Line data    Source code

       1             : /*
       2             :  * jutils.c
       3             :  *
       4             :  * This file was part of the Independent JPEG Group's software:
       5             :  * Copyright (C) 1991-1996, Thomas G. Lane.
       6             :  * It was modified by The libjpeg-turbo Project to include only code
       7             :  * relevant to libjpeg-turbo.
       8             :  * For conditions of distribution and use, see the accompanying README.ijg
       9             :  * file.
      10             :  *
      11             :  * This file contains tables and miscellaneous utility routines needed
      12             :  * for both compression and decompression.
      13             :  * Note we prefix all global names with "j" to minimize conflicts with
      14             :  * a surrounding application.
      15             :  */
      16             : 
      17             : #define JPEG_INTERNALS
      18             : #include "jinclude.h"
      19             : #include "jpeglib.h"
      20             : 
      21             : 
      22             : /*
      23             :  * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element
      24             :  * of a DCT block read in natural order (left to right, top to bottom).
      25             :  */
      26             : 
      27             : #if 0                           /* This table is not actually needed in v6a */
      28             : 
      29             : const int jpeg_zigzag_order[DCTSIZE2] = {
      30             :    0,  1,  5,  6, 14, 15, 27, 28,
      31             :    2,  4,  7, 13, 16, 26, 29, 42,
      32             :    3,  8, 12, 17, 25, 30, 41, 43,
      33             :    9, 11, 18, 24, 31, 40, 44, 53,
      34             :   10, 19, 23, 32, 39, 45, 52, 54,
      35             :   20, 22, 33, 38, 46, 51, 55, 60,
      36             :   21, 34, 37, 47, 50, 56, 59, 61,
      37             :   35, 36, 48, 49, 57, 58, 62, 63
      38             : };
      39             : 
      40             : #endif
      41             : 
      42             : /*
      43             :  * jpeg_natural_order[i] is the natural-order position of the i'th element
      44             :  * of zigzag order.
      45             :  *
      46             :  * When reading corrupted data, the Huffman decoders could attempt
      47             :  * to reference an entry beyond the end of this array (if the decoded
      48             :  * zero run length reaches past the end of the block).  To prevent
      49             :  * wild stores without adding an inner-loop test, we put some extra
      50             :  * "63"s after the real entries.  This will cause the extra coefficient
      51             :  * to be stored in location 63 of the block, not somewhere random.
      52             :  * The worst case would be a run-length of 15, which means we need 16
      53             :  * fake entries.
      54             :  */
      55             : 
      56             : const int jpeg_natural_order[DCTSIZE2+16] = {
      57             :   0,  1,  8, 16,  9,  2,  3, 10,
      58             :  17, 24, 32, 25, 18, 11,  4,  5,
      59             :  12, 19, 26, 33, 40, 48, 41, 34,
      60             :  27, 20, 13,  6,  7, 14, 21, 28,
      61             :  35, 42, 49, 56, 57, 50, 43, 36,
      62             :  29, 22, 15, 23, 30, 37, 44, 51,
      63             :  58, 59, 52, 45, 38, 31, 39, 46,
      64             :  53, 60, 61, 54, 47, 55, 62, 63,
      65             :  63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */
      66             :  63, 63, 63, 63, 63, 63, 63, 63
      67             : };
      68             : 
      69             : 
      70             : /*
      71             :  * Arithmetic utilities
      72             :  */
      73             : 
      74             : GLOBAL(long)
      75           0 : jdiv_round_up (long a, long b)
      76             : /* Compute a/b rounded up to next integer, ie, ceil(a/b) */
      77             : /* Assumes a >= 0, b > 0 */
      78             : {
      79           0 :   return (a + b - 1L) / b;
      80             : }
      81             : 
      82             : 
      83             : GLOBAL(long)
      84           0 : jround_up (long a, long b)
      85             : /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */
      86             : /* Assumes a >= 0, b > 0 */
      87             : {
      88           0 :   a += b - 1L;
      89           0 :   return a - (a % b);
      90             : }
      91             : 
      92             : 
      93             : GLOBAL(void)
      94           0 : jcopy_sample_rows (JSAMPARRAY input_array, int source_row,
      95             :                    JSAMPARRAY output_array, int dest_row,
      96             :                    int num_rows, JDIMENSION num_cols)
      97             : /* Copy some rows of samples from one place to another.
      98             :  * num_rows rows are copied from input_array[source_row++]
      99             :  * to output_array[dest_row++]; these areas may overlap for duplication.
     100             :  * The source and destination arrays must be at least as wide as num_cols.
     101             :  */
     102             : {
     103             :   register JSAMPROW inptr, outptr;
     104           0 :   register size_t count = (size_t) (num_cols * sizeof(JSAMPLE));
     105             :   register int row;
     106             : 
     107           0 :   input_array += source_row;
     108           0 :   output_array += dest_row;
     109             : 
     110           0 :   for (row = num_rows; row > 0; row--) {
     111           0 :     inptr = *input_array++;
     112           0 :     outptr = *output_array++;
     113           0 :     MEMCOPY(outptr, inptr, count);
     114             :   }
     115           0 : }
     116             : 
     117             : 
     118             : GLOBAL(void)
     119           0 : jcopy_block_row (JBLOCKROW input_row, JBLOCKROW output_row,
     120             :                  JDIMENSION num_blocks)
     121             : /* Copy a row of coefficient blocks from one place to another. */
     122             : {
     123           0 :   MEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * sizeof(JCOEF)));
     124           0 : }
     125             : 
     126             : 
     127             : GLOBAL(void)
     128           0 : jzero_far (void *target, size_t bytestozero)
     129             : /* Zero out a chunk of memory. */
     130             : /* This might be sample-array data, block-array data, or alloc_large data. */
     131             : {
     132           0 :   MEMZERO(target, bytestozero);
     133           0 : }