Android Question Decoding quoted-printable html

William Hunter

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Longtime User
I normally have success decoding quoted-printable using the sub below. I have tried to display Last Week's Most Popular Topics in a WebView, which I have done in previous weeks without a problem. This time I cannot display the decoded html properly. I am attaching the unprocessed rawmail for this weeks topic. I expect that something has changed in the way it has been encoded. I cannot decode it correctly, in the way I have done previously, and hope someone can tell my why, and also how I might change my method of decoding quoted-printable. Any help greatly appreciated.

Best regards
B4X: 
Sub DecodeQuotePrintable(q As String) As String
    Dim m As Matcher
    m = Regex.Matcher("=\?([^?]*)\?Q\?(.*)\?=$", q)
    If m.Find Then
        Dim charset As String
        Dim data As String
        charset = m.Group(1)
        data = m.Group(2)
        Dim bytes As List
        bytes.Initialize
        Dim i As Int
        Do While i < data.Length
            Dim c As String
            c = data.CharAt(i)
            If c = "_" Then
                bytes.AddAll(" ".GetBytes(charset))
            Else If c = "=" Then
                Dim hex As String
                hex = data.CharAt(i + 1) & data.CharAt(i + 2)
                i = i + 2
                bytes.Add(Bit.ParseInt(hex, 16))
            Else
                bytes.AddAll(c.GetBytes(charset))
            End If
            i = i + 1
        Loop
        Dim b(bytes.Size) As Byte
        For i = 0 To bytes.Size - 1
            b(i) = bytes.Get(i)
        Next
        Return BytesToString(b, 0, b.Length, charset)
    Else
        Return q
    End If
End Sub
 

Attachments

  • RawMailB4A.txt
    15.3 KB · Views: 567
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William Hunter

Active Member
Licensed User
Longtime User
Erel said:
This regex will only catch single line quote-printable text. Such as in the subject field.
Click to expand...
Thank you for your reply. This has me at a bit of a loss. This AM I received seven messages in quoted-printable/html. The sub in post #1 decoded them flawlessly, and each was displayed correctly in a WebView. The message B4A sent me, in connection with post #2, is in quoted-printable/html and is one of the seven that decoded and displayed correctly. I have attached the unprocessed message, and an image showing how it was displayed.

I should be able to decode and display the message attached in post #1. Up until this last issue, I have been able to decode and display Last Week's Most Popular Topics using this same sub. So, I think that the encoding of the current issue of Last Week's Most Popular Topics has changed in some way that I cannot see. This is the reason for my question - "what has changed in the encoding?".

Best regards
 

Attachments

  • RawMailB4A2.txt
    10.5 KB · Views: 496
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William Hunter

Active Member
Licensed User
Longtime User
Erel said:
Nothing in the forum software or configuration was changed.
Click to expand...
Thank you Erel. I’ve been working on the parsing of email for quite some time. I can correctly decode/extract the majority of emails received, but not all. The two subs I have tried for decoding quoted-printable were found on the forum. Exhibit A, while intended to decode single line text as in a header, is far more effective at decoding message body than Exhibit B, which is intended for that purpose. Neither of these subs will decode all message body quoted-printable.

I have done a lot of searching on the Internet looking for a sample of an all embracing mail parser. While I have found examples of Mime parsers in Java, there is nothing beyond that. The only common theme I have found in posings by others, is that the parsing of email is a nightmare. I think I’m at the point of agreeing, and will have to give up my quest. Maybe one day I’ll have an epiphany, or one of our resident experts will create a fully functional mailparser. In any event, thank you for your help.

Regards
B4X: 
' Exhibit A - https://www.b4x.com/android/forum/threads/using-pop3-to-communicate-with-android-devices.11310/
Sub DecodeQuotePrintable(q As String) As String
    Dim m As Matcher
    m = Regex.Matcher("=\?([^?]*)\?Q\?(.*)\?=$", q)
    If m.Find Then
        Dim charset As String
        Dim data As String
        charset = m.Group(1)
        data = m.Group(2)
        Dim bytes As List
        bytes.Initialize
        Dim i As Int
        Do While i < data.Length
            Dim c As String
            c = data.CharAt(i)
            If c = "_" Then
                bytes.AddAll(" ".GetBytes(charset))
            Else If c = "=" Then
                Dim hex As String
                hex = data.CharAt(i + 1) & data.CharAt(i + 2)
                i = i + 2
                bytes.Add(Bit.ParseInt(hex, 16))
            Else
                bytes.AddAll(c.GetBytes(charset))
            End If
            i = i + 1
        Loop
        Dim b(bytes.Size) As Byte
        For i = 0 To bytes.Size - 1
            b(i) = bytes.Get(i)
        Next
        Return BytesToString(b, 0, b.Length, charset)
    Else
        Return q
    End If
End Sub
B4X: 
' Exhibit B - https://www.b4x.com/android/forum/threads/using-pop3-and-mailparser.66978/#post-424042
Sub DecodeQuotePrintable(q As String) As String
    Dim bytes As List
    bytes.Initialize
    Dim i As Int
    Do While i < q.Length
        Dim c As String
        c = q.CharAt(i)
        If c = "_" Then
            bytes.AddAll(" ".GetBytes("utf8"))
        Else If c = "=" And i < q.Length - 1 Then
            Dim hex As String
            hex = q.CharAt(i + 1) & q.CharAt(i + 2)
            i = i + 2
            Try
                bytes.Add(Bit.ParseInt(hex, 16))
            Catch
                bytes.AddAll(hex.GetBytes("utf8"))
            End Try
        Else
            bytes.AddAll(c.GetBytes("utf8"))
        End If
        i = i + 1
    Loop
    Dim b(bytes.Size) As Byte
    For i = 0 To bytes.Size - 1
        b(i) = bytes.Get(i)
    Next
    Return BytesToString(b, 0, b.Length, "utf8")
End Sub
 
Last edited:
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