[Chromecast] Remove usage of nonreentrant functions.

chromecast/base/file_utils.cc

Index: chromecast/base/file_utils.cc
diff --git a/chromecast/base/file_utils.cc b/chromecast/base/file_utils.cc
new file mode 100644
index 0000000000000000000000000000000000000000..6b71a5594e93f45569044180641a5139c6a26edc
--- /dev/null
+++ b/chromecast/base/file_utils.cc
@@ -0,0 +1,37 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chromecast/base/file_utils.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <sys/file.h>
+
+namespace {
+
+bool AttemptLockOnFileWithFlag(const char* file, int flag) {
+  int fd;
+  if ((fd = open(file, O_RDONLY)) < 0) {
+    LOG(ERROR) << "Error finding " << file << " error = " << strerror(errno);

[bcf, 2016/08/03 02:40:23]

Error opening . open may fail for other reasons too.

[ameyak, 2016/08/03 18:50:32]

Done.

+    return false;
+  }
+
+  flag = flock(fd, flag);

[bcf, 2016/08/03 02:40:23]

Handle EINTR with TEMP_FAILURE_RETRY
https://www.gnu.org/software/libc/manual/html_node/Interrupted-Primitives.html

[ameyak, 2016/08/03 18:50:32]

Done.

+  close(fd);
+  return !flag;
+}
+
+}  // namespace
+
+namespace chromecast {
+
+bool LockFile(const base::FilePath& path) {
+  return AttemptLockOnFileWithFlag(path.value().c_str(), LOCK_EX);
+}
+
+bool UnlockFile(const base::FilePath& path) {
+  return AttemptLockOnFileWithFlag(path.value().c_str(), LOCK_UN);
+}
+
+}  // namspace chromecast