1## pwalkdir: parallel implementation of filepath.WalkDir
2
3This is a wrapper for [filepath.WalkDir](https://pkg.go.dev/path/filepath#WalkDir)
4which may speed it up by calling multiple callback functions (WalkDirFunc)
5in parallel, utilizing goroutines.
6
7By default, it utilizes 2\*runtime.NumCPU() goroutines for callbacks.
8This can be changed by using WalkN function which has the additional
9parameter, specifying the number of goroutines (concurrency).
10
11### pwalk vs pwalkdir
12
13This package is very similar to
14[pwalk](https://pkg.go.dev/github.com/opencontainers/selinux/pkg/pwalkdir),
15but utilizes `filepath.WalkDir` (added to Go 1.16), which does not call stat(2)
16on every entry and is therefore faster (up to 3x, depending on usage scenario).
17
18Users who are OK with requiring Go 1.16+ should switch to this
19implementation.
20
21### Caveats
22
23Please note the following limitations of this code:
24
25* Unlike filepath.WalkDir, the order of calls is non-deterministic;
26
27* Only primitive error handling is supported:
28
29 * fs.SkipDir is not supported;
30
31 * no errors are ever passed to WalkDirFunc;
32
33 * once any error is returned from any walkDirFunc instance, no more calls
34 to WalkDirFunc are made, and the error is returned to the caller of WalkDir;
35
36 * if more than one WalkDirFunc instance will return an error, only one
37 of such errors will be propagated to and returned by WalkDir, others
38 will be silently discarded.
39
40### Documentation
41
42For the official documentation, see
43https://pkg.go.dev/github.com/opencontainers/selinux/pkg/pwalkdir
44
45### Benchmarks
46
47For a WalkDirFunc that consists solely of the return statement, this
48implementation is about 15% slower than the standard library's
49filepath.WalkDir.
50
51Otherwise (if a WalkDirFunc is actually doing something) this is usually
52faster, except when the WalkDirN(..., 1) is used. Run `go test -bench .`
53to see how different operations can benefit from it, as well as how the
54level of paralellism affects the speed.
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