[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..bd3ee2ef5c9bc635d0947c33a125f3f60d762251
--- /dev/null
+++ b/chromecast/base/file_utils.cc
@@ -0,0 +1,47 @@
+// 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 {
+
+// Calls flock on valid file descriptor |fd| with flag |flag|. Returns true
+// on success, false on failure.
+bool CallFlockOnFileWithFlag(const int fd, int flag) {
+  int ret = -1;
+  if ((ret = TEMP_FAILURE_RETRY(flock(fd, flag))) < 0)
+    PLOG(ERROR) << "Error locking " << fd;
+
+  return !ret;
+}
+
+}  // namespace
+
+namespace chromecast {
+
+int OpenAndLockFile(const base::FilePath& path, bool write) {
+  int fd = -1;
+  const char* file = path.value().c_str();
+
+  if ((fd = open(file, write ? O_RDWR : O_RDONLY)) < 0) {
+    PLOG(ERROR) << "Error opening " << file;
+  } else if (!CallFlockOnFileWithFlag(fd, LOCK_EX)) {
+    close(fd);
+    fd = -1;
+  }
+
+  return fd;
+}
+
+bool UnlockAndCloseFile(const int fd) {
+  if (!CallFlockOnFileWithFlag(fd, LOCK_UN))
+    return false;
+  return !close(fd);
+}
+
+}  // namespace chromecast