AppendChunk 和 GetChunk 方法范例
该范例使用 AppendChunk 和 GetChunk 方法用其他记录中的数据填写图像字段。Public Sub AppendChunkX() Dim cnn1 As ADODB.Connection
Dim rstPubInfo As ADODB.Recordset
Dim strCnn As String
Dim strPubID As String
Dim strPRInfo As String
Dim lngOffset As Long
Dim lngLogoSize As Long
Dim varLogo As Variant
Dim varChunk As Variant
Const conChunkSize = 100 ' 打开连接
Set cnn1 = New ADODB.Connection
strCnn = "Provider=sqloledb;" & _
"Data Source=srv;Initial Catalog=pubs;User Id=sa;Password=; "
cnn1.Open strCnn
' 打开 pub_info 表。
Set rstPubInfo = New ADODB.Recordset
rstPubInfo.CursorType = adOpenKeyset
rstPubInfo.LockType = adLockOptimistic
rstPubInfo.Open "pub_info", cnn1, , , adCmdTable
' 提示复制徽标。
strMsg = "Available logos are : " & vbCr & vbCr
Do While Not rstPubInfo.EOF
strMsg = strMsg & rstPubInfo!pub_id & vbCr & _
Left(rstPubInfo!pr_info, InStr(rstPubInfo!pr_info, ",") - 1) & _
vbCr & vbCr
rstPubInfo.MoveNext
Loop
strMsg = strMsg & "Enter the ID of a logo to copy:"
strPubID = InputBox(strMsg)
' 将徽标复制到大块中的变量。
rstPubInfo.Filter = "pub_id = '" & strPubID & "'"
lngLogoSize = rstPubInfo!logo.ActualSize
Do While lngOffset < lngLogoSize
varChunk = rstPubInfo!logo.GetChunk(conChunkSize)
varLogo = varLogo & varChunk
lngOffset = lngOffset + conChunkSize
Loop
' 从用户得到数据。
strPubID = Trim(InputBox("Enter a new pub ID:"))
strPRInfo = Trim(InputBox("Enter descriptive text:"))
' 添加新记录,将徽标复制到大块中。
rstPubInfo.AddNew
rstPubInfo!pub_id = strPubID
rstPubInfo!pr_info = strPRInfo lngOffset = 0 ' 重置位移。
Do While lngOffset < lngLogoSize
varChunk = LeftB(RightB(varLogo, lngLogoSize - lngOffset), _
conChunkSize)
rstPubInfo!logo.AppendChunk varChunk
lngOffset = lngOffset + conChunkSize
Loop
rstPubInfo.Update
' 显示新添加的数据。
MsgBox "New record: " & rstPubInfo!pub_id & vbCr & _
"Description: " & rstPubInfo!pr_info & vbCr & _
"Logo size: " & rstPubInfo!logo.ActualSize ' 删除新记录,因为这只是演示。
rstPubInfo.Requery
cnn1.Execute "DELETE FROM pub_info " & _
"WHERE pub_id = '" & strPubID & "'" rstPubInfo.Close
cnn1.Close End Sub
该范例使用 AppendChunk 和 GetChunk 方法用其他记录中的数据填写图像字段。Public Sub AppendChunkX() Dim cnn1 As ADODB.Connection
Dim rstPubInfo As ADODB.Recordset
Dim strCnn As String
Dim strPubID As String
Dim strPRInfo As String
Dim lngOffset As Long
Dim lngLogoSize As Long
Dim varLogo As Variant
Dim varChunk As Variant
Const conChunkSize = 100 ' 打开连接
Set cnn1 = New ADODB.Connection
strCnn = "Provider=sqloledb;" & _
"Data Source=srv;Initial Catalog=pubs;User Id=sa;Password=; "
cnn1.Open strCnn
' 打开 pub_info 表。
Set rstPubInfo = New ADODB.Recordset
rstPubInfo.CursorType = adOpenKeyset
rstPubInfo.LockType = adLockOptimistic
rstPubInfo.Open "pub_info", cnn1, , , adCmdTable
' 提示复制徽标。
strMsg = "Available logos are : " & vbCr & vbCr
Do While Not rstPubInfo.EOF
strMsg = strMsg & rstPubInfo!pub_id & vbCr & _
Left(rstPubInfo!pr_info, InStr(rstPubInfo!pr_info, ",") - 1) & _
vbCr & vbCr
rstPubInfo.MoveNext
Loop
strMsg = strMsg & "Enter the ID of a logo to copy:"
strPubID = InputBox(strMsg)
' 将徽标复制到大块中的变量。
rstPubInfo.Filter = "pub_id = '" & strPubID & "'"
lngLogoSize = rstPubInfo!logo.ActualSize
Do While lngOffset < lngLogoSize
varChunk = rstPubInfo!logo.GetChunk(conChunkSize)
varLogo = varLogo & varChunk
lngOffset = lngOffset + conChunkSize
Loop
' 从用户得到数据。
strPubID = Trim(InputBox("Enter a new pub ID:"))
strPRInfo = Trim(InputBox("Enter descriptive text:"))
