compiler/libjpeg/main/jutils.c

   1 /*
   2     $Id$
   3 */
   4
   5 /*
   6  * jutils.c
   7  *
   8  * Copyright (C) 1991-1996, Thomas G. Lane.
   9  * This file is part of the Independent JPEG Group's software.
  10  * For conditions of distribution and use, see the accompanying README file.
  11  *
  12  * This file contains tables and miscellaneous utility routines needed
  13  * for both compression and decompression.
  14  * Note we prefix all global names with "j" to minimize conflicts with
  15  * a surrounding application.
  16  */
  17
  18 #define JPEG_INTERNALS
  19 #include "jinclude.h"
  20 #include "jpeglib.h"
  21
  22
  23 /*
  24  * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element
  25  * of a DCT block read in natural order (left to right, top to bottom).
  26  */
  27
  28 #if 0                           /* This table is not actually needed in v6a */
  29
  30 const int jpeg_zigzag_order[DCTSIZE2] = {
  31    0,  1,  5,  6, 14, 15, 27, 28,
  32    2,  4,  7, 13, 16, 26, 29, 42,
  33    3,  8, 12, 17, 25, 30, 41, 43,
  34    9, 11, 18, 24, 31, 40, 44, 53,
  35   10, 19, 23, 32, 39, 45, 52, 54,
  36   20, 22, 33, 38, 46, 51, 55, 60,
  37   21, 34, 37, 47, 50, 56, 59, 61,
  38   35, 36, 48, 49, 57, 58, 62, 63
  39 };
  40
  41 #endif
  42
  43 /*
  44  * jpeg_natural_order[i] is the natural-order position of the i'th element
  45  * of zigzag order.
  46  *
  47  * When reading corrupted data, the Huffman decoders could attempt
  48  * to reference an entry beyond the end of this array (if the decoded
  49  * zero run length reaches past the end of the block).  To prevent
  50  * wild stores without adding an inner-loop test, we put some extra
  51  * "63"s after the real entries.  This will cause the extra coefficient
  52  * to be stored in location 63 of the block, not somewhere random.
  53  * The worst case would be a run-length of 15, which means we need 16
  54  * fake entries.
  55  */
  56
  57 const int jpeg_natural_order[DCTSIZE2+16] = {
  58   0,  1,  8, 16,  9,  2,  3, 10,
  59  17, 24, 32, 25, 18, 11,  4,  5,
  60  12, 19, 26, 33, 40, 48, 41, 34,
  61  27, 20, 13,  6,  7, 14, 21, 28,
  62  35, 42, 49, 56, 57, 50, 43, 36,
  63  29, 22, 15, 23, 30, 37, 44, 51,
  64  58, 59, 52, 45, 38, 31, 39, 46,
  65  53, 60, 61, 54, 47, 55, 62, 63,
  66  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
  67  63, 63, 63, 63, 63, 63, 63, 63
  68 };
  69
  70
  71 /*
  72  * Arithmetic utilities
  73  */
  74
  75 JGLOBAL(long)
  76 jdiv_round_up (long a, long b)
  77 /* Compute a/b rounded up to next integer, ie, ceil(a/b) */
  78 /* Assumes a >= 0, b > 0 */
  79 {
  80   return (a + b - 1L) / b;
  81 }
  82
  83
  84 JGLOBAL(long)
  85 jround_up (long a, long b)
  86 /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */
  87 /* Assumes a >= 0, b > 0 */
  88 {
  89   a += b - 1L;
  90   return a - (a % b);
  91 }
  92
  93
  94 /* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays
  95  * and coefficient-block arrays.  This won't work on 80x86 because the arrays
  96  * are FAR and we're assuming a small-pointer memory model.  However, some
  97  * DOS compilers provide far-pointer versions of memcpy() and memset() even
  98  * in the small-model libraries.  These will be used if USE_FMEM is defined.
  99  * Otherwise, the routines below do it the hard way.  (The performance cost
 100  * is not all that great, because these routines aren't very heavily used.)
 101  */
 102
 103 #ifndef NEED_FAR_POINTERS       /* normal case, same as regular macros */
 104 #define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size)
 105 #define FMEMZERO(target,size)   MEMZERO(target,size)
 106 #else                           /* 80x86 case, define if we can */
 107 #ifdef USE_FMEM
 108 #define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size))
 109 #define FMEMZERO(target,size)   _fmemset((void FAR *)(target), 0, (size_t)(size))
 110 #endif
 111 #endif
 112
 113
 114 JGLOBAL(void)
 115 jcopy_sample_rows (JSAMPARRAY input_array, int source_row,
 116                    JSAMPARRAY output_array, int dest_row,
 117                    int num_rows, JDIMENSION num_cols)
 118 /* Copy some rows of samples from one place to another.
 119  * num_rows rows are copied from input_array[source_row++]
 120  * to output_array[dest_row++]; these areas may overlap for duplication.
 121  * The source and destination arrays must be at least as wide as num_cols.
 122  */
 123 {
 124   register JSAMPROW inptr, outptr;
 125 #ifdef FMEMCOPY
 126   register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE));
 127 #else
 128   register JDIMENSION count;
 129 #endif
 130   register int row;
 131
 132   input_array += source_row;
 133   output_array += dest_row;
 134
 135   for (row = num_rows; row > 0; row--) {
 136     inptr = *input_array++;
 137     outptr = *output_array++;
 138 #ifdef FMEMCOPY
 139     FMEMCOPY(outptr, inptr, count);
 140 #else
 141     for (count = num_cols; count > 0; count--)
 142       *outptr++ = *inptr++;     /* needn't bother with GETJSAMPLE() here */
 143 #endif
 144   }
 145 }
 146
 147
 148 JGLOBAL(void)
 149 jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row,
 150                  JDIMENSION num_blocks)
 151 /* Copy a row of coefficient blocks from one place to another. */
 152 {
 153 #ifdef FMEMCOPY
 154   FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF)));
 155 #else
 156   register JCOEFPTR inptr, outptr;
 157   register long count;
 158
 159   inptr = (JCOEFPTR) input_row;
 160   outptr = (JCOEFPTR) output_row;
 161   for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) {
 162     *outptr++ = *inptr++;
 163   }
 164 #endif
 165 }
 166
 167
 168 JGLOBAL(void)
 169 jzero_far (void FAR * target, size_t bytestozero)
 170 /* Zero out a chunk of FAR memory. */
 171 /* This might be sample-array data, block-array data, or alloc_large data. */
 172 {
 173 #ifdef FMEMZERO
 174   FMEMZERO(target, bytestozero);
 175 #else
 176   register char FAR * ptr = (char FAR *) target;
 177   register size_t count;
 178
 179   for (count = bytestozero; count > 0; count--) {
 180     *ptr++ = 0;
 181   }
 182 #endif
 183 }