diff options
Diffstat (limited to 'vendor/github.com/sevlyar/go-daemon/lock_file.go')
-rw-r--r-- | vendor/github.com/sevlyar/go-daemon/lock_file.go | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/vendor/github.com/sevlyar/go-daemon/lock_file.go b/vendor/github.com/sevlyar/go-daemon/lock_file.go new file mode 100644 index 0000000..1ec81db --- /dev/null +++ b/vendor/github.com/sevlyar/go-daemon/lock_file.go @@ -0,0 +1,109 @@ +package daemon + +import ( + "errors" + "fmt" + "os" +) + +var ( + // ErrWouldBlock 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 + } + + return os.Remove(file.Name()) +} |