// Module initialization routine for progressive Huffman entropy decoding.
public static void jinit_phuff_decoder(jpeg_decompress cinfo)
{
jpeg_lossy_d_codec lossyd = (jpeg_lossy_d_codec)cinfo.coef;
phuff_entropy_decoder entropy = null;
try
{
entropy = new phuff_entropy_decoder();
entropy.saved.last_dc_val = new int[MAX_COMPS_IN_SCAN];
}
catch
{
ERREXIT1(cinfo, J_MESSAGE_CODE.JERR_OUT_OF_MEMORY, 4);
}
lossyd.entropy_private = entropy;
lossyd.entropy_start_pass = start_pass_phuff_decoder;
// Mark derived tables unallocated
for (int i = 0; i < NUM_HUFF_TBLS; i++)
{
entropy.derived_tbls[i] = null;
}
try
{
// Create progression status table
cinfo.coef_bits = new int[cinfo.num_components][];
for (int ci = 0; ci < cinfo.num_components; ci++)
{
int[] coef_bit_ptr = cinfo.coef_bits[ci] = new int[DCTSIZE2];
for (int i = 0; i < DCTSIZE2; i++)
{
coef_bit_ptr[i] = -1;
}
}
}
catch
{
ERREXIT1(cinfo, J_MESSAGE_CODE.JERR_OUT_OF_MEMORY, 4);
}
}
//#define HUFF_EXTEND(x,s) ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))
// Check for a restart marker & resynchronize decoder.
// Returns false if must suspend.
static bool process_restart_dphuff(jpeg_decompress cinfo)
{
jpeg_lossy_d_codec lossyd = (jpeg_lossy_d_codec)cinfo.coef;
phuff_entropy_decoder entropy = (phuff_entropy_decoder)lossyd.entropy_private;
// 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 += (uint)(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 (int 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.insufficient_data = false;
}
return(true);
}
// Module initialization routine for progressive Huffman entropy decoding.
public static void jinit_phuff_decoder(jpeg_decompress cinfo)
{
jpeg_lossy_d_codec lossyd=(jpeg_lossy_d_codec)cinfo.coef;
phuff_entropy_decoder entropy=null;
try
{
entropy=new phuff_entropy_decoder();
entropy.saved.last_dc_val=new int[MAX_COMPS_IN_SCAN];
}
catch
{
ERREXIT1(cinfo, J_MESSAGE_CODE.JERR_OUT_OF_MEMORY, 4);
}
lossyd.entropy_private=entropy;
lossyd.entropy_start_pass=start_pass_phuff_decoder;
// Mark derived tables unallocated
for(int i=0; i<NUM_HUFF_TBLS; i++) entropy.derived_tbls[i]=null;
try
{
// Create progression status table
cinfo.coef_bits=new int[cinfo.num_components][];
for(int ci=0; ci<cinfo.num_components; ci++)
{
int[] coef_bit_ptr=cinfo.coef_bits[ci]=new int[DCTSIZE2];
for(int i=0; i<DCTSIZE2; i++) coef_bit_ptr[i]=-1;
}
}
catch
{
ERREXIT1(cinfo, J_MESSAGE_CODE.JERR_OUT_OF_MEMORY, 4);
}
}
// MCU decoding for AC successive approximation refinement scan.
static bool decode_mcu_AC_refine(jpeg_decompress cinfo, short[][] MCU_data)
{
jpeg_lossy_d_codec lossyd = (jpeg_lossy_d_codec)cinfo.coef;
phuff_entropy_decoder entropy = (phuff_entropy_decoder)lossyd.entropy_private;
int Se = cinfo.Se;
short p1 = (short)(1 << cinfo.Al); // 1 in the bit position being coded
short m1 = (short)((-1) << cinfo.Al); // -1 in the bit position being coded
short[] block = null;
// 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.
int num_newnz = 0;
int[] newnz_pos = new int[DCTSIZE2];
// Process restart marker if needed; may have to suspend
if (cinfo.restart_interval != 0)
{
if (entropy.restarts_to_go == 0)
{
if (!process_restart_dphuff(cinfo))
{
return(false);
}
}
}
// If we've run out of data, don't modify the MCU.
