Android Code Snippet [B4X] Simple URL Encoding and Decoding Routines (Using B4X Code Only)

    Dim s As String = $"https://www.b4x.com/android/forum/whats-new/posts/4054187/"$
    Log(URL_Encode(s))
    Log(URL_Decode(URL_Encode(s)))

Public Sub URL_Encode(s As String) As String
    Dim Output As StringBuilder
    Output.Initialize
    For i = 0 To s.Length - 1
        Dim c As Char = s.CharAt(i)
        If IsAlphanumeric(Asc(c)) Or c="-" Or c="_" Or c="." Or c="~" Then
            Output.Append(c)
        Else
            Output.Append("%").Append(Bit.ToHexString(Asc(c)).ToUpperCase)
        End If
    Next
    Return Output.ToString
End Sub

Private Sub IsAlphanumeric(c As Int) As Boolean
    Return (c>=48 And c <=57) Or (c>=65 And c<=90) Or (c>=97 And c<=122)
End Sub

Public Sub URL_Decode(s As String) As String
    Dim Output As StringBuilder
    Output.Initialize
    Dim i = 0 As Int
    Do While i < s.Length
        Dim c As Char = s.CharAt(i)
        If c = "%" And i + 2 < s.Length Then
            Dim HexCode As String = s.SubString2(i + 1, i + 3)
            Dim Code As Int = Bit.ParseInt(HexCode,16)
            Output.Append(Chr(Code))
            i = i + 3
        Else
            Output.Append(c)
            i = i + 1
        End If
    Loop
    Return Output.ToString
End Sub