butterfly

One day I wanted to edit my md RAID’s superblock, but my go-to hex editor at the
time (Okteta) did not want to allow me to edit more than 2 GB.

How hard can it be?

“Notable” features

Note that all of the following are written in indicative mood, i.e. “does X”,
but they are actually meant as “should do X, and if it does not, that is a bug”.

Works with arbitrarily large files while using few resources
Infinite and persistent undo/redo (files are remembered based on their
realpath)
Will not modify a file until you explicitly change from the default “READ”
mode into some other (currently “MODIFY” and “REPLACE”)
Modifications are carried out instantly (not sure if that is a feature, but
that is how it is right now)
Structure definitions through a stupidly complicated turing-complete (I know
this is a bad thing) byte code interpreter (op code list in
doc/struct-opcodes)

Tips on using it

You may want to clone
my dot-butterfly repository, build
it and and move the result into ~/.butterfly (or even better: link it) before
launching butterfly so that you have access to all of the structure definitions.

TODO

Simple status line (with different modes, i.e. “READ” and “REPLACE”)
Cursor movement (with main loop)
Additional char-column cursor
Scrolling
Proper commands (e.g. for goto)

Actual replacement (“REPLACE”) + Writing

(No need for buffering with infinite undo, and performance-wise, who cares.
 User input is slow anyway.)

Jump stack (^T)
Infinite undo by writing modification steps into some file
Mouse support
Data display: u8, i8, LE/BE, … (hex in LE) – this is the scalars
```
structure now (use it through `:struct scalars`)
```

Structures: User should be able to define structures in JSON files – this

is considered complete when I have a usable qcow2 definition
(for this, I will need links (“this value is an offset for that value”))

Structure section folding
Do not update structure views that do not depend on the cursor position
```
when moving the cursor
```
Structure highlighting: When you click on a value, it should be
```
highlighted in the data stream
```

Be able to display the list of installed structs (this requires some way

for commands to display a lengthy output, which would be quite nice to
implement a :help also).

Allow appending
Proper command separation: Currently, all command logic and data is kept
```
in src/buffer.rs.  That needs to change.
```
Find things: Every website has this now, so we need that, too

Overwrite unusable undo files: Instead of just aborting or doing random

things when some undo file cannot be read, we should just overwrite it
(or maybe tell the user where it is and create a new one, so if they want
 to debug the issue...)

Also, allow the user to discard specific undo history (e.g. “everything
```
more than 1000 steps ago”)
```
Make some things configurable (themes, scroll length, etc.)
Proper terminfo support (for arbitrary escape sequences at least)
Compress prehistoric undo history to save space