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IWinHttpRequest::ResponseStream property

The ResponseStream property retrieves the response entity body as an IStream.

This property is read-only.

Syntax


HRESULT get_ResponseStream(
  [out, retval]  VARIANT *Body
);

Property value

A Variant that receives a pointer to an IUnknown interface that can be queried for an IStream interface. This stream returns the raw data as received directly from the server.

Error codes

The return value is S_OK on success or an error value otherwise.

It will be E_PENDING if the previous Send operation is not complete.

Remarks

Call QueryInterface on the returned pointer to obtain a pointer to an IStream interface. This property returns the response data as an IStream. This property can only be invoked after the Send method has been called.

Note  For Windows XP and Windows 2000, see the Run-Time Requirements section of the WinHTTP Start Page.

Examples

The following example shows how to open an HTTP connection, send an HTTP request, and read the response as an IStream. The data from the IStream is written to the file Temp1.gif.


#include <windows.h>
#include <stdio.h>
#include <objbase.h>

#include "httprequest.h"

#pragma comment(lib, "ole32.lib")
#pragma comment(lib, "oleaut32.lib")

// IID for IWinHttpRequest.
const IID IID_IWinHttpRequest =
{
  0x06f29373,
  0x5c5a,
  0x4b54,
  {0xb0, 0x25, 0x6e, 0xf1, 0xbf, 0x8a, 0xbf, 0x0e}
};

#define Trace(_s) fprintf(stderr, _s) 
#define TraceErr(_s, _hr) fprintf(stderr, _s, _hr) 
#define Check(_hr,_s) if (FAILED(_hr)) { fprintf(stderr, _s ## " 0x%08lx\n", _hr); return -1; }

int main(int argc, char* argv[])
{
    UNREFERENCED_PARAMETER(argc);
    UNREFERENCED_PARAMETER(argv);
    
    // Variable for return value.
    HRESULT    hr;

    // Initialize COM.
    hr = CoInitialize( NULL );

    IWinHttpRequest *  pIWinHttpRequest = NULL;

    BSTR            bstrResponse = NULL;
    VARIANT         varFalse;
    VARIANT         varEmpty;
    VARIANT            varResponse;

    VariantInit(&varResponse);
    
    CLSID           clsid;

    VariantInit(&varFalse);
    V_VT(&varFalse)   = VT_BOOL;
    V_BOOL(&varFalse) = VARIANT_FALSE;

    VariantInit(&varEmpty);
    V_VT(&varEmpty) = VT_ERROR;

    hr = CLSIDFromProgID(L"WinHttp.WinHttpRequest.5.1", &clsid);

    if (SUCCEEDED(hr))
    {
        hr = CoCreateInstance(clsid, NULL, 
                              CLSCTX_INPROC_SERVER, 
                              IID_IWinHttpRequest, 
                              (void **)&pIWinHttpRequest);
    }

    // ==== Get binary (.gif) file and write it to disk. =========
    if (SUCCEEDED(hr))
    {    // Open WinHttpRequest for synchronous access.
        BSTR bstrMethod = SysAllocString(L"GET");
        BSTR bstrUrl = SysAllocString(
            L"http://www.microsoft.com/library/homepage/images/ms-banner.gif");
        hr = pIWinHttpRequest->Open(bstrMethod, bstrUrl, varFalse);
        SysFreeString(bstrMethod);
        SysFreeString(bstrUrl);
    }
    if (SUCCEEDED(hr))
    {    // Send Request.
        hr = pIWinHttpRequest->Send(varEmpty);
    }
    if (SUCCEEDED(hr))
    {    // Get response body.
        hr = pIWinHttpRequest->get_ResponseBody(&varResponse);
    }
    if (SUCCEEDED(hr))
    {    // Print response to file temp1.gif.
        long UpperBounds;
        long LowerBounds;
        unsigned char* buff;
        // Verify that varResponse contains array of unsigned bytes.
        if (varResponse.vt == (VT_ARRAY | VT_UI1)) {
            long Dims = SafeArrayGetDim(varResponse.parray);
            // The array should only have 1 dimension.
            if (Dims == 1) {
                // Get upper and lower array bounds.
                SafeArrayGetLBound(varResponse.parray, 1, 
                                   &LowerBounds);
                SafeArrayGetUBound(varResponse.parray, 1, 
                                   &UpperBounds);
                UpperBounds++;
                // Lock SAFEARRAY for access.
                SafeArrayAccessData (varResponse.parray, 
                                     (void**)&buff);
                // Output array to file temp.gif.
                HANDLE hFile; 
                DWORD  dwBytesWritten;
                // Create file.
                hFile = CreateFile(TEXT("Temp1.gif"),     
                    GENERIC_WRITE,              // Open for writing. 
                    0,                          // Do not share. 
                    NULL,                       // No security. 
                    CREATE_ALWAYS,              // Overwrite existing.
                    FILE_ATTRIBUTE_NORMAL,      // Normal file.
                    NULL);                      // No attribute template.

