jdmarker.pas

DELPHI版的JPEG文件解码源程序

  next_input_byte := datasrc^.next_input_byte;
  bytes_in_buffer := datasrc^.bytes_in_buffer;

{ Read two bytes interpreted as an unsigned 16-bit integer.
  length should be declared unsigned int or perhaps INT32. }

{ make a byte available.
  Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
  but we must reload the local copies after a successful fill. }
  if (bytes_in_buffer = 0) then
  begin
    if (not datasrc^.fill_input_buffer(cinfo)) then
    begin
      get_dac := FALSE;
      exit;
    end;
    { Reload the local copies }
    next_input_byte := datasrc^.next_input_byte;
    bytes_in_buffer := datasrc^.bytes_in_buffer;
  end;
  Dec( bytes_in_buffer );

  length := (uint( GETJOCTET(next_input_byte^)) shl 8);
  Inc( next_input_byte );
  { make a byte available.
    Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
    but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dac := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

  Inc( length, GETJOCTET( next_input_byte^));
  Inc( next_input_byte );

  Dec(length,  2);

  while (length > 0) do
  begin
    { Read a byte into variable index. If must suspend, return FALSE. }
    { make a byte available.
      Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
      but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dac := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

    index := GETJOCTET(next_input_byte^);
    Inc(next_input_byte);

    { Read a byte into variable val. If must suspend, return FALSE. }
    { make a byte available.
      Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
      but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dac := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

    val := GETJOCTET(next_input_byte^);
    Inc(next_input_byte);

    Dec( length, 2);

    {$IFDEF DEBUG}
    TRACEMS2(j_common_ptr(cinfo), 1, JTRC_DAC, index, val);
    {$ENDIF}

    if (index < 0) or (index >= (2*NUM_ARITH_TBLS)) then
      ERREXIT1(j_common_ptr(cinfo) , JERR_DAC_INDEX, index);

    if (index >= NUM_ARITH_TBLS) then
    begin { define AC table }
      cinfo^.arith_ac_K[index-NUM_ARITH_TBLS] := UINT8(val);
    end
    else
    begin { define DC table }
      cinfo^.arith_dc_L[index] := UINT8(val and $0F);
      cinfo^.arith_dc_U[index] := UINT8(val shr 4);
      if (cinfo^.arith_dc_L[index] > cinfo^.arith_dc_U[index]) then
	ERREXIT1(j_common_ptr(cinfo) , JERR_DAC_VALUE, val);
    end;
  end;

  if (length <> 0) then
    ERREXIT(j_common_ptr(cinfo), JERR_BAD_LENGTH);

  { Unload the local copies --- do this only at a restart boundary }
  datasrc^.next_input_byte := next_input_byte;
  datasrc^.bytes_in_buffer := bytes_in_buffer;

  get_dac := TRUE;
end;  { get_dac }

{$ELSE}

{LOCAL}
function get_dac (cinfo : j_decompress_ptr) : boolean;
begin
  get_dac := skip_variable(cinfo);
end;

{$ENDIF}

{LOCAL}
function get_dht (cinfo : j_decompress_ptr) : boolean;
{ Process a DHT marker }
var
  length : INT32;
  bits : Array[0..17-1] of UINT8;
  huffval : Array[0..256-1] of UINT8;
  i, index, count : int;
  htblptr : ^JHUFF_TBL_PTR;
var
  datasrc : jpeg_source_mgr_ptr;
  next_input_byte : JOCTETptr;
  bytes_in_buffer : size_t;
begin
  datasrc := cinfo^.src;
  next_input_byte := datasrc^.next_input_byte;
  bytes_in_buffer := datasrc^.bytes_in_buffer;

{ Read two bytes interpreted as an unsigned 16-bit integer.
  length should be declared unsigned int or perhaps INT32. }

