JNA 分配缓冲区 FIXED_INFO 抛出无效内存访问

Question

我对 new FIXED_INFO(buffer) 进行了简单调用，导致 java.lang.Error：无效内存访问。我一辈子都弄不明白为什么会失败：

import com.sun.jna.platform.win32.IPHlpAPI;
import com.sun.jna.platform.win32.IPHlpAPI.FIXED_INFO;

public void fixedInfoTest() {
  int bufferSize = 648;
  Memory buffer = new Memory(bufferSize);
  FIXED_INFO fixedInfo = new FIXED_INFO(buffer);
}

"new FIXED_INFO(buffer)" 调用引发异常。

java.lang.Error: Invalid memory access
    at com.sun.jna.Native._getPointer(Native Method)
    at com.sun.jna.Native.getPointer(Native.java:2211)
    at com.sun.jna.Pointer.getPointer(Pointer.java:642)
    at com.sun.jna.Pointer.getValue(Pointer.java:367)
    at com.sun.jna.Structure.readField(Structure.java:732)
    at com.sun.jna.Structure.read(Structure.java:591)
    at com.sun.jna.Structure.autoRead(Structure.java:2141)
    at com.sun.jna.Structure.conditionalAutoRead(Structure.java:561)
    at com.sun.jna.Structure.updateStructureByReference(Structure.java:690)
    at com.sun.jna.Pointer.getValue(Pointer.java:367)
    at com.sun.jna.Structure.readField(Structure.java:732)
    at com.sun.jna.Structure.read(Structure.java:591)
    at com.sun.jna.platform.win32.IPHlpAPI$FIXED_INFO.<init>(IPHlpAPI.java:208)
    at com.magnicomp.test.unit.WindowsNativeTest.fixedInfoTest(WindowsNativeTest.java:43)

上述测试有时确实有效，但经常失败。测试系统为Win 10, Win Server 2016. JNA version 5.4.0

在我的生产代码中，fixedInfo 用于：

IntByReference bufferSize = new IntByReference();
int result = IPHlpAPI.INSTANCE.GetNetworkParams(Pointer.NULL, bufferSize);
Validate.isTrue(result == WinNT.ERROR_BUFFER_OVERFLOW, 
                "GetNetworkParams buffer size failed: " + Win32Error.getErrorMessage(result));      

Memory buffer = new Memory(bufferSize.getValue());
FIXED_INFO fixedInfo = new FIXED_INFO(buffer);

result = IPHlpAPI.INSTANCE.GetNetworkParams(fixedInfo.getPointer(), bufferSize);
if (result != WinNT.ERROR_SUCCESS) {
    log.error("GetNetworkParams failed: %s", Win32Error.getErrorMessage(result));
    return;
}
String domain = new String(fixedInfo.DomainName).trim(); 

log.info("GetNetworkParams gave domain=\"%s\"", domain);

以下是我找到的一些示例：

https://www.javatips.net/api/oshi-master/oshi-core/src/main/java/oshi/software/os/windows/WindowsNetworkParams.java

Answer 1

问题是您正在向 FIXED_INFO 的构造函数提供一个 Memory 实例 - 该构造函数用于在结构中包含正确数据的内存，而您只是传递清空未初始化的内存。 FIXED_INFO的构造函数会尝试读取其中的结构体和指针，发现结构体中的数据无效。

您应该做的是调用 FIXED_INFO 的不带任何参数的构造函数。此构造函数将为您分配适量的内存并正确初始化它。

将您的代码更改为：

// Memory buffer = new Memory(bufferSize); -- remove this line
FIXED_INFO fixedInfo = new FIXED_INFO();

此信息的来源：查看 JNA 的源代码和包含 FIXED_INFO 的库。

JNA Structure class（来自您的堆栈跟踪）
FIXED_INFO

Answer 2

我明白了。此代码有效：

IntByReference bufferSize = new IntByReference();
int result = IPHlpAPI.INSTANCE.GetNetworkParams(Pointer.NULL, bufferSize);
Validate.isTrue(result == WinNT.ERROR_BUFFER_OVERFLOW, 
        "GetNetworkParams buffer size failed: " + Win32Error.getErrorMessage(result));
log.info("BufferSize=%d", bufferSize.getValue());

Memory buffer = new Memory(bufferSize.getValue());

// Now retrieve the actual FIXED_INFO
result = IPHlpAPI.INSTANCE.GetNetworkParams(buffer, bufferSize);
if (result != WinNT.ERROR_SUCCESS) {
    log.error("GetNetworkParams failed: %s", Win32Error.getErrorMessage(result));
    return;
}
FIXED_INFO fixedInfo = new FIXED_INFO(buffer);

String domain = new String(fixedInfo.DomainName).trim(); 

log.info("GetNetworkParams gave domain=\"%s\"", domain);

JNA 分配缓冲区 FIXED_INFO 抛出无效内存访问

JNA allocate buffer FIXED_INFO throws Invalid memory access

java

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