make storage lib separate so we can build without storage libs

platform/default/default_file_source.cpp

@@ -0,0 +1,239 @@
+#include <mbgl/storage/default/default_file_source.hpp>
+#include <mbgl/storage/default/request.hpp>
+#include <mbgl/storage/default/asset_request.hpp>
+#include <mbgl/storage/default/http_request.hpp>
+
+#include <mbgl/storage/response.hpp>
+
+#include <mbgl/util/async_queue.hpp>
+#include <mbgl/util/util.hpp>
+
+#include <mbgl/util/variant.hpp>
+
+#include <boost/algorithm/string.hpp>
+
+#include <thread>
+#include <algorithm>
+#include <cassert>
+
+
+namespace algo = boost::algorithm;
+
+namespace mbgl {
+
+struct DefaultFileSource::ActionDispatcher {
+    DefaultFileSource &fileSource;
+    template <typename T> void operator()(T &t) { fileSource.process(t); }
+};
+
+struct DefaultFileSource::AddRequestAction {
+    Request *const request;
+};
+
+struct DefaultFileSource::RemoveRequestAction {
+    Request *const request;
+};
+
+struct DefaultFileSource::ResultAction {
+    const Resource resource;
+    std::unique_ptr<Response> response;
+};
+
+struct DefaultFileSource::StopAction {
+};
+
+
+DefaultFileSource::DefaultFileSource(FileCache *cache_)
+    : loop(uv_loop_new()),
+      cache(cache_),
+      queue(new Queue(loop, [this](Action &action) {
+          mapbox::util::apply_visitor(ActionDispatcher{*this}, action);
+      })),
+      thread([this]() {
+#ifdef __APPLE__
+          pthread_setname_np("FileSource");
+#endif
+          uv_run(loop, UV_RUN_DEFAULT);
+      }) {
+}
+
+DefaultFileSource::DefaultFileSource(FileCache *cache_, uv_loop_t *loop_)
+    : loop(loop_),
+      cache(cache_),
+      queue(new Queue(loop, [this](Action &action) {
+          mapbox::util::apply_visitor(ActionDispatcher{*this}, action);
+      })) {
+    // Make sure that the queue doesn't block the loop from exiting.
+    queue->unref();
+}
+
+DefaultFileSource::~DefaultFileSource() {
+    MBGL_VERIFY_THREAD(tid);
+
+    if (thread.joinable()) {
+        if (queue) {
+            queue->send(StopAction{ });
+        }
+        thread.join();
+        uv_loop_delete(loop);
+    } else {
+        // Assume that the loop we received is running in the current thread.
+        StopAction action {};
+        process(action);
+    }
+}
+
+SharedRequestBase *DefaultFileSource::find(const Resource &resource) {
+    // We're using a set of pointers here instead of a map between url and SharedRequestBase because
+    // we need to find the requests both by pointer and by URL. Given that the number of requests
+    // is generally very small (typically < 10 at a time), hashing by URL incurs too much overhead
+    // anyway.
+    const auto it = pending.find(resource);
+    if (it != pending.end()) {
+        return it->second;
+    }
+    return nullptr;
+}
+
+Request *DefaultFileSource::request(const Resource &resource, uv_loop_t *l, Callback callback) {
+    auto req = new Request(resource, l, std::move(callback));
+
+    // This function can be called from any thread. Make sure we're executing the actual call in the
+    // file source loop by sending it over the queue. It will be processed in processAction().
+    queue->send(AddRequestAction{ req });
+    return req;
+}
+
+void DefaultFileSource::request(const Resource &resource, Callback callback) {
+    auto req = new Request(resource, nullptr, std::move(callback));
+
+    // This function can be called from any thread. Make sure we're executing the actual call in the
+    // file source loop by sending it over the queue. It will be processed in processAction().
+    queue->send(AddRequestAction{ req });
+}
+
+void DefaultFileSource::cancel(Request *req) {
+    req->cancel();
+
+    // This function can be called from any thread. Make sure we're executing the actual call in the
+    // file source loop by sending it over the queue. It will be processed in processAction().
