/*

 * jdphuff.c

 *

 * Copyright (C) 1995-1997, Thomas G. Lane.

 * This file is part of the Independent JPEG Group's software.

 * For conditions of distribution and use, see the accompanying README file.

 *

 * This file contains Huffman entropy decoding routines for progressive JPEG.

 *

 * Much of the complexity here has to do with supporting input suspension.

 * If the data source module demands suspension, we want to be able to back

 * up to the start of the current MCU.  To do this, we copy state variables

 * into local working storage, and update them back to the permanent

 * storage only upon successful completion of an MCU.

 */

#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

#include "jdhuff.h"		/* Declarations shared with jdhuff.c */

#ifdef D_PROGRESSIVE_SUPPORTED

/*

 * Expanded entropy decoder object for progressive 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 {

  unsigned int EOBRUN;			/* remaining EOBs in EOBRUN */

  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).EOBRUN = (src).EOBRUN, \

	 (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

#endif

typedef 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 * derived_tbls[NUM_HUFF_TBLS];

  d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */

} phuff_entropy_decoder;

typedef phuff_entropy_decoder * phuff_entropy_ptr;

/* Forward declarations */

METHODDEF(boolean) decode_mcu_DC_first JPP((j_decompress_ptr cinfo,

					    JBLOCKROW *MCU_data));

METHODDEF(boolean) decode_mcu_AC_first JPP((j_decompress_ptr cinfo,

					    JBLOCKROW *MCU_data));

METHODDEF(boolean) decode_mcu_DC_refine JPP((j_decompress_ptr cinfo,

					     JBLOCKROW *MCU_data));

METHODDEF(boolean) decode_mcu_AC_refine JPP((j_decompress_ptr cinfo,

					     JBLOCKROW *MCU_data));

/*

 * Initialize for a Huffman-compressed scan.

 */

METHODDEF(void)

start_pass_phuff_decoder (j_decompress_ptr cinfo)

{

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  boolean is_DC_band, bad;

  int ci, coefi, tbl;

  int *coef_bit_ptr;

  jpeg_component_info * compptr;

  is_DC_band = (cinfo->Ss == 0);

  /* Validate scan parameters */

  bad = FALSE;

  if (is_DC_band) {

    if (cinfo->Se != 0)

      bad = TRUE;

  } else {

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

    if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)

      bad = TRUE;

    /* AC scans may have only one component */

    if (cinfo->comps_in_scan != 1)

      bad = TRUE;

  }

  if (cinfo->Ah != 0) {

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

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

      bad = TRUE;

  }

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

    bad = TRUE;

  /* Arguably the maximum Al value should be less than 13 for 8-bit precision,

   * but the spec doesn't say so, and we try to be liberal about what we

   * accept.  Note: large Al values could result in out-of-range DC

   * coefficients during early scans, leading to bizarre displays due to

   * overflows in the IDCT math.  But we won't crash.

   */

  if (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 cindex = cinfo->cur_comp_info[ci]->component_index;

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

    if (!is_DC_band && 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 (is_DC_band)

      entropy->pub.decode_mcu = decode_mcu_DC_first;

    else

      entropy->pub.decode_mcu = decode_mcu_AC_first;

  } else {

    if (is_DC_band)

      entropy->pub.decode_mcu = decode_mcu_DC_refine;

    else

      entropy->pub.decode_mcu = decode_mcu_AC_refine;

  }

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

    compptr = cinfo->cur_comp_info[ci];

    /* Make sure requested tables are present, and compute derived tables.

     * We may build same derived table more than once, but it's not expensive.

     */

    if (is_DC_band) {

      if (cinfo->Ah == 0) {	/* DC refinement needs no table */

	tbl = compptr->dc_tbl_no;

	jpeg_make_d_derived_tbl(cinfo, TRUE, tbl,

				& entropy->derived_tbls[tbl]);

      }

    } else {

      tbl = compptr->ac_tbl_no;

      jpeg_make_d_derived_tbl(cinfo, FALSE, tbl,

			      & entropy->derived_tbls[tbl]);

      /* remember the single active table */

      entropy->ac_derived_tbl = entropy->derived_tbls[tbl];

    }

    /* 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->pub.insufficient_data = FALSE;

  /* Initialize private state variables */

  entropy->saved.EOBRUN = 0;

  /* Initialize restart counter */

  entropy->restarts_to_go = cinfo->restart_interval;

}

/*

 * Figure F.12: extend sign bit.

