From 7d500e9330eaf096fdbe89e33b1bf00526873e0e Mon Sep 17 00:00:00 2001
From: "Thiago Marcos P. Santos" <thiago@mapbox.com>
Date: Tue, 14 Jul 2015 17:01:20 +0300
Subject: [PATCH] Introduce the WorkQueue

The WorkQueue allow other threads to submit tasks to be executed in
the thread that the WorkQueue lives on.

The WorkQueue will cancel all the pending tasks when it gets
destructed, to make sure the tasks won't get called with
invalid references.
---
 src/mbgl/util/work_queue.cpp | 37 ++++++++++++++++++++++++++++++++++++
 src/mbgl/util/work_queue.hpp | 36 +++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 src/mbgl/util/work_queue.cpp
 create mode 100644 src/mbgl/util/work_queue.hpp

diff --git a/src/mbgl/util/work_queue.cpp b/src/mbgl/util/work_queue.cpp
new file mode 100644
index 000000000..7e1406bba
--- /dev/null
+++ b/src/mbgl/util/work_queue.cpp
@@ -0,0 +1,37 @@
+#include <mbgl/util/work_queue.hpp>
+
+#include <mbgl/util/run_loop.hpp>
+
+namespace mbgl {
+namespace util {
+
+WorkQueue::WorkQueue() : runLoop(RunLoop::Get()) {
+}
+
+WorkQueue::~WorkQueue() {
+    assert(runLoop == RunLoop::Get());
+
+    // Cancel all pending WorkRequests.
+    while (!queue.empty()) {
+        queue.pop();
+    }
+}
+
+void WorkQueue::push(std::function<void()>&& fn) {
+    std::lock_guard<std::mutex> lock(queueMutex);
+
+    auto workRequest = runLoop->invokeCancellable(std::bind(&WorkQueue::pop, this, std::move(fn)));
+    queue.push(std::move(workRequest));
+}
+
+void WorkQueue::pop(const std::function<void()>& fn) {
+    assert(runLoop == RunLoop::Get());
+
+    fn();
+
+    std::lock_guard<std::mutex> lock(queueMutex);
+    queue.pop();
+}
+
+}
+}
diff --git a/src/mbgl/util/work_queue.hpp b/src/mbgl/util/work_queue.hpp
new file mode 100644
index 000000000..dcec5668b
--- /dev/null
+++ b/src/mbgl/util/work_queue.hpp
@@ -0,0 +1,36 @@
+#ifndef MBGL_UTIL_WORK_QUEUE
+#define MBGL_UTIL_WORK_QUEUE
+
+#include <mbgl/util/noncopyable.hpp>
+#include <mbgl/util/work_request.hpp>
+
+#include <functional>
+#include <memory>
+#include <mutex>
+#include <queue>
+
+namespace mbgl {
+namespace util {
+
+class RunLoop;
+
+class WorkQueue : private util::noncopyable {
+public:
+    WorkQueue();
+    virtual ~WorkQueue();
+
+    void push(std::function<void()>&&);
+
+private:
+    void pop(const std::function<void()>&);
+
+    std::queue<std::unique_ptr<WorkRequest>> queue;
+    std::mutex queueMutex;
+
+    RunLoop* runLoop;
+};
+
+}
+}
+
+#endif