nonzero value v */
-      /* Figure F.22: Decoding the sign of v */
-      sign = arith_decode(cinfo, st + 1);
-      st += 2; st += sign;
-      /* Figure F.23: Decoding the magnitude category of v */
-      if ((m = arith_decode(cinfo, st)) != 0) {
-	st = entropy->dc_stats[tbl] + 20;	/* Table F.4: X1 = 20 */
-	while (arith_decode(cinfo, st)) {
-	  if ((m <<= 1) == 0x8000) {
-	    WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
-	    entropy->ct = -1;			/* magnitude overflow */
-	    return TRUE;
-	  }
-	  st += 1;
-	}
-      }
-      /* Section F.1.4.4.1.2: Establish dc_context conditioning category */
-      if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1))
-	entropy->dc_context[ci] = 0;		   /* zero diff category */
-      else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1))
-	entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */
-      else
-	entropy->dc_context[ci] = 4 + (sign * 4);  /* small diff category */
-      v = m;
-      /* Figure F.24: Decoding the magnitude bit pattern of v */
-      st += 14;
-      while (m >>= 1)
-	if (arith_decode(cinfo, st)) v |= m;
-      v += 1; if (sign) v = -v;
-      entropy->last_dc_val[ci] += v;
-    }
-
-    /* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */
-    (*block)[0] = (JCOEF) (entropy->last_dc_val[ci] << cinfo->Al);
-  }
-
-  return TRUE;
-}
-
-
-/*
- * MCU decoding for AC initial scan (either spectral selection,
- * or first pass of successive approximation).
- */
-
-METHODDEF(boolean)
-decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
-  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
-  JBLOCKROW block;
-  unsigned char *st;
-  int tbl, sign, k;
-  int v, m;
-  const int * natural_order;
-
-  /* Process restart marker if needed */
-  if (cinfo->restart_interval) {
-    if (entropy->restarts_to_go == 0)
-      process_restart(cinfo);
-    entropy->restarts_to_go--;
-  }
-
-  if (entropy->ct == -1) return TRUE;	/* if error do nothing */
-
-  natural_order = cinfo->natural_order;
-
-  /* There is always only one block per MCU */
-  block = MCU_data[0];
-  tbl = cinfo->cur_comp_info[0]->ac_tbl_no;
-
-  /* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */
-
-  /* Figure F.20: Decode_AC_coefficients */
-  for (k = cinfo->Ss; k <= cinfo->Se; k++) {
-    st = entropy->ac_stats[tbl] + 3 * (k - 1);
-    if (arith_decode(cinfo, st)) break;		/* EOB flag */
-    while (arith_decode(cinfo, st + 1) == 0) {
-      st += 3; k++;
-      if (k > cinfo->Se) {
-	WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
-	entropy->ct = -1;			/* spectral overflow */
-	return TRUE;
-      }
-    }
-    /* Figure F.21: Decoding nonzero value v */
-    /* Figure F.22: Decoding the sign of v */
-    sign = arith_decode(cinfo, entropy->fixed_bin);
-    st += 2;
-    /* Figure F.23: Decoding the magnitude category of v */
-    if ((m = arith_decode(cinfo, st)) != 0) {
-      if (arith_decode(cinfo, st)) {
-	m <<= 1;
-	st = entropy->ac_stats[tbl] +
-	     (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
-	while (arith_decode(cinfo, st)) {
-	  if ((m <<= 1) == 0x8000) {
-	    WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
-	    entropy->ct = -1;			/* magnitude overflow */
-	    return TRUE;
-	  }
-	  st += 1;
-	}
-      }
-    }
-    v = m;
-    /* Figure F.24: Decoding the magnitude bit pattern of v */
-    st += 14;
-    while (m >>= 1)
-      if (arith_decode(cinfo, st)) v |= m;
-    v += 1; if (sign) v = -v;
-    /* Scale and output coefficient in natural (dezigzagged) order */
-    (*block)[natural_order[k]] = (JCOEF) (v << cinfo->Al);
-  }
-
-  return TRUE;
-}
-
-
-/*
- * MCU decoding for DC successive approximation refinement scan.
- */
-
-METHODDEF(boolean)
-decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
-  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
-  unsigned char *st;
-  int p1, blkn;
-
-  /* Process restart marker if needed */
-  if (cinfo->restart_interval) {
-    if (entropy->restarts_to_go == 0)
-      process_restart(cinfo);
-    entropy->restarts_to_go--;
-  }
-
-  st = entropy->fixed_bin;	/* use fixed probability estimation */
-  p1 = 1 << cinfo->Al;		/* 1 in the bit position being coded */
-
-  /* Outer loop handles each block in the MCU */
-
-  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
-    /* Encoded data is simply the next bit of the two's-complement DC value */
-    if (arith_decode(cinfo, st))
-      MCU_data[blkn][0][0] |= p1;
-  }
-
-  return TRUE;
-}
-
-
-/*
- * MCU decoding for AC successive approximation refinement scan.
- */
-
-METHODDEF(boolean)
-decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
-  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
-  JBLOCKROW block;
-  JCOEFPTR thiscoef;
-  unsigned char *st;
-  int tbl, k, kex;
-  int p1, m1;
-  const int * natural_order;
-
-  /* Process restart marker if needed */
-  if (cinfo->restart_interval) {
-    if (entropy->restarts_to_go == 0)
-      process_restart(cinfo);
-    entropy->restarts_to_go--;
-  }
-
-  if (entropy->ct == -1) return TRUE;	/* if error do nothing */
-
-  natural_order = cinfo->natural_order;
-
