180 lines
5.1 KiB
C
180 lines
5.1 KiB
C
/*
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* jutils.c
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*
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* Copyright (C) 1991-1996, 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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*
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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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*/
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#define JPEG_INTERNALS
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#include "jinclude.h"
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#include "jpeglib.h"
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/*
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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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*/
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#if 0 /* This table is not actually needed in v6a */
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const int jpeg_zigzag_order[DCTSIZE2] = {
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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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};
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#endif
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/*
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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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*
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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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*/
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const int jpeg_natural_order[DCTSIZE2+16] = {
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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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};
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/*
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* Arithmetic utilities
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*/
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GLOBAL(long)
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jdiv_round_up (long a, long b)
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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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{
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return (a + b - 1L) / b;
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}
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GLOBAL(long)
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jround_up (long a, long b)
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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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{
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a += b - 1L;
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return a - (a % b);
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}
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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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*/
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#ifndef NEED_FAR_POINTERS /* normal case, same as regular macros */
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#define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size)
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#define FMEMZERO(target,size) MEMZERO(target,size)
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#else /* 80x86 case, define if we can */
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#ifdef USE_FMEM
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#define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size))
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#define 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(void)
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jcopy_sample_rows (JSAMPARRAY input_array, int source_row,
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JSAMPARRAY output_array, int dest_row,
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int num_rows, JDIMENSION num_cols)
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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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*/
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{
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register JSAMPROW inptr, outptr;
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#ifdef FMEMCOPY
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register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE));
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#else
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register JDIMENSION count;
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#endif
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register int row;
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input_array += source_row;
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output_array += dest_row;
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for (row = num_rows; row > 0; row--) {
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inptr = *input_array++;
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outptr = *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 = num_cols; count > 0; count--)
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*outptr++ = *inptr++; /* needn't bother with GETJSAMPLE() here */
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#endif
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}
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}
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GLOBAL(void)
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jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row,
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JDIMENSION num_blocks)
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/* Copy a row of coefficient blocks from one place to another. */
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{
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#ifdef FMEMCOPY
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FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF)));
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#else
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register JCOEFPTR inptr, outptr;
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register long count;
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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; count > 0; count--) {
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*outptr++ = *inptr++;
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}
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#endif
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}
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GLOBAL(void)
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jzero_far (void FAR * target, size_t bytestozero)
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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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{
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#ifdef FMEMZERO
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FMEMZERO(target, bytestozero);
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#else
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register char FAR * ptr = (char FAR *) target;
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register size_t count;
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for (count = bytestozero; count > 0; count--) {
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*ptr++ = 0;
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}
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#endif
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}
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