只有在用户选择保存附件的情况下,才需要进行解码工作。此时用户需要先选定要保存的文件,然后按Save As按钮。代码如下:Private Sub cmdSave_Click()Dim strFileName As String Dim strMessage As String Dim strAttachment As String Dim lngPosA As Long Dim lngPosB As Long'Extract full text of the message strMessage = m_colMessages(lvMessages.SelectedItem.Key).MessageText 'Extract name of the file strFileName = lvAttachments.SelectedItem.Key ' Do Until lngPosA = 0 'Looking for the file's name in the message's text lngPosA = InStr(lngPosA + 1, strMessage, " " & strFileName) If lngPosA > 0 Then 'End of string with the file's name lngPosB = InStrRev(strMessage, vbCrLf, lngPosA) + 2 If lngPosB > 2 Then 'Check whether the string with the file's name 'is the part of the "begin" er If (Mid$(strMessage, lngPosB, lngPosA - lngPosB _ + Len(strFileName) + 1)) Like _ ("begin ### " & strFileName) Then 'Position of the end er lngPosA = InStr(lngPosA, strMessage, "'" & _ vbCrLf & "end" & vbCrLf) If lngPosA > 0 Then With ComDialog 'Bring up the file selection dialog .FileName = strFileName .ShowSave If Err = 0 Then 'Encoding data save to the strAttachment 'variable strAttachment = Mid$(strMessage, lngPosB, _ lngPosA + 8 - lngPosB) 'Pass it to the UUDecodeToFile routine 'in order to decode and save as file UUDecodeToFile strAttachment, .FileName End If End With End If End If End If End If Loop End Sub最后是UUDecodeToFile函数的代码: Public Function UUDecodeToFile(strUUCodeData As String, strFilePath As String)Dim vDataLine As Variant Dim vDataLines As Variant Dim strDataLine As String Dim intSymbols As Integer Dim intFile As Integer Dim strTemp As String ' 'Remove first er If Left$(strUUCodeData, 6) = "begin " Then strUUCodeData = Mid$(strUUCodeData, InStr(1, strUUCodeData, vbLf) + 1) End If ' 'Remove er of the attachment's end If Right$(strUUCodeData, 5) = "end" + vbCrLf Then strUUCodeData = Left$(strUUCodeData, Len(strUUCodeData) - 10) End If intFile = FreeFile Open strFilePath For Binary As intFile 'Break decoded data to the strings 'From now each member of the array vDataLines contains 'one line of the encoded data vDataLines = Split(strUUCodeData, vbCrLf) For Each vDataLine In vDataLines 'Decode data line by line ' strDataLine = CStr(vDataLine) 'Extract the number of characters in the string 'We can figure it out by means of the first string character intSymbols = Asc(Left$(strDataLine, 1)) 'which we delete because of its uselessness strDataLine = Mid$(strDataLine, 2, intSymbols) 'Decode the string by 4 bytes portion. 'From each byte remove two oldest bits. 'From remain 24 bits make 3 bytes For i = 1 To Len(strDataLine) Step 4 '1 byte strTemp = strTemp + Chr((Asc(Mid(strDataLine, i, 1)) _ - 32) * 4 + (Asc(Mid(strDataLine, i + 1, 1)) _ - 32) \ 16) '2 byte strTemp = strTemp + Chr((Asc(Mid(strDataLine, i + 1, 1))_ Mod 16) * 16 + (Asc(Mid(strDataLine, i + 2, 1))_ - 32) \ 4) '3 byte strTemp = strTemp + Chr((Asc(Mid(strDataLine, i + 2, 1)) _ Mod 4) * 64 + Asc(Mid(strDataLine, i + 3, 1)) - 32) Next i 'Write decoded string to the file Put intFile, , strTemp 'Clear the buffer in order to receive the next _ 'line of the encoded data strTemp = "" Next Close intFile End Function 看上去似乎就这么多了。其实不然。要想编写出现代电子邮件程序,你必须了解Base 64和MIME用的Quoted-Printalbe算法。不过你放心,本站介绍的算法大多数的邮件程序还是能识别的。只不过它的年纪比较老,现在的电子邮件程序往往是最后才用这种算法。
发送电子邮件附件(一)
只有在用户选择保存附件的情况下,才需要进行解码工作。此时用户需要先选定要保存的文件,然后按Save As按钮。代码如下:Private Sub cmdSave_Click()Dim strFileName As String
Dim strMessage As String
Dim strAttachment As String
Dim lngPosA As Long
Dim lngPosB As Long'Extract full text of the message
