www.pudn.com > jpeg-src.rar > Jdatasrc.c

/*note:this is not a core library module, so it doesn't define JPEG_INTERNALS */ 
  
#include "jinclude.h" 
#include "jpeglib.h" 
#include "jerror.h" 
 
 
typedef struct { 
  struct jpeg_source_mgr pub;	/* public fields */ 
	unsigned char *pSourceData;	/*add lurui datasource*/ 
	int dataLength; 
  JOCTET * buffer;		/* start of buffer */ 
  boolean start_of_file;	/* have we gotten any data yet? */ 
} my_source_mgr; 
 
typedef my_source_mgr * my_src_ptr; 
 
#define INPUT_BUF_SIZE  4096	/* choose an efficiently fread'able size */ 
 
 
METHODDEF(void) 
init_source (j_decompress_ptr cinfo) 
{ 
  my_src_ptr src = (my_src_ptr) cinfo->src; 
	if (src->dataLength<=0)  
		ERREXIT(cinfo, JERR_INPUT_EMPTY); 
  src->start_of_file = TRUE; 
} 
 
 
METHODDEF(boolean) 
fill_input_buffer (j_decompress_ptr cinfo) 
{ 
  my_src_ptr src = (my_src_ptr) cinfo->src; 
 size_t nbytes; 
 
  if (!src->start_of_file) 
  { 
    WARNMS(cinfo, JWRN_JPEG_EOF); 
    src->buffer[0] = (JOCTET) 0xFF; 
    src->buffer[1] = (JOCTET) JPEG_EOI; 
    nbytes = 2; 
	src->pub.next_input_byte = src->buffer; 
	src->pub.bytes_in_buffer = nbytes; 
  } 
else 
	{ 
		src->pub.next_input_byte = src->pSourceData; 
		src->pub.bytes_in_buffer = src->dataLength; 
		src->start_of_file = FALSE; 
	} 
  return TRUE; 
} 
 
 
METHODDEF(void) 
skip_input_data (j_decompress_ptr cinfo, long num_bytes) 
{ 
  my_src_ptr src = (my_src_ptr) cinfo->src; 
 
  if (num_bytes > 0) { 
    while (num_bytes > (long) src->pub.bytes_in_buffer) { 
      num_bytes -= (long) src->pub.bytes_in_buffer; 
      (void) fill_input_buffer(cinfo); 
     } 
    src->pub.next_input_byte += (size_t) num_bytes; 
    src->pub.bytes_in_buffer -= (size_t) num_bytes; 
  } 
} 
 
 
METHODDEF(void) 
term_source (j_decompress_ptr cinfo) 
{ 
  /* no work necessary here */ 
} 
 
 
 
GLOBAL(void) 
jpeg_stdio_src (j_decompress_ptr cinfo, unsigned char *pSourceData, int dataLength) 
{ 
  my_src_ptr src; 
 
  if (cinfo->src == NULL) {	/* first time for this JPEG object? */ 
    cinfo->src = (struct jpeg_source_mgr *) 
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, 
				  SIZEOF(my_source_mgr)); 
    src = (my_src_ptr) cinfo->src; 
    src->buffer = (JOCTET *) 
      (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT, 
				  INPUT_BUF_SIZE * SIZEOF(JOCTET)); 
  } 
 
  src = (my_src_ptr) cinfo->src; 
  src->pub.init_source = init_source; 
  src->pub.fill_input_buffer = fill_input_buffer; 
  src->pub.skip_input_data = skip_input_data; 
  src->pub.resync_to_restart = jpeg_resync_to_restart; /* use default method */ 
  src->pub.term_source = term_source; 
  src->dataLength=dataLength;  
  src->pSourceData=pSourceData; 
  src->pub.bytes_in_buffer = 0; /* forces fill_input_buffer on first read */ 
  src->pub.next_input_byte = NULL; /* until buffer loaded */ 
}