1 /*
   2  * jutils.c
   3  *
   4  * Copyright (C) 1991-1996, Thomas G. Lane.
   5  * Modified 2009-2011 by Guido Vollbeding.
   6  * This file is part of the Independent JPEG Group's software.
   7  * For conditions of distribution and use, see the accompanying README file.
   8  *
   9  * This file contains tables and miscellaneous utility routines needed
  10  * for both compression and decompression.
  11  * Note we prefix all global names with "j" to minimize conflicts with
  12  * a surrounding application.
  13  */
  14 
  15 #define JPEG_INTERNALS
  16 #include "jinclude.h"
  17 #include "jpeglib.h"
  18 
  19 
  20 /*
  21  * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element
  22  * of a DCT block read in natural order (left to right, top to bottom).
  23  */
  24 
  25 #if 0                           /* This table is not actually needed in v6a */
  26 
  27 const int jpeg_zigzag_order[DCTSIZE2] = {
  28    0,  1,  5,  6, 14, 15, 27, 28,
  29    2,  4,  7, 13, 16, 26, 29, 42,
  30    3,  8, 12, 17, 25, 30, 41, 43,
  31    9, 11, 18, 24, 31, 40, 44, 53,
  32   10, 19, 23, 32, 39, 45, 52, 54,
  33   20, 22, 33, 38, 46, 51, 55, 60,
  34   21, 34, 37, 47, 50, 56, 59, 61,
  35   35, 36, 48, 49, 57, 58, 62, 63
  36 };
  37 
  38 #endif
  39 
  40 /*
  41  * jpeg_natural_order[i] is the natural-order position of the i'th element
  42  * of zigzag order.
  43  *
  44  * When reading corrupted data, the Huffman decoders could attempt
  45  * to reference an entry beyond the end of this array (if the decoded
  46  * zero run length reaches past the end of the block).  To prevent
  47  * wild stores without adding an inner-loop test, we put some extra
  48  * "63"s after the real entries.  This will cause the extra coefficient
  49  * to be stored in location 63 of the block, not somewhere random.
  50  * The worst case would be a run-length of 15, which means we need 16
  51  * fake entries.
  52  */
  53 
  54 const int jpeg_natural_order[DCTSIZE2+16] = {
  55   0,  1,  8, 16,  9,  2,  3, 10,
  56  17, 24, 32, 25, 18, 11,  4,  5,
  57  12, 19, 26, 33, 40, 48, 41, 34,
  58  27, 20, 13,  6,  7, 14, 21, 28,
  59  35, 42, 49, 56, 57, 50, 43, 36,
  60  29, 22, 15, 23, 30, 37, 44, 51,
  61  58, 59, 52, 45, 38, 31, 39, 46,
  62  53, 60, 61, 54, 47, 55, 62, 63,
  63  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
  64  63, 63, 63, 63, 63, 63, 63, 63
  65 };
  66 
  67 const int jpeg_natural_order7[7*7+16] = {
  68   0,  1,  8, 16,  9,  2,  3, 10,
  69  17, 24, 32, 25, 18, 11,  4,  5,
  70  12, 19, 26, 33, 40, 48, 41, 34,
  71  27, 20, 13,  6, 14, 21, 28, 35,
  72  42, 49, 50, 43, 36, 29, 22, 30,
  73  37, 44, 51, 52, 45, 38, 46, 53,
  74  54,
  75  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
  76  63, 63, 63, 63, 63, 63, 63, 63
  77 };
  78 
  79 const int jpeg_natural_order6[6*6+16] = {
  80   0,  1,  8, 16,  9,  2,  3, 10,
  81  17, 24, 32, 25, 18, 11,  4,  5,
  82  12, 19, 26, 33, 40, 41, 34, 27,
  83  20, 13, 21, 28, 35, 42, 43, 36,
  84  29, 37, 44, 45,
  85  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
  86  63, 63, 63, 63, 63, 63, 63, 63
  87 };
  88 
  89 const int jpeg_natural_order5[5*5+16] = {
  90   0,  1,  8, 16,  9,  2,  3, 10,
  91  17, 24, 32, 25, 18, 11,  4, 12,
  92  19, 26, 33, 34, 27, 20, 28, 35,
  93  36,
  94  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
  95  63, 63, 63, 63, 63, 63, 63, 63
  96 };
  97 
  98 const int jpeg_natural_order4[4*4+16] = {
  99   0,  1,  8, 16,  9,  2,  3, 10,
 100  17, 24, 25, 18, 11, 19, 26, 27,
 101  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
 102  63, 63, 63, 63, 63, 63, 63, 63
 103 };
 104 
 105 const int jpeg_natural_order3[3*3+16] = {
 106   0,  1,  8, 16,  9,  2, 10, 17,
 107  18,
 108  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
 109  63, 63, 63, 63, 63, 63, 63, 63
 110 };
 111 