' 添加新记录,将徽标复制到大块中。
rstPubInfo.AddNew
rstPubInfo!pub_id = strPubID
rstPubInfo!pr_info = strPRInfo lngOffset = 0 ' 重置位移。
Do While lngOffset < lngLogoSize
varChunk = LeftB(RightB(varLogo, lngLogoSize - lngOffset), _
conChunkSize)
rstPubInfo!logo.AppendChunk varChunk
lngOffset = lngOffset + conChunkSize
Loop
rstPubInfo.Update
' 显示新添加的数据。
MsgBox "New record: " & rstPubInfo!pub_id & vbCr & _
"Description: " & rstPubInfo!pr_info & vbCr & _
"Logo size: " & rstPubInfo!logo.ActualSize ' 删除新记录,因为这只是演示。
rstPubInfo.Requery
cnn1.Execute "DELETE FROM pub_info " & _
"WHERE pub_id = '" & strPubID & "'" rstPubInfo.Close
cnn1.Close End Sub
'存文件到数据库
Const BLOCKSIZE = 4096 '每次读写块的大小Public rsBinary As New ADODB.Recordset
Public Function AddFile(ByVal FileID As Long)
'Return boolean to decide whether refresh files list
Dim strBin As String * 3000
Dim btyGet() As Byte
Dim lngBlockIndex As Long
Dim lngBlocks As Long
Dim lngLastBlock As Long
Dim lngPosition As Long
Dim lngFileLenth As Long
Dim lngIndex As Long
With frmBinary.CommonDialog1
'.InitDir = App.Path
.Filter = "All image files¦*.bmp;*.ico;*.jpg;*.gif¦Bitmap files¦*.bmp¦Icon files¦*.ico¦All files¦*.*"
.filename = ""
On Error GoTo ErrorHandle
.ShowOpen
On Error GoTo 0
If .filename <> "" Then
Open .filename For Binary As #1
lngFileLenth = LOF(1)
lngPosition = 0
'Get block count for loop
lngBlocks = lngFileLenth / BLOCKSIZE
'Get lngth of last block for the last read
lngLastBlock = lngFileLenth Mod BLOCKSIZE
TypeCode = Right(.filename, 3)
rsBinary.AddNew
rsBinary.Fields("typecode") = TypeCode
For lngBlockIndex = 1 To lngBlocks
ReDim btyGet(BLOCKSIZE)
Get #1, , btyGet()
rsBinary.Fields("content").AppendChunk btyGet()
lngPosition = lngPosition + BLOCKSIZE
Next If lngLastBlock > 0 Then
ReDim btyGet(lngLastBlock)
Get #1, , btyGet()
rsBinary.Fields("content").AppendChunk btyGet()
End If
rsBinary.Fields("id") = FileID
rsBinary.Update
rsBinary.UpdateBatch
Close #1
AddFile = True
MsgBox "Save finished", vbInformation
Else
AddFile = False
End If
End With
Exit Function
ErrorHandle:
AddFile = False
End Function'从数据库取文件出来
Public Sub SaveFile(ByVal FileID As Long)
Dim lngBlockCount As Long
Dim lngLastBlock As Long
Dim lngI As Long
Dim btyBlock() As Byte
Dim lngResult As Long
If rsBinary.EOF And rsBinary.BOF Then Exit Sub
rsBinary.Requery
rsBinary.MoveFirst
rsBinary.Find " id=" & FileID
If Not rsBinary.EOF Then
With frmBinary.CommonDialog1
.filename = "TempSave" & "." & rsBinary.Fields("typecode")
'.InitDir = App.Path
'If user cancel save the goto handle
On Error GoTo ErrorHandle
.ShowSave
If .filename <> "" Then
lngBlockCount = rsBinary.Fields("content").ActualSize \ BLOCKSIZE
lngLastBlock = rsBinary.Fields("content").ActualSize Mod BLOCKSIZE
If Dir(.filename) <> "" Then
If MsgBox("File " & .filename & " is exist,overwrite?", vbYesNo + vbQuestion) = vbYes Then
Kill .filename
Else
Exit Sub
End If
Else
End If
Open .filename For Binary As #1
ReDim btyBinary(BLOCKSIZE)
For lngI = 1 To lngBlockCount
btyBlock() = rsBinary.Fields("content").GetChunk(BLOCKSIZE)
Put #1, , btyBlock
Next
If lngLastBlock <> 0 Then
ReDim btyBlock(lngLastBlock)
btyBlock() = rsBinary.Fields("content").GetChunk(lngLastBlock)
Put #1, , btyBlock
End If
Close #1
MsgBox .filename & " is saved", vbInformation
Else
End If
End With
End If
Exit Sub
ErrorHandle:
End Sub