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 /*

  * 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

 }