使用BHO技术检测IE在浏览网页时下载到IE cache中的文件
关于BHO的使用介绍，可以参见
（1）Building Browser Helper Objects with Visual Studio 2005
链接地址：http://msdn.microsoft.com/en-us/library/bb250489.aspx
（2）Browser Helper Objects: The Browser the Way You Want It
链接地址：http://msdn.microsoft.com/en-us/library/bb250436%28v=vs.85%29.aspx
这两篇文章都已经在我前面的文章中进行了详细地介绍。
简单描述一下检测检测过程：
首先，我们需要捕获DISPID_STATUSTEXTCHANGE事件（因为我一直没有找到合适的事件来捕获所有的文件下载过程，当然，你可以试一试DISPID_DOCUMENTCOMPLETE，DISPID_DOWNLOADCOMPLETE以及DISPID_FILEDOWNLOAD等事件）
在Invoke函数中，添加如下事件处理代码：
STDMETHODIMP CIECacheFileDetecter::Invoke(DISPID dispidMember, REFIID riid, LCID lcid, WORD wFlags, DISPPARAMS* pDispParams, VARIANT* pvarResult, EXCEPINFO* pExcepInfo, UINT* puArgErr)
{
USES_CONVERSION;
strstream strEventInfo;
if (!pDispParams)
return E_INVALIDARG;
switch (dispidMember)
{
...
case DISPID_STATUSTEXTCHANGE:
LPOLESTR lpStatusText;
m_spWebBrowser2->get_StatusText(&lpStatusText);
strEventInfo << "StatusTextChange: ";
if (!StrCmp(OLE2T(lpStatusText), _T("")))
{
ATLTRACE(_T("Status Text: NULL/n"));
}
else
{
LPCTSTR pszStatusText = OLE2T(lpStatusText);
LPCTSTR pszMatchKey = _T("http");
LPTSTR pszSubText = StrStr(pszStatusText,pszMatchKey);
if (NULL != pszSubText)
{
ATLTRACE(_T("Status Text Change: %s/n"),pszStatusText);
LPTSTR pszEnd = StrStr(pszSubText,_T("..."));
if (NULL != pszEnd)
{
TCHAR *pszUrl = new TCHAR[_tcslen(pszSubText)];
_tcsncpy(pszUrl,pszSubText,_tcslen(pszSubText)-3);
pszUrl[_tcslen(pszSubText)-3] = '/0';
ATLTRACE(_T("URL: %s/n"),pszUrl);
DetectMimeType(pszUrl);
delete[] pszUrl;
}
}
}
break;
...
}
}
这里，DetectMimeType(pszUrl)从IE cache中查找对应的文件，并检测出相应的Mime Type，其具体实现如下：
BOOL CIECacheFileDetecter::DetectMimeType(LPCTSTR pszUrl)
{
USES_CONVERSION;
LPCTSTR strUrl = pszUrl;
DWORD dwEntrySize=0;
LPINTERNET_CACHE_ENTRY_INFO lpCacheEntry;
if (!GetUrlCacheEntryInfo(strUrl,NULL,&dwEntrySize))
{
if (GetLastError()!=ERROR_INSUFFICIENT_BUFFER)
{
return FALSE;
}
else
{
lpCacheEntry = (LPINTERNET_CACHE_ENTRY_INFO)
new char[dwEntrySize];
}
}
else
{
return FALSE;
}
if (!GetUrlCacheEntryInfo(strUrl,lpCacheEntry,&dwEntrySize))
{
return FALSE;
}
else
{
if ((lpCacheEntry->dwHeaderInfoSize)!=0)
{
// Read header information LPSTR(lpCacheEntry->lpHeaderInfo)[lpCacheEntry->dwHeaderInfoSize]=TEXT('/0');
ATLTRACE(_T("Header Info:/n%s/n"),lpCacheEntry->lpHeaderInfo);
}
// Read file information
const int BUF_SIZE = 200;
BYTE buffer[BUF_SIZE];
FILE* fh = fopen(T2A(lpCacheEntry->lpszLocalFileName),"r");
fread(buffer,sizeof(char),BUF_SIZE,fh);
fclose(fh);
LPWSTR strMime;
HRESULT hr = FindMimeFromData(NULL,NULL,(LPVOID)buffer,
BUF_SIZE,NULL,FMFD_DEFAULT,&strMime,0);
if (SUCCEEDED(hr))
{
LPCTSTR pszMimeType = W2CT(strMime);
ATLTRACE(_T("Mime Type: %s/n"),pszMimeType);
}
else
{
ATLTRACE(_T("Detect Mime Type Failed./n"));
}
return TRUE;
}
return 0;
}
这里，我们使用FindMimeFromData从文件中检测相应的Mime type。具体的函数信息如下：
FindMimeFromData Function
Determines the MIME type from the data provided.
