[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..acf9b954a4cee2253d19689b943db98d430c57be
--- /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 {
+
+bool CallFlockOnFileWithFlag(const int fd, int flag) {

[slan, 2016/08/08 16:37:10]

nit: Add a comment explaining retval.

[ameyak, 2016/08/08 18:00:43]

Done.

+  int ret;

[slan, 2016/08/08 16:37:10]

nit: init this.

[ameyak, 2016/08/08 18:00:43]

Done.

+  if ((ret = TEMP_FAILURE_RETRY(flock(fd, flag))) < 0) {
+    LOG(ERROR) << "Error locking " << fd << " error = " << strerror(errno);

[slan, 2016/08/08 16:37:10]

PLOG would be appropriate here:

https://cs.chromium.org/chromium/src/base/logging.h?rcl=0&l=122

[ameyak, 2016/08/08 18:00:43]

Done.

+    return false;
+  }
+
+  return true;
+}
+
+}  // namespace
+
+namespace chromecast {
+
+int OpenAndLockFile(const base::FilePath& path) {
+  int fd;

[slan, 2016/08/08 16:37:10]

nit: init this.

[ameyak, 2016/08/08 18:00:43]

Done.

+  const char* file = path.value().c_str();
+
+  if ((fd = open(file, O_RDONLY)) < 0) {

[slan, 2016/08/08 16:37:10]

The comment on this function doesn't indicate that this file is opened
read-only. Maybe change the name of the function to OpenAndLockReadOnlyFile? Or
pass a param in to indicate write permissions.

[ameyak, 2016/08/08 18:00:43]

Done.

+    LOG(ERROR) << "Error opening " << file << " error = " << strerror(errno);

[slan, 2016/08/08 16:37:10]

nit: PLOG

[ameyak, 2016/08/08 18:00:43]

Done.

+  } 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