michael@0: /*
michael@0:  * jutils.c
michael@0:  *
michael@0:  * Copyright (C) 1991-1996, Thomas G. Lane.
michael@0:  * This file is part of the Independent JPEG Group's software.
michael@0:  * For conditions of distribution and use, see the accompanying README file.
michael@0:  *
michael@0:  * This file contains tables and miscellaneous utility routines needed
michael@0:  * for both compression and decompression.
michael@0:  * Note we prefix all global names with "j" to minimize conflicts with
michael@0:  * a surrounding application.
michael@0:  */
michael@0: 
michael@0: #define JPEG_INTERNALS
michael@0: #include "jinclude.h"
michael@0: #include "jpeglib.h"
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element
michael@0:  * of a DCT block read in natural order (left to right, top to bottom).
michael@0:  */
michael@0: 
michael@0: #if 0				/* This table is not actually needed in v6a */
michael@0: 
michael@0: const int jpeg_zigzag_order[DCTSIZE2] = {
michael@0:    0,  1,  5,  6, 14, 15, 27, 28,
michael@0:    2,  4,  7, 13, 16, 26, 29, 42,
michael@0:    3,  8, 12, 17, 25, 30, 41, 43,
michael@0:    9, 11, 18, 24, 31, 40, 44, 53,
michael@0:   10, 19, 23, 32, 39, 45, 52, 54,
michael@0:   20, 22, 33, 38, 46, 51, 55, 60,
michael@0:   21, 34, 37, 47, 50, 56, 59, 61,
michael@0:   35, 36, 48, 49, 57, 58, 62, 63
michael@0: };
michael@0: 
michael@0: #endif
michael@0: 
michael@0: /*
michael@0:  * jpeg_natural_order[i] is the natural-order position of the i'th element
michael@0:  * of zigzag order.
michael@0:  *
michael@0:  * When reading corrupted data, the Huffman decoders could attempt
michael@0:  * to reference an entry beyond the end of this array (if the decoded
michael@0:  * zero run length reaches past the end of the block).  To prevent
michael@0:  * wild stores without adding an inner-loop test, we put some extra
michael@0:  * "63"s after the real entries.  This will cause the extra coefficient
michael@0:  * to be stored in location 63 of the block, not somewhere random.
michael@0:  * The worst case would be a run-length of 15, which means we need 16
michael@0:  * fake entries.
michael@0:  */
michael@0: 
michael@0: const int jpeg_natural_order[DCTSIZE2+16] = {
michael@0:   0,  1,  8, 16,  9,  2,  3, 10,
michael@0:  17, 24, 32, 25, 18, 11,  4,  5,
michael@0:  12, 19, 26, 33, 40, 48, 41, 34,
michael@0:  27, 20, 13,  6,  7, 14, 21, 28,
michael@0:  35, 42, 49, 56, 57, 50, 43, 36,
michael@0:  29, 22, 15, 23, 30, 37, 44, 51,
michael@0:  58, 59, 52, 45, 38, 31, 39, 46,
michael@0:  53, 60, 61, 54, 47, 55, 62, 63,
michael@0:  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
michael@0:  63, 63, 63, 63, 63, 63, 63, 63
michael@0: };
michael@0: 
michael@0: 
michael@0: /*
michael@0:  * Arithmetic utilities
michael@0:  */
michael@0: 
michael@0: GLOBAL(long)
michael@0: jdiv_round_up (long a, long b)
michael@0: /* Compute a/b rounded up to next integer, ie, ceil(a/b) */
michael@0: /* Assumes a >= 0, b > 0 */
michael@0: {
michael@0:   return (a + b - 1L) / b;
michael@0: }
michael@0: 
michael@0: 
michael@0: GLOBAL(long)
michael@0: jround_up (long a, long b)
michael@0: /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */
michael@0: /* Assumes a >= 0, b > 0 */
michael@0: {
michael@0:   a += b - 1L;
michael@0:   return a - (a % b);
michael@0: }
michael@0: 
michael@0: 
michael@0: /* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays
michael@0:  * and coefficient-block arrays.  This won't work on 80x86 because the arrays
michael@0:  * are FAR and we're assuming a small-pointer memory model.  However, some
michael@0:  * DOS compilers provide far-pointer versions of memcpy() and memset() even
michael@0:  * in the small-model libraries.  These will be used if USE_FMEM is defined.