if (!entropy.insufficient_data)
{
// Load up working state
//was BITREAD_STATE_VARS;
bitread_working_state br_state = new bitread_working_state();
//was BITREAD_LOAD_STATE(cinfo, entropy.bitstate);
br_state.cinfo = cinfo;
br_state.input_bytes = cinfo.src.input_bytes;
br_state.next_input_byte = cinfo.src.next_input_byte;
br_state.bytes_in_buffer = cinfo.src.bytes_in_buffer;
ulong get_buffer = entropy.bitstate.get_buffer;
int bits_left = entropy.bitstate.bits_left;
uint EOBRUN = entropy.saved.EOBRUN; // only part of saved state we need
// There is always only one block per MCU
block = MCU_data[0];
d_derived_tbl tbl = entropy.ac_derived_tbl;
// initialize coefficient loop counter to start of band
int k = cinfo.Ss;
if (EOBRUN == 0)
{
for (; k <= Se; k++)
{
int s = 0, r;
//was HUFF_DECODE(s, br_state, tbl, goto undoit, label3);
{
int nb, look;
bool label = false;
if (bits_left < HUFF_LOOKAHEAD)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, 0))
{
goto undoit;
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
if (bits_left < HUFF_LOOKAHEAD)
{
nb = 1;
label = true;
if ((s = jpeg_huff_decode(ref br_state, get_buffer, bits_left, tbl, nb)) < 0)
{
goto undoit;
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
}
}
if (!label)
{
//was look=PEEK_BITS(HUFF_LOOKAHEAD);
look = ((int)(get_buffer >> (bits_left - HUFF_LOOKAHEAD))) & ((1 << HUFF_LOOKAHEAD) - 1);
if ((nb = tbl.look_nbits[look]) != 0)
{
//was DROP_BITS(nb);
bits_left -= nb;
s = tbl.look_sym[look];
}
else
{
nb = HUFF_LOOKAHEAD + 1;
if ((s = jpeg_huff_decode(ref br_state, get_buffer, bits_left, tbl, nb)) < 0)
{
goto undoit;
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
}
}
}
r = s >> 4;
s &= 15;
if (s != 0)
{
if (s != 1)
{
WARNMS(cinfo, J_MESSAGE_CODE.JWRN_HUFF_BAD_CODE); // size of new coef should always be 1
}
//was CHECK_BIT_BUFFER(br_state, 1, goto undoit);
if (bits_left < 1)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, 1))
{
goto undoit;
}
get_buffer = br_state.get_buffer; bits_left = br_state.bits_left;
}
//was if (GET_BITS(1))
if ((((int)(get_buffer >> (bits_left -= 1))) & 1) != 0)
{
s = p1; // newly nonzero coef is positive
}
else
{
s = m1; // newly nonzero coef is negative
}
}
else
{
if (r != 15)
{
EOBRUN = (uint)(1 << r); // EOBr, run length is 2^r + appended bits
if (r != 0)
{
//was CHECK_BIT_BUFFER(br_state, r, goto undoit);
if (bits_left < r)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, r))
{
goto undoit;
}
get_buffer = br_state.get_buffer; bits_left = br_state.bits_left;
}
//was r = GET_BITS(r);
r = ((int)(get_buffer >> (bits_left -= r))) & ((1 << r) - 1);
EOBRUN += (uint)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
{
int thiscoef = jpeg_natural_order[k];
if (block[thiscoef] != 0)
{
//was CHECK_BIT_BUFFER(br_state, 1, goto undoit);
if (bits_left < 1)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, 1))
{
goto undoit;
}
get_buffer = br_state.get_buffer; bits_left = br_state.bits_left;
}
//was if (GET_BITS(1))
if ((((int)(get_buffer >> (bits_left -= 1))) & 1) != 0)
{
if ((block[thiscoef] & p1) == 0)
{ // do nothing if already set it
if (block[thiscoef] >= 0)
{
block[thiscoef] += p1;
}
else
{
block[thiscoef] += m1;
}
}
}
}
else
{
if (--r < 0)
{
break; // reached target zero coefficient
}
}
k++;
} while(k <= Se);
if (s != 0)
{
int pos = jpeg_natural_order[k];
// Output newly nonzero coefficient
block[pos] = (short)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++)
{
int thiscoef = jpeg_natural_order[k];
if (block[thiscoef] != 0)
{
//was CHECK_BIT_BUFFER(br_state, 1, goto undoit);
if (bits_left < 1)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, 1))
{
goto undoit;
}
get_buffer = br_state.get_buffer; bits_left = br_state.bits_left;
}
//was if (GET_BITS(1))
if ((((int)(get_buffer >> (bits_left -= 1))) & 1) != 0)
{
if ((block[thiscoef] & p1) == 0)
{ // do nothing if already changed it
if (block[thiscoef] >= 0)
{
block[thiscoef] += p1;
}
else
{
block[thiscoef] += m1;
}
}
}
}
}
// Count one block completed in EOB run
EOBRUN--;
}
// Completed MCU, so update state
//was BITREAD_SAVE_STATE(cinfo, entropy.bitstate);
cinfo.src.input_bytes = br_state.input_bytes;
cinfo.src.next_input_byte = br_state.next_input_byte;
cinfo.src.bytes_in_buffer = br_state.bytes_in_buffer;
entropy.bitstate.get_buffer = get_buffer;
entropy.bitstate.bits_left = bits_left;
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);
}
// 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.
