sfn = fileopen (source, StreamMode!, Read!, Shared!)
IF sfn < 0 THEN
return sfn
END IF
dfn = fileopen (dest, StreamMode!, Write!, LockWrite!, Replace!)
IF dfn < 0 THEN
fileclose(sfn)
return dfn
END IF
//逐块读写数据
bytes_num = fileread(sfn, bytes_read)
DO WHILE bytes_num > 0
bytes_num = filewrite(dfn,bytes_read)
IF bytes_num <= 0 THEN
fileclose(sfn)
fileclose(dfn)
return bytes_num
END IF
bytes_num = fileread(sfn, bytes_read)
LOOP