java - Jna，指针已经映射到代理接口(interface)

Question

我正在尝试做一个 kotlin port的 openvr java binding并将其更新到 1.0.3

我正要写 IVRSystem struct/class

我手动编写了所有方法，以确保 Intellij 中的自动翻译器不会出现任何错误

我从 getFieldOrder() 中消除了来自不同数量字段的所有错误，但现在我仍然收到错误:

Exception in thread "main" java.lang.IllegalStateException: Pointer native@0xffffffff already mapped to Proxy interface to native function@0xffffffff (IVRSystem$GetEyeToHeadTransform_callback).
Native code may be re-using a default function pointer, in which case you may need to use a common Callback class wherever the function pointer is reused.
    at com.sun.jna.CallbackReference.getCallback(CallbackReference.java:124)
    at com.sun.jna.CallbackReference.getCallback(CallbackReference.java:107)
    at com.sun.jna.Pointer.getValue(Pointer.java:430)
    at com.sun.jna.Structure.readField(Structure.java:705)
    at com.sun.jna.Structure.read(Structure.java:565)
    at IVRSystem.<init>(vr.kt:2091)
    at VrKt.VR_Init(vr.kt:2116)
    at VrKt.main(vr.kt:2133)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

根据 this comment , 看起来好像有多次调用特定的回调 (GetEyeToHeadTransform_callback?)，但事实并非如此，我检查并仔细检查了代码，只有一个对该回调的引用..

还可能是什么？

编辑:

首先，当我在 IVRSysten 类上 read() 时会发生这种情况，但我无法避免...

其次，我看到了 here之前的所有方法都获取真实地址，例如native@0x7fee4bebfd0，只有GetEyeToHeadTransform总是获取native@0xffffffff...

编辑2:

调查原始代码

dprintf("GetRecommendedRenderTargetSize %p\n", &vr::IVRSystem::GetRecommendedRenderTargetSize);
dprintf("GetProjectionMatrix %p\n", &vr::IVRSystem::GetProjectionMatrix);
dprintf("GetProjectionRaw %p\n", &vr::IVRSystem::GetProjectionRaw);
dprintf("ComputeDistortion %p\n", &vr::IVRSystem::ComputeDistortion);
dprintf("GetEyeToHeadTransform %p\n", &vr::IVRSystem::GetEyeToHeadTransform);
dprintf("GetTimeSinceLastVsync %p\n", &vr::IVRSystem::GetTimeSinceLastVsync);
dprintf("GetD3D9AdapterIndex %p\n", &vr::IVRSystem::GetD3D9AdapterIndex);
dprintf("GetDXGIOutputInfo %p\n", &vr::IVRSystem::GetDXGIOutputInfo);
dprintf("IsDisplayOnDesktop %p\n", &vr::IVRSystem::IsDisplayOnDesktop);
dprintf("SetDisplayVisibility %p\n", &vr::IVRSystem::SetDisplayVisibility);
dprintf("GetDeviceToAbsoluteTrackingPose %p\n", &vr::IVRSystem::GetDeviceToAbsoluteTrackingPose);
dprintf("ResetSeatedZeroPose %p\n", &vr::IVRSystem::ResetSeatedZeroPose);
dprintf("GetSeatedZeroPoseToStandingAbsoluteTrackingPose %p\n", &vr::IVRSystem::GetSeatedZeroPoseToStandingAbsoluteTrackingPose);

打印出来

GetRecommendedRenderTargetSize 0109871D
GetProjectionMatrix 0109AACC
GetProjectionRaw 0109AAD1
ComputeDistortion 0109AAF9
GetEyeToHeadTransform 0109AAC2
GetTimeSinceLastVsync 0109AAE5
GetD3D9AdapterIndex 0109AAF4
GetDXGIOutputInfo 0109AADB
IsDisplayOnDesktop 0109AAEA
SetDisplayVisibility 0109AAE0
GetDeviceToAbsoluteTrackingPose 0109AAEF
ResetSeatedZeroPose 0109AAD6
GetSeatedZeroPoseToStandingAbsoluteTrackingPose 0109AAC7

GetEyeToHeadTransform 和 GetSeatedZeroPoseToStandingAbsoluteTrackingPose 有不同的指针..

Answer 1

native 代码为多个回调签名使用了一个“神奇”值 -1。编写 JNA 的回调代码时，假设将相同的函数指针映射到两个不同的签名应该是错误的。

我猜 -1 值意味着类似于“使用默认回调”(当可以说只是一个 NULL 指针可能就足够了，除非库使用 NULL 来指示不调用回调)。

您可以通过重写 Structure.read() 或 Structure.readField() 来解决这个问题，当您看到 时返回一个魔法值或常量回调对象>-1 值，例如

public void read() {
    Memory old = getPointer();
    Memory m = autoAllocate(size());
    // horribly inefficient, but it'll do
    m.write(0, old.getByteArray(0, size()), 0, size());
    useMemory(m);
    // Zero out the problematic callbacks
    for (field : problematic_fields) {
        m.setPointer(field_offset, null);
    }
    super.read();
    useMemory(old);
}