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/*
* jutils.c
*
* This file was part of the Independent JPEG Group's software:
* Copyright (C) 1991-1996, Thomas G. Lane.
* libjpeg-turbo Modifications:
* Copyright (C) 2022, D. R. Commander.
* For conditions of distribution and use, see the accompanying README.ijg
* 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
*/
GLOBAL(long)
jdiv_round_up(long a, long b)
/* Compute a/b rounded up to next integer, ie, ceil(a/b) */
/* Assumes a >= 0, b > 0 */
{
return (a + b - 1L) / b;
}
GLOBAL(long)
jround_up(long a, long b)
/* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */
/* Assumes a >= 0, b > 0 */
{
a += b - 1L;
return a - (a % b);
}
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 size_t count = (size_t)(num_cols * sizeof(JSAMPLE));
register int row;
input_array += source_row;
output_array += dest_row;
for (row = num_rows; row > 0; row--) {
inptr = *input_array++;
outptr = *output_array++;
memcpy(outptr, inptr, count);
}
}
GLOBAL(void)
jcopy_block_row(JBLOCKROW input_row, JBLOCKROW output_row,
JDIMENSION num_blocks)
/* Copy a row of coefficient blocks from one place to another. */
{
memcpy(output_row, input_row, num_blocks * (DCTSIZE2 * sizeof(JCOEF)));
}
GLOBAL(void)
jzero_far(void *target, size_t bytestozero)
/* Zero out a chunk of memory. */
/* This might be sample-array data, block-array data, or alloc_large data. */
{
memset(target, 0, bytestozero);
}
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