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Copy pathlock_nix.go
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// +build !windows,!plan9,!solaris
/*
* Minio Cloud Storage, (C) 2016 Minio, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package lock
import (
"fmt"
"os"
"syscall"
)
// Internal function implements support for both
// blocking and non blocking lock type.
func lockedOpenFile(path string, flag int, perm os.FileMode, lockType int) (*LockedFile, error) {
switch flag {
case syscall.O_RDONLY:
lockType |= syscall.LOCK_SH
case syscall.O_WRONLY:
fallthrough
case syscall.O_RDWR:
fallthrough
case syscall.O_WRONLY | syscall.O_CREAT:
fallthrough
case syscall.O_RDWR | syscall.O_CREAT:
lockType |= syscall.LOCK_EX
default:
return nil, fmt.Errorf("Unsupported flag (%d)", flag)
}
f, err := os.OpenFile(path, flag|syscall.O_SYNC, perm)
if err != nil {
return nil, err
}
if err = syscall.Flock(int(f.Fd()), lockType); err != nil {
f.Close()
if err == syscall.EWOULDBLOCK {
err = ErrAlreadyLocked
}
return nil, err
}
st, err := os.Stat(path)
if err != nil {
f.Close()
return nil, err
}
if st.IsDir() {
f.Close()
return nil, &os.PathError{
Op: "open",
Path: path,
Err: syscall.EISDIR,
}
}
return &LockedFile{File: f}, nil
}
// TryLockedOpenFile - tries a new write lock, functionality
// it is similar to LockedOpenFile with with syscall.LOCK_EX
// mode but along with syscall.LOCK_NB such that the function
// doesn't wait forever but instead returns if it cannot
// acquire a write lock.
func TryLockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
return lockedOpenFile(path, flag, perm, syscall.LOCK_NB)
}
// LockedOpenFile - initializes a new lock and protects
// the file from concurrent access across mount points.
// This implementation doesn't support all the open
// flags and shouldn't be considered as replacement
// for os.OpenFile().
func LockedOpenFile(path string, flag int, perm os.FileMode) (*LockedFile, error) {
return lockedOpenFile(path, flag, perm, 0)
}