media/libjpeg/jutils.c

   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  * libjpeg-turbo Modifications:
   7  * Copyright (C) 2022, D. R. Commander.
   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 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   return (a + b - 1L) / b;
  80 }
  81
  82
  83 GLOBAL(long)
  84 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   a += b - 1L;
  89   return a - (a % b);
  90 }
  91
  92
  93 GLOBAL(void)
  94 jcopy_sample_rows(JSAMPARRAY input_array, int source_row,
  95                   JSAMPARRAY output_array, int dest_row, int num_rows,
  96                   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   register size_t count = (size_t)(num_cols * sizeof(JSAMPLE));
 105   register int row;
 106
 107   input_array += source_row;
 108   output_array += dest_row;
 109
 110   for (row = num_rows; row > 0; row--) {
 111     inptr = *input_array++;
 112     outptr = *output_array++;
 113     memcpy(outptr, inptr, count);
 114   }
 115 }
 116
 117
 118 GLOBAL(void)
 119 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   memcpy(output_row, input_row, num_blocks * (DCTSIZE2 * sizeof(JCOEF)));
 124 }
 125
 126
 127 GLOBAL(void)
 128 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   memset(target, 0, bytestozero);
 133 }