Initial commit

vendor/github.com/cockroachdb/pebble/vfs/file_lock_unix.go

@@ -0,0 +1,70 @@
+// Copyright 2014 The LevelDB-Go and Pebble Authors. All rights reserved. Use
+// of this source code is governed by a BSD-style license that can be found in
+// the LICENSE file.
+
+//go:build darwin || dragonfly || freebsd || linux || netbsd || openbsd || solaris
+// +build darwin dragonfly freebsd linux netbsd openbsd solaris
+
+package vfs
+
+import (
+	"io"
+	"os"
+	"sync"
+	"syscall"
+
+	"github.com/cockroachdb/errors"
+)
+
+var lockedFiles struct {
+	mu struct {
+		sync.Mutex
+		files map[string]bool
+	}
+}
+
+// lockCloser hides all of an os.File's methods, except for Close.
+type lockCloser struct {
+	name string
+	f    *os.File
+}
+
+func (l lockCloser) Close() error {
+	lockedFiles.mu.Lock()
+	defer lockedFiles.mu.Unlock()
+	if !lockedFiles.mu.files[l.name] {
+		panic(errors.Errorf("lock file %q is not locked", l.name))
+	}
+	delete(lockedFiles.mu.files, l.name)
+
+	return l.f.Close()
+}
+
+func (defaultFS) Lock(name string) (io.Closer, error) {
+	lockedFiles.mu.Lock()
+	defer lockedFiles.mu.Unlock()
+	if lockedFiles.mu.files == nil {
+		lockedFiles.mu.files = map[string]bool{}
+	}
+	if lockedFiles.mu.files[name] {
+		return nil, errors.New("lock held by current process")
+	}
+
+	f, err := os.Create(name)
+	if err != nil {
+		return nil, err
+	}
+	spec := syscall.Flock_t{
+		Type:   syscall.F_WRLCK,
+		Whence: io.SeekStart,
+		Start:  0,
+		Len:    0, // 0 means to lock the entire file.
+		Pid:    int32(os.Getpid()),
+	}
+	if err := syscall.FcntlFlock(f.Fd(), syscall.F_SETLK, &spec); err != nil {
+		f.Close()
+		return nil, err
+	}
+	lockedFiles.mu.files[name] = true
+	return lockCloser{name, f}, nil
+}