jutils.c 3.7 KB

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