-  /* There is always only one block per MCU */
-  block = MCU_data[0];
-  tbl = cinfo->cur_comp_info[0]->ac_tbl_no;
-
-  p1 = 1 << cinfo->Al;		/* 1 in the bit position being coded */
-  m1 = (-1) << cinfo->Al;	/* -1 in the bit position being coded */
-
-  /* Establish EOBx (previous stage end-of-block) index */
-  for (kex = cinfo->Se; kex > 0; kex--)
-    if ((*block)[natural_order[kex]]) break;
-
-  for (k = cinfo->Ss; k <= cinfo->Se; k++) {
-    st = entropy->ac_stats[tbl] + 3 * (k - 1);
-    if (k > kex)
-      if (arith_decode(cinfo, st)) break;	/* EOB flag */
-    for (;;) {
-      thiscoef = *block + natural_order[k];
-      if (*thiscoef) {				/* previously nonzero coef */
-	if (arith_decode(cinfo, st + 2)) {
-	  if (*thiscoef < 0)
-	    *thiscoef += m1;
-	  else
-	    *thiscoef += p1;
-	}
-	break;
-      }
-      if (arith_decode(cinfo, st + 1)) {	/* newly nonzero coef */
-	if (arith_decode(cinfo, entropy->fixed_bin))
-	  *thiscoef = m1;
-	else
-	  *thiscoef = p1;
-	break;
-      }
-      st += 3; k++;
-      if (k > cinfo->Se) {
-	WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
-	entropy->ct = -1;			/* spectral overflow */
-	return TRUE;
-      }
-    }
-  }
-
-  return TRUE;
-}
-
-
-/*
- * Decode one MCU's worth of arithmetic-compressed coefficients.
- */
-
-METHODDEF(boolean)
-decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)
-{
-  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
-  jpeg_component_info * compptr;
-  JBLOCKROW block;
-  unsigned char *st;
-  int blkn, ci, tbl, sign, k;
-  int v, m;
-  const int * natural_order;
-
-  /* Process restart marker if needed */
-  if (cinfo->restart_interval) {
-    if (entropy->restarts_to_go == 0)
-      process_restart(cinfo);
-    entropy->restarts_to_go--;
-  }
-
-  if (entropy->ct == -1) return TRUE;	/* if error do nothing */
-
-  natural_order = cinfo->natural_order;
-
-  /* Outer loop handles each block in the MCU */
-
-  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {
-    block = MCU_data[blkn];
-    ci = cinfo->MCU_membership[blkn];
-    compptr = cinfo->cur_comp_info[ci];
-
-    /* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */
-
-    tbl = compptr->dc_tbl_no;
-
-    /* Table F.4: Point to statistics bin S0 for DC coefficient coding */
-    st = entropy->dc_stats[tbl] + entropy->dc_context[ci];
-
-    /* Figure F.19: Decode_DC_DIFF */
-    if (arith_decode(cinfo, st) == 0)
-      entropy->dc_context[ci] = 0;
-    else {
-      /* Figure F.21: Decoding nonzero value v */
-      /* Figure F.22: Decoding the sign of v */
-      sign = arith_decode(cinfo, st + 1);
-      st += 2; st += sign;
-      /* Figure F.23: Decoding the magnitude category of v */
-      if ((m = arith_decode(cinfo, st)) != 0) {
-	st = entropy->dc_stats[tbl] + 20;	/* Table F.4: X1 = 20 */
-	while (arith_decode(cinfo, st)) {
-	  if ((m <<= 1) == 0x8000) {
-	    WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
-	    entropy->ct = -1;			/* magnitude overflow */
-	    return TRUE;
-	  }
-	  st += 1;
-	}
-      }
-      /* Section F.1.4.4.1.2: Establish dc_context conditioning category */
-      if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1))
-	entropy->dc_context[ci] = 0;		   /* zero diff category */
-      else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1))
-	entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */
-      else
-	entropy->dc_context[ci] = 4 + (sign * 4);  /* small diff category */
-      v = m;
-      /* Figure F.24: Decoding the magnitude bit pattern of v */
-      st += 14;
-      while (m >>= 1)
-	if (arith_decode(cinfo, st)) v |= m;
-      v += 1; if (sign) v = -v;
-      entropy->last_dc_val[ci] += v;
-    }
-
-    (*block)[0] = (JCOEF) entropy->last_dc_val[ci];
-
-    /* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */
-
-    if (cinfo->lim_Se == 0) continue;
-    tbl = compptr->ac_tbl_no;
-    k = 0;
-
-    /* Figure F.20: Decode_AC_coefficients */
-    do {
-      st = entropy->ac_stats[tbl] + 3 * k;
-      if (arith_decode(cinfo, st)) break;	/* EOB flag */
-      for (;;) {
-	k++;
-	if (arith_decode(cinfo, st + 1)) break;
-	st += 3;
-	if (k >= cinfo->lim_Se) {
-	  WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
-	  entropy->ct = -1;			/* spectral overflow */
-	  return TRUE;
-	}
-      }
-      /* Figure F.21: Decoding nonzero value v */
-      /* Figure F.22: Decoding the sign of v */
-      sign = arith_decode(cinfo, entropy->fixed_bin);
-      st += 2;
-      /* Figure F.23: Decoding the magnitude category of v */
-      if ((m = arith_decode(cinfo, st)) != 0) {
-	if (arith_decode(cinfo, st)) {
-	  m <<= 1;
-	  st = entropy->ac_stats[tbl] +
-	       (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);
-	  while (arith_decode(cinfo, st)) {
-	    if ((m <<= 1) == 0x8000) {
-	      WARNMS(cinfo, JWRN_ARITH_BAD_CODE);
-	      entropy->ct = -1;			/* magnitude overflow */
-	      return TRUE;
-	    }
-	    st += 1;
-	  }
-	}
-      }
-      v = m;
-      /* Figure F.24: Decoding the magnitude bit pattern of v */
-      st += 14;
-      while (m >>= 1)
-	if (arith_decode(cinfo, st)) v |= m;
-      v += 1; if (sign) v = -v;
