/* * 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 */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);}/* 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.) */#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#endifGLOBAL(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;  input_array += source_row;  output_array += dest_row;  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  }}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;  inptr = (JCOEFPTR) input_row;  outptr = (JCOEFPTR) output_row;  for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) {    *outptr++ = *inptr++;  }#endif}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;  for (count = bytestozero; count > 0; count--) {    *ptr++ = 0;  }#endif}