Text Parser

I want to optimize this code in the following areas: internal error checking (not just try...catch, but if...then as well) and for speed. See below for code to be optimized. I'll post a reply that has some test code.

VB Code:

Public Function ParseText( _
           ByVal TextToParse As String, _
           ByVal ParseStartDelim As Char, _
           ByVal ParseEndDelim As Char, _
           ByVal ClassCollection As Collection, _
           Optional ByVal ClassFieldSeparator As Char = ".", _
           Optional ByVal DebugMode As Boolean = False, _
           Optional ByVal DebugEndBlockPrefix As Char = "/", _
           Optional ByVal StartTag As String = "[template start]", _
           Optional ByVal EndTag As String = "[template end]") _
    As String
        'For use with web pages that need data access
        '
        'Parses text based on start and end delim char. Uses CallByName to determine
        'what to replace parsed values with. Debug mode helps make debuging final
        'output easier.
        'Assuming that ClassCollection has an item that is a class with a field named
        ''name' that was set to 'Jack Schitt' and said item's Key in the collection
        'was 'Profile'. Also assume 'ParseStartDelim', 'ParseEndDelim',
        ''ClassFieldSeperator' and are '[', ']', and '.', respectivly, then the
        'samples can be shown as:
        '
        '"test test [profile.name] test"
        '
        'With DebugMode=False, this function would return
        '"test test Jack Schitt test"
        '
        'With DebugMode=True, this function would return
        '"test test [profile.name]Jack Schitt[/profile.name] test"
        '
        'Classes and/or members that don't exist raise an exception that is trapped
        'internally, causeing the tag to be replaced with "". (This is useful for
        'comments.) In debug mode, it will be replaced by the message of the exception.
        '
        'Last but not least, there are the 'StartTag' and 'EndTag' params. Basically,
        'only text between those tags is returned. Text outside of those tags is
        'removed prior to parsing.
 
        Dim Pos As Integer 'current position in string
        Dim SubStringHolder As String 'Holds a substring between a particular [ and ]
        '                              [ is shorthand for ParseStartDelim
        '                              (and viceversa)
        Dim ClassName As String
        Dim FieldName As String
        Dim [Class] As Object
        Dim ReturnValue As Object
 
        'check for start tag
        If TextToParse.IndexOf(StartTag) <> -1 Then
            'remove everything before [template start]
            TextToParse = TextToParse.Remove(0, TextToParse.IndexOf(StartTag) + StartTag.Length)
        End If
 
        'check for end tag
        If TextToParse.IndexOf(EndTag) <> -1 Then
            'remove everything after end tag
            TextToParse = TextToParse.Remove(TextToParse.IndexOf(EndTag), TextToParse.Length - TextToParse.IndexOf(EndTag))
        End If
 
        While Pos < (TextToParse.Length)
            'if [character at Pos] = ParseStartDelim
            '...The complicated, but efficient way...
            If (TextToParse.Substring(Pos, 1).Chars(0).Equals(ParseStartDelim)) Then
                'In Tag
 
                Try
                    'we need the substring from the current [ to the next ]
                    'get everything from Pos on
                    SubStringHolder = TextToParse.Substring(Pos + 1)
                    'trim it to the next ]
 
                    If SubStringHolder.IndexOf(ParseEndDelim) = -1 Then
                        Throw New ParseException("Reached end of file without closing delimiter.", True)
                    End If
 
                    SubStringHolder = SubStringHolder.Substring(0, SubStringHolder.IndexOf(ParseEndDelim))
 
                    'remove the existing text
                    TextToParse = TextToParse.Remove(Pos, SubStringHolder.Length + 2)
 
                    If SubStringHolder.IndexOf(ClassFieldSeparator) = -1 Then
                        'contains no '.'
                        ClassName = SubStringHolder
                        Throw New ParseException("No class name specified", False)
                    End If
 
                    ClassName = SubStringHolder.Substring(0, SubStringHolder.IndexOf(ClassFieldSeparator))
 
                    FieldName = SubStringHolder.Substring(SubStringHolder.IndexOf(ClassFieldSeparator) + 1)
 
                    If ClassName = "" Then
                        '[.foo]
                        Throw New ParseException("No class name specified", False)
                    End If
 
                    If FieldName = "" Then
                        '[foo.]
                        Throw New ParseException("No field name specified", False)
                    End If
 
                    [Class] = ClassCollection(ClassName)
                    ReturnValue = CallByName([Class], FieldName, CallType.Get)
 
