417 lines
15 KiB
Plaintext
417 lines
15 KiB
Plaintext
unit imjdinput;
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{ Original: jdinput.c ; Copyright (C) 1991-1997, Thomas G. Lane. }
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{ This file is part of the Independent JPEG Group's software.
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For conditions of distribution and use, see the accompanying README file.
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This file contains input control logic for the JPEG decompressor.
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These routines are concerned with controlling the decompressor's input
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processing (marker reading and coefficient decoding). The actual input
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reading is done in jdmarker.c, jdhuff.c, and jdphuff.c. }
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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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imjpeglib,
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imjdeferr,
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imjerror,
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imjinclude, imjutils;
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{ Initialize the input controller module.
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This is called only once, when the decompression object is created. }
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{GLOBAL}
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procedure jinit_input_controller (cinfo : j_decompress_ptr);
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implementation
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{ Private state }
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type
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my_inputctl_ptr = ^my_input_controller;
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my_input_controller = record
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pub : jpeg_input_controller; { public fields }
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inheaders : boolean; { TRUE until first SOS is reached }
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end; {my_input_controller;}
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{ Forward declarations }
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{METHODDEF}
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function consume_markers (cinfo : j_decompress_ptr) : int; forward;
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{ Routines to calculate various quantities related to the size of the image. }
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{LOCAL}
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procedure initial_setup (cinfo : j_decompress_ptr);
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{ Called once, when first SOS marker is reached }
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var
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ci : int;
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compptr : jpeg_component_info_ptr;
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begin
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{ Make sure image isn't bigger than I can handle }
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if (long(cinfo^.image_height) > long (JPEG_MAX_DIMENSION)) or
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(long(cinfo^.image_width) > long(JPEG_MAX_DIMENSION)) then
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ERREXIT1(j_common_ptr(cinfo), JERR_IMAGE_TOO_BIG, uInt(JPEG_MAX_DIMENSION));
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{ For now, precision must match compiled-in value... }
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if (cinfo^.data_precision <> BITS_IN_JSAMPLE) then
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ERREXIT1(j_common_ptr(cinfo), JERR_BAD_PRECISION, cinfo^.data_precision);
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{ Check that number of components won't exceed internal array sizes }
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if (cinfo^.num_components > MAX_COMPONENTS) then
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ERREXIT2(j_common_ptr(cinfo), JERR_COMPONENT_COUNT, cinfo^.num_components,
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MAX_COMPONENTS);
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{ Compute maximum sampling factors; check factor validity }
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cinfo^.max_h_samp_factor := 1;
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cinfo^.max_v_samp_factor := 1;
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compptr := jpeg_component_info_ptr(cinfo^.comp_info);
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for ci := 0 to pred(cinfo^.num_components) do
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begin
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if (compptr^.h_samp_factor<=0) or (compptr^.h_samp_factor>MAX_SAMP_FACTOR) or
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(compptr^.v_samp_factor<=0) or (compptr^.v_samp_factor>MAX_SAMP_FACTOR) then
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ERREXIT(j_common_ptr(cinfo), JERR_BAD_SAMPLING);
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{cinfo^.max_h_samp_factor := MAX(cinfo^.max_h_samp_factor,
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compptr^.h_samp_factor);
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cinfo^.max_v_samp_factor := MAX(cinfo^.max_v_samp_factor,
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compptr^.v_samp_factor);}
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if cinfo^.max_h_samp_factor < compptr^.h_samp_factor then
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cinfo^.max_h_samp_factor := compptr^.h_samp_factor;
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if cinfo^.max_v_samp_factor < compptr^.v_samp_factor then
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cinfo^.max_v_samp_factor := compptr^.v_samp_factor;
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Inc(compptr);
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end;
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{ We initialize DCT_scaled_size and min_DCT_scaled_size to DCTSIZE.
