1 files changed, 99 insertions, 0 deletions
diff --git a/net/dns/serial_worker.cc b/net/dns/serial_worker.cc
new file mode 100644
index 0000000..d2e42c0
--- /dev/null
+++ b/net/dns/serial_worker.cc
@@ -0,0 +1,99 @@
+// Copyright (c) 2011 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 "net/dns/serial_worker.h"
+
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/message_loop_proxy.h"
+#include "base/threading/worker_pool.h"
+
+namespace net {
+
+SerialWorker::SerialWorker()
+  : message_loop_(base::MessageLoopProxy::current()),
+    state_(IDLE) {}
+
+SerialWorker::~SerialWorker() {}
+
+void SerialWorker::WorkNow() {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  switch (state_) {
+    case IDLE:
+      if (!base::WorkerPool::PostTask(FROM_HERE, base::Bind(
+          &SerialWorker::DoWorkJob, this), false)) {
+#if defined(OS_POSIX)
+        // See worker_pool_posix.cc.
+        NOTREACHED() << "WorkerPool::PostTask is not expected to fail on posix";
+#else
+        LOG(WARNING) << "Failed to WorkerPool::PostTask, will retry later";
+        message_loop_->PostDelayedTask(
+            FROM_HERE,
+            base::Bind(&SerialWorker::RetryWork, this),
+            kWorkerPoolRetryDelayMs);
+        state_ = WAITING;
+        return;
+#endif
+      }
+      state_ = WORKING;
+      return;
+    case WORKING:
+      // Remember to re-read after |DoRead| finishes.
+      state_ = PENDING;
+      return;
+    case CANCELLED:
+    case PENDING:
+    case WAITING:
+      return;
+    default:
+      NOTREACHED() << "Unexpected state " << state_;
+  }
+}
+
+void SerialWorker::Cancel() {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  state_ = CANCELLED;
+}
+
+void SerialWorker::DoWorkJob() {
+  this->DoWork();
+  // If this fails, the loop is gone, so there is no point retrying.
+  message_loop_->PostTask(FROM_HERE, base::Bind(
+      &SerialWorker::OnWorkJobFinished, this));
+}
+
+void SerialWorker::OnWorkJobFinished() {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  switch (state_) {
+    case CANCELLED:
+      return;
+    case WORKING:
+      state_ = IDLE;
+      this->OnWorkFinished();
+      return;
+    case PENDING:
+      state_ = IDLE;
+      WorkNow();
+      return;
+    default:
+      NOTREACHED() << "Unexpected state " << state_;
+  }
+}
+
+void SerialWorker::RetryWork() {
+  DCHECK(message_loop_->BelongsToCurrentThread());
+  switch (state_) {
+    case CANCELLED:
+      return;
+    case WAITING:
+      state_ = IDLE;
+      WorkNow();
+      return;
+    default:
+      NOTREACHED() << "Unexpected state " << state_;
+  }
+}
+
+}  // namespace net
+