-      (*block)[natural_order[k]] = (JCOEF) v;
-    } while (k < cinfo->lim_Se);
-  }
-
-  return TRUE;
-}
-
-
-/*
- * Initialize for an arithmetic-compressed scan.
- */
-
-METHODDEF(void)
-start_pass (j_decompress_ptr cinfo)
-{
-  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;
-  int ci, tbl;
-  jpeg_component_info * compptr;
-
-  if (cinfo->progressive_mode) {
-    /* Validate progressive scan parameters */
-    if (cinfo->Ss == 0) {
-      if (cinfo->Se != 0)
-	goto bad;
-    } else {
-      /* need not check Ss/Se < 0 since they came from unsigned bytes */
-      if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)
-	goto bad;
-      /* AC scans may have only one component */
-      if (cinfo->comps_in_scan != 1)
-	goto bad;
-    }
-    if (cinfo->Ah != 0) {
-      /* Successive approximation refinement scan: must have Al = Ah-1. */
-      if (cinfo->Ah-1 != cinfo->Al)
-	goto bad;
-    }
-    if (cinfo->Al > 13) {	/* need not check for < 0 */
-      bad:
-      ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
-	       cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
-    }
-    /* Update progression status, and verify that scan order is legal.
-     * Note that inter-scan inconsistencies are treated as warnings
-     * not fatal errors ... not clear if this is right way to behave.
-     */
-    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
-      int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;
-      int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];
-      if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */
-	WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);
-      for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {
-	int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];
-	if (cinfo->Ah != expected)
-	  WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);
-	coef_bit_ptr[coefi] = cinfo->Al;
-      }
-    }
-    /* Select MCU decoding routine */
-    if (cinfo->Ah == 0) {
-      if (cinfo->Ss == 0)
-	entropy->pub.decode_mcu = decode_mcu_DC_first;
-      else
-	entropy->pub.decode_mcu = decode_mcu_AC_first;
-    } else {
-      if (cinfo->Ss == 0)
-	entropy->pub.decode_mcu = decode_mcu_DC_refine;
-      else
-	entropy->pub.decode_mcu = decode_mcu_AC_refine;
-    }
-  } else {
-    /* 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.
-     */
-    if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||
-	(cinfo->Se < DCTSIZE2 && cinfo->Se != cinfo->lim_Se))
-      WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);
-    /* Select MCU decoding routine */
-    entropy->pub.decode_mcu = decode_mcu;
-  }
-
-  /* Allocate & initialize requested statistics areas */
-  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
-    compptr = cinfo->cur_comp_info[ci];
-    if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) {
-      tbl = compptr->dc_tbl_no;
-      if (tbl < 0 || tbl >= NUM_ARITH_TBLS)
-	ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);
-      if (entropy->dc_stats[tbl] == NULL)
-	entropy->dc_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)
-	  ((j_common_ptr) cinfo, JPOOL_IMAGE, DC_STAT_BINS);
-      MEMZERO(entropy->dc_stats[tbl], DC_STAT_BINS);
-      /* Initialize DC predictions to 0 */
-      entropy->last_dc_val[ci] = 0;
-      entropy->dc_context[ci] = 0;
-    }
-    if ((! cinfo->progressive_mode && cinfo->lim_Se) ||
-	(cinfo->progressive_mode && cinfo->Ss)) {
-      tbl = compptr->ac_tbl_no;
-      if (tbl < 0 || tbl >= NUM_ARITH_TBLS)
-	ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);
-      if (entropy->ac_stats[tbl] == NULL)
-	entropy->ac_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)
-	  ((j_common_ptr) cinfo, JPOOL_IMAGE, AC_STAT_BINS);
-      MEMZERO(entropy->ac_stats[tbl], AC_STAT_BINS);
-    }
-  }
-
-  /* Initialize arithmetic decoding variables */
-  entropy->c = 0;
-  entropy->a = 0;
-  entropy->ct = -16;	/* force reading 2 initial bytes to fill C */
-
-  /* Initialize restart counter */
-  entropy->restarts_to_go = cinfo->restart_interval;
-}
-
-
-/*
- * Module initialization routine for arithmetic entropy decoding.
- */
-
-GLOBAL(void)
-jinit_arith_decoder (j_decompress_ptr cinfo)
-{
-  arith_entropy_ptr entropy;
-  int i;
-
-  entropy = (arith_entropy_ptr)
-    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
-				SIZEOF(arith_entropy_decoder));
-  cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;
-  entropy->pub.start_pass = start_pass;
-
-  /* Mark tables unallocated */
-  for (i = 0; i < NUM_ARITH_TBLS; i++) {
-    entropy->dc_stats[i] = NULL;
-    entropy->ac_stats[i] = NULL;
-  }
-
-  /* Initialize index for fixed probability estimation */
-  entropy->fixed_bin[0] = 113;
-
-  if (cinfo->progressive_mode) {
-    /* Create progression status table */
-    int *coef_bit_ptr, ci;
-    cinfo->coef_bits = (int (*)[DCTSIZE2])
-      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
-				  cinfo->num_components*DCTSIZE2*SIZEOF(int));
-    coef_bit_ptr = & cinfo->coef_bits[0][0];
-    for (ci = 0; ci < cinfo->num_components; ci++) 
-      for (i = 0; i < DCTSIZE2; i++)
-	*coef_bit_ptr++ = -1;
-  }
-}
+/*