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In the full decompressor, this will be overridden by jdmaster.c;
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but in the transcoder, jdmaster.c is not used, so we must do it here. }
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cinfo^.min_DCT_scaled_size := DCTSIZE;
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{ Compute dimensions of components }
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compptr := jpeg_component_info_ptr(cinfo^.comp_info);
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for ci := 0 to pred(cinfo^.num_components) do
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begin
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compptr^.DCT_scaled_size := DCTSIZE;
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{ Size in DCT blocks }
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compptr^.width_in_blocks := JDIMENSION(
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jdiv_round_up( long(cinfo^.image_width) * long(compptr^.h_samp_factor),
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long(cinfo^.max_h_samp_factor * DCTSIZE)) );
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compptr^.height_in_blocks := JDIMENSION (
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jdiv_round_up(long (cinfo^.image_height) * long(compptr^.v_samp_factor),
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long (cinfo^.max_v_samp_factor * DCTSIZE)) );
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{ downsampled_width and downsampled_height will also be overridden by
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jdmaster.c if we are doing full decompression. The transcoder library
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doesn't use these values, but the calling application might. }
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{ Size in samples }
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compptr^.downsampled_width := JDIMENSION (
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jdiv_round_up(long (cinfo^.image_width) * long(compptr^.h_samp_factor),
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long (cinfo^.max_h_samp_factor)) );
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compptr^.downsampled_height := JDIMENSION (
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jdiv_round_up(long (cinfo^.image_height) * long(compptr^.v_samp_factor),
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long (cinfo^.max_v_samp_factor)) );
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{ Mark component needed, until color conversion says otherwise }
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compptr^.component_needed := TRUE;
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{ Mark no quantization table yet saved for component }
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compptr^.quant_table := NIL;
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Inc(compptr);
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end;
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{ Compute number of fully interleaved MCU rows. }
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cinfo^.total_iMCU_rows := JDIMENSION(
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jdiv_round_up(long(cinfo^.image_height),
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long(cinfo^.max_v_samp_factor*DCTSIZE)) );
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{ Decide whether file contains multiple scans }
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if (cinfo^.comps_in_scan < cinfo^.num_components) or
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(cinfo^.progressive_mode) then
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cinfo^.inputctl^.has_multiple_scans := TRUE
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else
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cinfo^.inputctl^.has_multiple_scans := FALSE;
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end;
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{LOCAL}
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procedure per_scan_setup (cinfo : j_decompress_ptr);
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{ Do computations that are needed before processing a JPEG scan }
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{ cinfo^.comps_in_scan and cinfo^.cur_comp_info[] were set from SOS marker }
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var
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ci, mcublks, tmp : int;
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compptr : jpeg_component_info_ptr;
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begin
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if (cinfo^.comps_in_scan = 1) then
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begin
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{ Noninterleaved (single-component) scan }
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compptr := cinfo^.cur_comp_info[0];
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{ Overall image size in MCUs }
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cinfo^.MCUs_per_row := compptr^.width_in_blocks;
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cinfo^.MCU_rows_in_scan := compptr^.height_in_blocks;
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{ For noninterleaved scan, always one block per MCU }
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compptr^.MCU_width := 1;
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compptr^.MCU_height := 1;
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compptr^.MCU_blocks := 1;
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compptr^.MCU_sample_width := compptr^.DCT_scaled_size;
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compptr^.last_col_width := 1;
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{ For noninterleaved scans, it is convenient to define last_row_height
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as the number of block rows present in the last iMCU row. }
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tmp := int (LongInt(compptr^.height_in_blocks) mod compptr^.v_samp_factor);
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if (tmp = 0) then
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tmp := compptr^.v_samp_factor;
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compptr^.last_row_height := tmp;
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{ Prepare array describing MCU composition }
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cinfo^.blocks_in_MCU := 1;
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cinfo^.MCU_membership[0] := 0;
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end
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else
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begin
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{ Interleaved (multi-component) scan }
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if (cinfo^.comps_in_scan <= 0) or (cinfo^.comps_in_scan > MAX_COMPS_IN_SCAN) then
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ERREXIT2(j_common_ptr(cinfo), JERR_COMPONENT_COUNT, cinfo^.comps_in_scan,
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MAX_COMPS_IN_SCAN);
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{ Overall image size in MCUs }
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cinfo^.MCUs_per_row := JDIMENSION (
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jdiv_round_up(long (cinfo^.image_width),
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long (cinfo^.max_h_samp_factor*DCTSIZE)) );
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cinfo^.MCU_rows_in_scan := JDIMENSION (
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jdiv_round_up(long (cinfo^.image_height),
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long (cinfo^.max_v_samp_factor*DCTSIZE)) );
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cinfo^.blocks_in_MCU := 0;
