c++下利用URLOpenStream下载

URLDownloadToFile实现文件下载很方便

#include <Urlmon.h>
#pragma comment(lib, "urlmon.lib")

bool downloadFile(const char* url, const char* fileName)
{
	HRESULT res = URLDownloadToFileA(NULL, url, fileName, 0, NULL);
	 
	return (res == S_OK);
}

但你可能想利用URLOpenStream实现更复杂的需求（比如不保存磁盘文件）

但查msdn还是比较麻烦的，这里直接上示例代码：

#include <iostream>
#include <cstdio>
#include <UrlMon.h>
#pragma comment(lib, "urlmon.lib")
#include <tchar.h>
#include <fstream>

class MyListener : public IBindStatusCallback
{
public:

    STDMETHOD(OnStartBinding)(
        DWORD dwReserved,
        IBinding __RPC_FAR *pib)
    {
        return E_NOTIMPL;
    }

    STDMETHOD(GetPriority)(
        LONG __RPC_FAR *pnPriority)
    {
        return E_NOTIMPL;
    }

    STDMETHOD(OnLowResource)(
        DWORD reserved)
    {
        return E_NOTIMPL;
    }

    STDMETHOD(OnProgress)(
        ULONG ulProgress,    //当前大小
        ULONG ulProgressMax, //总大小
        ULONG ulStatusCode,
        LPCWSTR szStatusText)
    {
        if (ulProgressMax != 0)
        {
            std::cout << ulProgress * 100.0 / ulProgressMax << "%	" << ulStatusCode << "
";
        }
        return S_OK;
    }

    STDMETHOD(OnStopBinding)(
        HRESULT hresult,
        LPCWSTR szError)
    {
        return E_NOTIMPL;
    }

    STDMETHOD(GetBindInfo)(
        DWORD __RPC_FAR *grfBINDF,
        BINDINFO __RPC_FAR *pbindinfo)
    {
        return E_NOTIMPL;
    }

    STDMETHOD(OnDataAvailable)(
        DWORD grfBSCF,
        DWORD dwSize,
        FORMATETC __RPC_FAR *pformatetc,
        STGMEDIUM __RPC_FAR *pstgmed)
    {
            //BSCF_FIRSTDATANOTIFICATION = 0x00000001,
            //BSCF_INTERMEDIATEDATANOTIFICATION = 0x00000002,
            //BSCF_LASTDATANOTIFICATION = 0x00000004,
        //有可能为BSCF_FIRSTDATANOTIFICATION, BSCF_FIRSTDATANOTIFICATION & BSCF_LASTDATANOTIFICATION, BSCF_INTERMEDIATEDATANOTIFICATION, BSCF_LASTDATANOTIFICATION
        //即可能为一个包、两个包或多个包
        if (grfBSCF & BSCF_FIRSTDATANOTIFICATION) 
        {
            pstgmed->pstm->Read(mData, dwSize, &mSize);
        }
        else
        {
            ULONG size;
            pstgmed->pstm->Read(mData + mSize, dwSize, &size);
            mSize += size;
            std::cout << dwSize << "	" << size << "	" << mSize << "
";
        }

        
        return S_OK;
    }

    STDMETHOD(OnObjectAvailable)(
        REFIID riid,
        IUnknown __RPC_FAR *punk)
    {
        return E_NOTIMPL;
    }

    STDMETHOD_(ULONG, AddRef)()
    {
        return 0;
    }

    STDMETHOD_(ULONG, Release)()
    {
        return 0;
    }

    STDMETHOD(QueryInterface)(
        REFIID riid,
        void __RPC_FAR *__RPC_FAR *ppvObject)
    {
        return E_NOTIMPL;
    }

    void save(char* fileName)
    {
        file.open(fileName, std::ios::binary);
        file.write(mData, mSize);
        file.close();
    }
private:
    std::ofstream file;
    ULONG mSize;
    char mData[64 * 1024];
};


int main(int argc, char* argv[])
{
    char url[256];
    char fileName[256];

    MyListener* listener = new MyListener;
    HRESULT result = URLOpenStream(0, url, 0, listener);
            if (result == S_OK)
            {
                listener->save(fileName);
            }
            else
            {
                std::cout << result << "    failure!
";
            }
152 
    delete listener;

    system("pause");
}