                    'this next block is required incase field is a sub or
                    'otherwise doesn't return a value
                    If ReturnValue Is Nothing Then
                        If DebugMode Then
                            SubStringHolder = "Field was called but returned 'Nothing'"
                        Else
                            SubStringHolder = ""
                        End If
                    Else
                        SubStringHolder = ReturnValue.ToString
                    End If
                Catch nope As MissingMemberException
                    'CallByName throws this.
                    '[foo.bar] 'bar' is not found
                    If DebugMode Then
                        SubStringHolder = "Field name not found"
                    Else
                        SubStringHolder = ""
                    End If
                Catch nope As ArgumentException
                    '[Class] = ClassCollection(ClassName) throws this
                    '[foo.bar] 'foo' not found in collection
                    If DebugMode Then
                        SubStringHolder = "Class name not found"
                    Else
                        SubStringHolder = ""
                    End If
                Catch nope As ParseException
                    'Several If...Then blocks above throw this
                    If DebugMode Then
                        SubStringHolder = nope.Message
                    Else
                        SubStringHolder = ""
                    End If
 
                    If nope.IsFatal Then
                        Return TextToParse & " " & SubStringHolder
                        Exit Function
                    End If
 
                Finally
                    If DebugMode Then
                        'if debug mode, wrap the string with tags
 
                        '[foo.bar]{value}
                        SubStringHolder = ParseStartDelim & _
                        ClassName & ClassFieldSeparator & FieldName & _
                        ParseEndDelim & SubStringHolder
 
                        '+=[/foo.bar]
                        SubStringHolder += ParseStartDelim & DebugEndBlockPrefix & _
                        ClassName & ClassFieldSeparator & FieldName & _
                        ParseEndDelim
                    End If
                End Try
 
                'insert the value into the main text where the tag originally
                'was. if DebugMode, the tags were wrapped above.
                TextToParse = TextToParse.Insert(Pos, SubStringHolder)
 
                'increment the position by the length of the new value. -1 for
                'the statement after this one
                Pos += SubStringHolder.Length - 1
            End If
            Pos += 1
            If Pos < 0 Then Exit While
        End While
 
        Return TextToParse
    End Function
 
    Public Class ParseException
        'this exception used internally by the parser
        '
        ''message' is the text sent to the output when the parser's
        ''debugmode' is true
        '
        ''IsFatal' tells the parser to stop parseing. If true, ''Message' is
        'appended to the end of the output.
 
        Inherits Exception
 
        Sub New(ByVal message As String, ByVal IsFatal As Boolean)
            MyBase.New(message)
            _IsFatal = IsFatal
        End Sub
 
        Private _IsFatal As Boolean 'private copy
 
        Public ReadOnly Property IsFatal() As Boolean
            Get
                Return _IsFatal
            End Get
        End Property
    End Class

To test it

VB Code:

Public Sub testit()
        Dim a As New Collection()
        Dim DebugMode As Boolean
        Dim TextToParse As String
 
        a.Add(New TesterClass(), "test")
 
        TextToParse = "blahblahblah...[template start]Hello my name is [test.name]. I live at [test.address] in the city of [test.city]. My favorite porno website[To test urls (and comments)] is [test.favepr0n]. [template end] blah blah blah, everything here is ignored."
 
        Debug.WriteLine("Param: DebugMode = False")
        Debug.WriteLine(ParseText(TextToParse, "[", "]", a, , DebugMode))
 
        DebugMode = True
 
        Debug.WriteLine("Param: DebugMode = True")
        Debug.WriteLine(ParseText(TextToParse, "[", "]", a, , DebugMode))
    End Sub
 
    Public Class TesterClass
        Public name As String = "Dr. Melora Vanhasian"
        Public address As String = "11333 Roscoe Blvd., #318"
 
        Public ReadOnly Property city() As String
            Get
                Return "Van Nuys, CA"
            End Get
        End Property
 
        Public Function favepr0n() As Uri
            Return New Uri("http://www.mufftorrent.com")
        End Function
    End Class

Output window should read:

Code:

---

Param: DebugMode = False
Hello my name is Dr. Melora Vanhasian. I live at 11333 Roscoe Blvd., #318 in the city of Van Nuys, CA. My favorite porno website is http://www.mufftorrent.com/.
Param: DebugMode = True
Hello my name is [test.name]Dr. Melora Vanhasian[/test.name]. I live at [test.address]11333 Roscoe Blvd., #318[/test.address] in the city of [test.city]Van Nuys, CA[/test.city]. My favorite porno website[To test urls (and comments).city]No class name specified[/To test urls (and comments).city] is [test.favepr0n]http://www.mufftorrent.com/[/test.favepr0n].

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Have you looked into using regularexpressions?