+ * jdarith.c

+ *

+ * Developed 1997-2012 by Guido Vollbeding.

+ * 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 portable arithmetic entropy decoding routines for JPEG

+ * (implementing the ISO/IEC IS 10918-1 and CCITT Recommendation ITU-T T.81).

+ *

+ * Both sequential and progressive modes are supported in this single module.

+ *

+ * Suspension is not currently supported in this module.

+ */

+

+#define JPEG_INTERNALS

+#include "jinclude.h"

+#include "jpeglib.h"

+

+

+/* Expanded entropy decoder object for arithmetic decoding. */

+

+typedef struct {

+  struct jpeg_entropy_decoder pub; /* public fields */

+

+  INT32 c;       /* C register, base of coding interval + input bit buffer */

+  INT32 a;               /* A register, normalized size of coding interval */

+  int ct;     /* bit shift counter, # of bits left in bit buffer part of C */

+                                                         /* init: ct = -16 */

+                                                         /* run: ct = 0..7 */

+                                                         /* error: ct = -1 */

+  int last_dc_val[MAX_COMPS_IN_SCAN]; /* last DC coef for each component */

+  int dc_context[MAX_COMPS_IN_SCAN]; /* context index for DC conditioning */

+

+  unsigned int restarts_to_go;	/* MCUs left in this restart interval */

+

+  /* Pointers to statistics areas (these workspaces have image lifespan) */

+  unsigned char * dc_stats[NUM_ARITH_TBLS];

+  unsigned char * ac_stats[NUM_ARITH_TBLS];

+

+  /* Statistics bin for coding with fixed probability 0.5 */

+  unsigned char fixed_bin[4];

+} arith_entropy_decoder;

+

+typedef arith_entropy_decoder * arith_entropy_ptr;

+

+/* The following two definitions specify the allocation chunk size

+ * for the statistics area.

+ * According to sections F.1.4.4.1.3 and F.1.4.4.2, we need at least

+ * 49 statistics bins for DC, and 245 statistics bins for AC coding.

+ *

+ * We use a compact representation with 1 byte per statistics bin,

+ * thus the numbers directly represent byte sizes.

+ * This 1 byte per statistics bin contains the meaning of the MPS

+ * (more probable symbol) in the highest bit (mask 0x80), and the

+ * index into the probability estimation state machine table

+ * in the lower bits (mask 0x7F).

+ */

+

+#define DC_STAT_BINS 64

+#define AC_STAT_BINS 256

+

+

+LOCAL(int)

+get_byte (j_decompress_ptr cinfo)

+/* Read next input byte; we do not support suspension in this module. */

+{

+  struct jpeg_source_mgr * src = cinfo->src;

+

+  if (src->bytes_in_buffer == 0)

+    if (! (*src->fill_input_buffer) (cinfo))

+      ERREXIT(cinfo, JERR_CANT_SUSPEND);

+  src->bytes_in_buffer--;

+  return GETJOCTET(*src->next_input_byte++);

+}

+

+

+/*

+ * The core arithmetic decoding routine (common in JPEG and JBIG).

+ * This needs to go as fast as possible.

+ * Machine-dependent optimization facilities

+ * are not utilized in this portable implementation.

+ * However, this code should be fairly efficient and

+ * may be a good base for further optimizations anyway.

+ *

+ * Return value is 0 or 1 (binary decision).

+ *

+ * Note: I've changed the handling of the code base & bit

+ * buffer register C compared to other implementations

+ * based on the standards layout & procedures.

+ * While it also contains both the actual base of the

+ * coding interval (16 bits) and the next-bits buffer,

+ * the cut-point between these two parts is floating

+ * (instead of fixed) with the bit shift counter CT.

+ * Thus, we also need only one (variable instead of

+ * fixed size) shift for the LPS/MPS decision, and

+ * we can get away with any renormalization update

+ * of C (except for new data insertion, of course).

+ *

+ * I've also introduced a new scheme for accessing

+ * the probability estimation state machine table,

+ * derived from Markus Kuhn's JBIG implementation.

+ */

+

+LOCAL(int)

+arith_decode (j_decompress_ptr cinfo, unsigned char *st)

+{

+  register arith_entropy_ptr e = (arith_entropy_ptr) cinfo->entropy;

+  register unsigned char nl, nm;

+  register INT32 qe, temp;

+  register int sv, data;

+

+  /* Renormalization & data input per section D.2.6 */

+  while (e->a < 0x8000L) {

+    if (--e->ct < 0) {

+      /* Need to fetch next data byte */

+      if (cinfo->unread_marker)

+	data = 0;		/* stuff zero data */

+      else {

+	data = get_byte(cinfo);	/* read next input byte */

+	if (data == 0xFF) {	/* zero stuff or marker code */

+	  do data = get_byte(cinfo);

+	  while (data == 0xFF);	/* swallow extra 0xFF bytes */

+	  if (data == 0)

+	    data = 0xFF;	/* discard stuffed zero byte */

+	  else {

+	    /* Note: Different from the Huffman decoder, hitting

+	     * a marker while processing the compressed data

+	     * segment is legal in arithmetic coding.

+	     * The convention is to supply zero data

+	     * then until decoding is complete.

+	     */

+	    cinfo->unread_marker = data;

+	    data = 0;

+	  }

+	}

+      }

+      e->c = (e->c << 8) | data; /* insert data into C register */

+      if ((e->ct += 8) < 0)	 /* update bit shift counter */

+	/* Need more initial bytes */

+	if (++e->ct == 0)

+	  /* Got 2 initial bytes -> re-init A and exit loop */

+	  e->a = 0x8000L; /* => e->a = 0x10000L after loop exit */

+    }

+    e->a <<= 1;

+  }

+

+  /* Fetch values from our compact representation of Table D.3(D.2):

+   * Qe values and probability estimation state machine

+   */

+  sv = *st;

+  qe = jpeg_aritab[sv & 0x7F];	/* => Qe_Value */

+  nl = qe & 0xFF; qe >>= 8;	/* Next_Index_LPS + Switch_MPS */

+  nm = qe & 0xFF; qe >>= 8;	/* Next_Index_MPS */

+

+  /* Decode & estimation procedures per sections D.2.4 & D.2.5 */

+  temp = e->a - qe;

