如何在 C/C++ 中使用 WinHTTP 下载文件？
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How to download a file with WinHTTP in C/C++?
提问by
I know how to download an html/txt page. For example :
我知道如何下载 html/txt 页面。例如 ：
//Variables
DWORD dwSize = 0;
DWORD dwDownloaded = 0;
LPSTR pszOutBuffer;
vector <string> vFileContent;
BOOL bResults = FALSE;
HINTERNET hSession = NULL,
hConnect = NULL,
hRequest = NULL;
// Use WinHttpOpen to obtain a session handle.
hSession = WinHttpOpen( L"WinHTTP Example/1.0",
WINHTTP_ACCESS_TYPE_DEFAULT_PROXY,
WINHTTP_NO_PROXY_NAME,
WINHTTP_NO_PROXY_BYPASS, 0);
// Specify an HTTP server.
if (hSession)
hConnect = WinHttpConnect( hSession, L"nytimes.com",
INTERNET_DEFAULT_HTTP_PORT, 0);
// Create an HTTP request handle.
if (hConnect)
hRequest = WinHttpOpenRequest( hConnect, L"GET", L"/ref/multimedia/podcasts.html",
NULL, WINHTTP_NO_REFERER,
NULL,
NULL);
// Send a request.
if (hRequest)
bResults = WinHttpSendRequest( hRequest,
WINHTTP_NO_ADDITIONAL_HEADERS,
0, WINHTTP_NO_REQUEST_DATA, 0,
0, 0);
// End the request.
if (bResults)
bResults = WinHttpReceiveResponse( hRequest, NULL);
// Keep checking for data until there is nothing left.
if (bResults)
do
{
// Check for available data.
dwSize = 0;
if (!WinHttpQueryDataAvailable( hRequest, &dwSize))
printf( "Error %u in WinHttpQueryDataAvailable.\n",
GetLastError());
// Allocate space for the buffer.
pszOutBuffer = new char[dwSize+1];
if (!pszOutBuffer)
{
printf("Out of memory\n");
dwSize=0;
}
else
{
// Read the Data.
ZeroMemory(pszOutBuffer, dwSize+1);
if (!WinHttpReadData( hRequest, (LPVOID)pszOutBuffer,
dwSize, &dwDownloaded))
{
printf( "Error %u in WinHttpReadData.\n",
GetLastError());
}
else
{
printf("%s", pszOutBuffer);
// Data in vFileContent
vFileContent.push_back(pszOutBuffer);
}
// Free the memory allocated to the buffer.
delete [] pszOutBuffer;
}
} while (dwSize>0);
// Report any errors.
if (!bResults)
printf("Error %d has occurred.\n",GetLastError());
// Close any open handles.
if (hRequest) WinHttpCloseHandle(hRequest);
if (hConnect) WinHttpCloseHandle(hConnect);
if (hSession) WinHttpCloseHandle(hSession);
// Write vFileContent to file
ofstream out("test.txt",ios::binary);
for (int i = 0; i < (int) vFileContent.size();i++)
out << vFileContent[i];
out.close();
When I try to download a picture, I get only the first lines of the file and no error message. The problem seems related to this parameter (ppwszAcceptTypes) in WinHttpOpenRequest Function.
当我尝试下载图片时，我只得到文件的第一行，没有错误消息。该问题似乎与 WinHttpOpenRequest 函数中的此参数 (ppwszAcceptTypes) 有关。
采纳答案by Lou Franco
Looks like this thread on MSDN is the same and has the solution
看起来 MSDN 上的这个线程是相同的并且有解决方案
http://social.msdn.microsoft.com/forums/en-US/vclanguage/thread/45ccd91c-6794-4f9b-8f4f-865c76cc146d
http://social.msdn.microsoft.com/forums/en-US/vclanguage/thread/45ccd91c-6794-4f9b-8f4f-865c76cc146d
回答by
Solution :
解决方案 ：
FILE * pFile; // NEW
pFile = fopen("file.bin", "w+b"); // NEW
if (bResults)
do
{
// Check for available data.
dwSize = 0;
if (!WinHttpQueryDataAvailable( hRequest, &dwSize))
printf( "Error %u in WinHttpQueryDataAvailable.\n",
GetLastError());
// Allocate space for the buffer.
pszOutBuffer = new char[dwSize+1];
if (!pszOutBuffer)
{
printf("Out of memory\n");
dwSize=0;
}
else
{
// Read the Data.
ZeroMemory(pszOutBuffer, dwSize+1);
if (!WinHttpReadData( hRequest, (LPVOID)pszOutBuffer,
dwSize, &dwDownloaded))
{
printf( "Error %u in WinHttpReadData.\n",
GetLastError());
}
else
{
printf("%s", pszOutBuffer);
fwrite(pszOutBuffer, (size_t)dwDownloaded, (size_t)1, pFile); // NEW
}
// Free the memory allocated to the buffer.
delete [] pszOutBuffer;
}
} while (dwSize>0);
fclose (pFile); // NEW
回答by
Merely opening the ofstream in binary mode does not change the way that the << operators work - they will always perfform formatted output. You need to use the stream's write() function, which does unformatted output.
仅以二进制模式打开 ofstream 不会改变 << 运算符的工作方式 - 它们将始终执行格式化输出。您需要使用流的 write() 函数，该函数执行未格式化的输出。
