ACC: Sample Function CopyFile() to Copy Disk Files

• Microsoft Access versions 1.0, 1.1, 2.0

SUMMARY

Advanced: Requires expert coding, interoperability, and multiuser skills.

Access Basic does not have a command, such as the MS-DOS COPY command, to copy a disk file.

This article includes two variations of an Access Basic function called CopyFile(), both of which allow you to copy disk files.

This article assumes that you are familiar with Access Basic and with creating Microsoft Access applications using the programming tools provided with Microsoft Access. For more information on Access Basic, please refer to the "Introduction to Programming" manual in Microsoft Access version 1.x, or the "Building Applications" manual, Chapter 3, "Introducing Access Basic" in version 2.0.

NOTE: Microsoft Access for Windows 95 can copy files with the new FileCopy statement. For more information about FileCopy, search for "FileCopy Statement" using the Microsoft Access for Windows 95 Help Index.

MORE INFORMATION

Two variations of the Access Basic CopyFile() function are provided below. The first version uses only Microsoft Access Basic code; the second leverages some function calls to the Windows application programming interface (API) to optimize performance, particularly with larger files.

NOTE: You may have some Windows API functions defined in an existing Microsoft Access library; therefore, your declarations may be duplicates. If you receive the duplicate procedure name error message when you compile or run your code, remove or comment out the appropriate declarations statement from your code.

Method 1: CopyFile() Function Using Standard Access Basic Code

   '**************************************************************
   ' DECLARATION SECTION
   '**************************************************************
   Option Explicit

   '**************************************************************
   ' FUNCTION: CopyFile()
   ' PURPOSE:
   '   Facilitates copying a disk file.
   ' ARGUMENTS:
   '   Source      - The path\filename of the file to copy from.
   '   Destination - The path\filename of the file to copy to.
   ' RETURN:
   '   The length of the file copied.
   '**************************************************************
   Function CopyFile (ByVal Source$, ByVal Destination$) As Long
       Dim Index1 As Integer, NumBlocks As Integer
       Dim FileLength As Long, LeftOver As Long, AmountCopied As Long
       Dim SourceFile As Integer, DestFile As Integer
       Dim FileData As String
       Dim RetVal As Variant
       Const BlockSize = 32768

       On Error GoTo Err_CopyFile

       ' Remove the destination file.
       DestFile = FreeFile
       Open Destination For Output As DestFile
       Close DestFile

       ' Open the source file to read from.
       SourceFile = FreeFile
       Open Source For Binary Access Read As FreeFile

       ' Open the destination file to write to.
       DestFile = FreeFile
       Open Destination For Binary As DestFile

       ' Get the length of the source file.
       FileLength = LOF(SourceFile)

       ' Calculate the number of blocks in the file and left over.
       NumBlocks = FileLength \ BlockSize
       LeftOver = FileLength Mod BlockSize

       ' Create a buffer for the leftover amount.
       FileData = String$(LeftOver, 32)

       ' Read and write the leftover amount.
       Get SourceFile, , FileData
       Put DestFile, , FileData

       ' Create a buffer for a block to be read.
       FileData = String$(BlockSize, 32)

       ' Read and write the remaining blocks of data.
       For Index1 = 1 To NumBlocks
          ' Read and write one block of data.
          Get SourceFile, , FileData
          Put DestFile, , FileData
       Next Index1

       Close SourceFile, DestFile
       CopyFile = AmountCopied

   Bye_CopyFile:
       Exit Function

   Err_CopyFile:
       CopyFile = -1 * Err
       Resume Bye_CopyFile

   End Function

Method 2: CopyFile() Function Using Windows API function calls

   '****************************************************************
   ' DECLARATION SECTION
   '****************************************************************
   Declare Function fWrite Lib "kernel" Alias "_lwrite" (ByVal hFile%, _
                       ByVal lpBuff&, ByVal nBuff%) As Long
   Declare Function fRead Lib "kernel" Alias "_lread" (ByVal hFile%, _
                       ByVal lpBuff&, ByVal nBuff%) As Long
   Declare Function GlobalAlloc Lib "Kernel" (ByVal wFlags%, _
                       ByVal dwBytes&) As Integer
   Declare Function GLobalFree Lib "kernel" (ByVal hMem%) As Long
   Declare Function GlobalLock Lib "Kernel" (ByVal hMem%) As Long
   Declare Function GLobalUnlock Lib "kernel" (ByVal hMem%) As Long

   '****************************************************************
   ' FUNCTION: CopyFile()
   ' PURPOSE:
   '   Facilitates copying a disk file.
   ' ARGUMENTS:
   '   Source      - The path\filename of the file to copy from.
   '   Destination - The path\filename of the file to copy to.
   ' RETURN:
   '   The length of the file copied, if successful.
   '***********************************************************
   Function CopyFile (ByVal Source$, ByVal Destination$) As Long
       Dim FileLength As Long, AmountCopied As Long
       Dim RetVal As Variant, lpBuff As Long
       Dim DestFile As Integer, SourceFile As Integer
       Dim DestDOS As Integer, SourceDOS As Integer
       Dim ApiErr As Integer, AmtRead As Integer
       Dim hMem As Integer
       Const nBuff = 32767
       Const wFlags = &H20

       On Error GoTo Err_CopyFile

       ' Get the size of the file.
       SourceFile = FreeFile
       Open Source For Binary Access Read As SourceFile
       FileLength = LOF(SourceFile)
       Close SourceFile

       ' Allocate and lock memory to buffer file contents.
       hMem = GlobalAlloc(wFlags, nBuff)
       lpBuff = GlobalLock(hMem)

       ' Open the source file to read from.
       SourceFile = FreeFile
       Open Source For Input As SourceFile Len = 1

       ' Open the destination file to write to.
       DestFile = FreeFile
       Open Destination For Output As DestFile Len = 1

       ' Get the operating system file handles.
       DestDOS = FileAttr(DestFile, 2)
       SourceDOS = FileAttr(SourceFile, 2)

       Do
          ' Read and write nBuff worth of data.
          AmtRead = fRead(SourceDOS, ByVal lpBuff, nBuff)
          ApiErr = fWrite(DestDOS, ByVal lpBuff, AmtRead)
          AmountCopied = AmountCopied + AmtRead
       Loop Until AmtRead = 0

       Close SourceFile, DestFile

       ' Unlock and free the file buffer memory.
       lpBuff = GLobalUnlock(hMem)
       hMem = GLobalFree(hMem)

       CopyFile = AmountCopied

   Bye_CopyFile:
       Exit Function

   Err_CopyFile:
       CopyFile = -1 * Err
       Resume Bye_CopyFile
   End Function

1. Create or open a module in Microsoft Access.

2. From the View menu, choose Immediate Window.

3. Type the following line, and then press ENTER:

         ? CopyFile("C:\WINDOWS\CHESS.BMP", "C:\CHESS.BMP")
   

   The CopyFile() function can be invoked from an Access Basic function

         Dim RetVal As Long
         RetVal = CopyFile("C:\WINDOWS\CHESS.BMP", "C:\CHESS.BMP")
   

   or by using the RunCode macro action:

         RunCode
         Function Name: CopyFile("C:\WINDOWS\CHESS.BMP", "C:\CHESS.BMP")