added dependency github.com/sevlyar/go-daemon

vendor/github.com/sevlyar/go-daemon/lock_file.go

@@ -0,0 +1,124 @@
+package daemon
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"syscall"
+)
+
+var (
+	// ErrWoldBlock indicates on locking pid-file by another process.
+	ErrWouldBlock = errors.New("daemon: Resource temporarily unavailable")
+)
+
+// LockFile wraps *os.File and provide functions for locking of files.
+type LockFile struct {
+	*os.File
+}
+
+// NewLockFile returns a new LockFile with the given File.
+func NewLockFile(file *os.File) *LockFile {
+	return &LockFile{file}
+}
+
+// CreatePidFile opens the named file, applies exclusive lock and writes
+// current process id to file.
+func CreatePidFile(name string, perm os.FileMode) (lock *LockFile, err error) {
+	if lock, err = OpenLockFile(name, perm); err != nil {
+		return
+	}
+	if err = lock.Lock(); err != nil {
+		lock.Remove()
+		return
+	}
+	if err = lock.WritePid(); err != nil {
+		lock.Remove()
+	}
+	return
+}
+
+// OpenLockFile opens the named file with flags os.O_RDWR|os.O_CREATE and specified perm.
+// If successful, function returns LockFile for opened file.
+func OpenLockFile(name string, perm os.FileMode) (lock *LockFile, err error) {
+	var file *os.File
+	if file, err = os.OpenFile(name, os.O_RDWR|os.O_CREATE, perm); err == nil {
+		lock = &LockFile{file}
+	}
+	return
+}
+
+// Lock apply exclusive lock on an open file. If file already locked, returns error.
+func (file *LockFile) Lock() error {
+	return lockFile(file.Fd())
+}
+
+// Unlock remove exclusive lock on an open file.
+func (file *LockFile) Unlock() error {
+	return unlockFile(file.Fd())
+}
+
+// ReadPidFile reads process id from file with give name and returns pid.
+// If unable read from a file, returns error.
+func ReadPidFile(name string) (pid int, err error) {
+	var file *os.File
+	if file, err = os.OpenFile(name, os.O_RDONLY, 0640); err != nil {
+		return
+	}
+	defer file.Close()
+
+	lock := &LockFile{file}
+	pid, err = lock.ReadPid()
+	return
+}
+
+// WritePid writes current process id to an open file.
+func (file *LockFile) WritePid() (err error) {
+	if _, err = file.Seek(0, os.SEEK_SET); err != nil {
+		return
+	}
+	var fileLen int
+	if fileLen, err = fmt.Fprint(file, os.Getpid()); err != nil {
+		return
+	}
+	if err = file.Truncate(int64(fileLen)); err != nil {
+		return
+	}
+	err = file.Sync()
+	return
+}
+
+// ReadPid reads process id from file and returns pid.
+// If unable read from a file, returns error.
+func (file *LockFile) ReadPid() (pid int, err error) {
+	if _, err = file.Seek(0, os.SEEK_SET); err != nil {
+		return
+	}
+	_, err = fmt.Fscan(file, &pid)
+	return
+}
+
+// Remove removes lock, closes and removes an open file.
+func (file *LockFile) Remove() error {
+	defer file.Close()
+
+	if err := file.Unlock(); err != nil {
+		return err
+	}
+
+	// TODO(yar): keep filename?
+	name, err := GetFdName(file.Fd())
+	if err != nil {
+		return err
+	}
+
+	err = syscall.Unlink(name)
+	return err
+}
+
+// GetFdName returns file name for given descriptor.
+//
+// BUG(yar): GetFdName returns an error for some *nix platforms when full name length of the file is greater than 0x1000.
+func GetFdName(fd uintptr) (name string, err error) {
+	return getFdName(fd)
+}