/
scanner.go
108 lines (96 loc) · 2.16 KB
/
scanner.go
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// Copyright 2020 cloudeng llc. All rights reserved.
// Use of this source code is governed by the Apache-2.0
// license that can be found in the LICENSE file.
package localfs
import (
"context"
"fmt"
"io"
"io/fs"
"os"
"time"
"cloudeng.io/file/filewalk"
)
type scanner struct {
path string
openWait time.Duration
err error
file *os.File
entries []fs.DirEntry
}
func (s *scanner) Contents() []filewalk.Entry {
return newContents(s.entries)
}
func (s *scanner) Scan(ctx context.Context, n int) bool {
if n == 0 {
return false
}
// Check for ctx.Done() before performing any IO since
// readdir operations may be very slow.
select {
case <-ctx.Done():
s.err = ctx.Err()
return false
default:
}
if s.file == nil {
if !s.open(ctx, s.path, s.openWait) {
return false
}
}
dirEntries, err := s.file.ReadDir(n)
if err != nil {
s.entries = nil
s.file.Close()
if err = io.EOF; err != nil {
return false
}
s.err = err
return false
}
s.entries = dirEntries
return true
}
func (s *scanner) Err() error {
return s.err
}
type openState struct {
file *os.File
err error
}
func (s *scanner) open(ctx context.Context, path string, waitDuration time.Duration) bool {
if waitDuration == 0 {
s.file, s.err = os.Open(path)
return s.err == nil
}
ch := make(chan openState, 1)
start := time.Now()
go func() {
// This will leak a gorooutine if os.Open hangs.
f, err := os.Open(path)
ch <- openState{file: f, err: err}
}()
select {
case <-ctx.Done():
s.err = ctx.Err()
return false
case state := <-ch:
s.file, s.err = state.file, state.err
case <-time.After(waitDuration):
s.err = fmt.Errorf("os.Open took too long for: %v: %v", time.Since(start), path)
}
return s.err == nil
}
func NewLevelScanner(path string, openwait time.Duration) filewalk.LevelScanner {
return &scanner{path: path, openWait: openwait}
}
func (f *T) LevelScanner(prefix string) filewalk.LevelScanner {
return NewLevelScanner(prefix, f.opts.scannerOpenWait)
}
func newContents(des []fs.DirEntry) []filewalk.Entry {
c := make([]filewalk.Entry, len(des))
for i, de := range des {
c[i] = filewalk.Entry{Name: de.Name(), Type: de.Type()}
}
return c
}