gzdoom/jpeg-6b/jutils.c

/*
* jutils.c
*
* Copyright (C) 1991-1996, Thomas G. Lane.
* This file is part of the Independent JPEG Group's software.
* For conditions of distribution and use, see the accompanying README file.
*
* This file contains tables and miscellaneous utility routines needed
* for both compression and decompression.
* Note we prefix all global names with "j" to minimize conflicts with
* a surrounding application.
*/

#define JPEG_INTERNALS
#include "jinclude.h"
#include "jpeglib.h"


/*
* jpeg_zigzag_order[i] is the zigzag-order position of the i'th element
* of a DCT block read in natural order (left to right, top to bottom).
*/

#if 0				/* This table is not actually needed in v6a */

const int jpeg_zigzag_order[DCTSIZE2] = {
	0,  1,  5,  6, 14, 15, 27, 28,
	2,  4,  7, 13, 16, 26, 29, 42,
	3,  8, 12, 17, 25, 30, 41, 43,
	9, 11, 18, 24, 31, 40, 44, 53,
	10, 19, 23, 32, 39, 45, 52, 54,
	20, 22, 33, 38, 46, 51, 55, 60,
	21, 34, 37, 47, 50, 56, 59, 61,
	35, 36, 48, 49, 57, 58, 62, 63
};

#endif

/*
* jpeg_natural_order[i] is the natural-order position of the i'th element
* of zigzag order.
*
* When reading corrupted data, the Huffman decoders could attempt
* to reference an entry beyond the end of this array (if the decoded
* zero run length reaches past the end of the block).  To prevent
* wild stores without adding an inner-loop test, we put some extra
* "63"s after the real entries.  This will cause the extra coefficient
* to be stored in location 63 of the block, not somewhere random.
* The worst case would be a run-length of 15, which means we need 16
* fake entries.
*/

const int jpeg_natural_order[DCTSIZE2+16] = {
	0,  1,  8, 16,  9,  2,  3, 10,
	17, 24, 32, 25, 18, 11,  4,  5,
	12, 19, 26, 33, 40, 48, 41, 34,
	27, 20, 13,  6,  7, 14, 21, 28,
	35, 42, 49, 56, 57, 50, 43, 36,
	29, 22, 15, 23, 30, 37, 44, 51,
	58, 59, 52, 45, 38, 31, 39, 46,
	53, 60, 61, 54, 47, 55, 62, 63,
	63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
	63, 63, 63, 63, 63, 63, 63, 63
};


/*
* Arithmetic utilities
*/

/* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays
* and coefficient-block arrays.  This won't work on 80x86 because the arrays
* are FAR and we're assuming a small-pointer memory model.  However, some
* DOS compilers provide far-pointer versions of memcpy() and memset() even
* in the small-model libraries.  These will be used if USE_FMEM is defined.
* Otherwise, the routines below do it the hard way.  (The performance cost
* is not all that great, because these routines aren't very heavily used.)
*/

GLOBAL(void)
jcopy_sample_rows (JSAMPARRAY input_array, int source_row,
				   JSAMPARRAY output_array, int dest_row,
				   int num_rows, JDIMENSION num_cols)
				   /* Copy some rows of samples from one place to another.
				   * num_rows rows are copied from input_array[source_row++]
				   * to output_array[dest_row++]; these areas may overlap for duplication.
				   * The source and destination arrays must be at least as wide as num_cols.
				   */
{
	register JSAMPROW inptr, outptr;
	register JDIMENSION count;
	register int row;

	input_array += source_row;
	output_array += dest_row;

	for (row = num_rows; row > 0; row--) {
		inptr = *input_array++;
		outptr = *output_array++;
		for (count = num_cols; count > 0; count--)
			*outptr++ = *inptr++;	/* needn't bother with GETJSAMPLE() here */
	}
}