by Brian Cidern (4 Submissions)
Category: String Manipulation
Compatability: Visual Basic 3.0
Difficulty: Beginner
Date Added: Wed 3rd February 2021
Rating: 
(14 Votes)
Sort arrays much faster with a better string
swapping routine!
Wow, I couldn't believe all the rewrites of the
same sorting routines in VBC. "Look at
mine", "No, use mine", yadda, yadda, yadda. They
all use the horribly slow:
vTemp = String1
String1 = String2
String1 = vTemp
Geezzzz - When you have to sort 30,000+ strings
this is slllooooowwwwwww.
Here's a solution. It uses the the same sorting
routine (or choose your own), but implements a much
faster swap routine using the CopyMemory() API. Now,
instead of swapping strings, which in my case could
be up to 9,000 characters, you are only swapping a
4 byte memory address.
Rock On!!
Assumes
Create a new EXE and throw in Command1 - Paste the rest.
VBcodersOption Explicit
Private Declare Sub CopyMemory _
Lib "kernel32" _
Alias "RtlMoveMemory" ( _
lpDest As Any, _
lpSource As Any, _
ByVal cbCopy As Long _
)
Private Sub Command1_Click()
' Sort an array with CopyMemory()
Dim i As Integer
Dim str_Unsorted As String, _
str_Sorted As String
' Populate some sample data
Dim vArray(25) As String
vArray(0) = "EFGHIJKLMNOPQRSTUVWXYZABCD"
vArray(1) = "RSTUVWXYZABCDEFGHIJKLMNOPQ"
vArray(2) = "PQRSTUVWXYZABCDEFGHIJKLMNO"
vArray(3) = "DEFGHIJKLMNOPQRSTUVWXYZABC"
vArray(4) = "IJKLMNOPQRSTUVWXYZABCDEFGH"
vArray(5) = "ZABCDEFGHIJKLMNOPQRSTUVWXY"
vArray(6) = "HIJKLMNOPQRSTUVWXYZABCDEFG"
vArray(7) = "LMNOPQRSTUVWXYZABCDEFGHIJK"
vArray(8) = "STUVWXYZABCDEFGHIJKLMNOPQR"
vArray(9) = "TUVWXYZABCDEFGHIJKLMNOPQRS"
vArray(10) = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
vArray(11) = "CDEFGHIJKLMNOPQRSTUVWXYZAB"
vArray(12) = "VWXYZABCDEFGHIJKLMNOPQRSTU"
vArray(13) = "MNOPQRSTUVWXYZABCDEFGHIJKL"
vArray(14) = "FGHIJKLMNOPQRSTUVWXYZABCDE"
vArray(15) = "JKLMNOPQRSTUVWXYZABCDEFGHI"
vArray(16) = "YZABCDEFGHIJKLMNOPQRSTUVWX"
vArray(17) = "XYZABCDEFGHIJKLMNOPQRSTUVW"
vArray(18) = "OPQRSTUVWXYZABCDEFGHIJKLMN"
vArray(19) = "BCDEFGHIJKLMNOPQRSTUVWXYZA"
vArray(20) = "GHIJKLMNOPQRSTUVWXYZABCDEF"
vArray(21) = "KLMNOPQRSTUVWXYZABCDEFGHIJ"
vArray(22) = "NOPQRSTUVWXYZABCDEFGHIJKLM"
vArray(23) = "WXYZABCDEFGHIJKLMNOPQRSTUV"
vArray(24) = "QRSTUVWXYZABCDEFGHIJKLMNOP"
vArray(25) = "UVWXYZABCDEFGHIJKLMNOPQRST"
' Here's the unsorted array
For i = 0 To UBound(vArray)
str_Unsorted = str_Unsorted & vArray(i) & vbCrLf
Next i
MsgBox str_Unsorted
' Sort the array
SortMe vArray
' Here's the sorted array
For i = 0 To UBound(vArray)
str_Sorted = str_Sorted & vArray(i) & vbCrLf
Next i
MsgBox str_Sorted
End Sub
Sub SortMe(varArray() As String)
Dim i As Long, j As Long
Dim l_Count As Long
Dim l_Hold As Long
' Typical sorting routine
l_Count = UBound(varArray)
For i = 0 To l_Count
For j = i + 1 To l_Count
If varArray(i) > varArray(j) Then
' Here's the juice!
SwapStrings varArray(i), varArray(j)
End If
Next
Next
End Sub
Sub SwapStrings(pbString1 As String, pbString2 As String)
Dim l_Hold As Long
CopyMemory l_Hold, ByVal VarPtr(pbString1), 4
CopyMemory ByVal VarPtr(pbString1), ByVal VarPtr(pbString2), 4
CopyMemory ByVal VarPtr(pbString2), l_Hold, 4
End Sub