+  e->a = temp;

+  temp <<= e->ct;

+  if (e->c >= temp) {

+    e->c -= temp;

+    /* Conditional LPS (less probable symbol) exchange */

+    if (e->a < qe) {

+      e->a = qe;

+      *st = (sv & 0x80) ^ nm;	/* Estimate_after_MPS */

+    } else {

+      e->a = qe;

+      *st = (sv & 0x80) ^ nl;	/* Estimate_after_LPS */

+      sv ^= 0x80;		/* Exchange LPS/MPS */

+    }

+  } else if (e->a < 0x8000L) {

+    /* Conditional MPS (more probable symbol) exchange */

+    if (e->a < qe) {

+      *st = (sv & 0x80) ^ nl;	/* Estimate_after_LPS */

+      sv ^= 0x80;		/* Exchange LPS/MPS */

+    } else {

+      *st = (sv & 0x80) ^ nm;	/* Estimate_after_MPS */

+    }

+  }

+

+  return sv >> 7;

+}

+

+

+/*

+ * Check for a restart marker & resynchronize decoder.

+ */

+

+LOCAL(void)

+process_restart (j_decompress_ptr cinfo)

+{

+  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;

+  int ci;

+  jpeg_component_info * compptr;

+

+  /* Advance past the RSTn marker */

+  if (! (*cinfo->marker->read_restart_marker) (cinfo))

+    ERREXIT(cinfo, JERR_CANT_SUSPEND);

+

+  /* Re-initialize statistics areas */

+  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

+    compptr = cinfo->cur_comp_info[ci];

+    if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) {

+      MEMZERO(entropy->dc_stats[compptr->dc_tbl_no], DC_STAT_BINS);

+      /* Reset DC predictions to 0 */

+      entropy->last_dc_val[ci] = 0;

+      entropy->dc_context[ci] = 0;

+    }

+    if ((! cinfo->progressive_mode && cinfo->lim_Se) ||

+	(cinfo->progressive_mode && cinfo->Ss)) {

+      MEMZERO(entropy->ac_stats[compptr->ac_tbl_no], AC_STAT_BINS);

+    }

+  }

+

+  /* Reset arithmetic decoding variables */

+  entropy->c = 0;

+  entropy->a = 0;

+  entropy->ct = -16;	/* force reading 2 initial bytes to fill C */

+

+  /* Reset restart counter */

+  entropy->restarts_to_go = cinfo->restart_interval;

+}

+

+

+/*

+ * Arithmetic MCU decoding.

+ * Each of these routines decodes and returns one MCU's worth of

+ * arithmetic-compressed coefficients.

+ * The coefficients are reordered from zigzag order into natural array order,

+ * but are not dequantized.

+ *

+ * The i'th block of the MCU is stored into the block pointed to by

+ * MCU_data[i].  WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.

+ */

+

+/*

+ * MCU decoding for DC initial scan (either spectral selection,

+ * or first pass of successive approximation).

+ */

+

+METHODDEF(boolean)

+decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

+{

+  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;

+  JBLOCKROW block;

+  unsigned char *st;

+  int blkn, ci, tbl, sign;

+  int v, m;

+

+  /* Process restart marker if needed */

+  if (cinfo->restart_interval) {

+    if (entropy->restarts_to_go == 0)

+      process_restart(cinfo);

+    entropy->restarts_to_go--;

+  }

+

+  if (entropy->ct == -1) return TRUE;	/* if error do nothing */

+

+  /* Outer loop handles each block in the MCU */

+

+  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {

+    block = MCU_data[blkn];

+    ci = cinfo->MCU_membership[blkn];

+    tbl = cinfo->cur_comp_info[ci]->dc_tbl_no;

+

+    /* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */

+

+    /* Table F.4: Point to statistics bin S0 for DC coefficient coding */

+    st = entropy->dc_stats[tbl] + entropy->dc_context[ci];

+

+    /* Figure F.19: Decode_DC_DIFF */

+    if (arith_decode(cinfo, st) == 0)

+      entropy->dc_context[ci] = 0;

+    else {

+      /* Figure F.21: Decoding nonzero value v */

+      /* Figure F.22: Decoding the sign of v */

+      sign = arith_decode(cinfo, st + 1);

+      st += 2; st += sign;

+      /* Figure F.23: Decoding the magnitude category of v */

+      if ((m = arith_decode(cinfo, st)) != 0) {

+	st = entropy->dc_stats[tbl] + 20;	/* Table F.4: X1 = 20 */

+	while (arith_decode(cinfo, st)) {

+	  if ((m <<= 1) == 0x8000) {

+	    WARNMS(cinfo, JWRN_ARITH_BAD_CODE);

+	    entropy->ct = -1;			/* magnitude overflow */

+	    return TRUE;

+	  }

+	  st += 1;

+	}

+      }

+      /* Section F.1.4.4.1.2: Establish dc_context conditioning category */

+      if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1))

+	entropy->dc_context[ci] = 0;		   /* zero diff category */

+      else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1))

+	entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */

+      else

+	entropy->dc_context[ci] = 4 + (sign * 4);  /* small diff category */

+      v = m;

+      /* Figure F.24: Decoding the magnitude bit pattern of v */

+      st += 14;

+      while (m >>= 1)

+	if (arith_decode(cinfo, st)) v |= m;

+      v += 1; if (sign) v = -v;

+      entropy->last_dc_val[ci] += v;

+    }

+

+    /* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */

+    (*block)[0] = (JCOEF) (entropy->last_dc_val[ci] << cinfo->Al);

+  }

+

+  return TRUE;

+}

+

+

+/*

+ * MCU decoding for AC initial scan (either spectral selection,

+ * or first pass of successive approximation).

