    /*
     * 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
    }