 112 const int jpeg_natural_order2[2*2+16] = {
 113   0,  1,  8,  9,
 114  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
 115  63, 63, 63, 63, 63, 63, 63, 63
 116 };
 117 
 118 
 119 /*
 120  * Arithmetic utilities
 121  */
 122 
 123 GLOBAL(long)
 124 jdiv_round_up (long a, long b)
 125 /* Compute a/b rounded up to next integer, ie, ceil(a/b) */
 126 /* Assumes a >= 0, b > 0 */
 127 {
 128   return (a + b - 1L) / b;
 129 }
 130 
 131 
 132 GLOBAL(long)
 133 jround_up (long a, long b)
 134 /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */
 135 /* Assumes a >= 0, b > 0 */
 136 {
 137   a += b - 1L;
 138   return a - (a % b);
 139 }
 140 
 141 
 142 /* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays
 143  * and coefficient-block arrays.  This won't work on 80x86 because the arrays
 144  * are FAR and we're assuming a small-pointer memory model.  However, some
 145  * DOS compilers provide far-pointer versions of memcpy() and memset() even
 146  * in the small-model libraries.  These will be used if USE_FMEM is defined.
 147  * Otherwise, the routines below do it the hard way.  (The performance cost
 148  * is not all that great, because these routines aren't very heavily used.)
 149  */
 150 
 151 #ifndef NEED_FAR_POINTERS       /* normal case, same as regular macro */
 152 #define FMEMCOPY(dest,src,size) MEMCOPY(dest,src,size)
 153 #else                           /* 80x86 case, define if we can */
 154 #ifdef USE_FMEM
 155 #define FMEMCOPY(dest,src,size) _fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size))
 156 #else
 157 /* This function is for use by the FMEMZERO macro defined in jpegint.h.
 158  * Do not call this function directly, use the FMEMZERO macro instead.
 159  */
 160 GLOBAL(void)
 161 jzero_far (void FAR * target, size_t bytestozero)
 162 /* Zero out a chunk of FAR memory. */
 163 /* This might be sample-array data, block-array data, or alloc_large data. */
 164 {
 165   register char FAR * ptr = (char FAR *) target;
 166   register size_t count;
 167 
 168   for (count = bytestozero; count > 0; count--) {
 169     *ptr++ = 0;
 170   }
 171 }
 172 #endif
 173 #endif
 174 
 175 
 176 GLOBAL(void)
 177 jcopy_sample_rows (JSAMPARRAY input_array, int source_row,
 178                    JSAMPARRAY output_array, int dest_row,
 179                    int num_rows, JDIMENSION num_cols)
 180 /* Copy some rows of samples from one place to another.
 181  * num_rows rows are copied from input_array[source_row++]
 182  * to output_array[dest_row++]; these areas may overlap for duplication.
 183  * The source and destination arrays must be at least as wide as num_cols.
 184  */
 185 {
 186   register JSAMPROW inptr, outptr;
 187 #ifdef FMEMCOPY
 188   register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE));
 189 #else
 190   register JDIMENSION count;
 191 #endif
 192   register int row;
 193 
 194   input_array += source_row;
 195   output_array += dest_row;
 196 
 197   for (row = num_rows; row > 0; row--) {
 198     inptr = *input_array++;
 199     outptr = *output_array++;
 200 #ifdef FMEMCOPY
 201     FMEMCOPY(outptr, inptr, count);
 202 #else
 203     for (count = num_cols; count > 0; count--)
 204       *outptr++ = *inptr++;     /* needn't bother with GETJSAMPLE() here */
 205 #endif
 206   }
 207 }
 208 
 209 
 210 GLOBAL(void)
 211 jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row,
 212                  JDIMENSION num_blocks)
 213 /* Copy a row of coefficient blocks from one place to another. */
 214 {
 215 #ifdef FMEMCOPY
 216   FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF)));
 217 #else
 218   register JCOEFPTR inptr, outptr;
 219   register long count;
 220 
 221   inptr = (JCOEFPTR) input_row;
 222   outptr = (JCOEFPTR) output_row;
 223   for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) {
 224     *outptr++ = *inptr++;
 225   }
 226 #endif
 227 }