static bool decode_mcu_DC_refine(jpeg_decompress cinfo, short[][] MCU_data)
{
jpeg_lossy_d_codec lossyd = (jpeg_lossy_d_codec)cinfo.coef;
phuff_entropy_decoder entropy = (phuff_entropy_decoder)lossyd.entropy_private;
short p1 = (short)(1 << cinfo.Al); // 1 in the bit position being coded
// Process restart marker if needed; may have to suspend
if (cinfo.restart_interval != 0)
{
if (entropy.restarts_to_go == 0)
{
if (!process_restart_dphuff(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
//was BITREAD_STATE_VARS;
bitread_working_state br_state = new bitread_working_state();
//was BITREAD_LOAD_STATE(cinfo, entropy.bitstate);
br_state.cinfo = cinfo;
br_state.input_bytes = cinfo.src.input_bytes;
br_state.next_input_byte = cinfo.src.next_input_byte;
br_state.bytes_in_buffer = cinfo.src.bytes_in_buffer;
ulong get_buffer = entropy.bitstate.get_buffer;
int bits_left = entropy.bitstate.bits_left;
// Outer loop handles each block in the MCU
for (int blkn = 0; blkn < cinfo.blocks_in_MCU; blkn++)
{
short[] block = MCU_data[blkn];
// Encoded data is simply the next bit of the two's-complement DC value
//was CHECK_BIT_BUFFER(br_state, 1, return false);
if (bits_left < 1)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, 1))
{
return(false);
}
get_buffer = br_state.get_buffer; bits_left = br_state.bits_left;
}
//was if(GET_BITS(1))
if ((((int)(get_buffer >> (bits_left -= 1))) & 1) != 0)
{
block[0] |= p1;
}
// Note: since we use |=, repeating the assignment later is safe
}
// Completed MCU, so update state
//was BITREAD_SAVE_STATE(cinfo, entropy.bitstate);
cinfo.src.input_bytes = br_state.input_bytes;
cinfo.src.next_input_byte = br_state.next_input_byte;
cinfo.src.bytes_in_buffer = br_state.bytes_in_buffer;
entropy.bitstate.get_buffer = get_buffer;
entropy.bitstate.bits_left = bits_left;
// Account for restart interval (no-op if not using restarts)
entropy.restarts_to_go--;
return(true);
}
// Initialize for a Huffman-compressed scan.
static void start_pass_phuff_decoder(jpeg_decompress cinfo)
{
jpeg_lossy_d_codec lossyd = (jpeg_lossy_d_codec)cinfo.coef;
phuff_entropy_decoder entropy = (phuff_entropy_decoder)lossyd.entropy_private;
bool is_DC_band = (cinfo.Ss == 0);
// Validate scan parameters
bool 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;
}
}
// 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 (cinfo.Al > 13)
{
bad = true; // need not check for < 0
}
if (bad)
{
ERREXIT4(cinfo, J_MESSAGE_CODE.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 (int ci = 0; ci < cinfo.comps_in_scan; ci++)
{
int cindex = cinfo.cur_comp_info[ci].component_index;
int[] coef_bit_ptr = cinfo.coef_bits[cindex];
if (!is_DC_band && coef_bit_ptr[0] < 0)
{
WARNMS2(cinfo, J_MESSAGE_CODE.JWRN_BOGUS_PROGRESSION, cindex, 0); // AC without prior DC scan
}
for (int 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, J_MESSAGE_CODE.JWRN_BOGUS_PROGRESSION, cindex, coefi);
}
coef_bit_ptr[coefi] = cinfo.Al;
}
}
// Select MCU decoding routine
if (cinfo.Ah == 0)
{
if (is_DC_band)
{
lossyd.entropy_decode_mcu = decode_mcu_DC_first;
}
else
{
lossyd.entropy_decode_mcu = decode_mcu_AC_first;
}
}
else
{
if (is_DC_band)
{
lossyd.entropy_decode_mcu = decode_mcu_DC_refine;
}
else
{
lossyd.entropy_decode_mcu = decode_mcu_AC_refine;
}
}
for (int ci = 0; ci < cinfo.comps_in_scan; ci++)
{
jpeg_component_info 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
int tbl = compptr.dc_tbl_no;
jpeg_make_d_derived_tbl(cinfo, true, tbl, ref entropy.derived_tbls[tbl]);
}
}
else
{
int tbl = compptr.ac_tbl_no;
jpeg_make_d_derived_tbl(cinfo, false, tbl, ref 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.insufficient_data = false;
// Initialize private state variables
entropy.saved.EOBRUN = 0;
// Initialize restart counter
entropy.restarts_to_go = cinfo.restart_interval;
}
// MCU decoding for AC initial scan (either spectral selection,
// or first pass of successive approximation).
