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string chunker for vba - stringbuilder to avoid garbage collection issues http://ramblings.mcpher.com
'gistThat@mcpher.com :do not modify this line - see ramblings.mcpher.com for details: updated on 5/3/2014 6:30:52 PM : from manifest:7471153 gist https://gist.github.com/brucemcpherson/5102369/raw/cStringChunker.cls
' stringChunker class for VBA because string concat takes ages
Option Explicit
' v1.06 5102369
Private pContent As String
Private pSize As Long
' minimum amount to increment by each time
Const defaultChunkSize = 64
Public Property Get size() As Long
' this is how much content is real
size = pSize
End Property
Public Property Get content() As String
' return the real part of the content
If pSize > 0 Then
content = getLeft(size)
Else
content = vbNullString
End If
End Property
Public Property Get getLeft(howMany As Long) As String
' return the left part of the content
' c.getLeft(howmany) is equivalent to left(c.content,howmany), but avoids extra assignment
getLeft = getMid(1, howMany)
End Property
Public Property Get getRight(howMany As Long) As String
' return the right part of the content
' c.getRight(howmany) is equivalent to right(c.content,howmany), but avoids extra assignment
getRight = getMid(pSize - howMany + 1, howMany)
End Property
Public Property Get getMid(startPos As Long, Optional howMany As Long = -1) As String
' extract from content
' c.getMid(startPos,howmany) is equivalent to mid(c.content,startPos, howmany), but avoids extra assignment
Dim n As Long
Debug.Assert startPos > 0 And startPos <= pSize
n = howMany
If n = -1 Then
n = pSize - startPos + 1
End If
n = minNumber(pSize - startPos + 1, n)
If n > 0 Then
getMid = Mid(pContent, startPos, n)
Else
getMid = vbNullString
End If
End Property
Public Property Get self() As cStringChunker
' convenience for with in with
Set self = Me
End Property
Public Function clear() As cStringChunker
' easy to clear out.. may as well keep the same buffer going
pSize = 0
Set clear = Me
End Function
Public Function uri(addstring As String) As cStringChunker
Set uri = add(URLEncode(addstring))
End Function
Public Function toString() As String
toString = content()
End Function
Public Function add(addstring As String) As cStringChunker
Dim k As Long
' add some content to end
k = Len(addstring)
If k > 0 Then
adjustSize (k)
Mid(pContent, size + 1, k) = addstring
pSize = size + k
End If
Set add = Me
End Function
Public Function addLine(addstring As String) As cStringChunker
Set addLine = add(addstring).add(vbCrLf)
End Function
Public Function insert(Optional insertString As String = " ", _
Optional insertBefore As Long = 1) As cStringChunker
'default position is at beginning, insert a space
'c.insert("x",c.size+1) is equivalent to c.add("x")
If insertBefore = pSize + 1 Then
Set insert = add(insertString)
Else
' 'todo .. how to handle programming errors?
Debug.Assert insertBefore > 0 And insertBefore <= pSize
' regular string concatenation is better since there is overlap
pContent = getLeft(insertBefore - 1) & insertString & getMid(insertBefore)
pSize = Len(pContent)
Set insert = Me
End If
Set insert = Me
End Function
Public Function overWrite(Optional overWriteString As String = " ", _
Optional overWriteAt As Long = 1) As cStringChunker
'default position is at beginning, overwrite with a space
Dim k As Long
k = Len(overWriteString)
If k > 0 Then
' 'todo .. how to handle programming errors?
Debug.Assert overWriteAt >= 0
'' we'll allow overwrite to extend past end, be greedy
adjustSize (k)
pSize = maxNumber(pSize, k + overWriteAt - 1)
Mid(pContent, overWriteAt, k) = overWriteString
End If
Set overWrite = Me
End Function
Public Function shift(Optional startPos As Long = 1, _
Optional howManyChars As Long = 0, _
Optional replaceWith As String = vbNullString) As cStringChunker
' shift by howmany chars .. negative= left, positive = right
'TODO how to deal with programming errors? message, raise error, assert?
Dim howMany As Long
howMany = howManyChars
If howMany = 0 Then
howMany = Len(replaceWith)
End If
Debug.Assert howMany + startPos > 0
Debug.Assert startPos <= pSize And startPos > 0
' make space
If howMany <> 0 Then
If howMany > 0 Then
' its a right shift, use insert
Set shift = insert(Space(howMany), startPos)
Else
' a left shift
If startPos > 1 Then
' we can do an overwrite
overWrite getMid(startPos + howMany, pSize - startPos + 1), startPos
pSize = pSize + howMany
End If
End If
End If
Set shift = Me
End Function
Public Function chop(Optional n As Long = 1) As cStringChunker
' chop n charaters from end of content
pSize = maxNumber(0, pSize - n)
Set chop = Me
End Function
Public Function chopIf(t As String) As cStringChunker
' chop if its t
Dim k As Long
k = Len(t)
If k <= pSize Then
If getRight(k) = t Then
chop (k)
End If
End If
Set chopIf = Me
End Function
Public Function chopWhile(t As String) As cStringChunker
' chop if its t
Dim k As Long, x As Long
Set chopWhile = Me
x = pSize
While chopIf(t).size <> x
x = pSize
Wend
End Function
Private Function maxNumber(a As Long, b As Long) As Long
If a > b Then
maxNumber = a
Else
maxNumber = b
End If
End Function
Private Function minNumber(a As Long, b As Long) As Long
If a < b Then
minNumber = a
Else
minNumber = b
End If
End Function
Private Function adjustSize(needMore As Long) As cStringChunker
Dim need As Long
need = pSize + needMore
If Len(pContent) < need Then
pContent = pContent & Space(needMore + maxNumber(defaultChunkSize, Len(pContent)))
End If
Set adjustSize = Me
End Function
Private Sub class_initialize()
pSize = 0
pContent = Space(defaultChunkSize)
End Sub
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