URLDownloadToCacheFile function

项目
07/13/2016

Downloads data to the Internet cache and returns the file name of the cache location for retrieving the bits.

Syntax

HRESULT URLDownloadToCacheFile(
  _In_       LPUNKNOWN           lpUnkcaller,
  _In_       LPCSTR              szURL,
  _Out_      LPTSTR              szFileName,
  _In_       DWORD               cchFileName,
  _Reserved_ DWORD               dwReserved,
  _In_opt_   IBindStatusCallback *pBSC
);

Parameters

lpUnkcaller [in]
A pointer to the controlling IUnknown interface of the calling ActiveX component, if the caller is an ActiveX component. If the caller is not an ActiveX component, this value can be set to NULL. Otherwise, the caller is a COM object that is contained in another component, such as an ActiveX control in the context of an HTML page. This parameter represents the outermost IUnknown of the calling component. The function attempts the download in the context of the ActiveX client framework, and allows the caller container to receive callbacks on the progress of the download.
szURL [in]
A pointer to a string value that contains the URL to download. Cannot be set to NULL.
szFileName [out]
A pointer to a string value that contains the name of the downloaded file. Cannot be set to NULL.
cchFileName [in]
An unsigned long integer value that contains the number of characters of the szFileName value.
dwReserved
Reserved. Must be set to 0.
pBSC [in, optional]
A pointer to the IBindStatusCallback interface of the caller. By using IBindStatusCallback::OnProgress, a caller can receive download status. URLDownloadToCacheFile calls the IBindStatusCallback::OnProgress and IBindStatusCallback::OnDataAvailable methods as data is received. The download operation can be canceled by returning E_ABORT from any callback. This parameter can be set to NULL if status is not required.

Return value

Returns one of the following values.

Return code	Description
E_FAIL	The operation failed.
E_OUTOFMEMORY	The buffer length is invalid, or there is insufficient memory to complete the operation.
S_OK	The operation succeeded.

Remarks

The client can choose to be notified of progress through a notification callback.

This function always returns a file name, if the download operation succeeds. If the given URL is a "file:" URL, URLDownloadToCacheFile directly returns the file name for the "file:" URL, instead of making a copy to the cache. If the given URL is an Internet URL, such as "http:" or "ftp:," URLDownloadToCacheFile downloads this file and returns the local file name of the cached copy. Use this function to ensure that a file name is returned without unnecessary copying of data.

Windows Internet Explorer 8. URLDownloadToCacheFile does not support IBindStatusCallbackEx and cannot be used to download files over 4 gigabytes (GB) in size. Refer instead to IBindStatusCallbackEx::GetBindInfoEx for a code example.

Requirements

Minimum supported client	Windows XP
Minimum supported server	Windows 2000 Server
Product	Internet Explorer 3.0
Header	Urlmon.h
Library	Urlmon.lib
DLL	Urlmon.dll
Unicode and ANSI names	URLDownloadToCacheFileW (Unicode) and URLDownloadToCacheFileA (ANSI)

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