Overlay and Editing Model

ByteOverlay is the central edit model.

Overwrite Mode

In overwrite mode:

the logical length stays equal to the original reader length
changed bytes are stored in a sorted overwrite map
writing the original byte value removes the overwrite entry

This is the cheapest editing mode when you only need in-place changes.

Insert Mode

In insert mode:

logical length can diverge from the original file length
inserts are stored in an append-only insert buffer
piece metadata tracks how original bytes and inserted bytes are stitched together
deletes and replace operations update the piece list instead of the original source

Undo and Redo

EditJournal records:

overwrite operations
insert operations
delete operations
replace operations
batches

Undo and redo replay those operations against the same ByteOverlay.

Higher-level editing flows are intentionally separate:

SelectionService mutates ranges
NavigationService tracks history, bookmarks, and next-change lookup
HexSearchService finds byte patterns and can drive replace workflows

This makes it easier to reuse the control in read-only viewers or custom editors.