VB6 - URLencode & URLdecode

[Merri]

URLencode and URLdecode are functions that take a string and convert it to/from string that can be used as a GET item or it's value in a URL.

Rules:

• A-Z, a-z and 0-9 are retained as-is
• Space is converted to + (but %20 is also valid)
• Any other character is converted to two character hex number prepended with a %
• Optional: Unicode characters support (all versions below are ANSI only)

Make shorter than these:

Public Function URLdecshort(ByRef Text As String) As String
    Dim strArray() As String, lngA As Long
    strArray = Split(Replace(Text, "+", " "), "%")
    For lngA = 1 To UBound(strArray)
        strArray(lngA) = Chr$("&H" & Left$(strArray(lngA), 2)) & Mid$(strArray(lngA), 3)
    Next lngA
    URLdecshort = Join(strArray, vbNullString)
End Function

Public Function URLencshort(ByRef Text As String) As String
    Dim lngA As Long, strChar As String
    For lngA = 1 To Len(Text)
        strChar = Mid$(Text, lngA, 1)
        If strChar Like "[A-Za-z0-9]" Then
        ElseIf strChar = " " Then
            strChar = "+"
        Else
            strChar = "%" & Right$("0" & Hex$(Asc(strChar)), 2)
        End If
        URLencshort = URLencshort & strChar
    Next lngA
End Function

Make faster than these:

Public Function URLdecode(ByRef Text As String) As String
    Const Hex = "0123456789ABCDEF"
    Dim lngA As Long, lngB As Long, lngChar As Long, lngChar2 As Long
    URLdecode = Text
    lngB = 1
    For lngA = 1 To LenB(Text) - 1 Step 2
        lngChar = Asc(MidB$(URLdecode, lngA, 2))
        Select Case lngChar
            Case 37
                lngChar = InStr(Hex, MidB$(Text, lngA + 2, 2)) - 1
                If lngChar >= 0 Then
                    lngChar2 = InStr(Hex, MidB$(Text, lngA + 4, 2)) - 1
                    If lngChar2 >= 0 Then
                        MidB$(URLdecode, lngB, 2) = Chr$((lngChar * &H10&) Or lngChar2)
                        lngA = lngA + 4
                    Else
                        If lngB < lngA Then MidB$(URLdecode, lngB, 2) = MidB$(Text, lngA, 2)
                    End If
                Else
                    If lngB < lngA Then MidB$(URLdecode, lngB, 2) = MidB$(Text, lngA, 2)
                End If
            Case 43
                MidB$(URLdecode, lngB, 2) = " "
            Case Else
                If lngB < lngA Then MidB$(URLdecode, lngB, 2) = MidB$(Text, lngA, 2)
        End Select
        lngB = lngB + 2
    Next lngA
    URLdecode = LeftB$(URLdecode, lngB - 1)
End Function

Public Function URLencode(ByRef Text As String) As String
    Const Hex = "0123456789ABCDEF"
    Dim lngA As Long, lngChar As Long
    URLencode = Text
    For lngA = LenB(URLencode) - 1 To 1 Step -2
        lngChar = Asc(MidB$(URLencode, lngA, 2))
        Select Case lngChar
            Case 48 To 57, 65 To 90, 97 To 122
            Case 32
                MidB$(URLencode, lngA, 2) = "+"
            Case Else
                URLencode = LeftB$(URLencode, lngA - 1) & "%" & Mid$(Hex, (lngChar And &HF0) \ &H10 + 1, 1) & Mid$(Hex, (lngChar And &HF&) + 1, 1) & MidB$(URLencode, lngA + 2)
        End Select
    Next lngA
End Function

Code for timing:

Option Explicit

Private Declare Function QueryPerformanceCounter Lib "kernel32" (X As Currency) As Boolean
Private Declare Function QueryPerformanceFrequency Lib "kernel32" (X As Currency) As Boolean

Dim m_Time As Double
Dim m_TimeFreq As Double
Dim m_TimeStart As Currency

Public Property Get Timing() As Double
    Dim curTime As Currency
    QueryPerformanceCounter curTime
    Timing = (curTime - m_TimeStart) * m_TimeFreq + m_Time
End Property

Public Property Let Timing(ByVal NewValue As Double)
    Dim curFreq As Currency, curOverhead As Currency
    m_Time = NewValue
    QueryPerformanceFrequency curFreq
    m_TimeFreq = 1 / curFreq
    QueryPerformanceCounter curOverhead
    QueryPerformanceCounter m_TimeStart
    m_TimeStart = m_TimeStart + (m_TimeStart - curOverhead)
End Property

Timing usage:

' before benchmark
Timing = 0

' after benchmark
Debug.Print "Result: " & Format$(Timing, "0.000000")

As far as I know, you can make a shorter code than the first two examples above and you can also make (much) faster than the next two examples above

[dilettante]

You can also do this via API calls, with some interesting differences. See the comments in URLUtility.cls for one oddity.

I haven't timed this, but without the hack for "space to +" encoding it should be reasonably quick.

[batori]

Great!

[dilettante]

Caution:

It doesn't appear that any of the code above handles URLs that are encoded as UTF-8 before URL Encoding. UTF-8 is now common and standard, so be cautious.

The API calls I used don't help either, the flag needed to support UTF-8 doesn't exist until Windows 8.