如何使用JNA處理結構內的結構成員？

Question

我正在JNA上返回本機函數調用的嵌套結構指針。嵌套結構具有unsigned char和struct類型的成員。我能夠讀取原始類型，但是在處理嵌套結構成員時遇到了，例如， OBISCODE的迴應。我的嵌套的結構看起來象下面這樣：

typedef struct ObisCode 
{ 
    unsigned char a; 
    unsigned char b; 
    unsigned char c; 
    unsigned char d; 
    unsigned char e; 
    unsigned char f; 
} OBISCODE; 

typedef struct Response 
{ 
    unsigned char result; 
    OBISCODE obis; 
} RESPONSE; 

和原生功能爲：

RESPONSE* getStruct(OBISCODE * obis) 

我的Java代碼調用下面這個原生功能：

package struct; 

    import com.sun.jna.Native; 
    import com.sun.jna.Pointer; 

public class JNATest { 

    static { 
     Native.register("StructTest"); 
    } 


    public static class OBISCODE { 
     private Pointer pointer; 

     public OBISCODE() { 
      long memory = Native.malloc(6); 
      pointer = new Pointer(memory); 
     } 

     public OBISCODE(Pointer pointer) { 
      this.pointer = pointer;   
     } 

     Pointer getPointer() { 
      return pointer; 
     } 

     int getA() { 
      return pointer.getByte(0); 
     } 

     int getB() { 
      return pointer.getByte(1); 
     } 

     int getC() { 
      return pointer.getByte(2); 
     } 

     int getD() { 
      return pointer.getByte(3); 
     } 

     int getE() { 
      return pointer.getByte(4); 
     } 

     int getF() { 
      return pointer.getByte(5); 
     } 

     void setA(byte a) { 
      pointer.setByte(0, a); 
     } 

     void setB(byte b) { 
      pointer.setByte(1, b); 
     } 

     void setC(byte c) { 
      pointer.setByte(2, c); 
     } 

     void setD(byte d) { 
      pointer.setByte(3, d); 
     } 
     void setE(byte e) { 
      pointer.setByte(4, e); 
     } 
     void setF(byte f) { 
      pointer.setByte(5, f); 
     } 

     void free() { 
      Native.free(Pointer.nativeValue(pointer)); 
     } 

    } 


    public static native void printStruct(Pointer obis); 

    public static native Pointer getStruct(Pointer obis); 
    /** 
    * @param args 
    */ 
    public static void main(String[] args) { 
     try { 

      struct.JNATest.OBISCODE obis = new struct.JNATest.OBISCODE(); 
      obis.setA((byte) 0); 
      obis.setB((byte) 0); 
      obis.setC((byte) 8); 
      obis.setD((byte) 0); 
      obis.setE((byte) 0); 
      obis.setF((byte) 255); 

      Pointer ptr = obis.getPointer(); 
      System.out.println("ptr = " + ptr.toString()); 
      printStruct(obis.getPointer()); 

      Pointer resptr = getStruct(obis.getPointer()); 
      Response response = new Response(resptr); 
      System.out.println("result = " + response.getResult()); 
      System.out.println("1=" + resptr.getInt(1) + "2=" + resptr.getInt(2) 
        ); 

      obis.free(); 

     } catch (UnsatisfiedLinkError e) { 
      System.out.println("Exception" + e); 
     } 
    } 
} 

我相當於天然結構Response類如低於

package struct; 

import com.sun.jna.Native; 
import com.sun.jna.Pointer; 

public class Response { 

    private Pointer pointer; 

    public Response() { 
     long memory = Native.malloc(6); 
     pointer = new Pointer(memory); 
    } 

    public Response(Pointer pointer) { 
     this.pointer = pointer;   
    } 

    Pointer getPointer() { 
     return pointer; 
    } 

    int getResult() { 
     return pointer.getByte(0); 
    } 

    int getOBIS() { 
     return pointer.getByte(1); 
    } 

    void setResult(byte a) { 
     pointer.setByte(0, a); 
    } 

    void setOBIS(byte b) { 
     pointer.setByte(1, b); 
    } 

    void free() { 
     Native.free(Pointer.nativeValue(pointer)); 
    } 

} 

我跑這個測試在紅帽Linux和如下

result = 12 
1=5242882=2048 

請糾正我，如果我失去了一些東西在Java代碼來處理結構獲得的輸出。任何幫助是極大的讚賞？提前致謝。

Answer 1

JNA爲Structures提供直接支持。

例如：

public class ObisCode extends Structure 
{ 
    public byte a; 
    public byte b; 
    public byte c; 
    public byte d; 
    public byte e; 
    public byte f; 
    protected List getFieldOrder() { return Arrays.asList(new String[] { "a", "b", "c", "d", "e", "f" }); } 
    public OBISCODE() { } 
    public OBISCODE(Pointer p) { super(p); read(); } 
} 

public class Response extends Structure 
{ 
    public byte result; 
    public OBISCODE obis; 
    protected List getFieldOrder() { return Arrays.asList(new String[] { "result", "obis" }); } 
    public Response() { } 
    public Response(Pointer p) { super(p); read(); } 
}