What is best data structure suitable to implement editor like notepad?

Question

Which data structure/s is used in implementation of editors like notepad. This data structure should be extensible, and should support various features like edition, deletion, s

Answer 1

There is an excellent article about Piece Chains by James Brown, author of HexEdit.

In a nutshell: Piece chains allow you to record the changes made to the text. After loading, you have a piece chain that spans the entire text. Now you insert somewhere in the middle.

Instead of allocating a new buffer, copying the text around, etc., you create two new pieces and modify the existing one: The existing one now contains the text up to the insertion point (i.e. you just change the length of the piece), then you have a piece with the new text and after that a new piece with all the text after the insertion. The original text is left unchanged.

For undo/redo, you simple remember which pieces you added/removed/changed.

The most complex area when using piece chains is that there is no longer a 1:1 mapping between an offset in the visible text and the memory structure. You either have to search the chain or you must maintain a binary tree structure of some kind.