michael@0:  * Otherwise, the routines below do it the hard way.  (The performance cost
michael@0:  * is not all that great, because these routines aren't very heavily used.)
michael@0:  */
michael@0: 
michael@0: #ifndef NEED_FAR_POINTERS	/* normal case, same as regular macros */
michael@0: #define FMEMCOPY(dest,src,size)	MEMCOPY(dest,src,size)
michael@0: #define FMEMZERO(target,size)	MEMZERO(target,size)
michael@0: #else				/* 80x86 case, define if we can */
michael@0: #ifdef USE_FMEM
michael@0: #define FMEMCOPY(dest,src,size)	_fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size))
michael@0: #define FMEMZERO(target,size)	_fmemset((void FAR *)(target), 0, (size_t)(size))
michael@0: #endif
michael@0: #endif
michael@0: 
michael@0: 
michael@0: GLOBAL(void)
michael@0: jcopy_sample_rows (JSAMPARRAY input_array, int source_row,
michael@0: 		   JSAMPARRAY output_array, int dest_row,
michael@0: 		   int num_rows, JDIMENSION num_cols)
michael@0: /* Copy some rows of samples from one place to another.
michael@0:  * num_rows rows are copied from input_array[source_row++]
michael@0:  * to output_array[dest_row++]; these areas may overlap for duplication.
michael@0:  * The source and destination arrays must be at least as wide as num_cols.
michael@0:  */
michael@0: {
michael@0:   register JSAMPROW inptr, outptr;
michael@0: #ifdef FMEMCOPY
michael@0:   register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE));
michael@0: #else
michael@0:   register JDIMENSION count;
michael@0: #endif
michael@0:   register int row;
michael@0: 
michael@0:   input_array += source_row;
michael@0:   output_array += dest_row;
michael@0: 
michael@0:   for (row = num_rows; row > 0; row--) {
michael@0:     inptr = *input_array++;
michael@0:     outptr = *output_array++;
michael@0: #ifdef FMEMCOPY
michael@0:     FMEMCOPY(outptr, inptr, count);
michael@0: #else
michael@0:     for (count = num_cols; count > 0; count--)
michael@0:       *outptr++ = *inptr++;	/* needn't bother with GETJSAMPLE() here */
michael@0: #endif
michael@0:   }
michael@0: }
michael@0: 
michael@0: 
michael@0: GLOBAL(void)
michael@0: jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row,
michael@0: 		 JDIMENSION num_blocks)
michael@0: /* Copy a row of coefficient blocks from one place to another. */
michael@0: {
michael@0: #ifdef FMEMCOPY
michael@0:   FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF)));
michael@0: #else
michael@0:   register JCOEFPTR inptr, outptr;
michael@0:   register long count;
michael@0: 
michael@0:   inptr = (JCOEFPTR) input_row;
michael@0:   outptr = (JCOEFPTR) output_row;
michael@0:   for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) {
michael@0:     *outptr++ = *inptr++;
michael@0:   }
michael@0: #endif
michael@0: }
michael@0: 
michael@0: 
michael@0: GLOBAL(void)
michael@0: jzero_far (void FAR * target, size_t bytestozero)
michael@0: /* Zero out a chunk of FAR memory. */
michael@0: /* This might be sample-array data, block-array data, or alloc_large data. */
michael@0: {
michael@0: #ifdef FMEMZERO
michael@0:   FMEMZERO(target, bytestozero);
michael@0: #else
michael@0:   register char FAR * ptr = (char FAR *) target;
michael@0:   register size_t count;
michael@0: 
michael@0:   for (count = bytestozero; count > 0; count--) {
michael@0:     *ptr++ = 0;
michael@0:   }
michael@0: #endif
michael@0: }