Syntax
HRESULT FindMimeFromData(
LPBC pBC,
LPCWSTR pwzUrl,
LPVOID pBuffer,
DWORD cbSize,
LPCWSTR pwzMimeProposed,
DWORD dwMimeFlags,
LPWSTR *ppwzMimeOut,
DWORD dwReserved
);
Parameters
pBC
A pointer to the IBindCtx interface. Can be set to NULL.
pwzUrl
A pointer to a string value that contains the URL of the data. Can be set to NULL if pBuffer contains the data to be sniffed.
pBuffer
A pointer to the buffer that contains the data to be sniffed. Can be set to NULL if pwzUrl contains a valid URL.
cbSize
An unsigned long integer value that contains the size of the buffer.
pwzMimeProposed
A pointer to a string value that contains the proposed MIME type. This value is authoritative if type cannot be determined from the data. If the proposed type contains a semi-colon (;) it is removed. This parameter can be set to NULL.
dwMimeFlags
One of the following required values:
FMFD_DEFAULT
No flags specified. Use default behavior for the function.
FMFD_URLASFILENAME
Treat the specified pwzUrl as a file name.
FMFD_ENABLEMIMESNIFFING
Microsoft Internet Explorer 6 for Windows XP Service Pack 2 (SP2) and later. Use MIME-type detection even if FEATURE_MIME_SNIFFING is detected. Usually, this feature control key would disable MIME-type detection.
FMFD_IGNOREMIMETEXTPLAIN
Internet Explorer 6 for Windows XP SP2 and later. Perform MIME-type detection if "text/plain" is proposed, even if data sniffing is otherwise disabled. Plain text may be converted to text/html if HTML tags are detected.
FMFD_SERVERMIME
Windows Internet Explorer 8. Use the authoritative MIME type specified in pwzMimeProposed. Unless FMFD_IGNOREMIMETEXTPLAIN is specified, no data sniffing is performed.
FMFD_RESPECTTEXTPLAIN
Internet Explorer 9. Do not perform detection if "text/plain" is specified in pwzMimeProposed.
ppwzMimeOut
The address of a string value that receives the suggested MIME type.
dwReserved
Reserved. Must be set to 0.
Return Value
Returns one of the following values.
| S_OK |
The operation completed successfully. |
| E_FAIL |
The operation failed. |
| E_INVALIDARG |
One or more arguments are invalid. |
| E_OUTOFMEMORY |
There is insufficient memory to complete the operation. |
Remarks
MIME type detection, or "data sniffing," refers to the process of determining an appropriate MIME type from binary data. The final result depends on a combination of server-supplied MIME type headers, file name extension, and/or the data itself. Usually, only the first 256 bytes of data are significant. For more information and a complete list of recognized MIME types, see MIME Type Detection in Internet Explorer.
If pwzUrl is specified without data to be sniffed (pBuffer), the file name extension determines the MIME type. If the file name extension cannot be mapped to a MIME type, this method returns E_FAIL unless a proposed MIME type is supplied in pwzMimeProposed.
After ppwzMimeOut returns and is read, the memory allocated for it should be freed with the operator delete function.
Internet Explorer 8 and later. FindMimeFromData will not promote image types to "text/html" even if the data lacks signature bytes.