+ */

+

+METHODDEF(boolean)

+decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

+{

+  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;

+  JBLOCKROW block;

+  unsigned char *st;

+  int tbl, sign, k;

+  int v, m;

+  const int * natural_order;

+

+  /* Process restart marker if needed */

+  if (cinfo->restart_interval) {

+    if (entropy->restarts_to_go == 0)

+      process_restart(cinfo);

+    entropy->restarts_to_go--;

+  }

+

+  if (entropy->ct == -1) return TRUE;	/* if error do nothing */

+

+  natural_order = cinfo->natural_order;

+

+  /* There is always only one block per MCU */

+  block = MCU_data[0];

+  tbl = cinfo->cur_comp_info[0]->ac_tbl_no;

+

+  /* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */

+

+  /* Figure F.20: Decode_AC_coefficients */

+  k = cinfo->Ss - 1;

+  do {

+    st = entropy->ac_stats[tbl] + 3 * k;

+    if (arith_decode(cinfo, st)) break;		/* EOB flag */

+    for (;;) {

+      k++;

+      if (arith_decode(cinfo, st + 1)) break;

+      st += 3;

+      if (k >= cinfo->Se) {

+	WARNMS(cinfo, JWRN_ARITH_BAD_CODE);

+	entropy->ct = -1;			/* spectral overflow */

+	return TRUE;

+      }

+    }

+    /* Figure F.21: Decoding nonzero value v */

+    /* Figure F.22: Decoding the sign of v */

+    sign = arith_decode(cinfo, entropy->fixed_bin);

+    st += 2;

+    /* Figure F.23: Decoding the magnitude category of v */

+    if ((m = arith_decode(cinfo, st)) != 0) {

+      if (arith_decode(cinfo, st)) {

+	m <<= 1;

+	st = entropy->ac_stats[tbl] +

+	     (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);

+	while (arith_decode(cinfo, st)) {

+	  if ((m <<= 1) == 0x8000) {

+	    WARNMS(cinfo, JWRN_ARITH_BAD_CODE);

+	    entropy->ct = -1;			/* magnitude overflow */

+	    return TRUE;

+	  }

+	  st += 1;

+	}

+      }

+    }

+    v = m;

+    /* Figure F.24: Decoding the magnitude bit pattern of v */

+    st += 14;

+    while (m >>= 1)

+      if (arith_decode(cinfo, st)) v |= m;

+    v += 1; if (sign) v = -v;

+    /* Scale and output coefficient in natural (dezigzagged) order */

+    (*block)[natural_order[k]] = (JCOEF) (v << cinfo->Al);

+  } while (k < cinfo->Se);

+

+  return TRUE;

+}

+

+

+/*

+ * MCU decoding for DC successive approximation refinement scan.

+ */

+

+METHODDEF(boolean)

+decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

+{

+  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;

+  unsigned char *st;

+  int p1, blkn;

+

+  /* Process restart marker if needed */

+  if (cinfo->restart_interval) {

+    if (entropy->restarts_to_go == 0)

+      process_restart(cinfo);

+    entropy->restarts_to_go--;

+  }

+

+  st = entropy->fixed_bin;	/* use fixed probability estimation */

+  p1 = 1 << cinfo->Al;		/* 1 in the bit position being coded */

+

+  /* Outer loop handles each block in the MCU */

+

+  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {

+    /* Encoded data is simply the next bit of the two's-complement DC value */

+    if (arith_decode(cinfo, st))

+      MCU_data[blkn][0][0] |= p1;

+  }

+

+  return TRUE;

+}

+

+

+/*

+ * MCU decoding for AC successive approximation refinement scan.

+ */

+

+METHODDEF(boolean)

+decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

+{

+  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;

+  JBLOCKROW block;

+  JCOEFPTR thiscoef;

+  unsigned char *st;

+  int tbl, k, kex;

+  int p1, m1;

+  const int * natural_order;

+

+  /* Process restart marker if needed */

+  if (cinfo->restart_interval) {

+    if (entropy->restarts_to_go == 0)

+      process_restart(cinfo);

+    entropy->restarts_to_go--;

+  }

+

+  if (entropy->ct == -1) return TRUE;	/* if error do nothing */

+

+  natural_order = cinfo->natural_order;

+

+  /* There is always only one block per MCU */

+  block = MCU_data[0];

+  tbl = cinfo->cur_comp_info[0]->ac_tbl_no;

+

+  p1 = 1 << cinfo->Al;		/* 1 in the bit position being coded */

+  m1 = (-1) << cinfo->Al;	/* -1 in the bit position being coded */

+

+  /* Establish EOBx (previous stage end-of-block) index */

+  kex = cinfo->Se;

+  do {

+    if ((*block)[natural_order[kex]]) break;

+  } while (--kex);

+

+  k = cinfo->Ss - 1;

+  do {

+    st = entropy->ac_stats[tbl] + 3 * k;

+    if (k >= kex)

+      if (arith_decode(cinfo, st)) break;	/* EOB flag */

+    for (;;) {

+      thiscoef = *block + natural_order[++k];

+      if (*thiscoef) {				/* previously nonzero coef */

+	if (arith_decode(cinfo, st + 2)) {

+	  if (*thiscoef < 0)

+	    *thiscoef += m1;

+	  else

+	    *thiscoef += p1;

+	}

+	break;

+      }

+      if (arith_decode(cinfo, st + 1)) {	/* newly nonzero coef */

+	if (arith_decode(cinfo, entropy->fixed_bin))

+	  *thiscoef = m1;

+	else

+	  *thiscoef = p1;

+	break;

+      }

+      st += 3;

+      if (k >= cinfo->Se) {

+	WARNMS(cinfo, JWRN_ARITH_BAD_CODE);

+	entropy->ct = -1;			/* spectral overflow */

+	return TRUE;

+      }

+    }

+  } while (k < cinfo->Se);

+

+  return TRUE;

+}

+

+

+/*

+ * Decode one MCU's worth of arithmetic-compressed coefficients.

