text: /*
   * 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
  #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_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
  }
  