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KJ Filesystem API #384

Merged
merged 5 commits into from Apr 29, 2017
Merged

KJ Filesystem API #384

merged 5 commits into from Apr 29, 2017

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kentonv
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@kentonv kentonv commented Oct 24, 2016

I've long wanted a filesystem API that:

  • Is resistant to path injection bugs.
  • Uses a representation of paths that is easy to manipulate (flat strings with / as separators are actually incredibly tedious!).
  • Canonicalizes ".." logically (by removing the previous path component) rather than physically (by climbing the directory tree), especially when dealing with the current working directory.
  • Is RAII.
  • Does not assume a singleton filesystem (= implements abstract interfaces so that you can provide a different implementation when desired).
  • Throws exceptions on error, but lets you opt-in to programatically handling the kinds of errors that one commonly wants to handle (namely, doesn't-exist and already-exists).
  • Directly supports the write-to-temp-then-atomically-replace pattern.
  • Directly supports the common operations "recursively delete directory" and "automatically create parent directories".
  • Directly supports a copy operation, with smart semantics around sparse files.
  • Makes mmap easy.
  • Automatically opens all file descriptors close-on-exec.
  • Utilizes Linux features like renameat2(), FICLONE (copy-on-write files), O_TMPFILE, etc. when available, but falls back to generic POSIX when not.
  • Much more...

So this is my attempt.

@kentonv
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kentonv commented Apr 7, 2017

(I just merged everything except the filesystem API itself. Github seems very confused about this...)

@kentonv kentonv force-pushed the filesystem branch 3 times, most recently from d13f449 to e0d3908 Compare April 27, 2017 19:27
This has three main parts:
* The Path data structure, a more-explicit approach to file paths.
* The File/Directory abstract interfaces.
* The "InMemory" implementations of File and Directory.

Disk-based implementations will come in a future commit.
@kentonv
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kentonv commented Apr 29, 2017

Gonna merge this because I'm using it in a project, although currently only Ekam will build it. I guess we need a Win32 version before we can make it part of the main builds.

I already cut the 0.6 release branch so this will land in 0.7.

@kentonv kentonv merged commit b1701b8 into master Apr 29, 2017
@kentonv kentonv deleted the filesystem branch April 29, 2017 00:57
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