搭建框架

vendor/github.com/cznic/kv/lock.go

@@ -0,0 +1,58 @@
+// Copyright 2014 The kv Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package kv
+
+import (
+	"crypto/sha1"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"sync"
+)
+
+func lockName(dbname string) string {
+	base := filepath.Base(filepath.Clean(dbname)) + "lockfile"
+	h := sha1.New()
+	io.WriteString(h, base)
+	return filepath.Join(filepath.Dir(dbname), fmt.Sprintf(".%x", h.Sum(nil)))
+}
+
+func defaultLocker(dbname string) (io.Closer, error) {
+	lname := lockName(dbname)
+	abs, err := filepath.Abs(lname)
+	if err != nil {
+		return nil, err
+	}
+	f, err := os.OpenFile(abs, os.O_CREATE|os.O_EXCL|os.O_RDONLY, 0666)
+	if os.IsExist(err) {
+		return nil, fmt.Errorf("cannot access DB %q: lock file %q exists", dbname, abs)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &lockCloser{f: f, abs: abs}, nil
+}
+
+type lockCloser struct {
+	f    *os.File
+	abs  string
+	once sync.Once
+	err  error
+}
+
+func (lc *lockCloser) Close() error {
+	lc.once.Do(lc.close)
+	return lc.err
+}
+
+func (lc *lockCloser) close() {
+	if err := lc.f.Close(); err != nil {
+		lc.err = err
+	}
+	if err := os.Remove(lc.abs); err != nil {
+		lc.err = err
+	}
+}