do 304 requests and cache them in sqlite

src/storage/file_source.cpp

@@ -0,0 +1,80 @@
+#include <mbgl/storage/file_source.hpp>
+#include <mbgl/storage/file_request.hpp>
+#include <mbgl/storage/http_request.hpp>
+#include <mbgl/storage/sqlite_store.hpp>
+#include <mbgl/util/uv-messenger.h>
+
+#include <uv.h>
+
+namespace mbgl {
+
+FileSource::FileSource(uv_loop_t *loop_)
+    : thread_id(uv_thread_self()),
+      store(std::shared_ptr<SQLiteStore>(new SQLiteStore(loop_, "cache.db"))),
+      loop(loop_),
+      queue(new uv_messenger_t) {
+    uv_messenger_init(loop, queue, [](void *ptr) {
+        std::unique_ptr<std::function<void()>> fn { reinterpret_cast<std::function<void()> *>(ptr) };
+        (*fn)();
+    });
+}
+
+FileSource::~FileSource() {
+    assert(thread_id == uv_thread_self());
+    uv_messenger_stop(queue);
+}
+
+void FileSource::setBase(const std::string &value) {
+    assert(thread_id == uv_thread_self());
+    base = value;
+}
+
+const std::string &FileSource::getBase() const {
+    assert(thread_id == uv_thread_self());
+    return base;
+}
+
+std::unique_ptr<Request> FileSource::request(ResourceType type, const std::string &url) {
+    assert(thread_id == uv_thread_self());
+
+    // Make URL absolute.
+    const std::string absoluteURL = [&]() -> std::string {
+        const size_t separator = url.find("://");
+        if (separator == std::string::npos) {
+            // Relative URL.
+            return base + url;
+        } else {
+            return url;
+        }
+    }();
+
+    std::shared_ptr<BaseRequest> request;
+
+    // First, try to find an existing Request object.
+    auto it = pending.find(absoluteURL);
+    if (it != pending.end()) {
+        request = it->second.lock();
+    }
+
+    if (!request) {
+        if (absoluteURL.substr(0, 7) == "file://") {
+            request = std::make_shared<FileRequest>(absoluteURL.substr(7), loop);
+        } else {
+            request = std::make_shared<HTTPRequest>(type, absoluteURL, loop, store);
+        }
+
+        pending.emplace(absoluteURL, request);
+    }
+
+    return std::unique_ptr<Request>(new Request(request));
+}
+
+void FileSource::prepare(std::function<void()> fn) {
+    if (thread_id == uv_thread_self()) {
+        fn();
+    } else {
+        uv_messenger_send(queue, new std::function<void()>(std::move(fn)));
+    }
+}
+
+}