                if (hFile == INVALID_HANDLE_VALUE) 
                    {
                    wprintf(L"Could not open file."); // Process error.
                    }
                else
                    {
                    WriteFile(hFile, buff, UpperBounds - LowerBounds, 
                        &dwBytesWritten, NULL); 
                    }
                CloseHandle(hFile);
                SafeArrayUnaccessData (varResponse.parray);
            }
        }    
    }

    // ======== Get binary (.gif) file and write 
    // it to disk using IStream. ================
    if (SUCCEEDED(hr))
    {    // Open WinHttpRequest for synchronous access.
        BSTR bstrMethod = SysAllocString(L"GET");
        BSTR bstrUrl = SysAllocString(
            L"http://www.microsoft.com/library/homepage/images/ms-banner.gif");
        hr = pIWinHttpRequest->Open(bstrMethod, bstrUrl, varFalse);
        SysFreeString(bstrMethod);
        SysFreeString(bstrUrl);
    }
    if (SUCCEEDED(hr))
    {    // Send Request.
        hr = pIWinHttpRequest->Send(varEmpty);
    }
    if (SUCCEEDED(hr))
    {    // Get Response as an IStream.
        hr = pIWinHttpRequest->get_ResponseStream(&varResponse);
    }
    if (SUCCEEDED(hr))
    {    // Print response to file temp1.gif.
        IStream*    pStream = NULL; 
        BYTE        bBuffer[8192]; 
        DWORD       cb, cbRead, cbWritten; 
        // Check that an IStream was received.
        if (VT_UNKNOWN == V_VT(&varResponse) || 
            VT_STREAM == V_VT(&varResponse)) 
        { 
            // Get IStream interface pStream.
            hr = V_UNKNOWN(&varResponse)->QueryInterface(IID_IStream, 
                                 reinterpret_cast<void**>(&pStream)); 
            Check(hr, "QI for IStream"); 
        } 
        else 
        { 
            wprintf(L"Unexpected vartype for Response\n"); 
            return -1; 
        } 

        HANDLE hFile; 
        // Open file Temp2.gif for output.
        hFile = CreateFile(TEXT("Temp2.gif"),     
            GENERIC_WRITE,                // Open for writing. 
            0,                            // Do not share. 
            NULL,                         // No security. 
            CREATE_ALWAYS,                // Overwrite existing.
            FILE_ATTRIBUTE_NORMAL,        // Normal file.
            NULL);                        // No attribute template.
        if (hFile == INVALID_HANDLE_VALUE) 
            {
            wprintf(L"Could not open file.");  // Process error.
            }
        else
            {
            // Copy data from the response stream to file. 
            cb = sizeof(bBuffer); 
            hr = pStream->Read(bBuffer, cb, &cbRead); 
            while (SUCCEEDED(hr) && 0 != cbRead) 
                { 
                if (!WriteFile(hFile, bBuffer, 
                               cbRead, &cbWritten, NULL)) 
                    { 
                    TraceErr("WriteFile fails with 0x%08lx\n", 
                             HRESULT_FROM_WIN32(GetLastError())); 
                    return -1; 
                    } 
                hr = pStream->Read(bBuffer, cb, &cbRead); 
                } 
            }
        CloseHandle(hFile);
        pStream->Release(); 
        VariantClear(&varResponse); 
    }
    // Release memory.
    if (pIWinHttpRequest)
        pIWinHttpRequest->Release();
    if (bstrResponse)
        SysFreeString(bstrResponse);
    
    CoUninitialize();
    return 0;
}


Requirements

Minimum supported client

Windows XP, Windows 2000 Professional with SP3 [desktop apps only]

Minimum supported server

Windows Server 2003, Windows 2000 Server with SP3 [desktop apps only]

Redistributable

WinHTTP 5.0 and Internet Explorer 5.01 or later on Windows XP and Windows 2000.

IDL

HttpRequest.idl

Library

Winhttp.lib

DLL

Winhttp.dll

See also

IWinHttpRequest
WinHttpRequest
ResponseBody
ResponseText
WinHTTP Versions

 

 

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