strMessage = m_colMessages(lvMessages.SelectedItem.Key).MessageText
'Extract name of the file
strFileName = lvAttachments.SelectedItem.Key
'
Do Until lngPosA = 0
'Looking for the file's name in the message's text
lngPosA = InStr(lngPosA + 1, strMessage, " " & strFileName)
If lngPosA > 0 Then
'End of string with the file's name
lngPosB = InStrRev(strMessage, vbCrLf, lngPosA) + 2
If lngPosB > 2 Then
'Check whether the string with the file's name
'is the part of the "begin" er
If (Mid$(strMessage, lngPosB, lngPosA - lngPosB _
+ Len(strFileName) + 1)) Like _
("begin ### " & strFileName) Then
'Position of the end er
lngPosA = InStr(lngPosA, strMessage, "'" & _
vbCrLf & "end" & vbCrLf)
If lngPosA > 0 Then
With ComDialog
'Bring up the file selection dialog
.FileName = strFileName
.ShowSave
If Err = 0 Then
'Encoding data save to the strAttachment
'variable
strAttachment = Mid$(strMessage, lngPosB, _
lngPosA + 8 - lngPosB)
'Pass it to the UUDecodeToFile routine
'in order to decode and save as file
UUDecodeToFile strAttachment, .FileName
End If
End With
End If
End If
End If
End If
Loop
End Sub最后是UUDecodeToFile函数的代码: Public Function UUDecodeToFile(strUUCodeData As String, strFilePath As String)Dim vDataLine As Variant
Dim vDataLines As Variant
Dim strDataLine As String
Dim intSymbols As Integer
Dim intFile As Integer
Dim strTemp As String
'
'Remove first er
If Left$(strUUCodeData, 6) = "begin " Then
strUUCodeData = Mid$(strUUCodeData, InStr(1, strUUCodeData, vbLf) + 1)
End If
'
'Remove er of the attachment's end
If Right$(strUUCodeData, 5) = "end" + vbCrLf Then
strUUCodeData = Left$(strUUCodeData, Len(strUUCodeData) - 10)
End If
intFile = FreeFile
Open strFilePath For Binary As intFile
'Break decoded data to the strings
'From now each member of the array vDataLines contains
'one line of the encoded data
vDataLines = Split(strUUCodeData, vbCrLf)
For Each vDataLine In vDataLines
'Decode data line by line
'
strDataLine = CStr(vDataLine)
'Extract the number of characters in the string
'We can figure it out by means of the first string character
intSymbols = Asc(Left$(strDataLine, 1))
'which we delete because of its uselessness
strDataLine = Mid$(strDataLine, 2, intSymbols)
'Decode the string by 4 bytes portion.
'From each byte remove two oldest bits.
'From remain 24 bits make 3 bytes
For i = 1 To Len(strDataLine) Step 4
'1 byte
strTemp = strTemp + Chr((Asc(Mid(strDataLine, i, 1)) _
- 32) * 4 + (Asc(Mid(strDataLine, i + 1, 1)) _
- 32) \ 16)
'2 byte
strTemp = strTemp + Chr((Asc(Mid(strDataLine, i + 1, 1))_
Mod 16) * 16 + (Asc(Mid(strDataLine, i + 2, 1))_
- 32) \ 4)
'3 byte
strTemp = strTemp + Chr((Asc(Mid(strDataLine, i + 2, 1)) _
Mod 4) * 64 + Asc(Mid(strDataLine, i + 3, 1)) - 32)
Next i
'Write decoded string to the file
Put intFile, , strTemp
'Clear the buffer in order to receive the next _
'line of the encoded data
strTemp = ""
Next
Close intFile
End Function
看上去似乎就这么多了。其实不然。要想编写出现代电子邮件程序,你必须了解Base 64和MIME用的Quoted-Printalbe算法。不过你放心,本站介绍的算法大多数的邮件程序还是能识别的。只不过它的年纪比较老,现在的电子邮件程序往往是最后才用这种算法。
电子邮件是[email protected]
UUENCODE編碼的﹐現在的郵件客戶端軟件關于附件的編碼標准是Base64編碼﹐
Quoted Printble編碼由于可能每一個Byte都要加"="編碼﹐將大大增加編碼后的檔案大小﹐因此不實用用于二進制文件的編碼﹐但這并不是說不能對二進制文件編碼﹐
發送郵件妳仔細研究SMTP郵件傳輸協議(RFC821)﹐
http://rfc.sunsite.dk/rfc/rfc821.html
而妳要傳送附件的花﹐妳就要精通MIME格式﹐這妳應該清楚﹐包括Base64﹑Quoted Printable編碼﹐參考以下兩個RFC協議
http://rfc.sunsite.dk/rfc/rfc2045.html
http://rfc.sunsite.dk/rfc/rfc2046.html
當然妳要只是實現這個功能之后就不在研究這方面了﹐妳完全可以不安我上面說的研究協議﹐只要找個例子來參考改編一下就可以了﹐如果妳要研究原理﹐及怎樣實現還是要參考這几個RFC協議﹐當然涉及Mail的RFC協議不止這几個﹐但對SMTP發送來說﹐這是最基本的
http://rfc.sunsite.dk/rfc/rfc822.html