+    queue->send(RemoveRequestAction{ req });
+}
+
+void DefaultFileSource::process(AddRequestAction &action) {
+    const Resource &resource = action.request->resource;
+
+    // We're adding a new Request.
+    SharedRequestBase *sharedRequest = find(resource);
+    if (!sharedRequest) {
+        // There is no request for this URL yet. Create a new one and start it.
+        if (algo::starts_with(resource.url, "asset://")) {
+            sharedRequest = new AssetRequest(this, resource);
+        } else {
+            sharedRequest = new HTTPRequest(this, resource);
+        }
+
+        // Make sure the loop stays alive when we're not running the file source in it's own thread.
+        if (!thread.joinable() && pending.empty()) {
+            queue->ref();
+        }
+
+        const bool inserted = pending.emplace(resource, sharedRequest).second;
+        assert(inserted);
+        (void (inserted)); // silence unused variable warning on Release builds.
+
+        // But first, we're going to start querying the database if it exists.
+        if (!cache) {
+            sharedRequest->start(loop);
+        } else {
+            // Otherwise, first check the cache for existing data so that we can potentially
+            // revalidate the information without having to redownload everything.
+            cache->get(resource, [this, resource](std::unique_ptr<Response> response) {
+                queue->send(ResultAction { resource, std::move(response) });
+            });
+        }
+    }
+    sharedRequest->subscribe(action.request);
+}
+
+void DefaultFileSource::process(RemoveRequestAction &action) {
+    SharedRequestBase *sharedRequest = find(action.request->resource);
+    if (sharedRequest) {
+        // If the number of dependent requests of the SharedRequestBase drops to zero, the
+        // unsubscribe callback triggers the removal of the SharedRequestBase pointer from the list
+        // of pending requests and initiates cancelation.
+        sharedRequest->unsubscribe(action.request);
+    } else {
+        // There is no request for this URL anymore. Likely, the request already completed
+        // before we got around to process the cancelation request.
+    }
+
+    // Send a message back to the requesting thread and notify it that this request has been
+    // canceled and is now safe to be deleted.
+    action.request->destruct();
+}
+
+void DefaultFileSource::process(ResultAction &action) {
+    SharedRequestBase *sharedRequest = find(action.resource);
+    if (sharedRequest) {
+        if (action.response) {
+            // This entry was stored in the cache. Now determine if we need to revalidate.
+            const int64_t now = std::chrono::duration_cast<std::chrono::seconds>(
+                                    std::chrono::system_clock::now().time_since_epoch()).count();
+            if (action.response->expires > now) {
+                // The response is fresh. We're good to notify the caller.
+                sharedRequest->notify(std::move(action.response), FileCache::Hint::No);
+                sharedRequest->cancel();
+                return;
+            } else {
+                // The cached response is stale. Now run the real request.
+                sharedRequest->start(loop, std::move(action.response));
+            }
+        } else {
+            // There is no response. Now run the real request.
+            sharedRequest->start(loop);
+        }
+    } else {
+        // There is no request for this URL anymore. Likely, the request was canceled
+        // before we got around to process the cache result.
+    }
+}
+
+void DefaultFileSource::process(StopAction &) {
+    // Cancel all remaining requests.
+    for (auto it : pending) {
+        it.second->unsubscribeAll();
+    }
+    pending.clear();
+
+    assert(queue);
+    queue->stop();
+    queue = nullptr;
+}
+
+void DefaultFileSource::notify(SharedRequestBase *sharedRequest,
+                               const std::set<Request *> &observers,
+                               std::shared_ptr<const Response> response, FileCache::Hint hint) {
+    // First, remove the request, since it might be destructed at any point now.
+    assert(find(sharedRequest->resource) == sharedRequest);
+    pending.erase(sharedRequest->resource);
+
+    if (response) {
+        if (cache) {
+            // Store response in database
+            cache->put(sharedRequest->resource, response, hint);
+        }
+
+        // Notify all observers.
+        for (auto it : observers) {
+            it->notify(response);
+        }
+    }
+
+    if (!thread.joinable() && pending.empty()) {
+        // When there are no pending requests, we're going to allow the queue to stop.
+        queue->unref();
+    }
+}
+
+}