如何在C ++中的WinRT IBuffer中包装char *缓冲区 [英] How to wrap a char* buffer in a WinRT IBuffer in C++

问题描述

我想实现一个包装char *缓冲区的C ++ WinRT IBuffer，因此我可以将其与接受IBuffer ^参数的WinRT WriteAsync / ReadAsync操作一起使用。

I want to implement a C++ WinRT IBuffer that wraps a char* buffer, so i can use it with WinRT WriteAsync/ReadAsync operations that accept an IBuffer^ parameter.

编辑1（澄清）

我要避免数据复制。

推荐答案

大部分复制自 http://jeremiahmorrill.wordpress.com/2012 / 05/11 / http-winrt-client-for-c / ，但是可以直接包装我自己的字节[]：

Mostly copied from http://jeremiahmorrill.wordpress.com/2012/05/11/http-winrt-client-for-c/ but adapted to directly wrap my own byte[]:

NativeBuffer.h：

NativeBuffer.h:

#pragma once

#include <wrl.h>
#include <wrl/implements.h>
#include <windows.storage.streams.h>
#include <robuffer.h>
#include <vector>

// todo: namespace

class NativeBuffer : 
    public Microsoft::WRL::RuntimeClass<Microsoft::WRL::RuntimeClassFlags<Microsoft::WRL::RuntimeClassType::WinRtClassicComMix>,
    ABI::Windows::Storage::Streams::IBuffer,
    Windows::Storage::Streams::IBufferByteAccess>
{
public:
    virtual ~NativeBuffer()
    {
    }

    STDMETHODIMP RuntimeClassInitialize(byte *buffer, UINT totalSize)
    {
        m_length = totalSize;
        m_buffer = buffer;

        return S_OK;
    }

    STDMETHODIMP Buffer(byte **value)
    {
        *value = m_buffer;

        return S_OK;
    }

    STDMETHODIMP get_Capacity(UINT32 *value)
    {
        *value = m_length;

        return S_OK;
    }

    STDMETHODIMP get_Length(UINT32 *value)
    {
        *value = m_length;

        return S_OK;
    }

    STDMETHODIMP put_Length(UINT32 value)
    {
        m_length = value;

        return S_OK;
    }

private:
    UINT32 m_length;
    byte *m_buffer;
};

要创建IBuffer：

To create the IBuffer:

Streams::IBuffer ^CreateNativeBuffer(LPVOID lpBuffer, DWORD nNumberOfBytes)
{
    Microsoft::WRL::ComPtr<NativeBuffer> nativeBuffer;
    Microsoft::WRL::Details::MakeAndInitialize<NativeBuffer>(&nativeBuffer, (byte *)lpBuffer, nNumberOfBytes);
    auto iinspectable = (IInspectable *)reinterpret_cast<IInspectable *>(nativeBuffer.Get());
    Streams::IBuffer ^buffer = reinterpret_cast<Streams::IBuffer ^>(iinspectable);

    return buffer;
}

调用读取数据（lpBuffer为字节[]）：

And the call to read data (lpBuffer is the byte[]):

Streams::IBuffer ^buffer = CreateNativeBuffer(lpBuffer, nNumberOfbytes);
create_task(randomAccessStream->ReadAsync(buffer, (unsigned int)nNumberOfBytesToRead, Streams::InputStreamOptions::None)).wait();

我不确定ComPtr是否需要清理，因此欢迎提供有关内存管理的任何建议。

I am not so sure if the ComPtr needs some cleanup, so any suggestions regarding memory management are welcome.

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