//  * jdphuff.c
//  *
//  * Copyright (C) 1995, Thomas G. Lane.
//  * This file is part of the Independent JPEG Group's software.
//  * For conditions of distribution and use, see the accompanying README file.
//  *
//  * This file contains 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.



#ifdef _MSC_VER
    #pragma warning(push)
    #pragma warning(disable: 4127 4244)
#endif

#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;
  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;
	if (tbl < 0 || tbl >= NUM_HUFF_TBLS ||
	    cinfo->dc_huff_tbl_ptrs[tbl] == NULL)
	  ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
	jpeg_make_d_derived_tbl(cinfo, cinfo->dc_huff_tbl_ptrs[tbl],
				& entropy->derived_tbls[tbl]);
      }
    } else {
      tbl = compptr->ac_tbl_no;
      if (tbl < 0 || tbl >= NUM_HUFF_TBLS ||
          cinfo->ac_huff_tbl_ptrs[tbl] == NULL)
        ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);
      jpeg_make_d_derived_tbl(cinfo, cinfo->ac_huff_tbl_ptrs[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->bitstate.printed_eod = 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;

  // Next segment can get another out-of-data warning 
  entropy->bitstate.printed_eod = 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;
  }

  // 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 DC 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;
  }

//  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 care about 

  // 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 care about 

  // 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;
  }

  // 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;
  }

  // Load up working state 
  BITREAD_LOAD_STATE(cinfo,entropy->bitstate);
  EOBRUN = entropy->saved.EOBRUN; // only part of saved state we care about 

  // 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 position 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 changed 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 care about 

  // 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 

#ifdef _MSC_VER
    #pragma warning(pop)
#endif