+ */

+

+METHODDEF(boolean)

+decode_mcu (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

+{

+  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;

+  jpeg_component_info * compptr;

+  JBLOCKROW block;

+  unsigned char *st;

+  int blkn, ci, tbl, sign, k;

+  int v, m;

+  const int * natural_order;

+

+  /* Process restart marker if needed */

+  if (cinfo->restart_interval) {

+    if (entropy->restarts_to_go == 0)

+      process_restart(cinfo);

+    entropy->restarts_to_go--;

+  }

+

+  if (entropy->ct == -1) return TRUE;	/* if error do nothing */

+

+  natural_order = cinfo->natural_order;

+

+  /* Outer loop handles each block in the MCU */

+

+  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {

+    block = MCU_data[blkn];

+    ci = cinfo->MCU_membership[blkn];

+    compptr = cinfo->cur_comp_info[ci];

+

+    /* Sections F.2.4.1 & F.1.4.4.1: Decoding of DC coefficients */

+

+    tbl = compptr->dc_tbl_no;

+

+    /* Table F.4: Point to statistics bin S0 for DC coefficient coding */

+    st = entropy->dc_stats[tbl] + entropy->dc_context[ci];

+

+    /* Figure F.19: Decode_DC_DIFF */

+    if (arith_decode(cinfo, st) == 0)

+      entropy->dc_context[ci] = 0;

+    else {

+      /* Figure F.21: Decoding nonzero value v */

+      /* Figure F.22: Decoding the sign of v */

+      sign = arith_decode(cinfo, st + 1);

+      st += 2; st += sign;

+      /* Figure F.23: Decoding the magnitude category of v */

+      if ((m = arith_decode(cinfo, st)) != 0) {

+	st = entropy->dc_stats[tbl] + 20;	/* Table F.4: X1 = 20 */

+	while (arith_decode(cinfo, st)) {

+	  if ((m <<= 1) == 0x8000) {

+	    WARNMS(cinfo, JWRN_ARITH_BAD_CODE);

+	    entropy->ct = -1;			/* magnitude overflow */

+	    return TRUE;

+	  }

+	  st += 1;

+	}

+      }

+      /* Section F.1.4.4.1.2: Establish dc_context conditioning category */

+      if (m < (int) ((1L << cinfo->arith_dc_L[tbl]) >> 1))

+	entropy->dc_context[ci] = 0;		   /* zero diff category */

+      else if (m > (int) ((1L << cinfo->arith_dc_U[tbl]) >> 1))

+	entropy->dc_context[ci] = 12 + (sign * 4); /* large diff category */

+      else

+	entropy->dc_context[ci] = 4 + (sign * 4);  /* small diff category */

+      v = m;

+      /* Figure F.24: Decoding the magnitude bit pattern of v */

+      st += 14;

+      while (m >>= 1)

+	if (arith_decode(cinfo, st)) v |= m;

+      v += 1; if (sign) v = -v;

+      entropy->last_dc_val[ci] += v;

+    }

+

+    (*block)[0] = (JCOEF) entropy->last_dc_val[ci];

+

+    /* Sections F.2.4.2 & F.1.4.4.2: Decoding of AC coefficients */

+

+    if (cinfo->lim_Se == 0) continue;

+    tbl = compptr->ac_tbl_no;

+    k = 0;

+

+    /* Figure F.20: Decode_AC_coefficients */

+    do {

+      st = entropy->ac_stats[tbl] + 3 * k;

+      if (arith_decode(cinfo, st)) break;	/* EOB flag */

+      for (;;) {

+	k++;

+	if (arith_decode(cinfo, st + 1)) break;

+	st += 3;

+	if (k >= cinfo->lim_Se) {

+	  WARNMS(cinfo, JWRN_ARITH_BAD_CODE);

+	  entropy->ct = -1;			/* spectral overflow */

+	  return TRUE;

+	}

+      }

+      /* Figure F.21: Decoding nonzero value v */

+      /* Figure F.22: Decoding the sign of v */

+      sign = arith_decode(cinfo, entropy->fixed_bin);

+      st += 2;

+      /* Figure F.23: Decoding the magnitude category of v */

+      if ((m = arith_decode(cinfo, st)) != 0) {

+	if (arith_decode(cinfo, st)) {

+	  m <<= 1;

+	  st = entropy->ac_stats[tbl] +

+	       (k <= cinfo->arith_ac_K[tbl] ? 189 : 217);

+	  while (arith_decode(cinfo, st)) {

+	    if ((m <<= 1) == 0x8000) {

+	      WARNMS(cinfo, JWRN_ARITH_BAD_CODE);

+	      entropy->ct = -1;			/* magnitude overflow */

+	      return TRUE;

+	    }

+	    st += 1;

+	  }

+	}

+      }

+      v = m;

+      /* Figure F.24: Decoding the magnitude bit pattern of v */

+      st += 14;

+      while (m >>= 1)

+	if (arith_decode(cinfo, st)) v |= m;

+      v += 1; if (sign) v = -v;

+      (*block)[natural_order[k]] = (JCOEF) v;

+    } while (k < cinfo->lim_Se);

+  }

+

+  return TRUE;

+}

+

+

+/*

+ * Initialize for an arithmetic-compressed scan.

