0,0 → 1,179 |
/* |
* 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. |
*/ |
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#define JPEG_INTERNALS |
#include "jinclude.h" |
#include "jpeglib.h" |
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/* |
* 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). |
*/ |
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#if 0 /* This table is not actually needed in v6a */ |
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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 |
}; |
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#endif |
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/* |
* 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 |
}; |
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/* |
* Arithmetic utilities |
*/ |
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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; |
} |
|
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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); |
} |
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/* 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.) |
*/ |
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#ifndef NEED_FAR_POINTERS /* normal case, same as regular macros */ |
#define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size) |
#define FMEMZERO(target,size) MEMZERO(target,size) |
#else /* 80x86 case, define if we can */ |
#ifdef USE_FMEM |
#define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size)) |
#define FMEMZERO(target,size) _fmemset((void FAR *)(target), 0, (size_t)(size)) |
#endif |
#endif |
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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; |
#ifdef FMEMCOPY |
register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE)); |
#else |
register JDIMENSION count; |
#endif |
register int row; |
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input_array += source_row; |
output_array += dest_row; |
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for (row = num_rows; row > 0; row--) { |
inptr = *input_array++; |
outptr = *output_array++; |
#ifdef FMEMCOPY |
FMEMCOPY(outptr, inptr, count); |
#else |
for (count = num_cols; count > 0; count--) |
*outptr++ = *inptr++; /* needn't bother with GETJSAMPLE() here */ |
#endif |
} |
} |
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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. */ |
{ |
#ifdef FMEMCOPY |
FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF))); |
#else |
register JCOEFPTR inptr, outptr; |
register long count; |
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inptr = (JCOEFPTR) input_row; |
outptr = (JCOEFPTR) output_row; |
for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) { |
*outptr++ = *inptr++; |
} |
#endif |
} |
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GLOBAL(void) |
jzero_far (void FAR * target, size_t bytestozero) |
/* Zero out a chunk of FAR memory. */ |
/* This might be sample-array data, block-array data, or alloc_large data. */ |
{ |
#ifdef FMEMZERO |
FMEMZERO(target, bytestozero); |
#else |
register char FAR * ptr = (char FAR *) target; |
register size_t count; |
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for (count = bytestozero; count > 0; count--) { |
*ptr++ = 0; |
} |
#endif |
} |