函数指针模块化声明方法

#ifdef HAVE_PROTOTYPES

#define JMETHOD(type,methodname,arglist)  type (*methodname) arglist

#else

#define JMETHOD(type,methodname,arglist)  type (*methodname) ()

#endif

 

typedef JMETHOD(boolean, jpeg_marker_parser_method, (j_decompress_ptr cinfo));

    --->typedef boolean (* jpeg_marker_parser_method) (j_decompress_ptr cinfo);即函数指针

 

typedef struct jpeg_decompress_struct * j_decompress_ptr;