jutils.c

/*
 * jutils.c
 *
 * Copyright (C) 1991-1994, 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 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"


/*
 * 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
#endif


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;

  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_medium 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
}