{ make a byte available.
  Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
  but we must reload the local copies after a successful fill. }
  if (bytes_in_buffer = 0) then
  begin
    if (not datasrc^.fill_input_buffer(cinfo)) then
    begin
      get_dht := FALSE;
      exit;
    end;
    { Reload the local copies }
    next_input_byte := datasrc^.next_input_byte;
    bytes_in_buffer := datasrc^.bytes_in_buffer;
  end;
  Dec( bytes_in_buffer );

  length := (uint( GETJOCTET(next_input_byte^)) shl 8);
  Inc( next_input_byte );
  { make a byte available.
    Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
    but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dht := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

  Inc( length, GETJOCTET( next_input_byte^));
  Inc( next_input_byte );

  Dec(length,  2);

  while (length > 16) do
  begin
    { Read a byte into variable index. If must suspend, return FALSE. }
    { make a byte available.
      Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
      but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dht := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

    index := GETJOCTET(next_input_byte^);
    Inc(next_input_byte);

    {$IFDEF DEBUG}
    TRACEMS1(j_common_ptr(cinfo), 1, JTRC_DHT, index);
    {$ENDIF}

    bits[0] := 0;
    count := 0;
    for i := 1 to 16 do
    begin
      { Read a byte into variable bits[i]. If must suspend, return FALSE. }
      { make a byte available.
        Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
        but we must reload the local copies after a successful fill. }
      if (bytes_in_buffer = 0) then
      begin
        if (not datasrc^.fill_input_buffer(cinfo)) then
        begin
          get_dht := FALSE;
          exit;
        end;
        { Reload the local copies }
        next_input_byte := datasrc^.next_input_byte;
        bytes_in_buffer := datasrc^.bytes_in_buffer;
      end;
      Dec( bytes_in_buffer );

      bits[i] := GETJOCTET(next_input_byte^);
      Inc(next_input_byte);

      Inc( count, bits[i] );
    end;

    Dec( length, (1 + 16) );

    {$IFDEF DEBUG}
    TRACEMS8(j_common_ptr(cinfo), 2, JTRC_HUFFBITS,
	     bits[1], bits[2], bits[3], bits[4],
	     bits[5], bits[6], bits[7], bits[8]);
    TRACEMS8(j_common_ptr(cinfo), 2, JTRC_HUFFBITS,
	     bits[9], bits[10], bits[11], bits[12],
	     bits[13], bits[14], bits[15], bits[16]);
    {$ENDIF}

    { Here we just do minimal validation of the counts to avoid walking
      off the end of our table space.  jdhuff.c will check more carefully. }

    if (count > 256) or (INT32(count) > length) then
      ERREXIT(j_common_ptr(cinfo), JERR_BAD_HUFF_TABLE);

    for i := 0 to Pred(count) do
    begin
    { Read a byte into variable huffval[i]. If must suspend, return FALSE. }
    { make a byte available.
      Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
      but we must reload the local copies after a successful fill. }
      if (bytes_in_buffer = 0) then
      begin
        if (not datasrc^.fill_input_buffer(cinfo)) then
        begin
          get_dht := FALSE;
          exit;
        end;
        { Reload the local copies }
        next_input_byte := datasrc^.next_input_byte;
        bytes_in_buffer := datasrc^.bytes_in_buffer;
      end;
      Dec( bytes_in_buffer );

      huffval[i] := GETJOCTET(next_input_byte^);
      Inc(next_input_byte);
    end;

    Dec( length, count );

    if (index and $10)<>0 then
    begin  { AC table definition }
      Dec( index, $10 );
      htblptr := @cinfo^.ac_huff_tbl_ptrs[index];
    end
    else
    begin { DC table definition }
      htblptr := @cinfo^.dc_huff_tbl_ptrs[index];
    end;

    if (index < 0) or (index >= NUM_HUFF_TBLS) then
      ERREXIT1(j_common_ptr(cinfo), JERR_DHT_INDEX, index);

    if (htblptr^ = NIL) then
      htblptr^ := jpeg_alloc_huff_table(j_common_ptr(cinfo));

