233 lines
6.4 KiB
Plaintext
233 lines
6.4 KiB
Plaintext
unit imjutils;
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{ This file contains tables and miscellaneous utility routines needed
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for both compression and decompression.
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Note we prefix all global names with "j" to minimize conflicts with
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a surrounding application. }
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{ Source: jutils.c; Copyright (C) 1991-1996, Thomas G. Lane. }
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interface
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{$I imjconfig.inc}
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uses
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imjmorecfg,
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imjinclude,
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imjpeglib;
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{ jpeg_zigzag_order[i] is the zigzag-order position of the i'th element
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of a DCT block read in natural order (left to right, top to bottom). }
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{$ifdef FALSE} { This table is not actually needed in v6a }
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const
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jpeg_zigzag_order : array[0..DCTSIZE2] of int =
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(0, 1, 5, 6, 14, 15, 27, 28,
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2, 4, 7, 13, 16, 26, 29, 42,
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3, 8, 12, 17, 25, 30, 41, 43,
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9, 11, 18, 24, 31, 40, 44, 53,
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10, 19, 23, 32, 39, 45, 52, 54,
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20, 22, 33, 38, 46, 51, 55, 60,
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21, 34, 37, 47, 50, 56, 59, 61,
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35, 36, 48, 49, 57, 58, 62, 63);
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{$endif}
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{ jpeg_natural_order[i] is the natural-order position of the i'th element
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of zigzag order.
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When reading corrupted data, the Huffman decoders could attempt
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to reference an entry beyond the end of this array (if the decoded
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zero run length reaches past the end of the block). To prevent
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wild stores without adding an inner-loop test, we put some extra
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"63"s after the real entries. This will cause the extra coefficient
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to be stored in location 63 of the block, not somewhere random.
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The worst case would be a run-length of 15, which means we need 16
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fake entries. }
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const
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jpeg_natural_order : array[0..DCTSIZE2+16-1] of int =
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(0, 1, 8, 16, 9, 2, 3, 10,
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17, 24, 32, 25, 18, 11, 4, 5,
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12, 19, 26, 33, 40, 48, 41, 34,
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27, 20, 13, 6, 7, 14, 21, 28,
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35, 42, 49, 56, 57, 50, 43, 36,
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29, 22, 15, 23, 30, 37, 44, 51,
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58, 59, 52, 45, 38, 31, 39, 46,
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53, 60, 61, 54, 47, 55, 62, 63,
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63, 63, 63, 63, 63, 63, 63, 63, { extra entries for safety in decoder }
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63, 63, 63, 63, 63, 63, 63, 63);
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{ Arithmetic utilities }
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{GLOBAL}
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function jdiv_round_up (a : long; b : long) : long;
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{GLOBAL}
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function jround_up (a : long; b : long) : long;
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{GLOBAL}
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procedure jcopy_sample_rows (input_array : JSAMPARRAY;
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source_row : int;
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output_array : JSAMPARRAY; dest_row : int;
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num_rows : int; num_cols : JDIMENSION);
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{GLOBAL}
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procedure jcopy_block_row (input_row : JBLOCKROW;
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output_row : JBLOCKROW;
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num_blocks : JDIMENSION);
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{GLOBAL}
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procedure jzero_far (target : pointer;{far} bytestozero : size_t);
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procedure FMEMZERO(target : pointer; size : size_t);
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procedure FMEMCOPY(dest,src : pointer; size : size_t);
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implementation
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{GLOBAL}
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function jdiv_round_up (a : long; b : long) : long;
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{ Compute a/b rounded up to next integer, ie, ceil(a/b) }
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{ Assumes a >= 0, b > 0 }
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begin
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jdiv_round_up := (a + b - long(1)) div b;
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end;
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{GLOBAL}
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function jround_up (a : long; b : long) : long;
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{ Compute a rounded up to next multiple of b, ie, ceil(a/b)*b }
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{ Assumes a >= 0, b > 0 }
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begin
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Inc(a, b - long(1));
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jround_up := a - (a mod b);
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end;
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{ On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays
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and coefficient-block arrays. This won't work on 80x86 because the arrays
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are FAR and we're assuming a small-pointer memory model. However, some
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DOS compilers provide far-pointer versions of memcpy() and memset() even
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in the small-model libraries. These will be used if USE_FMEM is defined.