 * On some machines, a shift and add will be faster than a table lookup.

 */

#ifdef AVOID_TABLES

#define HUFF_EXTEND(x,s)  ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))

#else

#define HUFF_EXTEND(x,s)  ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))

static const int extend_test[16] =   /* entry n is 2**(n-1) */

  { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,

    0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };

static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */

  { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,

    ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1,

    ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1,

    ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };

#endif /* AVOID_TABLES */

/*

 * Check for a restart marker & resynchronize decoder.

 * Returns FALSE if must suspend.

 */

LOCAL(boolean)

process_restart (j_decompress_ptr cinfo)

{

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int ci;

  /* Throw away any unused bits remaining in bit buffer; */

  /* include any full bytes in next_marker's count of discarded bytes */

  cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;

  entropy->bitstate.bits_left = 0;

  /* Advance past the RSTn marker */

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

    return FALSE;

  /* Re-initialize DC predictions to 0 */

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

    entropy->saved.last_dc_val[ci] = 0;

  /* Re-init EOB run count, too */

  entropy->saved.EOBRUN = 0;

  /* Reset restart counter */

  entropy->restarts_to_go = cinfo->restart_interval;

  /* Reset out-of-data flag, unless read_restart_marker left us smack up

   * against a marker.  In that case we will end up treating the next data

   * segment as empty, and we can avoid producing bogus output pixels by

   * leaving the flag set.

   */

  if (cinfo->unread_marker == 0)

    entropy->pub.insufficient_data = FALSE;

  return TRUE;

}

/*

 * Huffman MCU decoding.

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

 * Huffman-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.

 *

 * We return FALSE if data source requested suspension.  In that case no

 * changes have been made to permanent state.  (Exception: some output

 * coefficients may already have been assigned.  This is harmless for

 * spectral selection, since we'll just re-assign them on the next call.

 * Successive approximation AC refinement has to be more careful, however.)

 */

/*

 * 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)

{   

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int Al = cinfo->Al;

  register int s, r;

  int blkn, ci;

  JBLOCKROW block;

  BITREAD_STATE_VARS;

  savable_state state;

  d_derived_tbl * tbl;

  jpeg_component_info * compptr;

  /* Process restart marker if needed; may have to suspend */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! process_restart(cinfo))

	return FALSE;

  }

  /* If we've run out of data, just leave the MCU set to zeroes.

   * This way, we return uniform gray for the remainder of the segment.

   */

  if (! entropy->pub.insufficient_data) {

    /* Load up working state */

    BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

    ASSIGN_STATE(state, entropy->saved);

    /* 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];

      tbl = entropy->derived_tbls[compptr->dc_tbl_no];

      /* Decode a single block's worth of coefficients */

      /* Section F.2.2.1: decode the DC coefficient difference */

      HUFF_DECODE(s, br_state, tbl, return FALSE, label1);

      if (s) {

	CHECK_BIT_BUFFER(br_state, s, return FALSE);

	r = GET_BITS(s);

	s = HUFF_EXTEND(r, s);

      }

      /* Convert DC difference to actual value, update last_dc_val */

      s += state.last_dc_val[ci];

      state.last_dc_val[ci] = s;

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

      (*block)[0] = (JCOEF) (s << Al);

    }

    /* Completed MCU, so update state */

    BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

    ASSIGN_STATE(entropy->saved, state);

  }

  /* Account for restart interval (no-op if not using restarts) */

  entropy->restarts_to_go--;

  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)

{   

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int Se = cinfo->Se;

  int Al = cinfo->Al;

  register int s, k, r;

  unsigned int EOBRUN;

  JBLOCKROW block;

  BITREAD_STATE_VARS;

  d_derived_tbl * tbl;

  /* Process restart marker if needed; may have to suspend */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! process_restart(cinfo))

	return FALSE;

  }

  /* If we've run out of data, just leave the MCU set to zeroes.

