Make file request overridable by platform implementations

refs #579: Android can now rename AssetRequest to FileRequest and implement it differently

platform/default/file_request_libuv.cpp

@@ -0,0 +1,209 @@
+#include <mbgl/storage/file_request.hpp>
+#include <mbgl/storage/response.hpp>
+#include <mbgl/util/std.hpp>
+
+#include <uv.h>
+
+#include <limits>
+
+namespace mbgl {
+
+struct FileRequestBaton {
+    FileRequestBaton(FileRequest *request_, const std::string &path, uv_loop_t *loop);
+    ~FileRequestBaton();
+
+    void cancel();
+    static void file_opened(uv_fs_t *req);
+    static void file_stated(uv_fs_t *req);
+    static void file_read(uv_fs_t *req);
+    static void file_closed(uv_fs_t *req);
+    static void notify_error(uv_fs_t *req);
+    static void cleanup(uv_fs_t *req);
+
+    const std::thread::id thread_id;
+    FileRequest *request = nullptr;
+    uv_fs_t req;
+    uv_file fd = -1;
+    bool canceled = false;
+    std::string body;
+    uv_buf_t buffer;
+};
+
+FileRequestBaton::FileRequestBaton(FileRequest *request_, const std::string &path, uv_loop_t *loop)
+    : thread_id(std::this_thread::get_id()), request(request_) {
+    req.data = this;
+    uv_fs_open(loop, &req, path.c_str(), O_RDONLY, S_IRUSR, file_opened);
+}
+
+FileRequestBaton::~FileRequestBaton() {
+}
+
+void FileRequestBaton::cancel() {
+    canceled = true;
+
+    // uv_cancel fails frequently when the request has already been started.
+    // In that case, we have to let it complete and check the canceled bool
+    // instead.
+    uv_cancel((uv_req_t *)&req);
+}
+
+void FileRequestBaton::notify_error(uv_fs_t *req) {
+    FileRequestBaton *ptr = (FileRequestBaton *)req->data;
+    assert(ptr->thread_id == std::this_thread::get_id());
+
+    if (ptr->request && req->result < 0 && !ptr->canceled && req->result != UV_ECANCELED) {
+        ptr->request->response = util::make_unique<Response>();
+        ptr->request->response->code = req->result == UV_ENOENT ? 404 : 500;
+#if UV_VERSION_MAJOR == 0 && UV_VERSION_MINOR <= 10
+        ptr->request->response->message = uv_strerror(uv_last_error(req->loop));
+#else
+        ptr->request->response->message = uv_strerror(int(req->result));
+#endif
+        ptr->request->notify();
+    }
+}
+
+void FileRequestBaton::file_opened(uv_fs_t *req) {
+    FileRequestBaton *ptr = (FileRequestBaton *)req->data;
+    assert(ptr->thread_id == std::this_thread::get_id());
+
+    if (req->result < 0) {
+        // Opening failed or was canceled. There isn't much left we can do.
+        notify_error(req);
+        cleanup(req);
+    } else {
+        const uv_file fd = uv_file(req->result);
+
+        // We're going to reuse this handle, so we need to cleanup first.
+        uv_fs_req_cleanup(req);
+
+        if (ptr->canceled || !ptr->request) {
+            // Either the FileRequest object has been destructed, or the
+            // request was canceled.
+            uv_fs_close(req->loop, req, fd, file_closed);
+        } else {
+            ptr->fd = fd;
+            uv_fs_fstat(req->loop, req, fd, file_stated);
+        }
+    }
+}
+
+void FileRequestBaton::file_stated(uv_fs_t *req) {
+    FileRequestBaton *ptr = (FileRequestBaton *)req->data;
+    assert(ptr->thread_id == std::this_thread::get_id());
+
+    if (req->result != 0 || ptr->canceled || !ptr->request) {
+        // Stating failed or was canceled. We already have an open file handle
+        // though, which we'll have to close.
+        notify_error(req);
+
+        uv_fs_req_cleanup(req);
+        uv_fs_close(req->loop, req, ptr->fd, file_closed);
+    } else {
