golang filelock 代码
文件路径：/src/cmd/go/internal/lockedfile/internal/filelock/filelock.go
/ Copyright 2018 The Go 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 filelock provides a platform-independent API for advisory file
/ locking. Calls to functions in this package on platforms that do not support
/ advisory locks will return errors for which IsNotSupported returns true.
package filelock
import (
"errors"
"io/fs"
"os"
)
/ A File provides the minimal set of methods required to lock an open file.
/ File implementations must be usable as map keys.
/ The usual implementation is *os.File.
type File interface {
/ Name returns the name of the file.
Name() string
/ Fd returns a valid file descriptor.
/ (If the File is an *os.File, it must not be closed.)
Fd() uintptr
/ Stat returns the FileInfo structure describing file.
Stat() (fs.FileInfo, error)
}
/ Lock places an advisory write lock on the file, blocking until it can be
/ locked.
/
/ If Lock returns nil, no other process will be able to place a read or write
/ lock on the file until this process exits, closes f, or calls Unlock on it.
/
/ If f's descriptor is already read- or write-locked, the behavior of Lock is
/ unspecified.
/
/ Closing the file may or may not release the lock promptly. Callers should
/ ensure that Unlock is always called when Lock succeeds.
func Lock(f File) error {
return lock(f, writeLock)
}
/ RLock places an advisory read lock on the file, blocking until it can be locked.
/
/ If RLock returns nil, no other process will be able to place a write lock on
/ the file until this process exits, closes f, or calls Unlock on it.
/
/ If f is already read- or write-locked, the behavior of RLock is unspecified.
/
/ Closing the file may or may not release the lock promptly. Callers should
/ ensure that Unlock is always called if RLock succeeds.
func RLock(f File) error {
return lock(f, readLock)
}
/ Unlock removes an advisory lock placed on f by this process.
/
/ The caller must not attempt to unlock a file that is not locked.
func Unlock(f File) error {
return unlock(f)
}
/ String returns the name of the function corresponding to lt
/ (Lock, RLock, or Unlock).
func (lt lockType) String() string {
switch lt {
case readLock:
return "RLock"
case writeLock:
return "Lock"
default:
return "Unlock"
}
}
/ IsNotSupported returns a boolean indicating whether the error is known to
/ report that a function is not supported (possibly for a specific input).
/ It is satisfied by ErrNotSupported as well as some syscall errors.
func IsNotSupported(err error) bool {
return isNotSupported(underlyingError(err))
}
var ErrNotSupported = errors.New("operation not supported")
/ underlyingError returns the underlying error for known os error types.
func underlyingError(err error) error {
switch err := err.(type) {
case *fs.PathError:
return err.Err
case *os.LinkError:
return err.Err
case *os.SyscallError:
return err.Err
}
return err
}