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for ci := 0 to pred(cinfo^.comps_in_scan) do
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begin
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compptr := cinfo^.cur_comp_info[ci];
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{ Sampling factors give # of blocks of component in each MCU }
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compptr^.MCU_width := compptr^.h_samp_factor;
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compptr^.MCU_height := compptr^.v_samp_factor;
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compptr^.MCU_blocks := compptr^.MCU_width * compptr^.MCU_height;
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compptr^.MCU_sample_width := compptr^.MCU_width * compptr^.DCT_scaled_size;
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{ Figure number of non-dummy blocks in last MCU column & row }
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tmp := int (LongInt(compptr^.width_in_blocks) mod compptr^.MCU_width);
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if (tmp = 0) then
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tmp := compptr^.MCU_width;
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compptr^.last_col_width := tmp;
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tmp := int (LongInt(compptr^.height_in_blocks) mod compptr^.MCU_height);
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if (tmp = 0) then
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tmp := compptr^.MCU_height;
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compptr^.last_row_height := tmp;
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{ Prepare array describing MCU composition }
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mcublks := compptr^.MCU_blocks;
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if (LongInt(cinfo^.blocks_in_MCU) + mcublks > D_MAX_BLOCKS_IN_MCU) then
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ERREXIT(j_common_ptr(cinfo), JERR_BAD_MCU_SIZE);
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while (mcublks > 0) do
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begin
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Dec(mcublks);
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cinfo^.MCU_membership[cinfo^.blocks_in_MCU] := ci;
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Inc(cinfo^.blocks_in_MCU);
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end;
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end;
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end;
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end;
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{ Save away a copy of the Q-table referenced by each component present
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in the current scan, unless already saved during a prior scan.
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In a multiple-scan JPEG file, the encoder could assign different components
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the same Q-table slot number, but change table definitions between scans
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so that each component uses a different Q-table. (The IJG encoder is not
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currently capable of doing this, but other encoders might.) Since we want
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to be able to dequantize all the components at the end of the file, this
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means that we have to save away the table actually used for each component.
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We do this by copying the table at the start of the first scan containing
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the component.
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The JPEG spec prohibits the encoder from changing the contents of a Q-table
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slot between scans of a component using that slot. If the encoder does so
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anyway, this decoder will simply use the Q-table values that were current
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at the start of the first scan for the component.
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The decompressor output side looks only at the saved quant tables,
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not at the current Q-table slots. }
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{LOCAL}
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procedure latch_quant_tables (cinfo : j_decompress_ptr);
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var
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ci, qtblno : int;
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compptr : jpeg_component_info_ptr;
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qtbl : JQUANT_TBL_PTR;
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begin
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for ci := 0 to pred(cinfo^.comps_in_scan) do
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begin
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compptr := cinfo^.cur_comp_info[ci];
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{ No work if we already saved Q-table for this component }
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if (compptr^.quant_table <> NIL) then
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continue;
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{ Make sure specified quantization table is present }
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qtblno := compptr^.quant_tbl_no;
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if (qtblno < 0) or (qtblno >= NUM_QUANT_TBLS) or
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(cinfo^.quant_tbl_ptrs[qtblno] = NIL) then
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ERREXIT1(j_common_ptr(cinfo), JERR_NO_QUANT_TABLE, qtblno);
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{ OK, save away the quantization table }
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qtbl := JQUANT_TBL_PTR(
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cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_IMAGE,
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SIZEOF(JQUANT_TBL)) );
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MEMCOPY(qtbl, cinfo^.quant_tbl_ptrs[qtblno], SIZEOF(JQUANT_TBL));
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compptr^.quant_table := qtbl;
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end;
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end;
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{ Initialize the input modules to read a scan of compressed data.
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The first call to this is done by jdmaster.c after initializing
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the entire decompressor (during jpeg_start_decompress).
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Subsequent calls come from consume_markers, below. }
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{METHODDEF}
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procedure start_input_pass (cinfo : j_decompress_ptr);
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begin
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per_scan_setup(cinfo);
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latch_quant_tables(cinfo);
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cinfo^.entropy^.start_pass (cinfo);
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cinfo^.coef^.start_input_pass (cinfo);
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cinfo^.inputctl^.consume_input := cinfo^.coef^.consume_data;
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end;
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{ Finish up after inputting a compressed-data scan.
