Merge "lock: Merge added FreeBSD support from upstream."

third_party/github.com/camlistore/lock/lock.go

@@ -34,15 +34,15 @@ import (
 // A nil Closer is returned if an error occurred. Otherwise, close that
 // Closer to release the lock.
 //
-// On Linux and OSX, a lock has the same semantics as fcntl(2)'s advisory
+// On Linux, FreeBSD and OSX, a lock has the same semantics as fcntl(2)'s
-// locks.  In particular, closing any other file descriptor for the same
+// advisory locks.  In particular, closing any other file descriptor for the
-// file will release the lock prematurely.
+// same file will release the lock prematurely.
 //
 // Attempting to lock a file that is already locked by the current process
 // has undefined behavior.
 //
-// Lock is not yet implemented on other operating systems, and calling it
+// On other operating systems, lock will fallback to using the presence and
-// will return an error.
+// content of a file named name + '.lock' to implement locking behavior.
 func Lock(name string) (io.Closer, error) {
 	return lockFn(name)
 }

third_party/github.com/camlistore/lock/lock_freebsd.go

@@ -0,0 +1,79 @@
+/*
+Copyright 2013 The Go Authors
+
+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"
+	"io"
+	"os"
+	"path/filepath"
+	"syscall"
+	"unsafe"
+)
+
+func init() {
+	lockFn = lockFcntl
+}
+
+func lockFcntl(name string) (io.Closer, error) {
+	abs, err := filepath.Abs(name)
+	if err != nil {
+		return nil, err
+	}
+	lockmu.Lock()
+	if locked[abs] {
+		lockmu.Unlock()
+		return nil, fmt.Errorf("file %q already locked", abs)
+	}
+	locked[abs] = true
+	lockmu.Unlock()
+
+	fi, err := os.Stat(name)
+	if err == nil && fi.Size() > 0 {
+		return nil, fmt.Errorf("can't Lock file %q: has non-zero size", name)
+	}
+
+	f, err := os.Create(name)
+	if err != nil {
+		return nil, err
+	}
+
+	// This type matches C's "struct flock" defined in /usr/include/fcntl.h.
+	// TODO: move this into the standard syscall package.
+	k := struct {
+		Start  int64 /* off_t starting offset */
+		Len    int64 /* off_t len = 0 means until end of file */
+		Pid    int32 /* pid_t lock owner */
+		Type   int16 /* short lock type: read/write, etc. */
+		Whence int16 /* short type of l_start */
+		Sysid  int32 /* int   remote system id or zero for local */
+	}{
+		Start:  0,
+		Len:    0, // 0 means to lock the entire file.
+		Pid:    int32(os.Getpid()),
+		Type:   syscall.F_WRLCK,
+		Whence: int16(os.SEEK_SET),
+		Sysid:  0,
+	}
+
+	_, _, errno := syscall.Syscall(syscall.SYS_FCNTL, f.Fd(), uintptr(syscall.F_SETLK), uintptr(unsafe.Pointer(&k)))
+	if errno != 0 {
+		f.Close()
+		return nil, errno
+	}
+	return &unlocker{f, abs}, nil
+}