    MEMCOPY(@(htblptr^)^.bits, @bits, SIZEOF((htblptr^)^.bits));
    MEMCOPY(@(htblptr^)^.huffval, @huffval, SIZEOF((htblptr^)^.huffval));
  end;

  if (length <> 0) then
    ERREXIT(j_common_ptr(cinfo), JERR_BAD_LENGTH);

  { Unload the local copies --- do this only at a restart boundary }
  datasrc^.next_input_byte := next_input_byte;
  datasrc^.bytes_in_buffer := bytes_in_buffer;

  get_dht := TRUE;
end;  { get_dht }


{LOCAL}
function get_dqt (cinfo : j_decompress_ptr) : boolean;
{ Process a DQT marker }
var
  length : INT32;
  n, i, prec : int;
  tmp : uint;
  quant_ptr : JQUANT_TBL_PTR;
var
  datasrc : jpeg_source_mgr_ptr;
  next_input_byte : JOCTETptr;
  bytes_in_buffer : size_t;
begin
  datasrc := cinfo^.src;
  next_input_byte := datasrc^.next_input_byte;
  bytes_in_buffer := datasrc^.bytes_in_buffer;

{ Read two bytes interpreted as an unsigned 16-bit integer.
  length should be declared unsigned int or perhaps INT32. }

{ make a byte available.
  Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
  but we must reload the local copies after a successful fill. }
  if (bytes_in_buffer = 0) then
  begin
    if (not datasrc^.fill_input_buffer(cinfo)) then
    begin
      get_dqt := FALSE;
      exit;
    end;
    { Reload the local copies }
    next_input_byte := datasrc^.next_input_byte;
    bytes_in_buffer := datasrc^.bytes_in_buffer;
  end;
  Dec( bytes_in_buffer );

  length := (uint( GETJOCTET(next_input_byte^)) shl 8);
  Inc( next_input_byte );
  { make a byte available.
    Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
    but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dqt := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

  Inc( length, GETJOCTET( next_input_byte^));
  Inc( next_input_byte );

  Dec( length, 2 );

  while (length > 0) do
  begin
    { Read a byte into variable n. If must suspend, return FALSE. }
    { make a byte available.
      Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
      but we must reload the local copies after a successful fill. }
    if (bytes_in_buffer = 0) then
    begin
      if (not datasrc^.fill_input_buffer(cinfo)) then
      begin
        get_dqt := FALSE;
        exit;
      end;
      { Reload the local copies }
      next_input_byte := datasrc^.next_input_byte;
      bytes_in_buffer := datasrc^.bytes_in_buffer;
    end;
    Dec( bytes_in_buffer );

    n := GETJOCTET(next_input_byte^);
    Inc(next_input_byte);

    prec := n shr 4;
    n := n and $0F;

    {$IFDEF DEBUG}
    TRACEMS2(j_common_ptr(cinfo), 1, JTRC_DQT, n, prec);
    {$ENDIF}

    if (n >= NUM_QUANT_TBLS) then
      ERREXIT1(j_common_ptr(cinfo) , JERR_DQT_INDEX, n);

    if (cinfo^.quant_tbl_ptrs[n] = NIL) then
      cinfo^.quant_tbl_ptrs[n] := jpeg_alloc_quant_table(j_common_ptr(cinfo));
    quant_ptr := cinfo^.quant_tbl_ptrs[n];

    for i := 0 to Pred(DCTSIZE2) do
    begin
      if (prec <> 0) then
      begin
      { Read two bytes interpreted as an unsigned 16-bit integer.
        tmp should be declared unsigned int or perhaps INT32. }

      { make a byte available.
        Note we do *not* do INPUT_SYNC before calling fill_input_buffer,
        but we must reload the local copies after a successful fill. }
        if (bytes_in_buffer = 0) then
        begin
          if (not datasrc^.fill_input_buffer(cinfo)) then
          begin
            get_dqt := FALSE;
            exit;
          end;