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ncdu-zig/README.md
Yorhel 2390308883 Handle allocation failures 
In a similar way to the C version of ncdu: by wrapping malloc(). It's
simpler to handle allocation failures at the source to allow for easy
retries, pushing the retries up the stack will complicate code somewhat
more. Likewise, this is a best-effort approach to handling OOM,
allocation failures in ncurses aren't handled and display glitches may
occur when we get an OOM inside a drawing function.

This is a somewhat un-Zig-like way of handling errors and adds
scary-looking 'catch unreachable's all over the code, but that's okay.
2021-05-29 13:18:23 +02:00

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ncdu-zig

Description

Ncdu is a disk usage analyzer with an ncurses interface. It is designed to find space hogs on a remote server where you don't have an entire graphical setup available, but it is a useful tool even on regular desktop systems. Ncdu aims to be fast, simple and easy to use, and should be able to run in any minimal POSIX-like environment with ncurses installed.

This Zig implementation

This branch represents an experimental rewrite of ncdu using the Zig programming language. It is supposed to be fully compatible (in terms of behavior, UI and CLI flags) with the C version, so it can eventually be used as a drop-in replacement.

Since Zig itself is still very much unstable and things tend to break with each release, I can't in good conscience publish this rewrite as a proper release of ncdu (...yet). I intent to maintain the C version as long as necessary while Zig matures and gets more widely supported among Linux/BSD systems.

This rewrite is a test-bed for various improvements to the design of ncdu that would impact large parts of its codebase. The improvements may also be backported to the C version, depending on how viable a proper Zig release is.

Implementation status

Missing features:

  • Lots of informational UI windows
  • Directory refresh
  • File deletion
  • Opening a shell

Improvements compared to the C version

Already implemented:

  • Significantly reduced memory usage, achieved by:
    • Removing pointers between nodes that are not strictly necessary for basic tree traversal (this impacts all code in the C version of ncdu).
    • Using separate structs for directory, file and hard link nodes, each storing only the information necessary for that particular type of node.
    • Using an arena allocator and getting rid of data alignment.
  • Improved performance of hard link counting (fixing #121).
  • Add support for separate counting hard links that are shared with other directories or unique within the directory (issue #36). (Implemented in the data model, but not displayed in the UI yet)
  • Faster --exclude-kernfs thanks to statfs() caching.
  • Improved handling of Unicode and special characters.
  • Remembers item position when switching directories.

Potentially to be implemented:

  • Faster --exclude-pattern matching
  • Multithreaded scanning
  • Exporting a JSON dump after scanning into RAM
  • Transparent dump (de)compression by piping through gzip/bzip2/etc

Regressions compared to the C version

Aside from this implementation being unfinished:

  • Assumes a UTF-8 locale and terminal.
  • No doubt somewhat less portable.
  • Listing all paths for a particular hard link requires a full search through the in-memory directory tree.
  • Not nearly as well tested.
  • Directories that could not be opened are displayed as files.

Requirements

  • Latest Zig compiler
  • Some sort of POSIX-like OS
  • ncurses libraries and header files

Install

todo