jna使用心得

此文档陆续记录JNA的使用经验！

会根据实际操作陆续更新

 

1. 带有返回值的字符串形参

   • int lib_ver(unsinged char *buff);
     
     功 能：读取软件版本号
     
     参 数：buff：存放版本号的缓冲区，长度18字节(包括结束字符’\0’)。
     
     返 回：成功则返回 0
     
        例：unsigned char buff[18];
     
               lib_ver(buff);
     
                   printf(“software version is %s”,buff);
     

      
   • JNA JAVA对应方法： int lib_ver(byte[] buf);
   • Java调用方式：

     	public synchronized String version() throws RuntimeException {
     		byte[] buf = new byte[18];
     		machine.lib_ver(buf);
     		return Native.toString(buf);
     	}

       
   • 参考资料：官方解答How to return a out String paramter in the JNA? 
     

     How do I read back a function's string result?
     
     Suppose you have a function:
     // Returns the number of characters written to the buffer
     int getString(char* buffer, int bufsize);
     The native code is expecting a fixed-size buffer, which it will fill in with the requested data. A Java String is not appropriate here, since Strings are immutable. Nor is a Java StringBuffer, since the native code only fills the buffer and does not change its size. The appropriate argument type would be either byte[], Memory, or an NIO Buffer, with the size of the object passed as the second argument. The method Native.toString(byte[]) may then be used to convert the array of byte into a Java String.

     
     
   • 字符串转换指定编码，解决乱码问题：Native.toString(buf, "GBK")