+ */

+

+METHODDEF(void)

+start_pass (j_decompress_ptr cinfo)

+{

+  arith_entropy_ptr entropy = (arith_entropy_ptr) cinfo->entropy;

+  int ci, tbl;

+  jpeg_component_info * compptr;

+

+  if (cinfo->progressive_mode) {

+    /* Validate progressive scan parameters */

+    if (cinfo->Ss == 0) {

+      if (cinfo->Se != 0)

+	goto bad;

+    } else {

+      /* need not check Ss/Se < 0 since they came from unsigned bytes */

+      if (cinfo->Se < cinfo->Ss || cinfo->Se > cinfo->lim_Se)

+	goto bad;

+      /* AC scans may have only one component */

+      if (cinfo->comps_in_scan != 1)

+	goto bad;

+    }

+    if (cinfo->Ah != 0) {

+      /* Successive approximation refinement scan: must have Al = Ah-1. */

+      if (cinfo->Ah-1 != cinfo->Al)

+	goto bad;

+    }

+    if (cinfo->Al > 13) {	/* need not check for < 0 */

+      bad:

+      ERREXIT4(cinfo, JERR_BAD_PROGRESSION,

+	       cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);

+    }

+    /* Update progression status, and verify that scan order is legal.

+     * Note that inter-scan inconsistencies are treated as warnings

+     * not fatal errors ... not clear if this is right way to behave.

+     */

+    for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

+      int coefi, cindex = cinfo->cur_comp_info[ci]->component_index;

+      int *coef_bit_ptr = & cinfo->coef_bits[cindex][0];

+      if (cinfo->Ss && coef_bit_ptr[0] < 0) /* AC without prior DC scan */

+	WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);

+      for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {

+	int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];

+	if (cinfo->Ah != expected)

+	  WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);

+	coef_bit_ptr[coefi] = cinfo->Al;

+      }

+    }

+    /* Select MCU decoding routine */

+    if (cinfo->Ah == 0) {

+      if (cinfo->Ss == 0)

+	entropy->pub.decode_mcu = decode_mcu_DC_first;

+      else

+	entropy->pub.decode_mcu = decode_mcu_AC_first;

+    } else {

+      if (cinfo->Ss == 0)

+	entropy->pub.decode_mcu = decode_mcu_DC_refine;

+      else

+	entropy->pub.decode_mcu = decode_mcu_AC_refine;

+    }

+  } else {

+    /* 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.

+     */

+    if (cinfo->Ss != 0 || cinfo->Ah != 0 || cinfo->Al != 0 ||

+	(cinfo->Se < DCTSIZE2 && cinfo->Se != cinfo->lim_Se))

+      WARNMS(cinfo, JWRN_NOT_SEQUENTIAL);

+    /* Select MCU decoding routine */

+    entropy->pub.decode_mcu = decode_mcu;

+  }

+

+  /* Allocate & initialize requested statistics areas */

+  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

+    compptr = cinfo->cur_comp_info[ci];

+    if (! cinfo->progressive_mode || (cinfo->Ss == 0 && cinfo->Ah == 0)) {

+      tbl = compptr->dc_tbl_no;

+      if (tbl < 0 || tbl >= NUM_ARITH_TBLS)

+	ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);

+      if (entropy->dc_stats[tbl] == NULL)

+	entropy->dc_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)

+	  ((j_common_ptr) cinfo, JPOOL_IMAGE, DC_STAT_BINS);

+      MEMZERO(entropy->dc_stats[tbl], DC_STAT_BINS);

+      /* Initialize DC predictions to 0 */

+      entropy->last_dc_val[ci] = 0;

+      entropy->dc_context[ci] = 0;

+    }

+    if ((! cinfo->progressive_mode && cinfo->lim_Se) ||

+	(cinfo->progressive_mode && cinfo->Ss)) {

+      tbl = compptr->ac_tbl_no;

+      if (tbl < 0 || tbl >= NUM_ARITH_TBLS)

+	ERREXIT1(cinfo, JERR_NO_ARITH_TABLE, tbl);

+      if (entropy->ac_stats[tbl] == NULL)

+	entropy->ac_stats[tbl] = (unsigned char *) (*cinfo->mem->alloc_small)

+	  ((j_common_ptr) cinfo, JPOOL_IMAGE, AC_STAT_BINS);

+      MEMZERO(entropy->ac_stats[tbl], AC_STAT_BINS);

+    }

+  }

+

+  /* Initialize arithmetic decoding variables */

+  entropy->c = 0;

+  entropy->a = 0;

+  entropy->ct = -16;	/* force reading 2 initial bytes to fill C */

+

+  /* Initialize restart counter */

+  entropy->restarts_to_go = cinfo->restart_interval;

+}

+

+

+/*

+ * Module initialization routine for arithmetic entropy decoding.

+ */

+

+GLOBAL(void)

+jinit_arith_decoder (j_decompress_ptr cinfo)

+{

+  arith_entropy_ptr entropy;

+  int i;

+

+  entropy = (arith_entropy_ptr)

+    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

+				SIZEOF(arith_entropy_decoder));

+  cinfo->entropy = &entropy->pub;

+  entropy->pub.start_pass = start_pass;

+

+  /* Mark tables unallocated */

+  for (i = 0; i < NUM_ARITH_TBLS; i++) {

+    entropy->dc_stats[i] = NULL;

+    entropy->ac_stats[i] = NULL;

+  }

+

+  /* Initialize index for fixed probability estimation */

+  entropy->fixed_bin[0] = 113;

+

+  if (cinfo->progressive_mode) {

+    /* Create progression status table */

+    int *coef_bit_ptr, ci;

+    cinfo->coef_bits = (int (*)[DCTSIZE2])

+      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

+				  cinfo->num_components*DCTSIZE2*SIZEOF(int));

+    coef_bit_ptr = & cinfo->coef_bits[0][0];

+    for (ci = 0; ci < cinfo->num_components; ci++) 

+      for (i = 0; i < DCTSIZE2; i++)

+	*coef_bit_ptr++ = -1;

+  }

+}