[英]Passing a byte array from Unity C# into a C++ library method
I have a C++ library method that I'd like to call from a Unity C# script. 我有一个C ++库方法,我想从Unity C#脚本调用。
I understand there are three key steps. 我知道有三个关键步骤。 First, to declare the C++ methods to be extern "C"
. 首先,将C ++方法声明为extern "C"
。 Second, to use [DllImport('foobar')]
before the corresponding C# extern method declaration. 其次,在相应的C#extern方法声明之前使用[DllImport('foobar')]
。 Third, to name the library file with the lib prefix (eg libfoobar.so
) and place it in the Unity plugins folder. 第三,使用lib前缀(例如libfoobar.so
)命名库文件,并将其放在Unity插件文件夹中。
So far so good -- if I'm only passing simple parameter types like int
from C# into C++. 到目前为止一切都很好 - 如果我只是将简单的参数类型(如C#中的int
传递给C ++。 However, to pass a byte[]
parameter, I will need to account for the different ways C# and C++ handle memory and pointers. 但是,要传递byte[]
参数,我需要考虑C#和C ++处理内存和指针的不同方式。 I haven't been able to find a definitive example of how to this should be done. 我无法找到一个如何做到这一点的明确例子。
My question: how to pass a byte[]
from a Unity C# script into a external C++ library method? 我的问题:如何将一个byte[]
从Unity C#脚本传递到外部C ++库方法?
You have to change your method definition to take an IntPtr. 您必须更改方法定义以获取IntPtr。 This is the C# way to define a pointer to non-managed memory. 这是定义指向非托管内存的指针的C#方式。 To create this pointer use Marshal.AllocHGlobal()
and then copy the data to it using Marshal.Copy()
. 为了创建这个指针使用Marshal.AllocHGlobal()
然后使用数据复制到Marshal.Copy()
Example (not tested): 示例(未测试):
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Runtime.InteropServices;
namespace Assets.Scripts
{
public class DLLCall
{
[DllImport("thedll")]
public static extern void TheCall(IntPtr byteArray, int size);
public void PerformCall(byte[] data)
{
IntPtr unmanagedArray = Marshal.AllocHGlobal(data.Length);
Marshal.Copy(data, 0, unmanagedArray, data.Length);
TheCall(unmanagedArray, data.Length);
Marshal.FreeHGlobal(unmanagedArray);
}
}
}
Notice that you have to free the unmanaged memory manually by using Marshal.FreeHGlobal
. 请注意,您必须使用Marshal.FreeHGlobal
手动释放非托管内存。 After this the memory is no longer valid so the C++ library can't use it any more. 在此之后,内存不再有效,因此C ++库不能再使用它了。 If it needs to access the array at a later point remove the FreeHGlobal
call and make sure to delete the memory after the library no longer requires access to it. 如果稍后需要访问该阵列,请删除FreeHGlobal
调用,并确保在库不再需要访问它之后删除该内存。
works for me: 适合我:
in unity: 团结一致:
[DllImport ("dllplugin")]
public static extern void Method (byte[] bytes);
in c++ Plugin 在c ++插件中
#define EXPORT_API __declspec(dllexport)
extern "C" void EXPORT_API Method(unsigned char* bytes)
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