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55 lines
1.9 KiB
Markdown
55 lines
1.9 KiB
Markdown
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## pwalkdir: parallel implementation of filepath.WalkDir
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This is a wrapper for [filepath.WalkDir](https://pkg.go.dev/path/filepath#WalkDir)
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which may speed it up by calling multiple callback functions (WalkDirFunc)
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in parallel, utilizing goroutines.
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By default, it utilizes 2\*runtime.NumCPU() goroutines for callbacks.
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This can be changed by using WalkN function which has the additional
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parameter, specifying the number of goroutines (concurrency).
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### pwalk vs pwalkdir
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This package is very similar to
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[pwalk](https://pkg.go.dev/github.com/opencontainers/selinux/pkg/pwalkdir),
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but utilizes `filepath.WalkDir` (added to Go 1.16), which does not call stat(2)
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on every entry and is therefore faster (up to 3x, depending on usage scenario).
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Users who are OK with requiring Go 1.16+ should switch to this
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implementation.
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### Caveats
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Please note the following limitations of this code:
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* Unlike filepath.WalkDir, the order of calls is non-deterministic;
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* Only primitive error handling is supported:
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* fs.SkipDir is not supported;
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* no errors are ever passed to WalkDirFunc;
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* once any error is returned from any walkDirFunc instance, no more calls
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to WalkDirFunc are made, and the error is returned to the caller of WalkDir;
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* if more than one WalkDirFunc instance will return an error, only one
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of such errors will be propagated to and returned by WalkDir, others
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will be silently discarded.
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### Documentation
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For the official documentation, see
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https://pkg.go.dev/github.com/opencontainers/selinux/pkg/pwalkdir
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### Benchmarks
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For a WalkDirFunc that consists solely of the return statement, this
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implementation is about 15% slower than the standard library's
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filepath.WalkDir.
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Otherwise (if a WalkDirFunc is actually doing something) this is usually
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faster, except when the WalkDirN(..., 1) is used. Run `go test -bench .`
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to see how different operations can benefit from it, as well as how the
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level of paralellism affects the speed.
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