/* * jutils.c * * Copyright (C) 1991-1996, Thomas G. Lane. * This file is part of the Independent JPEG Group's software. * For conditions of distribution and use, see the accompanying README 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"/* * 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);}