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This is called by the coefficient controller after it's read all
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the expected data of the scan. }
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{METHODDEF}
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procedure finish_input_pass (cinfo : j_decompress_ptr);
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begin
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cinfo^.inputctl^.consume_input := consume_markers;
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end;
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{ Read JPEG markers before, between, or after compressed-data scans.
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Change state as necessary when a new scan is reached.
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Return value is JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
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The consume_input method pointer points either here or to the
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coefficient controller's consume_data routine, depending on whether
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we are reading a compressed data segment or inter-segment markers. }
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{METHODDEF}
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function consume_markers (cinfo : j_decompress_ptr) : int;
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var
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val : int;
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inputctl : my_inputctl_ptr;
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begin
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inputctl := my_inputctl_ptr (cinfo^.inputctl);
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if (inputctl^.pub.eoi_reached) then { After hitting EOI, read no further }
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begin
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consume_markers := JPEG_REACHED_EOI;
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exit;
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end;
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val := cinfo^.marker^.read_markers (cinfo);
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case (val) of
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JPEG_REACHED_SOS: { Found SOS }
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begin
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if (inputctl^.inheaders) then
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begin { 1st SOS }
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initial_setup(cinfo);
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inputctl^.inheaders := FALSE;
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{ Note: start_input_pass must be called by jdmaster.c
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before any more input can be consumed. jdapimin.c is
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responsible for enforcing this sequencing. }
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end
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else
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begin { 2nd or later SOS marker }
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if (not inputctl^.pub.has_multiple_scans) then
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ERREXIT(j_common_ptr(cinfo), JERR_EOI_EXPECTED); { Oops, I wasn't expecting this! }
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start_input_pass(cinfo);
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end;
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end;
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JPEG_REACHED_EOI: { Found EOI }
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begin
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inputctl^.pub.eoi_reached := TRUE;
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if (inputctl^.inheaders) then
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begin { Tables-only datastream, apparently }
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if (cinfo^.marker^.saw_SOF) then
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ERREXIT(j_common_ptr(cinfo), JERR_SOF_NO_SOS);
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end
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else
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begin
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{ Prevent infinite loop in coef ctlr's decompress_data routine
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if user set output_scan_number larger than number of scans. }
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if (cinfo^.output_scan_number > cinfo^.input_scan_number) then
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cinfo^.output_scan_number := cinfo^.input_scan_number;
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end;
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end;
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JPEG_SUSPENDED:;
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end;
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consume_markers := val;
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end;
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{ Reset state to begin a fresh datastream. }
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{METHODDEF}
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procedure reset_input_controller (cinfo : j_decompress_ptr);
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var
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inputctl : my_inputctl_ptr;
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begin
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inputctl := my_inputctl_ptr (cinfo^.inputctl);
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inputctl^.pub.consume_input := consume_markers;
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inputctl^.pub.has_multiple_scans := FALSE; { "unknown" would be better }
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inputctl^.pub.eoi_reached := FALSE;
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inputctl^.inheaders := TRUE;
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{ Reset other modules }
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cinfo^.err^.reset_error_mgr (j_common_ptr(cinfo));
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cinfo^.marker^.reset_marker_reader (cinfo);
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{ Reset progression state -- would be cleaner if entropy decoder did this }
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cinfo^.coef_bits := NIL;
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end;
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{ Initialize the input controller module.
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This is called only once, when the decompression object is created. }
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{GLOBAL}
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procedure jinit_input_controller (cinfo : j_decompress_ptr);
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var
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inputctl : my_inputctl_ptr;
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begin
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{ Create subobject in permanent pool }
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inputctl := my_inputctl_ptr(
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cinfo^.mem^.alloc_small (j_common_ptr(cinfo), JPOOL_PERMANENT,
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SIZEOF(my_input_controller)) );
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cinfo^.inputctl := jpeg_input_controller_ptr(inputctl);
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{ Initialize method pointers }
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inputctl^.pub.consume_input := consume_markers;
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inputctl^.pub.reset_input_controller := reset_input_controller;
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inputctl^.pub.start_input_pass := start_input_pass;
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inputctl^.pub.finish_input_pass := finish_input_pass;
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{ Initialize state: can't use reset_input_controller since we don't
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want to try to reset other modules yet. }
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inputctl^.pub.has_multiple_scans := FALSE; { "unknown" would be better }
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inputctl^.pub.eoi_reached := FALSE;
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inputctl^.inheaders := TRUE;
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end;
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end.
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