怎么用VB實現(xiàn)對庫文件的分割備份(doc 13頁).doc

用VB實現(xiàn)對庫文件的分割備份在設(shè)計信息管理程序時，數(shù)據(jù)庫的軟盤備份與恢復(fù)是我們經(jīng)常遇到的一個問題。如果僅僅使用文件復(fù)制指令，那么在文件大小超過軟盤容量時，就會出現(xiàn)錯誤。下面我來介紹一種用VB實現(xiàn)的對文件進(jìn)行分割備份的方法。假設(shè)在E:CLASS目錄下有一個名為CLASSES.MDB的文件，3.8M，我們現(xiàn)在要按照每個1.4M，把它分割成3個文件進(jìn)行備份，然后，再恢復(fù)成CLASSES1.MDB文件。啟動VB,新建一個工程，添加一個模塊，將下列代碼填入模塊的聲明中： Type FileSection Bytes() As Byte FileLen As LongEnd TypeType SectionedFile Files() As FileSection NumberOfFiles As LongEnd TypeType FileInfo OrigProjSize As Long OrigFileName As String FileCount As Integer FileStartNum As LongEnd Type 然后，在Form1中添加兩個按鈕，分別命名為cmdBackup,Caption:備份；cmdRestore，Caption:恢復(fù)。 分別雙擊按鈕，填入以下代碼：Private Sub cmdBackup_Click() Dim SplitFileName As String 待備份的文件名 Dim Split As Long 備份文件的大小 Dim SaveName As String 備份文件名 Dim fNum As Integer 可用的文件號 Dim NumFil As Long 備份文件的數(shù)目 Dim FilesLen As Long 待備份文件的大小 Dim CurrentFile As SectionedFile 參數(shù)結(jié)構(gòu) SplitFileName = e:classclasses.mdb Split = 1400000 FilesLen = FileLen(SplitFileName) fNum = FreeFile Open SplitFileName For Binary As fNum 計算備份參數(shù) NumFil = CInt(FilesLen / Split) ReDim CurrentFile.Files(1 To NumFil) For i = 1 To NumFil ReDim CurrentFile.Files(i).Bytes(1 To Split) CurrentFile.Files(i).FileLen = UBound(CurrentFile.Files(i).Bytes) Next For i = 1 To NumFil Get #fNum, , CurrentFile.Files(i).Bytes Next ReDim CurrentFile.Files(NumFil).Bytes(1 To FilesLen - (NumFil - 1) * Split) CurrentFile.NumberOfFiles = NumFil Get #fNum, , CurrentFile.Files(NumFil).Bytes CurrentFile.Files(NumFil).FileLen = UBound(CurrentFile.Files(NumFil).Bytes)Close #fNum For i = 1 To CurrentFile.NumberOfFiles 分割備份 SaveName = SplitFileName & . & Format(BeginningNumber - 1 + i, 00#) fNum = FreeFile Open SaveName For Binary As fNum Put #fNum, 1, CurrentFile.Files(i) Close #fNum Next Dim FileInfoFile As FileInfo 相關(guān)數(shù)據(jù)寫入臨時文件 FileInfoFile.FileCount = NumFil FileInfoFile.OrigFileName = SplitFileName FileInfoFile.OrigProjSize = FileLen(SplitFileName) FileInfoFile.FileStartNum = BeginningNumber SaveName = SplitFileName & .tpl fNum = FreeFile Open SaveName For Binary As #fNum Put #fNum, , FileInfoFile Close #fNum End Sub Private Sub cmdRestore_Click() Dim OutName As String 恢復(fù)后文件名 Dim fNum As Integer 可用的文件號 Dim tmpFileName As String 臨時文件名 Dim File As SectionedFile 參數(shù)結(jié)構(gòu) Dim FileInfo As FileInfo 臨時文件的結(jié)構(gòu) tmpFileName = e:classclasses.mdb.tpl OutName = e:classclasses1.mdb fNum = FreeFile Open tmpFileName For Binary As #fNum 取得相關(guān)數(shù)據(jù) Get #fNum, , FileInfo Close #fNum ReDim File.Files(1 To FileInfo.FileCount) 打開備份文件 For i = 1 To FileInfo.FileCount OpenName = FileInfo.OrigFileName & . & Format(FileInfo.FileStartNum - 1 + i), 00#) fNum = FreeFile Open OpenName For Binary As #fNum Get #fNum, 1, File.Files(i) Close #fNum Next fNum = FreeFile Open OutName For Binary As #fNum 恢復(fù) For i = 1 To FileInfo.FileCount Put #fNum, , File.Files(i).Bytes Next Close #fNum End Sub 運行該例程，點擊“備份”按鈕，用資源管理器看看E:CLASS目錄，可以看到分割后的三個文件：CLASSES.MDB.000、CLASSES.MDB.001、CLASSES.MDB.002，大小分別為：1.