//#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_dlhuff(jpeg_decompress cinfo)
{
jpeg_lossless_d_codec losslsd = (jpeg_lossless_d_codec)cinfo.coef;
lhuff_entropy_decoder entropy = (lhuff_entropy_decoder)losslsd.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);
}
// 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);
}
// Initialize for a Huffman-compressed scan.
static void start_pass_lhuff_decoder(jpeg_decompress cinfo)
{
jpeg_lossless_d_codec losslsd = (jpeg_lossless_d_codec)cinfo.coef;
lhuff_entropy_decoder entropy = (lhuff_entropy_decoder)losslsd.entropy_private;
for (int ci = 0; ci < cinfo.comps_in_scan; ci++)
{
jpeg_component_info compptr = cinfo.cur_comp_info[ci];
int dctbl = compptr.dc_tbl_no;
// Make sure requested tables are present
if (dctbl < 0 || dctbl >= NUM_HUFF_TBLS ||
cinfo.dc_huff_tbl_ptrs[dctbl] == null)
{
ERREXIT1(cinfo, J_MESSAGE_CODE.JERR_NO_HUFF_TABLE, dctbl);
}
// Compute derived values for Huffman tables
// We may do this more than once for a table, but it's not expensive
jpeg_make_d_derived_tbl(cinfo, true, dctbl, ref entropy.derived_tbls[dctbl]);
}
// Precalculate decoding info for each sample in an MCU of this scan
int ptrn = 0;
for (int sampn = 0; sampn < cinfo.blocks_in_MCU;)
{
jpeg_component_info compptr = cinfo.cur_comp_info[cinfo.MCU_membership[sampn]];
int ci = compptr.component_index;
for (int yoffset = 0; yoffset < compptr.MCU_height; yoffset++, ptrn++)
{
// Precalculate the setup info for each output pointer
entropy.output_ptr_info[ptrn].ci = ci;
entropy.output_ptr_info[ptrn].yoffset = yoffset;
entropy.output_ptr_info[ptrn].MCU_width = compptr.MCU_width;
for (int xoffset = 0; xoffset < compptr.MCU_width; xoffset++, sampn++)
{
// Precalculate the output pointer index for each sample
entropy.output_ptr_index[sampn] = ptrn;
// Precalculate which table to use for each sample
entropy.cur_tbls[sampn] = entropy.derived_tbls[compptr.dc_tbl_no];
}
}
}
entropy.num_output_ptrs = ptrn;
// Initialize bitread state variables
entropy.bitstate.bits_left = 0;
entropy.bitstate.get_buffer = 0; // unnecessary, but keeps Purify quiet
entropy.insufficient_data = false;
}
// Module initialization routine for lossless Huffman entropy decoding.
public static void jinit_lhuff_decoder(jpeg_decompress cinfo)
{
jpeg_lossless_d_codec losslsd = (jpeg_lossless_d_codec)cinfo.coef;
lhuff_entropy_decoder entropy = null;
try
{
entropy = new lhuff_entropy_decoder();
}
catch
{
ERREXIT1(cinfo, J_MESSAGE_CODE.JERR_OUT_OF_MEMORY, 4);
}
losslsd.entropy_private = entropy;
losslsd.entropy_start_pass = start_pass_lhuff_decoder;
losslsd.entropy_process_restart = process_restart_dlhuff;
losslsd.entropy_decode_mcus = decode_mcus_dlhuff;
// Mark tables unallocated
for (int i = 0; i < NUM_HUFF_TBLS; i++)
{
entropy.derived_tbls[i] = null;
}
}
// Decode and return nMCU's worth of Huffman-compressed differences.
// Each MCU is also disassembled and placed accordingly in diff_buf.
//
// MCU_col_num specifies the column of the first MCU being requested within
// the MCU-row. This tells us where to position the output row pointers in
// diff_buf.
//
// Returns the number of MCUs decoded. This may be less than nMCU if data
// source requested suspension. In that case no changes have been made to
// permanent state. (Exception: some output differences may already have
// been assigned. This is harmless for this module, since we'll just
// re-assign them on the next call.)
static uint decode_mcus_dlhuff(jpeg_decompress cinfo, int[][][] diff_buf, uint MCU_row_num, uint MCU_col_num, uint nMCU)
{
jpeg_lossless_d_codec losslsd = (jpeg_lossless_d_codec)cinfo.coef;
lhuff_entropy_decoder entropy = (lhuff_entropy_decoder)losslsd.entropy_private;
// Set output pointer locations based on MCU_col_num
for (int ptrn = 0; ptrn < entropy.num_output_ptrs; ptrn++)
{
int ci = entropy.output_ptr_info[ptrn].ci;
int yoffset = entropy.output_ptr_info[ptrn].yoffset;
int MCU_width = entropy.output_ptr_info[ptrn].MCU_width;
entropy.output_ptr[ptrn] = diff_buf[ci][MCU_row_num + yoffset];
entropy.output_ptr_ind[ptrn] = (int)(MCU_col_num * MCU_width);
}
// If we've run out of data, zero out the buffers and return.
// By resetting the undifferencer, the output samples will be CENTERJSAMPLE.
//
// NB: We should find a way to do this without interacting with the
// undifferencer module directly.
if (entropy.insufficient_data)
{
for (int ptrn = 0; ptrn < entropy.num_output_ptrs; ptrn++)
{
for (int i = 0; i < nMCU * entropy.output_ptr_info[ptrn].MCU_width; i++)
{
entropy.output_ptr[ptrn][entropy.output_ptr_ind[ptrn] + i] = 0;
}
}
losslsd.predict_process_restart(cinfo);
}
else
{
// 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 the number of MCU requested
for (uint mcu_num = 0; mcu_num < nMCU; mcu_num++)
{
// Inner loop handles the samples in the MCU
for (int sampn = 0; sampn < cinfo.blocks_in_MCU; sampn++)
{
d_derived_tbl dctbl = entropy.cur_tbls[sampn];
int s = 0, r;
// Section H.2.2: decode the sample difference
//was HUFF_DECODE(s, br_state, dctbl, return mcu_num, 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(mcu_num);
}
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, dctbl, nb)) < 0)
{
return(mcu_num);
}
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 = dctbl.look_nbits[look]) != 0)
{
//was DROP_BITS(nb);
bits_left -= nb;
s = dctbl.look_sym[look];
}
else
{
nb = HUFF_LOOKAHEAD + 1;
if ((s = jpeg_huff_decode(ref br_state, get_buffer, bits_left, dctbl, nb)) < 0)
{
return(mcu_num);
}
get_buffer = br_state.get_buffer;
bits_left = br_state.bits_left;
}
}
}
if (s != 0)
{
if (s == 16)
{
s = 32768; // special case: always output 32768
}
else
{ // normal case: fetch subsequent bits
//was CHECK_BIT_BUFFER(br_state, s, return mcu_num);
if (bits_left < s)
{
if (!jpeg_fill_bit_buffer(ref br_state, get_buffer, bits_left, s))
{
return(mcu_num);
}
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);
}
}
// Output the sample difference
int ind = entropy.output_ptr_index[sampn];
entropy.output_ptr[ind][entropy.output_ptr_ind[ind]++] = (int)s;
}
// 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;
}
}
return(nMCU);
}