static bool decode_mcu_AC_first(jpeg_decompress cinfo, short[][] MCU_data)
{
jpeg_lossy_d_codec lossyd = (jpeg_lossy_d_codec)cinfo.coef;
phuff_entropy_decoder entropy = (phuff_entropy_decoder)lossyd.entropy_private;
int Se = cinfo.Se;
int Al = cinfo.Al;
// Process restart marker if needed; may have to suspend
if (cinfo.restart_interval != 0)
{
if (entropy.restarts_to_go == 0)
{
if (!process_restart_dphuff(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.insufficient_data)
{
// Load up working state.
// We can avoid loading/saving bitread state if in an EOB run.
uint EOBRUN = entropy.saved.EOBRUN; // only part of saved state we need
// There is always only one block per MCU
if (EOBRUN > 0)
{
EOBRUN--; // if it's a band of zeroes... ...process it now (we do nothing)
}
else
{
//was BITREAD_STATE_VARS;
bitread_working_state br_state = new bitread_working_state();
//was BITREAD_LOAD_STATE(cinfo, entropy.bitstate);
br_state.cinfo = cinfo;
br_state.input_bytes = cinfo.src.input_bytes;
br_state.next_input_byte = cinfo.src.next_input_byte;
br_state.bytes_in_buffer = cinfo.src.bytes_in_buffer;
ulong get_buffer = entropy.bitstate.get_buffer;
int bits_left = entropy.bitstate.bits_left;
short[] block = MCU_data[0];
d_derived_tbl tbl = entropy.ac_derived_tbl;
for (int k = cinfo.Ss; k <= Se; k++)
{
int s = 0, r;
//was HUFF_DECODE(s, br_state, tbl, return false, label2);
{
int nb, look;
bool label = false;
if (bits_left < HUFF_LOOKAHEAD)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, 0))
{
return(false);
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
if (bits_left < HUFF_LOOKAHEAD)
{
nb = 1;
label = true;
if ((s = jpeg_huff_decode(ref br_state, get_buffer, bits_left, tbl, nb)) < 0)
{
return(false);
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
}
}
if (!label)
{
//was look=PEEK_BITS(HUFF_LOOKAHEAD);
look = ((int)(get_buffer >> (bits_left - HUFF_LOOKAHEAD))) & ((1 << HUFF_LOOKAHEAD) - 1);
if ((nb = tbl.look_nbits[look]) != 0)
{
//was DROP_BITS(nb);
bits_left -= nb;
s = tbl.look_sym[look];
}
else
{
nb = HUFF_LOOKAHEAD + 1;
if ((s = jpeg_huff_decode(ref br_state, get_buffer, bits_left, tbl, nb)) < 0)
{
return(false);
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
}
}
}
r = s >> 4;
s &= 15;
if (s != 0)
{
k += r;
//was CHECK_BIT_BUFFER(br_state, s, return false);
if (bits_left < s)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, s))
{
return(false);
}
get_buffer = br_state.get_buffer; bits_left = br_state.bits_left;
}
//was r = GET_BITS(s);
r = ((int)(get_buffer >> (bits_left -= s))) & ((1 << s) - 1);
//was s=HUFF_EXTEND(r, s);
s = (r < (1 << (s - 1))?r + (((-1) << s) + 1):r);
// Scale and output coefficient in natural (dezigzagged) order
block[jpeg_natural_order[k]] = (short)(s << Al);
}
else
{
if (r == 15)
{ // ZRL
k += 15; // skip 15 zeroes in band
}
else
{ // EOBr, run length is 2^r + appended bits
EOBRUN = (uint)(1 << r);
if (r != 0)
{ // EOBr, r > 0
//was CHECK_BIT_BUFFER(br_state, r, return false);
if (bits_left < r)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, r))
{
return(false);
}
get_buffer = br_state.get_buffer; bits_left = br_state.bits_left;
}
//was r = GET_BITS(r);
r = ((int)(get_buffer >> (bits_left -= r))) & ((1 << r) - 1);
EOBRUN += (uint)r;
}
EOBRUN--; // this band is processed at this moment
break; // force end-of-band
}
}
}
//was BITREAD_SAVE_STATE(cinfo, entropy.bitstate);
cinfo.src.input_bytes = br_state.input_bytes;
cinfo.src.next_input_byte = br_state.next_input_byte;
cinfo.src.bytes_in_buffer = br_state.bytes_in_buffer;
entropy.bitstate.get_buffer = get_buffer;
entropy.bitstate.bits_left = bits_left;
}
// 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);
}
// 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).
