從Windows獲取一個字節數組:: Storage :: Streams :: IBuffer

Question

我有一個對象實現了接口Windows::Storage::Streams::IBuffer，我想從中獲取一個字節數組，但是在查看文檔時界面看起來很沒用，而且文檔沒有提供任何可以與這個界面相結合的其他類的引用來實現我的目的。到目前爲止我發現的所有與谷歌是一個參考。NET類WindowsRuntimeBufferExtensions但我使用C++，所以這也是一個死衚衕。

有人可以提供一個關於如何在C++中獲得Windows::Storage::Streams::IBuffer字節數組的提示嗎？

Answer 1

可以使用IBufferByteAccess，通過異國COM轉換：

byte* GetPointerToPixelData(IBuffer^ buffer) 
{ 
    // Cast to Object^, then to its underlying IInspectable interface. 

    Object^ obj = buffer; 
    ComPtr<IInspectable> insp(reinterpret_cast<IInspectable*>(obj)); 

    // Query the IBufferByteAccess interface. 
    ComPtr<IBufferByteAccess> bufferByteAccess; 
    ThrowIfFailed(insp.As(&bufferByteAccess)); 

    // Retrieve the buffer data. 

    byte* pixels = nullptr; 
    ThrowIfFailed(bufferByteAccess->Buffer(&pixels)); 

    return pixels; 

} 

代碼示例從http://cm-bloggers.blogspot.fi/2012/09/accessing-image-pixel-data-in-ccx.html

Answer 2

Use the extension method like a static method：

IBuffer *buffer; 
array<unsigned char>^ result= System::Runtime::InteropServices::WindowsRuntime::WindowsRuntimeBufferExtensions::ToArray(buffer); 

Answer 3

如前所述，WindowsRuntimeBufferExtensions從命名空間System::Runtime::InteropServices::WindowsRuntime僅適用於.Net應用程序，而不是本機C++應用程序。

一種可能的解決辦法是使用Windows::Storage::Streams::DataReader：

void process(Windows::Storage::Streams::IBuffer^ uselessBuffer) 
{ 
    Windows::Storage::Streams::DataReader^ uselessReader = 
      Windows::Storage::Streams::DataReader::FromBuffer(uselessBuffer); 
    Platform::Array<Byte>^ managedBytes = 
         ref new Platform::Array<Byte>(uselessBuffer->Length); 
    uselessReader->ReadBytes(managedBytes);        
    BYTE * bytes = new BYTE[uselessBuffer->Length]; 
    for(int i = 0; i < uselessBuffer->Length; i++) 
     bytes[i] = managedBytes[i]; 

    (...) 
} 

Answer 4

這是一個C複製++/CX版本：

std::vector<unsigned char> getData(::Windows::Storage::Streams::IBuffer^ buf) 
{ 
    auto reader = ::Windows::Storage::Streams::DataReader::FromBuffer(buf); 

    std::vector<unsigned char> data(reader->UnconsumedBufferLength); 

    if (!data.empty()) 
     reader->ReadBytes(
      ::Platform::ArrayReference<unsigned char>(
       &data[0], data.size())); 

    return data; 
} 

欲瞭解更多信息，請參閱Array and WriteOnlyArray (C++/CX)。

Answer 5

還要檢查這個方法：

IBuffer - >平臺::陣列
CryptographicBuffer.CopyToByteArray

平臺::陣列 - > IBuffer
CryptographicBuffer.CreateFromByteArray

作爲一個側面說明，如果你想從簡單的C++數組創建Platform::Array，您可以使用Platform::ArrayReference，例如：

char* c = "sdsd"; 
Platform::ArrayReference<unsigned char> arraywrapper((unsigned char*) c, sizeof(c)); 

Answer 6

這應該與WinRT的擴展工作：

// Windows::Storage::Streams::DataReader 
// buffer is assumed to be of type Windows::Storage::Streams::IBuffer 
// BYTE = unsigned char 

DataReader^ reader = DataReader::FromBuffer(buffer); 

BYTE *extracted = new BYTE[buffer->Length]; 

// NOTE: This will read directly into the allocated "extracted" buffer 
reader->ReadBytes(Platform::ArrayReference<BYTE>(extracted, buffer->Length)); 

// ... do something with extracted... 

delete [] extracted; // don't forget to free the space