Article ID: 172551
Article Last Modified on 3/7/2005
APPLIES TO
- Microsoft Foundation Class Library 4.2, when used with:
- Microsoft Visual C++ 5.0 Enterprise Edition
- Microsoft Visual C++ 5.0 Professional Edition
- Microsoft Visual C++ 6.0 Enterprise Edition
- Microsoft Visual C++ 6.0 Professional Edition
- Microsoft Visual C++ 6.0 Standard Edition
This article was previously published under Q172551
SYMPTOMS
CInternetSession::OpenURL() fails if you use a URL that specifies a file that contains spaces or other unsafe characters. For example, the following will fail:
CMyInternetSession s("");
CStdioFile* p = s.OpenURL("file://c:/temp/Text Document.txt");
As a result, a File Exception is thrown and the following message appears:
CAUSE
The specifications for a URL designate certain characters that must be escaped when they are present in a URL. The space character is one of the characters that must be escaped.
The function CInternetSession::OpenURL() calls a function that converts unsafe characters in the URL to their escape sequences before processing the URL further. If the URL is using the file protocol it creates a CStdioFile and returns a pointer to this object. However, CStdioFile does not understand the escaped path and, as a result, an exception is thrown.
RESOLUTION
When you use the file protocol, you must not convert unsafe characters to their escape sequences. The following code demonstrates how to do this by writing a CInternetSession derived class to override OpenURL().
// class definition
class CMyInternetSession : CInternetSession
{
public:
CMyInternetSession::CMyInternetSession(LPCTSTR pstrAgent = NULL,
DWORD dwContext = 1, DWORD dwAccessType =
PRE_CONFIG_INTERNET_ACCESS, LPCTSTR pstrProxyName = NULL,
LPCTSTR pstrProxyBypass = NULL, DWORD dwFlags = 0);
CStdioFile* CMyInternetSession::OpenURL(LPCTSTR pstrURL,
DWORD dwContext = 1, DWORD dwFlags =
INTERNET_FLAG_TRANSFER_ASCII, LPCTSTR pstrHeaders = NULL,
DWORD dwHeadersLength = 0);
};
// CMyInternetSession constructor
CMyInternetSession::CMyInternetSession(LPCTSTR pstrAgent,
DWORD dwContext, DWORD dwAccessType, LPCTSTR pstrProxyName,
LPCTSTR pstrProxyBypass, DWORD dwFlags)
{
CInternetSession(pstrAgent, dwContext, dwAccessType, pstrProxyName,
pstrProxyBypass, dwFlags);
}
CStdioFile* CMyInternetSession::OpenURL(LPCTSTR pstrURL,
DWORD dwContext, DWORD dwFlags, LPCTSTR pstrHeaders,
DWORD dwHeadersLength)
{
ASSERT(pstrURL != NULL);
ASSERT(dwHeadersLength == 0 || pstrHeaders != NULL);
// must have TRANSFER_BINARY or TRANSFER_ASCII but not both
#define _AFX_TRANSFER_MASK (INTERNET_FLAG_TRANSFER_BINARY \
| INTERNET_FLAG_TRANSFER_ASCII)
ASSERT((dwFlags & _AFX_TRANSFER_MASK) != 0);
ASSERT((dwFlags & _AFX_TRANSFER_MASK) != _AFX_TRANSFER_MASK);
DWORD dwServiceType;
CString strServer;
CString strObject;
INTERNET_PORT nPort;
BOOL bParsed = AfxParseURL(pstrURL, dwServiceType,
strServer, strObject, nPort);
// if it turns out to be a file...
if (bParsed && dwServiceType == AFX_INET_SERVICE_FILE)
{
CString userName;
CString password;
// Get the normalized file name with out converting
// unsafe characters to escape sequence.
AfxParseURLEx(pstrURL, dwServiceType, strServer,
strObject, nPort, userName, password, ICU_NO_ENCODE);
int nMode = CFile::modeRead | CFile::shareCompat;
if (dwFlags & INTERNET_FLAG_TRANSFER_BINARY)
nMode |= CFile::typeBinary;
else
nMode |= CFile::typeText;
return new CStdioFile(strObject, nMode);
}
return CInternetSession::OpenURL(pstrURL, dwContext, dwFlags,
pstrHeaders, dwHeadersLength);
}
REFERENCES
The specification for URL's are published by The World Wide Web Consortium (W3C). The specifications define the escape sequences and unsafe characters. Its URL is:
NOTE: Web links may change without notice.
Additional query words: 4.20b space file OpenURL filename
Keywords: kbprb KB172551
