www.pudn.com > imgport.rar > jutils.c, change:2008-11-05,size:5419b


/* 
 * 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_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); 
} 
 
 
/* On normal machines we can apply MEMCOPY() and MEMZERO() to sample arrays 
 * and coefficient-block arrays.  This won't work on 80x86 because the arrays 
 * are FAR and we're assuming a small-pointer memory model.  However, some 
 * DOS compilers provide far-pointer versions of memcpy() and memset() even 
 * in the small-model libraries.  These will be used if USE_FMEM is defined. 
 * Otherwise, the routines below do it the hard way.  (The performance cost 
 * is not all that great, because these routines aren't very heavily used.) 
 */ 
 
#ifndef NEED_FAR_POINTERS	/* normal case, same as regular macros */ 
#define FMEMCOPY(dest,src,size)	MEMCOPY(dest,src,size) 
#define FMEMZERO(target,size)	MEMZERO(target,size) 
#else				/* 80x86 case, define if we can */ 
#ifdef USE_FMEM 
#define FMEMCOPY(dest,src,size)	_fmemcpy((void FAR *)(dest), (const void FAR *)(src), (size_t)(size)) 
#define FMEMZERO(target,size)	_fmemset((void FAR *)(target), 0, (size_t)(size)) 
#endif 
#endif 
 
 
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; 
#ifdef FMEMCOPY 
  register size_t count = (size_t) (num_cols * SIZEOF(JSAMPLE)); 
#else 
  register JDIMENSION count; 
#endif 
  register int row; 
 
  input_array += source_row; 
  output_array += dest_row; 
 
  for (row = num_rows; row > 0; row--) { 
    inptr = *input_array++; 
    outptr = *output_array++; 
#ifdef FMEMCOPY 
    FMEMCOPY(outptr, inptr, count); 
#else 
    for (count = num_cols; count > 0; count--) 
      *outptr++ = *inptr++;	/* needn't bother with GETJSAMPLE() here */ 
#endif 
  } 
} 
 
 
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. */ 
{ 
#ifdef FMEMCOPY 
  FMEMCOPY(output_row, input_row, num_blocks * (DCTSIZE2 * SIZEOF(JCOEF))); 
#else 
  register JCOEFPTR inptr, outptr; 
  register long count; 
 
  inptr = (JCOEFPTR) input_row; 
  outptr = (JCOEFPTR) output_row; 
  for (count = (long) num_blocks * DCTSIZE2; count > 0; count--) { 
    *outptr++ = *inptr++; 
  } 
#endif 
} 
 
 
GLOBAL(void) 
jzero_far (void FAR * target, size_t bytestozero) 
/* Zero out a chunk of FAR memory. */ 
/* This might be sample-array data, block-array data, or alloc_large data. */ 
{ 
#ifdef FMEMZERO 
  FMEMZERO(target, bytestozero); 
#else 
  register char FAR * ptr = (char FAR *) target; 
  register size_t count; 
 
  for (count = bytestozero; count > 0; count--) { 
    *ptr++ = 0; 
  } 
#endif 
}