   * This way, we return uniform gray for the remainder of the segment.

   */

  if (! entropy->pub.insufficient_data) {

    /* Load up working state.

     * We can avoid loading/saving bitread state if in an EOB run.

     */

    EOBRUN = entropy->saved.EOBRUN;	/* only part of saved state we need */

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

    if (EOBRUN > 0)		/* if it's a band of zeroes... */

      EOBRUN--;			/* ...process it now (we do nothing) */

    else {

      BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

      block = MCU_data[0];

      tbl = entropy->ac_derived_tbl;

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

	HUFF_DECODE(s, br_state, tbl, return FALSE, label2);

	r = s >> 4;

	s &= 15;

	if (s) {

	  k += r;

	  CHECK_BIT_BUFFER(br_state, s, return FALSE);

	  r = GET_BITS(s);

	  s = HUFF_EXTEND(r, s);

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

	  (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);

	} else {

	  if (r == 15) {	/* ZRL */

	    k += 15;		/* skip 15 zeroes in band */

	  } else {		/* EOBr, run length is 2^r + appended bits */

	    EOBRUN = 1 << r;

	    if (r) {		/* EOBr, r > 0 */

	      CHECK_BIT_BUFFER(br_state, r, return FALSE);

	      r = GET_BITS(r);

	      EOBRUN += r;

	    }

	    EOBRUN--;		/* this band is processed at this moment */

	    break;		/* force end-of-band */

	  }

	}

      }

      BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

    }

    /* Completed MCU, so update state */

    entropy->saved.EOBRUN = EOBRUN;	/* only part of saved state we need */

  }

  /* Account for restart interval (no-op if not using restarts) */

  entropy->restarts_to_go--;

  return TRUE;

}

/*

 * MCU decoding for DC successive approximation refinement scan.

 * Note: we assume such scans can be multi-component, although the spec

 * is not very clear on the point.

 */

METHODDEF(boolean)

decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{   

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

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

  int blkn;

  JBLOCKROW block;

  BITREAD_STATE_VARS;

  /* Process restart marker if needed; may have to suspend */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! process_restart(cinfo))

	return FALSE;

  }

  /* Not worth the cycles to check insufficient_data here,

   * since we will not change the data anyway if we read zeroes.

   */

  /* Load up working state */

  BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

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

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

    block = MCU_data[blkn];

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

    CHECK_BIT_BUFFER(br_state, 1, return FALSE);

    if (GET_BITS(1))

      (*block)[0] |= p1;

    /* Note: since we use |=, repeating the assignment later is safe */

  }

  /* Completed MCU, so update state */

  BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

  /* Account for restart interval (no-op if not using restarts) */

  entropy->restarts_to_go--;

  return TRUE;

}

/*

 * MCU decoding for AC successive approximation refinement scan.

 */

METHODDEF(boolean)

decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{   

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int Se = cinfo->Se;

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

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

  register int s, k, r;

  unsigned int EOBRUN;

  JBLOCKROW block;

  JCOEFPTR thiscoef;

  BITREAD_STATE_VARS;

  d_derived_tbl * tbl;

  int num_newnz;

  int newnz_pos[DCTSIZE2];

  /* Process restart marker if needed; may have to suspend */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! process_restart(cinfo))

	return FALSE;

  }

  /* If we've run out of data, don't modify the MCU.

   */

  if (! entropy->pub.insufficient_data) {

    /* Load up working state */

    BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

    EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we need */

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

    block = MCU_data[0];

    tbl = entropy->ac_derived_tbl;

    /* If we are forced to suspend, we must undo the assignments to any newly

     * nonzero coefficients in the block, because otherwise we'd get confused

     * next time about which coefficients were already nonzero.

     * But we need not undo addition of bits to already-nonzero coefficients;

     * instead, we can test the current bit to see if we already did it.