+#if UV_VERSION_MAJOR == 0 && UV_VERSION_MINOR <= 10
+        const uv_statbuf_t *stat = static_cast<const uv_statbuf_t *>(req->ptr);
+#else
+        const uv_stat_t *stat = static_cast<const uv_stat_t *>(req->ptr);
+#endif
+        if (stat->st_size > std::numeric_limits<int>::max()) {
+            // File is too large for us to open this way because uv_buf's only support unsigned
+            // ints as maximum size.
+            if (ptr->request) {
+                ptr->request->response = util::make_unique<Response>();
+                ptr->request->response->code = UV_EFBIG;
+#if UV_VERSION_MAJOR == 0 && UV_VERSION_MINOR <= 10
+                ptr->request->response->message = uv_strerror(uv_err_t {UV_EFBIG, 0});
+#else
+                ptr->request->response->message = uv_strerror(UV_EFBIG);
+#endif
+                ptr->request->notify();
+            }
+
+            uv_fs_req_cleanup(req);
+            uv_fs_close(req->loop, req, ptr->fd, file_closed);
+        } else {
+            const unsigned int size = (unsigned int)(stat->st_size);
+            ptr->body.resize(size);
+            ptr->buffer = uv_buf_init(const_cast<char *>(ptr->body.data()), size);
+            uv_fs_req_cleanup(req);
+#if UV_VERSION_MAJOR == 0 && UV_VERSION_MINOR <= 10
+            uv_fs_read(req->loop, req, ptr->fd, ptr->buffer.base, ptr->buffer.len, -1, file_read);
+#else
+            uv_fs_read(req->loop, req, ptr->fd, &ptr->buffer, 1, 0, file_read);
+#endif
+        }
+    }
+}
+
+void FileRequestBaton::file_read(uv_fs_t *req) {
+    FileRequestBaton *ptr = (FileRequestBaton *)req->data;
+    assert(ptr->thread_id == std::this_thread::get_id());
+
+    if (req->result < 0 || ptr->canceled || !ptr->request) {
+        // Stating failed or was canceled. We already have an open file handle
+        // though, which we'll have to close.
+        notify_error(req);
+    } else {
+        // File was successfully read.
+        if (ptr->request) {
+            ptr->request->response = util::make_unique<Response>();
+            ptr->request->response->code = 200;
+            ptr->request->response->data = std::move(ptr->body);
+            ptr->request->notify();
+        }
+    }
+
+    uv_fs_req_cleanup(req);
+    uv_fs_close(req->loop, req, ptr->fd, file_closed);
+}
+
+void FileRequestBaton::file_closed(uv_fs_t *req) {
+    assert(((FileRequestBaton *)req->data)->thread_id == std::this_thread::get_id());
+
+    if (req->result < 0) {
+        // Closing the file failed. But there isn't anything we can do.
+    }
+
+    cleanup(req);
+}
+
+void FileRequestBaton::cleanup(uv_fs_t *req) {
+    FileRequestBaton *ptr = (FileRequestBaton *)req->data;
+    assert(ptr->thread_id == std::this_thread::get_id());
+
+    if (ptr->request) {
+        ptr->request->ptr = nullptr;
+    }
+
+    uv_fs_req_cleanup(req);
+    delete ptr;
+}
+
+
+FileRequest::FileRequest(const std::string &path_, uv_loop_t *loop)
+    : BaseRequest(path_), ptr(new FileRequestBaton(this, path, loop)) {
+}
+
+void FileRequest::cancel() {
+    assert(thread_id == std::this_thread::get_id());
+
+    if (ptr) {
+        ptr->cancel();
+
+        // When deleting a FileRequest object with a uv_fs_* call is in progress, we are making sure
+        // that the callback doesn't accidentally reference this object again.
+        ptr->request = nullptr;
+        ptr = nullptr;
+    }
+
+    notify();
+}
+
+FileRequest::~FileRequest() {
+    assert(thread_id == std::this_thread::get_id());
+    cancel();
+
+    // Note: The FileRequestBaton object is deleted in FileRequestBaton::cleanup().
+}
+
+}