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Otherwise, the routines below do it the hard way. (The performance cost
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is not all that great, because these routines aren't very heavily used.) }
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{$ifndef NEED_FAR_POINTERS} { normal case, same as regular macros }
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procedure FMEMZERO(target : pointer; size : size_t);
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begin
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FillChar(target^, size, 0);
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end;
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procedure FMEMCOPY(dest,src : pointer; size : size_t);
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begin
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Move(src^, dest^, size);
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end;
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{$else} { 80x86 case, define if we can }
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{$ifdef USE_FMEM}
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FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size))
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FMEMZERO(target,size) _fmemset((void FAR *)(target), 0, (size_t)(size))
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{$endif}
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{$endif}
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{GLOBAL}
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procedure jcopy_sample_rows (input_array : JSAMPARRAY; source_row : int;
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output_array : JSAMPARRAY; dest_row : int;
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num_rows : int; num_cols : JDIMENSION);
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{ Copy some rows of samples from one place to another.
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num_rows rows are copied from input_array[source_row++]
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to output_array[dest_row++]; these areas may overlap for duplication.
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The source and destination arrays must be at least as wide as num_cols. }
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var
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inptr, outptr : JSAMPLE_PTR; {register}
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{$ifdef FMEMCOPY}
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count : size_t; {register}
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{$else}
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count : JDIMENSION; {register}
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{$endif}
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row : int; {register}
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begin
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{$ifdef FMEMCOPY}
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count := size_t(num_cols * SIZEOF(JSAMPLE));
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{$endif}
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Inc(JSAMPROW_PTR(input_array), source_row);
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Inc(JSAMPROW_PTR(output_array), dest_row);
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for row := pred(num_rows) downto 0 do
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begin
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inptr := JSAMPLE_PTR(input_array^[0]);
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Inc(JSAMPROW_PTR(input_array));
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outptr := JSAMPLE_PTR(output_array^[0]);
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Inc(JSAMPROW_PTR(output_array));
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{$ifdef FMEMCOPY}
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FMEMCOPY(outptr, inptr, count);
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{$else}
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for count := pred(num_cols) downto 0 do
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begin
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outptr^ := inptr^; { needn't bother with GETJSAMPLE() here }
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Inc(inptr);
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Inc(outptr);
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end;
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{$endif}
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end;
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end;
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{GLOBAL}
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procedure jcopy_block_row (input_row : JBLOCKROW;
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output_row : JBLOCKROW;
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num_blocks : JDIMENSION);
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{ Copy a row of coefficient blocks from one place to another. }
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{$ifdef FMEMCOPY}
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begin
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FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF)));
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{$else}
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var
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inptr, outptr : JCOEFPTR; {register}
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count : long; {register}
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begin
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inptr := JCOEFPTR (input_row);
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outptr := JCOEFPTR (output_row);
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for count := long(num_blocks) * DCTSIZE2 -1 downto 0 do
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begin
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outptr^ := inptr^;
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Inc(outptr);
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Inc(inptr);
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end;
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{$endif}
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end;
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{GLOBAL}
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procedure jzero_far (target : pointer;{far} bytestozero : size_t);
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{ Zero out a chunk of FAR memory. }
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{ This might be sample-array data, block-array data, or alloc_large data. }
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{$ifdef FMEMZERO}
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begin
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FMEMZERO(target, bytestozero);
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{$else}
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var
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ptr : byteptr;
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count : size_t; {register}
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begin
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ptr := target;
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for count := bytestozero-1 downto 0 do
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begin
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ptr^ := 0;
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Inc(ptr);
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end;
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{$endif}
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end;
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end.
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