| /* |
| * jutils.c |
| * |
| * This file was part of the Independent JPEG Group's software: |
| * Copyright (C) 1991-1996, Thomas G. Lane. |
| * libjpeg-turbo Modifications: |
| * Copyright (C) 2022, D. R. Commander. |
| * For conditions of distribution and use, see the accompanying README.ijg |
| * file. |
| * |
| * This file contains tables and miscellaneous utility routines needed |
| * for both compression and decompression. |
| * Note we prefix all global names with "j" to minimize conflicts with |
| * a surrounding application. |
| */ |
| |
| #define JPEG_INTERNALS |
| #include "jinclude.h" |
| #include "jpeglib.h" |
| #include "jsamplecomp.h" |
| |
| |
| #if BITS_IN_JSAMPLE == 8 |
| |
| /* |
| * jpeg_zigzag_order[i] is the zigzag-order position of the i'th element |
| * of a DCT block read in natural order (left to right, top to bottom). |
| */ |
| |
| #if 0 /* This table is not actually needed in v6a */ |
| |
| const int jpeg_zigzag_order[DCTSIZE2] = { |
| 0, 1, 5, 6, 14, 15, 27, 28, |
| 2, 4, 7, 13, 16, 26, 29, 42, |
| 3, 8, 12, 17, 25, 30, 41, 43, |
| 9, 11, 18, 24, 31, 40, 44, 53, |
| 10, 19, 23, 32, 39, 45, 52, 54, |
| 20, 22, 33, 38, 46, 51, 55, 60, |
| 21, 34, 37, 47, 50, 56, 59, 61, |
| 35, 36, 48, 49, 57, 58, 62, 63 |
| }; |
| |
| #endif |
| |
| /* |
| * jpeg_natural_order[i] is the natural-order position of the i'th element |
| * of zigzag order. |
| * |
| * When reading corrupted data, the Huffman decoders could attempt |
| * to reference an entry beyond the end of this array (if the decoded |
| * zero run length reaches past the end of the block). To prevent |
| * wild stores without adding an inner-loop test, we put some extra |
| * "63"s after the real entries. This will cause the extra coefficient |
| * to be stored in location 63 of the block, not somewhere random. |
| * The worst case would be a run-length of 15, which means we need 16 |
| * fake entries. |
| */ |
| |
| const int jpeg_natural_order[DCTSIZE2 + 16] = { |
| 0, 1, 8, 16, 9, 2, 3, 10, |
| 17, 24, 32, 25, 18, 11, 4, 5, |
| 12, 19, 26, 33, 40, 48, 41, 34, |
| 27, 20, 13, 6, 7, 14, 21, 28, |
| 35, 42, 49, 56, 57, 50, 43, 36, |
| 29, 22, 15, 23, 30, 37, 44, 51, |
| 58, 59, 52, 45, 38, 31, 39, 46, |
| 53, 60, 61, 54, 47, 55, 62, 63, |
| 63, 63, 63, 63, 63, 63, 63, 63, /* extra entries for safety in decoder */ |
| 63, 63, 63, 63, 63, 63, 63, 63 |
| }; |
| |
| |
| /* |
| * Arithmetic utilities |
| */ |
| |
| GLOBAL(long) |
| jdiv_round_up(long a, long b) |
| /* Compute a/b rounded up to next integer, ie, ceil(a/b) */ |
| /* Assumes a >= 0, b > 0 */ |
| { |
| return (a + b - 1L) / b; |
| } |
| |
| |
| GLOBAL(long) |
| jround_up(long a, long b) |
| /* Compute a rounded up to next multiple of b, ie, ceil(a/b)*b */ |
| /* Assumes a >= 0, b > 0 */ |
| { |
| a += b - 1L; |
| return a - (a % b); |
| } |
| |
| #endif /* BITS_IN_JSAMPLE == 8 */ |
| |
| |
| #if BITS_IN_JSAMPLE != 16 || \ |
| defined(C_LOSSLESS_SUPPORTED) || defined(D_LOSSLESS_SUPPORTED) |
| |
| GLOBAL(void) |
| _jcopy_sample_rows(_JSAMPARRAY input_array, int source_row, |
| _JSAMPARRAY output_array, int dest_row, int num_rows, |
| JDIMENSION num_cols) |
| /* Copy some rows of samples from one place to another. |
| * num_rows rows are copied from input_array[source_row++] |
| * to output_array[dest_row++]; these areas may overlap for duplication. |
| * The source and destination arrays must be at least as wide as num_cols. |
| */ |
| { |
| register _JSAMPROW inptr, outptr; |
| register size_t count = (size_t)(num_cols * sizeof(_JSAMPLE)); |
| register int row; |
| |
| input_array += source_row; |
| output_array += dest_row; |
| |
| for (row = num_rows; row > 0; row--) { |
| inptr = *input_array++; |
| outptr = *output_array++; |
| memcpy(outptr, inptr, count); |
| } |
| } |
| |
| #endif /* BITS_IN_JSAMPLE != 16 || |
| defined(C_LOSSLESS_SUPPORTED) || defined(D_LOSSLESS_SUPPORTED) */ |
| |
| |
| #if BITS_IN_JSAMPLE == 8 |
| |
| GLOBAL(void) |
| jcopy_block_row(JBLOCKROW input_row, JBLOCKROW output_row, |
| JDIMENSION num_blocks) |
| /* Copy a row of coefficient blocks from one place to another. */ |
| { |
| memcpy(output_row, input_row, num_blocks * (DCTSIZE2 * sizeof(JCOEF))); |
| } |
| |
| |
| GLOBAL(void) |
| jzero_far(void *target, size_t bytestozero) |
| /* Zero out a chunk of memory. */ |
| /* This might be sample-array data, block-array data, or alloc_large data. */ |
| { |
| memset(target, 0, bytestozero); |
| } |
| |
| #endif /* BITS_IN_JSAMPLE == 8 */ |