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I've previously written a (not very robust) text comparison procedure and would to make it a lot better. I'm doing the usual net search for algorithms and source code. I also looked on the forum but did not find any PowerBASIC code along those lines.
Basically, I'd like to put text in two RichEdit controls and use colors to highlight the differences - a WinDiff kind of comparison. But I don't want a separate utility. I already use my limited procedure in gbSnippets to compare snippets from different libraries, and would like to improve the procedure.
The code below is my starting point - it just basically does a look ahead for a fixed number of lines. It reads the left side, looks for a match within the next few lines (10 in this case) on the right side. When it discovers differences it offsets the differing lines, using "********" to fill in where an offset was displayed. Speed of the comparison shouldn't be an issue, given the relatively small snippet sizes I'm working with.
My procedure generally works for small differences, but has limitations. It does not address RichEdit coloration of the differences.
If anyone has something to share, I'd appreciate hearing about it.
Basically, I'd like to put text in two RichEdit controls and use colors to highlight the differences - a WinDiff kind of comparison. But I don't want a separate utility. I already use my limited procedure in gbSnippets to compare snippets from different libraries, and would like to improve the procedure.
The code below is my starting point - it just basically does a look ahead for a fixed number of lines. It reads the left side, looks for a match within the next few lines (10 in this case) on the right side. When it discovers differences it offsets the differing lines, using "********" to fill in where an offset was displayed. Speed of the comparison shouldn't be an issue, given the relatively small snippet sizes I'm working with.
My procedure generally works for small differences, but has limitations. It does not address RichEdit coloration of the differences.
If anyone has something to share, I'd appreciate hearing about it.
Code:
'Compilable Example:
#Compile Exe
#Dim All
#Include "win32api.inc"
#Include "richedit.inc"
#Include "commctrl.inc"
%ID_RELeft = 200 : %ID_RERight = 300
%ID_Button1 = 400 : %ID_Button2 = 500
Global hDlg As Dword, hRELeft As Dword, hRERight As Dword
Function PBMain () As Long
Local Style&
style& = %WS_Child Or %WS_Visible Or %ES_MultiLine Or %WS_VScroll Or %ES_AutoHScroll _
Or %WS_HScroll Or %ES_AutoVScroll Or %ES_WantReturn Or %ES_NoHideSel Or %WS_TabStop
Dialog New Pixels, 0, "Compare Text Example",400,400,400,200, %WS_OverlappedWindow To hDlg
Control Add Button, hDlg, %ID_Button1, "Compare", 30,10,100,20
Control Add Button, hDlg, %ID_Button2, "Reset", 150,10,100,20
LoadLibrary("riched32.dll") : InitCommonControls
Control Add "RichEdit", hDlg, %ID_RELeft, "",0,0,50,50, style&, %WS_Ex_ClientEdge
Control Add "RichEdit", hDlg, %ID_RERight, "",0,0,50,50, style&, %WS_Ex_ClientEdge
Control Handle hDlg, %ID_RELeft To hRELeft
Control Handle hDlg, %ID_RERight To hRERight
LoadText
Dialog Show Modal hDlg Call DlgProc
End Function
CallBack Function DlgProc() As Long
Select Case Cb.Msg
Case %WM_Command
If Cb.Ctl = %ID_Button1 Then ShowDifference
If Cb.Ctl = %ID_Button2 Then LoadText
Case %WM_Size
'resizes controls when form is resized
Dim w As Long, h As Long
Dialog Get Client Cb.Hndl To w,h
Control Set Loc Cb.Hndl, %ID_RELeft, 5,35
Control Set Size Cb.Hndl, %ID_RELeft, (w-20)/2, h-40
Control Set Loc Cb.Hndl, %ID_RERight, w/2+5, 35
Control Set Size Cb.Hndl, %ID_RERight, (w-20)/2, h-40
End Select
End Function
Sub LoadText
Local temp$
temp$ = "These are lines" + $CrLf + "of text to compare" + $CrLf + "to the right side."
Control Set Text hDlg, %ID_RELeft, temp$
temp$ = "These are lines" + $CrLf + "of text to compare" + $CrLf + "to the left side."
Control Set Text hDlg, %ID_RERight, temp$
End Sub
Sub ShowDifference
Local Found As Long, iStep As Long, A As String, B As String, SColor As String
Local i As Long, j As Long, n As Long, Done As Long, r As Long
Local A1() As String, B1() As String, S() As String, LText As String, RText As String
'get raw text data
Control Get Text hDlg, %ID_RELeft To A
Control Get Text hDlg, %ID_RERight To B
ReDim A1(ParseCount(A,$CrLf)-1), B1(ParseCount(B,$CrLf)-1)
Parse A, A1(), $CrLf : Parse B, B1(), $CrLf
LText = "" : RText = ""
'start by comparing lines A1(0) and B1(0)
Do While Not Done
If i > UBound(A1) Then
'no more A1() entries, so load all remaining B1() entries
For n = j To UBound(B1)
LText = LText + $CrLf + ""
RText = RText + $CrLf + B1(n)
SColor = SColor & ":" & Str$(n)
Next n
Done = %True
Exit Do
End If
If j > UBound(B1) Then
'no more B1() entries, so load all remaining A1() entries
For n = i To UBound(A1)
LText = LText + $CrLf + A1(n)
RText = RText + $CrLf + ""
SColor = SColor & ":" & Str$(n)
Next n
Done = %True
Exit Do
End If
If A1(i) = B1(j) Then
'they are equal so display them
LText = LText + $CrLf + A1(i)
RText = RText + $CrLf + B1(j)
'go to next pair of lines
i = i + 1
j = j + 1
Else
'they are not equal, so check to see if B1(j) is
'found within the next 10 lines of A1()
Found = %False
iStep = 20
If i + iStep > UBound(A1) Then iStep = UBound(A1) - i
For r = 1 To iStep
If A1(i + r) = B1(j) Then
Found = %True
Exit For
End If
Next r
If Found = %True Then
'B1(j) was found within 10 lines of A()
'print all of A1(i)-n/a up to the point it is found
'then print A1(i)-B1(j)
'If r > 1 Then
For n = 0 To r - 1
LText = LText + $CrLf + A1(i + n)
RText = RText + $CrLf + String$(200, "*")
SColor = SColor & ":" & Str$(i + n)
Next n
'End If
LText = LText + $CrLf + A1(i + r)
RText = RText + $CrLf + B1(j)
i = i + r + 1
j = j + 1
Else
'B1(j) was not found within 10 lines of A()
'print n/a-B1(j)
LText = LText + $CrLf + String$(200, "*")
RText = RText + $CrLf + B1(j)
SColor = SColor & ":" & Str$(j)
j = j + 1
End If
End If
Loop
'get rid of leading $crlf
If Len(LText) > 0 Then LText = Right$(LText, Len(LText) - 2)
If Len(RText) > 0 Then RText = Right$(RText, Len(RText) - 2)
'show differences
Control Set Text hDlg, %ID_RELeft, LText
Control Set Text hDlg, %ID_RERight, RText
End Sub
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