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db2cc393af
This is similar to the golang.org/x/tools/internal/fastwalk I'd
previously written but not recursive and using mem.RO.
The metrics package already had some Linux-specific directory reading
code in it. Move that out to a new general package that can be reused
by portlist too, which helps its scanning of all /proc files:
name old time/op new time/op delta
FindProcessNames-8 2.79ms ± 6% 2.45ms ± 7% -12.11% (p=0.000 n=10+10)
name old alloc/op new alloc/op delta
FindProcessNames-8 62.9kB ± 0% 33.5kB ± 0% -46.76% (p=0.000 n=9+10)
name old allocs/op new allocs/op delta
FindProcessNames-8 2.25k ± 0% 0.38k ± 0% -82.98% (p=0.000 n=9+10)
Change-Id: I75db393032c328f12d95c39f71c9742c375f207a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
55 lines
1.3 KiB
Go
55 lines
1.3 KiB
Go
// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package dirwalk contains code to walk a directory.
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package dirwalk
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import (
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"io"
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"io/fs"
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"os"
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"go4.org/mem"
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)
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var osWalkShallow func(name mem.RO, fn WalkFunc) error
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// WalkFunc is the callback type used with WalkShallow.
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//
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// The name and de are only valid for the duration of func's call
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// and should not be retained.
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type WalkFunc func(name mem.RO, de fs.DirEntry) error
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// WalkShallow reads the entries in the named directory and calls fn for each.
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// It does not recurse into subdirectories.
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//
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// If fn returns an error, iteration stops and WalkShallow returns that value.
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//
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// On Linux, WalkShallow does not allocate, so long as certain methods on the
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// WalkFunc's DirEntry are not called which necessarily allocate.
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func WalkShallow(dirName mem.RO, fn WalkFunc) error {
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if f := osWalkShallow; f != nil {
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return f(dirName, fn)
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}
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of, err := os.Open(dirName.StringCopy())
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if err != nil {
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return err
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}
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defer of.Close()
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for {
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fis, err := of.ReadDir(100)
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for _, de := range fis {
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if err := fn(mem.S(de.Name()), de); err != nil {
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return err
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}
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}
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if err != nil {
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if err == io.EOF {
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return nil
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}
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return err
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}
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}
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}
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