static bool decode_mcu_DC_first(jpeg_decompress cinfo, short[][] MCU_data)
{
jpeg_lossy_d_codec lossyd = (jpeg_lossy_d_codec)cinfo.coef;
phuff_entropy_decoder entropy = (phuff_entropy_decoder)lossyd.entropy_private;
int Al = cinfo.Al;
// Process restart marker if needed; may have to suspend
if (cinfo.restart_interval != 0)
{
if (entropy.restarts_to_go == 0)
{
if (!process_restart_dphuff(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.insufficient_data)
{
// Load up working state
//was BITREAD_STATE_VARS;
bitread_working_state br_state = new bitread_working_state();
savable_state state;
state.last_dc_val = new int[MAX_COMPS_IN_SCAN];
//was BITREAD_LOAD_STATE(cinfo, entropy.bitstate);
br_state.cinfo = cinfo;
br_state.input_bytes = cinfo.src.input_bytes;
br_state.next_input_byte = cinfo.src.next_input_byte;
br_state.bytes_in_buffer = cinfo.src.bytes_in_buffer;
ulong get_buffer = entropy.bitstate.get_buffer;
int bits_left = entropy.bitstate.bits_left;
//was state=entropy.saved;
state.EOBRUN = entropy.saved.EOBRUN;
entropy.saved.last_dc_val.CopyTo(state.last_dc_val, 0);
// Outer loop handles each block in the MCU
for (int blkn = 0; blkn < cinfo.blocks_in_MCU; blkn++)
{
short[] block = MCU_data[blkn];
int ci = cinfo.MCU_membership[blkn];
jpeg_component_info compptr = cinfo.cur_comp_info[ci];
d_derived_tbl tbl = entropy.derived_tbls[compptr.dc_tbl_no];
int s = 0;
// Decode a single block's worth of coefficients
// Section F.2.2.1: decode the DC coefficient difference
//was HUFF_DECODE(s, br_state, tbl, return false, label1);
{
int nb, look;
bool label = false;
if (bits_left < HUFF_LOOKAHEAD)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, 0))
{
return(false);
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
if (bits_left < HUFF_LOOKAHEAD)
{
nb = 1;
label = true;
if ((s = jpeg_huff_decode(ref br_state, get_buffer, bits_left, tbl, nb)) < 0)
{
return(false);
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
}
}
if (!label)
{
//was look=PEEK_BITS(HUFF_LOOKAHEAD);
look = ((int)(get_buffer >> (bits_left - HUFF_LOOKAHEAD))) & ((1 << HUFF_LOOKAHEAD) - 1);
if ((nb = tbl.look_nbits[look]) != 0)
{
//was DROP_BITS(nb);
bits_left -= nb;
s = tbl.look_sym[look];
}
else
{
nb = HUFF_LOOKAHEAD + 1;
if ((s = jpeg_huff_decode(ref br_state, get_buffer, bits_left, tbl, nb)) < 0)
{
return(false);
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
}
}
}
if (s != 0)
{
//was CHECK_BIT_BUFFER(br_state, s, return false);
if (bits_left < s)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, s))
{
return(false);
}
get_buffer = br_state.get_buffer; bits_left = br_state.bits_left;
}
//was r = GET_BITS(s);
int r = ((int)(get_buffer >> (bits_left -= s))) & ((1 << s) - 1);
//was s=HUFF_EXTEND(r, s);
s = (r < (1 << (s - 1))?r + (((-1) << s) + 1):r);
}
// 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] = (short)(s << Al);
}
// Completed MCU, so update state
//was BITREAD_SAVE_STATE(cinfo, entropy.bitstate);
cinfo.src.input_bytes = br_state.input_bytes;
cinfo.src.next_input_byte = br_state.next_input_byte;
cinfo.src.bytes_in_buffer = br_state.bytes_in_buffer;
entropy.bitstate.get_buffer = get_buffer;
entropy.bitstate.bits_left = bits_left;
//was entropy.saved=state;
entropy.saved.EOBRUN = state.EOBRUN;
state.last_dc_val.CopyTo(entropy.saved.last_dc_val, 0);
}
// Account for restart interval (no-op if not using restarts)
entropy.restarts_to_go--;
return(true);
}
