Internet技巧兩則

Internet技巧兩則
    一、判斷某一個(gè)連接是否保存在Cache中
    在使用Microsoft IE在網(wǎng)上沖浪時(shí)，IE會(huì)把你瀏覽過(guò)的網(wǎng)頁(yè)保存在Cache中以便你可以脫機(jī)瀏覽。
    下面這個(gè)程序可以判斷一個(gè)URL是否在瀏覽器的Cache中。
    首先建立一個(gè)新的VB工程文件，在Form1中加入一個(gè)CommandButton控件和一個(gè)TextBox控件，然后
    在Form1的代碼窗口中加入以下代碼：
    Option Explicit
    Private Const ERROR_INSUFFICIENT_BUFFER = 122
     Private Const eeErrorBase = 26720
    Private Type FILETIME
     dwLowDateTime As Long
     dwHighDateTime As Long
     End Type
    Private Type INTERNET_CACHE_ENTRY_INFO
     dwStructSize As Long
     lpszSourceUrlName As String
     lpszLocalFileName As String
     CacheEntryType As String
     dwUseCount As Long
     dwHitRate As Long
     dwSizeLow As Long
     dwSizeHigh As Long
     LastModifiedTime As FILETIME
     ExpireTIme As FILETIME
     LastAccessTime As FILETIME
     LastSyncTime As FILETIME
     lpHeaderInfo As Long
     dwHeaderInfoSize As Long
     lpszFileExtension As String
     dwReserved As Long
     End Type
    Private Declare Function GetUrlCacheEntryInfo Lib "wininet.dll" Alias _
     "GetUrlCacheEntryInfoA" _
     (ByVal sUrlName As String, _
     lpCacheEntryInfo As Any, _
     lpdwCacheEntryInfoBufferSize As Long _
     ) As Long
    Private Const FORMAT_MESSAGE_ALLOCATE_BUFFER = &H100
     Private Const FORMAT_MESSAGE_ARGUMENT_ARRAY = &H2000
     Private Const FORMAT_MESSAGE_FROM_HMODULE = &H800
     Private Const FORMAT_MESSAGE_FROM_STRING = &H400
     Private Const FORMAT_MESSAGE_FROM_SYSTEM = &H1000
     Private Const FORMAT_MESSAGE_IGNORE_INSERTS = &H200
     Private Const FORMAT_MESSAGE_MAX_WIDTH_MASK = &HFF
    Private Declare Function FormatMessage Lib "kernel32" Alias "FormatMessageA" _
     (ByVal dwFlags As Long, lpSource As Any, ByVal dwMessageId As Long, _
     ByVal dwLanguageId As Long, ByVal lpBuffer As String, ByVal nSize As _
     Long, Arguments As Long) As Long
    Public Function WinAPIError(ByVal lLastDLLError As Long) As String
     Dim sBuff As String
     Dim lCount As Long
    ´獲取錯(cuò)誤消息
     sBuff = String$(256, 0)
     lCount = FormatMessage( _
     FORMAT_MESSAGE_FROM_SYSTEM Or FORMAT_MESSAGE_IGNORE_INSERTS, _
     0, lLastDLLError, 0&, sBuff, Len(sBuff), ByVal 0)
     If lCount Then
     WinAPIError = Left$(sBuff, lCount)
     End If
     End Function
    Public Function GetCacheEntryInfo(ByVal hWnd As Long, ByVal lpszUrl As String) As Boolean
     Dim dwEntrySize As Long
     Dim lpCacheEntry As INTERNET_CACHE_ENTRY_INFO
     Dim dwTemp As Long
     Dim lErr As Long
    If (GetUrlCacheEntryInfo(lpszUrl, ByVal 0&, dwEntrySize)) = 0 Then
     lErr = Err.LastDllError
     If (lErr <> ERROR_INSUFFICIENT_BUFFER) Then
     ´URL沒(méi)有在Cache中
     Err.Raise eeErrorBase + 1, App.EXEName & ".mCacheEntry", WinAPIError(lErr)
     GetCacheEntryInfo = False
     Exit Function
     Else
     ´URL保存在Cache中
     GetCacheEntryInfo = True
     End If
     End If
     End Function
    Private Sub Command1_Click()
     On Error GoTo ErrorHandler
     If (GetCacheEntryInfo(Me.hWnd, Text1.Text)) Then
     MsgBox "URL 保存在Cache中.", vbInformation
     Else
     MsgBox "URL 沒(méi)有保存在Cache中.", vbInformation
     End If
    Exit Sub
    ErrorHandler:
     MsgBox "URL 沒(méi)有保存在Cache中 [" & Err.Description & "]", vbInformation
     End Sub
    Private Sub Form_Load()
     Form1.CurrentX = 150: Form1.CurrentY = 60
     Form1.Print "在Text1中輸入U(xiǎn)RL，按Command1檢測(cè)"
     Text1.Text = ""
     Command1.Default = True
     End Sub
    運(yùn)行程序，在TextBox中輸入U(xiǎn)RL地址（例如http://member.netease.com/~blackcat），然后點(diǎn)擊Command1按鈕，如果URL在Cache中，程序會(huì)彈出消息框顯示URL 保存在Cache中。