B4J Code Snippet [XUI] SD Base64 - Encode / Decode

Today I was looking for a method for encoding and decoding in Base64.
There are many libraries including the well-known StringUtils. But the decoding signaled me an error but it was not possible to understand exactly what the error was

So I created for B4J a class that using inline Java code decoded the string, but getting the same error. In any case it would not work for B4i
#if java
import java.util.Base64;

public byte[] decode(byte[] original) {
     byte[] decoded = Base64.getDecoder().decode(original);
     return decoded;
#END if

So I searched around a bit until I found this site and translated the code in B4X (hoping there are no errors). Want to share it, maybe it can be useful to someone else :D

Public Sub Base64Decode(S As String) As String
    Dim base64chars As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    Dim P,R = "" As String

    #IF B4J or B4A
    Dim Ob As JavaObject = S 'ignore
    S=Ob.RunMethod("replaceAll",Array As Object("[^ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=]",""))
    ' Don't known - Working Progress
    #End If

    If S.CharAt(S.Length-1)="=" Then
        If S.CharAt(S.Length-2)="=" Then
        End If
    End If
    S=S.SubString2(0,S.Length-P.Length) & P

    For C = 0 To S.Length-1 Step 4
            Dim n As Int = Bit.ShiftLeft(base64chars.IndexOf(S.CharAt(C)),18) + Bit.ShiftLeft(base64chars.IndexOf(S.CharAt(C+1)),12) + Bit.ShiftLeft(base64chars.IndexOf(S.CharAt(C+2)),6)+ base64chars.IndexOf(S.CharAt(C+3))
            r = r & Chr(Bit.And(Bit.ShiftRight(n,16),0xFF)) & Chr(Bit.And(Bit.ShiftRight(n,8),0xFF)) & Chr(Bit.And(n,0xFF))
            Log("Position: " & C)
        End Try

    Return R.SubString2(0, R.Length - P.Length)
End Sub

Public Sub Base64Encode(S As String) As String
    Dim c As Int = S.Length Mod 3
    Dim base64chars As String = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"
    Dim P = "",R = "" As String

    ' add a right zero pad To make this string a multiple of 3 characters
    If c>0 Then
        Do While c<3
            P = P & "="
            S = S & "0"
    End If

    For c = 0 To S.Length-1 Step 3
        If (c > 0 And (c / 3 * 4) Mod 76 = 0) Then R=R & Chr(10) & Chr(13)
        Dim n As Int = Bit.ShiftLeft(Asc(S.CharAt(c)),16) + Bit.ShiftLeft(Asc(S.CharAt(c+1)),8) + Asc(S.CharAt(c+2))
        Dim n1 As Int = Bit.And(Bit.ShiftRight(n,18),63)
        Dim n2 As Int = Bit.And(Bit.ShiftRight(n,12),63)
        Dim n3 As Int = Bit.And(Bit.ShiftRight(n,6),63)
        Dim n4 As Int = Bit.And(n,63)

        R = R & base64chars.CharAt(n1) & base64chars.CharAt(n2) & base64chars.CharAt(n3) & base64chars.CharAt(n4)
    Return r.substring2(0, r.length - p.length) & p
End Sub

Although it is slower than existing libraries, it is possible to compress and decompress with B4X code and therefore not linked to a specific platform and modifiable to adapt them to the many existing variants.
Especially if there is an error in the data to be decoded it is possible to do a more specific debugging
Last edited: