vim-hexedit

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Edit binary files as hex inside Vim or Neovim, backed by xxd. Supports four modes and can handle large files without loading them in full — see REQUIREMENTS.md for the full design and :help hexedit once installed for day-to-day usage.

Note: this README describes the v2.0 command set. If you're upgrading from an older install, the commands below replace :Hexedit/:Hexkeep/ :Hex2C/:Hex2Py, which no longer exist.

Modes and commands

Command	Mode	Editable	Notes
:Hedit	Hex 编辑模式 (Hex Edit)	Yes	offset / hex / ascii columns, in-place overwrite editing
:Hex	Hex 字串模式 (Hex string)	Yes	plain grouped hex text, allows insert/delete
:H2C	C 语言视图模式 (C view)	No	unsigned char buf[] = { 0x41, ... };
:H2Py	Python 视图模式 (Python view)	No	Python-3 bytes.fromhex(...)

:Hedit / :Hex / :H2C / :H2Py switch directly between each other from whichever mode you're currently in — you don't need to bounce back through Hex Edit mode first.

Two more commands cross the boundary between plain Vim text and this plugin:

• :HexLoad — treat the current buffer's text as a hex string and enter Hex Edit mode. If the buffer already has a filename, you're asked once whether saving should keep the file in its original (binary) form (decode and overwrite with raw bytes) or convert it to a hex string (keep writing the hex-string form) — there's no silent default, since the file started out as text.
• :HexDump — from any active mode (not just Hex Edit), convert to hex-string text and leave the plugin entirely, back to normal Vim editing. Use :HexLoad again to re-enter.

Plus search support inside Hex Edit mode:

• :Hsearch 41414141 searches for a hex byte sequence; n repeats it.
• :HsearchClean clears the search and restores n's normal behavior.

Tips

Tip 1: f| jumps straight to the | separator column, and the plugin's cursor-snapping then lands you at the start of the ascii column — the fastest way to hop from hex to ascii on the current line.

Tip 2: :Hsearch 41414141 temporarily takes over the n key to mean "repeat this hex search" instead of Vim's normal "repeat last search". Run :HsearchClean when you're done to give n back its usual meaning.

Tip 3: on a large file (see below), :HGoto 0x1000 jumps straight to a byte offset instead of scrolling — it works with either decimal or 0x-prefixed hex.

Tip 4: if you edit in :Hex (Hex string) mode and the byte count changes, saving on a large windowed file will ask you to confirm before falling back to a full-file rewrite — expect that prompt, it's not an error.

Auto-trigger

Hex Edit mode starts automatically when you:

• open a file in Vim's binary mode (vim -b file, :e ++bin file), or
• open a file matching g:hexedit_patterns (default *.bin,*.dat,*.hex,*.o).

Large files

Files over g:hexedit_large_file_threshold (default 1MB) are opened windowed: only a slice of the file is read via xxd -s/-l, and scrolling near the edge of what's loaded reloads a new window centered on your position. Every reload aligns the window to a multiple of g:octets_per_line bytes, so a given file byte always shows up in the same column regardless of which window loaded it — just like a normal hex dump. Use :HGoto {offset} (decimal or 0x-prefixed hex) to jump anywhere in the file directly, or plain G/gg to jump to the true end/start of the file (these are overridden from Vim's default buffer-relative behavior, which would otherwise only reach the edges of the loaded window). Saving a same-length edit patches just that byte range in place; changing the byte count requires a confirmed full-file rewrite. See :help hexedit-large-files for details.

Configuration

All of these are set with let g:... = ... in your vimrc before the plugin loads:

Variable	Default	Meaning
g:group_octets_num	2	bytes per hex "cell"
g:octets_per_line	16	bytes per line
g:hexedit_low_up	'lower'	hex digit case ('lower'/'upper')
g:hexedit_patterns	'*.bin,*.dat,*.hex,*.o'	auto binary-mode file patterns
g:hexedit_xxd_options	''	extra flags appended to the rendering xxd call
g:hexedit_large_file_threshold	1048576	bytes; above this, windowed editing kicks in
g:hexedit_window_size	65536	base window-size unit (bytes)
g:hexedit_cache_window_ratio	3	cache window = this × g:hexedit_window_size
g:hexedit_c_varname	'buf'	variable name used by C view mode
g:hexedit_highlight_byte_value	0	byte value (0-255) to highlight distinctly in the hex column (defaults to highlighting null bytes); set to -1 to disable
g:hexedit_highlight_byte_hlgroup	'NonText'	highlight group the target byte links to

Full reference: :help hexedit.

Install

Requires xxd, dd, sh, head, tail on $PATH (standard on Unix-like systems).

Install under blank environment

    $ git clone https://github.com/rootkiter/vim-hexedit.git ~/.vim

Install under Pathogen

    $ git clone https://github.com/rootkiter/vim-hexedit.git ~/.vim/bundle/vim-hexedit

Development

Design rationale and architecture live in REQUIREMENTS.md. Tests are dependency-free Vimscript, runnable headlessly:

    $ nvim --headless -u NONE -c "source tests/run.vim"

(or vim in place of nvim on a Vim 8.1+ install).