P-Invoke 解组在 DLL 中分配的结构数组
我需要将大量（理论上最多几 TB，仅受可用内存限制）数据从基于 C/C++ 的核心 DLL（用于管理、过滤和分配数据）铲到 C# GUI（仅读取数据）。如果数据从不重复而仅通过 C# 的引用进行访问，那将是最佳的。我的 DLL 方法的签名当前如下（我可以在那里进行更改）：
extern "C" {
typedef struct {
wchar_t* name;
__int32 t;
float v;
bool condition;
} TestData;
__declspec(dllexport) void fillTestArrayWithAlloc(TestData** td, __int32* size);
};
C# 不知道数组长度，可以是 1 到数百万之间的任何值......
我像这样映射结构：
[StructLayout(LayoutKind.Sequential)]
struct TestData
{
[MarshalAs(UnmanagedType.LPWStr)]
public String name;
public Int32 t;
[MarshalAs(UnmanagedType.R4)]
public float v;
public bool condition;
}
我尝试了手动解组像这样
static extern void fillTestArrayWithAlloc(ref IntPtr td, ref int size);
和自动解组这样
static extern void fillTestArrayWithAlloc([Out] TestData[] td, ref int size);
但是在这两种情况下它都会执行内存复制，这是不希望的。有没有办法在不复制数据的情况下做到这一点？
此致 彼得
I have a requirement to shovel large amounts (theoretically up to a few terabytes, only limited by available memory) of data from a C/C++ based core DLL which manages, filters and allocates the data, to a C# GUI (which only reads the data). It would be optimal if the data are never duplicated but only accessed per reference from the C#. The signature of my DLL's method is currently the following (I can make changes there):
extern "C" {
typedef struct {
wchar_t* name;
__int32 t;
float v;
bool condition;
} TestData;
__declspec(dllexport) void fillTestArrayWithAlloc(TestData** td, __int32* size);
};
The array length is not known to C# and can be anything between 1 and millions....
I mapped the structure like this:
[StructLayout(LayoutKind.Sequential)]
struct TestData
{
[MarshalAs(UnmanagedType.LPWStr)]
public String name;
public Int32 t;
[MarshalAs(UnmanagedType.R4)]
public float v;
public bool condition;
}
I tried both manual unmarshalling like this
static extern void fillTestArrayWithAlloc(ref IntPtr td, ref int size);
and automatic unmarshalling like this
static extern void fillTestArrayWithAlloc([Out] TestData[] td, ref int size);
But in both cases it performs a memory copy, which is undesired. Is there a way to do it without a data copy?
Best regards
Petr
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函数声明的第一个版本不应导致复制所有数据：仅对指针和长度值进行编组。
我认为您应该能够使用
实现一个迭代器或枚举器，一次直接从。您将需要执行一些IntPtr指向的非托管内存中编组一个TestData结构。 Marshal.PtrToStructure不安全指针算术，以便在迭代时从一个实例移动到另一个实例。这种方法应该避免大规模复制整个结构。祝你好运。
The first version of your function declaration should not cause all the data to be copied: only the pointer and length value will be marshalled.
I think you should then be able to implement an iterator or enumerator which marshals one
TestDatastructure at a time directly from the unmanaged memory pointed to by theIntPtr, usingMarshal.PtrToStructure. You will need to do someunsafepointer arithmetic to move from one instance to another as you iterate.This approach should avoid wholesale copying of the entire structure. Good luck.