JNA指向結構的指針

Question

我需要使用JNA傳遞一個結構。

的文檔，我有具有以下信息：

int rdGetStatusHardware (struct StatusHardware *stat) 

struct StatusHardware{ 
unsigned char SerialNumber[12]; 
unsigned long HWVersion; 
unsigned long FWVersion; 
unsigned long MemorySize; 
unsigned short BootVersion; 
unsigned short FPGAVersion; 
unsigned long Devices; 
unsigned char Reserved[8]; 
}; 

我映射結構爲：

public class StatusHardware extends Structure { 
    public byte SerialNumber[] = new byte[12]; 
    public byte HWVersion[] = new byte[4]; 
    public byte FWVersion[] = new byte[4];    
    public byte MemorySize[] = new byte[4]; 
    public byte BootVersion[] = new byte[2]; 
    public byte FPGAVersion[] = new byte[2]; 
    public byte Devices[] = new byte[4]; 
    public byte Reserved[] = new byte[8]; 
    public StatusHardware(Pointer p){ 
     super(p); 
    } 
} 

，這是在我的接口中的方法：

int rdGetStatusHardware(Pointer p); 

致電圖書館：

Pointer ptr = new Memory(40); 
int result = CLibrary.INSTANCE.rdGetStatusHardware(ptr); 

通過這種方法，我發現了以下錯誤：

# 
# A fatal error has been detected by the Java Runtime Environment: 
# 
# EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x00000000, pid=3108, tid=5492 
# 
# JRE version: 6.0_24-b50 
# Java VM: Java HotSpot(TM) Client VM (19.1-b02 mixed mode windows-x86) 
# Problematic frame: 
# C 0x00000000 

試過，我發現在互聯網上......同樣的結果和錯誤等方式。

結構或接口有問題嗎？

Answer 1

AFAIK，在這種情況下JNA可以通過參考結構給你，所以你的方法是這樣的：

int rdGetStatusHardware(StatusHardware p); 
... 
StatusHardware ptr = new StatusHardware(); 
int result = CLibrary.INSTANCE.rdGetStatusHardware(ptr); 

編輯

因爲你訪問衝突可能引起將long映射到固定大小的字節數組。長尺寸可以根據平臺的不同，所以你應該總是使用NativeLong：

public class StatusHardware extends Structure { 
    public byte SerialNumber[] = new byte[12]; 
    public NativeLong HWVersion; 
    public NativeLong FWVersion;    
    public NativeLong MemorySize; 
    public short BootVersion; 
    public short FPGAVersion; 
    public NativeLong Devices; 
    public byte Reserved[] = new byte[8]; 
}