Adds a modified copy of talk/base to webrtc/base. It is the first step in migrating talk/base to webrtc/base.

BUG=N/A
R=andrew@webrtc.org, wu@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12199004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6107 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/base/filelock.cc

@@ -0,0 +1,62 @@
+/*
+ *  Copyright 2009 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "webrtc/base/filelock.h"
+
+#include "webrtc/base/fileutils.h"
+#include "webrtc/base/logging.h"
+#include "webrtc/base/pathutils.h"
+#include "webrtc/base/stream.h"
+
+namespace rtc {
+
+FileLock::FileLock(const std::string& path, FileStream* file)
+    : path_(path), file_(file) {
+}
+
+FileLock::~FileLock() {
+  MaybeUnlock();
+}
+
+void FileLock::Unlock() {
+  LOG_F(LS_INFO);
+  MaybeUnlock();
+}
+
+void FileLock::MaybeUnlock() {
+  if (file_) {
+    LOG(LS_INFO) << "Unlocking:" << path_;
+    file_->Close();
+    Filesystem::DeleteFile(path_);
+    file_.reset();
+  }
+}
+
+FileLock* FileLock::TryLock(const std::string& path) {
+  FileStream* stream = new FileStream();
+  bool ok = false;
+#if defined(WEBRTC_WIN)
+  // Open and lock in a single operation.
+  ok = stream->OpenShare(path, "a", _SH_DENYRW, NULL);
+#else // WEBRTC_LINUX && !WEBRTC_ANDROID and WEBRTC_MAC && !defined(WEBRTC_IOS)
+  ok = stream->Open(path, "a", NULL) && stream->TryLock();
+#endif
+  if (ok) {
+    return new FileLock(path, stream);
+  } else {
+    // Something failed, either we didn't succeed to open the
+    // file or we failed to lock it. Anyway remove the heap
+    // allocated object and then return NULL to indicate failure.
+    delete stream;
+    return NULL;
+  }
+}
+
+}  // namespace rtc