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Waiting for URLDownloadToFile () to complete

I want the program to download a page from the Internet and do some parsing. The second part is simple, the first problem.

I want to use the URLDownloadToFile () function. But by default, it does not wait for the download to complete. MSDN says that the last parameter is a kind of callback function, but I cannot find any information on how to use it (when it is called and what it should do, even what type of function it is). Can someone explain to me that this is the last parameter and how to use it (in C ++) to revitalize my application?

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5 answers

Something simple, like the example below, should do the trick if you just want to download the file synchronously:

HRESULT hRez = URLDownloadToFile( NULL, _T(<url>), _T(<file>), 0, NULL );
if( hRez == 0 ){
 // download ok
}
else{
 // download failed
}
+2

, - .

URLDownloadToFile() syncronous , LPBINDSTATUSCALLBACK lpfnCB NULL.

"", , . URLDownloadToFile() TerminateThread() dlls, URLDownloadToFile() .

URLDownloadToFile() - , , .

URLDownloadToFile() , IE, IE , .

URLDownloadToFile() . URLDownloadToFile() , .

https://github.com/choptastic/OldCode-Public/blob/master/URLDownloadToFile/URLDownloadToFile.cpp

, , , - :

private:
    int progress, filesize;
    int AbortDownload;

public:

STDMETHOD(OnStartBinding)(
    { 
        AbortDownload=0;
        progress=0;
        filesize=0;
        return E_NOTIMPL; }

    STDMETHOD(GetProgress)()
        { return progress; }

    STDMETHOD(GetFileSize)()
        { return filesize; }
STDMETHOD(AbortDownl)()
    { 
        AbortDownload=1;
        return E_NOTIMPL; }

HRESULT DownloadStatus::OnProgress ( ULONG ulProgress, ULONG ulProgressMax,ULONG ulStatusCode, LPCWSTR wszStatusText )
{
    progress=ulProgress;
    filesize=ulProgressMax;
    if (AbortDownload) return E_ABORT;
    return S_OK;
}

.

, S_OK, URLDownloadToFile(), progress == filesize, URLDownloadToFile() S_OK, , - .

DeleteUrlCacheEntry() URLDownloadToFile(), , IE.

+8

, IBindStatusCallback. E_NOTIMPL . OnProgress(), . , :

#include "stdafx.h"
#include <windows.h>
#include <iostream>
#pragma comment(lib, "urlmon.lib")
using namespace std;

class DownloadProgress : public IBindStatusCallback {
public:
    HRESULT __stdcall QueryInterface(const IID &,void **) { 
        return E_NOINTERFACE;
    }
    ULONG STDMETHODCALLTYPE AddRef(void) { 
        return 1;
    }
    ULONG STDMETHODCALLTYPE Release(void) {
        return 1;
    }
    HRESULT STDMETHODCALLTYPE OnStartBinding(DWORD dwReserved, IBinding *pib) {
        return E_NOTIMPL;
    }
    virtual HRESULT STDMETHODCALLTYPE GetPriority(LONG *pnPriority) {
        return E_NOTIMPL;
    }
    virtual HRESULT STDMETHODCALLTYPE OnLowResource(DWORD reserved) {
        return S_OK;
    }
    virtual HRESULT STDMETHODCALLTYPE OnStopBinding(HRESULT hresult, LPCWSTR szError) {
        return E_NOTIMPL;
    }
    virtual HRESULT STDMETHODCALLTYPE GetBindInfo(DWORD *grfBINDF, BINDINFO *pbindinfo) {
        return E_NOTIMPL;
    }
    virtual HRESULT STDMETHODCALLTYPE OnDataAvailable(DWORD grfBSCF, DWORD dwSize, FORMATETC *pformatetc, STGMEDIUM *pstgmed) {
        return E_NOTIMPL;
    }        
    virtual HRESULT STDMETHODCALLTYPE OnObjectAvailable(REFIID riid, IUnknown *punk) {
        return E_NOTIMPL;
    }

    virtual HRESULT __stdcall OnProgress(ULONG ulProgress, ULONG ulProgressMax, ULONG ulStatusCode, LPCWSTR szStatusText)
    {
        wcout << ulProgress << L" of " << ulProgressMax;
        if (szStatusText) wcout << " " << szStatusText;
        wcout << endl;
        return S_OK;
    }
};


int _tmain(int argc, _TCHAR* argv[])
{
    DownloadProgress progress;
    HRESULT hr = URLDownloadToFile(0, 
        L"http://sstatic.net/stackoverflow/img/sprites.png?v=3", 
        L"c:/temp/test.png", 0,
        static_cast<IBindStatusCallback*>(&progress));
    return 0;
}

:

0 of 0 sstatic.net
0 of 0 64.34.119.12
0 of 0
0 of 0 image/x-png
3550 of 16542 http://sstatic.net/stackoverflow/img/sprites.png?v=3
3550 of 16542 C:\Users\hpassant\AppData\Local\Microsoft\Windows\Temporary Inter
et Files\Content.IE5\NRPH4KHK\sprites[1].png
7330 of 16542 http://sstatic.net/stackoverflow/img/sprites.png?v=3
8590 of 16542 http://sstatic.net/stackoverflow/img/sprites.png?v=3
12370 of 16542 http://sstatic.net/stackoverflow/img/sprites.png?v=3
13630 of 16542 http://sstatic.net/stackoverflow/img/sprites.png?v=3
16542 of 16542 http://sstatic.net/stackoverflow/img/sprites.png?v=3
+7

, " IBindStatusCallback ". , , , , . :

class CBindStatusCallback: public IBindStatusCallback
{
public:
  STDMETHODIMP OnProgress(ULONG ulProgress, ULONG ulProgressMax,
    ULONG ulStatusCode, LPCWSTR szStatusText)
  {
    // write your implementation here
  }
  // Override GetBindInfo and the other IBindStatusCallback methods
  // by simply returning E_NOTIMPL, like this:
  STDMETHODIMP GetBindInfo(DWORD* /*grfBINDF*/, BINDINFO* /*pbindinfo*/)
  {
    return E_NOTIMPL;
  }

  // Provide the usual implementations for these IUnknown methods.
  STDMETHODIMP QueryInterface(REFIID riid, void** ppv);
  STDMETHODIMP_(ULONG) AddRef();
  STDMETHODIMP_(ULONG) Release();
};

, IBindStatusCallback API. - :

CBindStatusCallback* obj = new CBindStatusCallback;
IBindStatusCallback* callback = NULL;
HResult hr = obj->QueryInterface(IID_IBindStatusCallback, &callback);
obj = NULL;
hr = URLDownloadToFile(..., callback);
callback->Release();
callback = NULL;

, , , . , .

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