     */

    num_newnz = 0;

    /* initialize coefficient loop counter to start of band */

    k = cinfo->Ss;

    if (EOBRUN == 0) {

      for (; k <= Se; k++) {

	HUFF_DECODE(s, br_state, tbl, goto undoit, label3);

	r = s >> 4;

	s &= 15;

	if (s) {

	  if (s != 1)		/* size of new coef should always be 1 */

	    WARNMS(cinfo, JWRN_HUFF_BAD_CODE);

	  CHECK_BIT_BUFFER(br_state, 1, goto undoit);

	  if (GET_BITS(1))

	    s = p1;		/* newly nonzero coef is positive */

	  else

	    s = m1;		/* newly nonzero coef is negative */

	} else {

	  if (r != 15) {

	    EOBRUN = 1 << r;	/* EOBr, run length is 2^r + appended bits */

	    if (r) {

	      CHECK_BIT_BUFFER(br_state, r, goto undoit);

	      r = GET_BITS(r);

	      EOBRUN += r;

	    }

	    break;		/* rest of block is handled by EOB logic */

	  }

	  /* note s = 0 for processing ZRL */

	}

	/* Advance over already-nonzero coefs and r still-zero coefs,

	 * appending correction bits to the nonzeroes.  A correction bit is 1

	 * if the absolute value of the coefficient must be increased.

	 */

	do {

	  thiscoef = *block + jpeg_natural_order[k];

	  if (*thiscoef != 0) {

	    CHECK_BIT_BUFFER(br_state, 1, goto undoit);

	    if (GET_BITS(1)) {

	      if ((*thiscoef & p1) == 0) { /* do nothing if already set it */

		if (*thiscoef >= 0)

		  *thiscoef += p1;

		else

		  *thiscoef += m1;

	      }

	    }

	  } else {

	    if (--r < 0)

	      break;		/* reached target zero coefficient */

	  }

	  k++;

	} while (k <= Se);

	if (s) {

	  int pos = jpeg_natural_order[k];

	  /* Output newly nonzero coefficient */

	  (*block)[pos] = (JCOEF) s;

	  /* Remember its position in case we have to suspend */

	  newnz_pos[num_newnz++] = pos;

	}

      }

    }

    if (EOBRUN > 0) {

      /* Scan any remaining coefficient positions after the end-of-band

       * (the last newly nonzero coefficient, if any).  Append a correction

       * bit to each already-nonzero coefficient.  A correction bit is 1

       * if the absolute value of the coefficient must be increased.

       */

      for (; k <= Se; k++) {

	thiscoef = *block + jpeg_natural_order[k];

	if (*thiscoef != 0) {

	  CHECK_BIT_BUFFER(br_state, 1, goto undoit);

	  if (GET_BITS(1)) {

	    if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */

	      if (*thiscoef >= 0)

		*thiscoef += p1;

	      else

		*thiscoef += m1;

	    }

	  }

	}

      }

      /* Count one block completed in EOB run */

      EOBRUN--;

    }

    /* Completed MCU, so update state */

    BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

    entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we need */

  }

  /* Account for restart interval (no-op if not using restarts) */

  entropy->restarts_to_go--;

  return TRUE;

undoit:

  /* Re-zero any output coefficients that we made newly nonzero */

  while (num_newnz > 0)

    (*block)[newnz_pos[--num_newnz]] = 0;

  return FALSE;

}

/*

 * Module initialization routine for progressive Huffman entropy decoding.

 */

GLOBAL(void)

jinit_phuff_decoder (j_decompress_ptr cinfo)

{

  phuff_entropy_ptr entropy;

  int *coef_bit_ptr;

  int ci, i;

  entropy = (phuff_entropy_ptr)

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

				SIZEOF(phuff_entropy_decoder));

  cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;

  entropy->pub.start_pass = start_pass_phuff_decoder;

  /* Mark derived tables unallocated */

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

    entropy->derived_tbls[i] = NULL;

  }

  /* Create progression status table */

  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;

}

#endif /* D_PROGRESSIVE_SUPPORTED */