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Text compare component for Delphi and Free Pascal

Source code for the freeware component TDiff is written in Delphi. This component dramatically simplify programming tasks that require calculations of 'shortest path' or 'longest common sequence' as typically required in file compare utilities.

TDiff is used in RJ TextEd to compare text or source files. You need to add the units "DiffTypes" and "Diff" to the uses section of your application.

The units "Diff_NP" and "Diff_ND" contains the available algorithms that can be used from the TDiff class.

PDF documents fully describing the principle algorithms used in Diff_NP and Diff_ND...
The algorithm in the Diff_ND unit is based on: "An O(ND) Difference Algorithm and its Variations" by E Myers - Algorithmica Vol. 1 No. 2, 1986, pp. 251-266
The algorithm in the Diff_NP unit is based on: "An O(NP) Sequence Comparison Algorithm" by Sun Wu, Udi Manber & Gene Myers

Getting Started

Download the files and include the units DiffTypes and Diff in your project.

Demo applications

Two very simple demo applications (with full source code) are include to demonstrate how the 'TDiff' component can be used in Delphi and Lazarus programs.

Authors

Author : Angus Johnson - angusj-AT-myrealbox-DOT-com
Copyright : © 2001-2008 Angus Johnson
Updated by : Rickard Johansson (RJ TextEd)

Version history

  • December 2001
    Original release (used Myer O(ND) Difference Algorithm)
  • 22 April 2008
    Complete rewrite to greatly improve the code and provide a much simpler view of differences through a new 'Compares' property.
  • 21 May 2008
    Another complete code rewrite to use Sun Wu et al. O(NP) Sequence Comparison Algorithm which more than halves times of typical comparisons.
  • 24 May 2008
    Reimplemented "divide-and-conquer" technique (which was omitted in 21 May release) so memory use is again minimal.
  • 25 May 2008
    Removed recursion to avoid the possibility of running out of stack memory during massive comparisons.
  • 2 June 2008
    Minor bugfixes.
  • 11 November 2018
    Added TList to store hash values.
    Made some minor code formatting and code changes
    Fixed Unicode string issues
  • 19 May 2020
    Added Lazarus support
  • 23 May 2020
    Replaced almost all code in demo 1. It should be much easier to understand now.
    Fixed a few issues in demo 2.
  • 13 July 2023
    Rewrote the component and made it easy to select the algorithm to use for comparison.
    Fixed several issues and updated the demos.