Fetch local files asynchronously.
This patch implements a new fetcher that only handles local files.
While libcurl supports file:// urls, the stream can't be suspended when
accessing local files.
This new FileFetcher is based on the brillo::FileStream class which
properly handles the asynchronous reads from regular files.
Bug: 28866512
TEST=Added unittest. Deployed an update from a file:// URL.
Change-Id: Ie9d07dda2d773312e55be3c0ab7c9e5b737be18b
diff --git a/common/file_fetcher.h b/common/file_fetcher.h
new file mode 100644
index 0000000..2368b1d
--- /dev/null
+++ b/common/file_fetcher.h
@@ -0,0 +1,119 @@
+//
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_COMMON_FILE_FETCHER_H_
+#define UPDATE_ENGINE_COMMON_FILE_FETCHER_H_
+
+#include <memory>
+#include <string>
+#include <utility>
+
+#include <base/logging.h>
+#include <base/macros.h>
+#include <brillo/message_loops/message_loop.h>
+#include <brillo/streams/stream.h>
+
+#include "update_engine/common/http_fetcher.h"
+
+// This is a concrete implementation of HttpFetcher that reads files
+// asynchronously.
+
+namespace chromeos_update_engine {
+
+class FileFetcher : public HttpFetcher {
+ public:
+ // Returns whether the passed url is supported.
+ static bool SupportedUrl(const std::string& url);
+
+ FileFetcher() : HttpFetcher(nullptr) {}
+
+ // Cleans up all internal state. Does not notify delegate.
+ ~FileFetcher() override;
+
+ // HttpFetcher overrides.
+ void SetOffset(off_t offset) override { offset_ = offset; }
+ void SetLength(size_t length) override { data_length_ = length; }
+ void UnsetLength() override { SetLength(0); }
+
+ // Begins the transfer if it hasn't already begun.
+ void BeginTransfer(const std::string& url) override;
+
+ // If the transfer is in progress, aborts the transfer early. The transfer
+ // cannot be resumed.
+ void TerminateTransfer() override;
+
+ // Ignore all extra headers for files.
+ void SetHeader(const std::string& header_name,
+ const std::string& header_value) override {};
+
+ // Suspend the asynchronous file read.
+ void Pause() override;
+
+ // Resume the suspended file read.
+ void Unpause() override;
+
+ size_t GetBytesDownloaded() override {
+ return static_cast<size_t>(bytes_copied_);
+ }
+
+ // Ignore all the time limits for files.
+ void set_low_speed_limit(int low_speed_bps, int low_speed_sec) override {}
+ void set_connect_timeout(int connect_timeout_seconds) override {}
+ void set_max_retry_count(int max_retry_count) override {}
+
+ private:
+ // Cleans up the fetcher, resetting its status to a newly constructed one.
+ void CleanUp();
+
+ // Schedule a new asynchronous read if the stream is not paused and no other
+ // read is in process. This method can be called at any point.
+ void ScheduleRead();
+
+ // Called from the main loop when a single read from |stream_| succeeds or
+ // fails, calling OnReadDoneCallback() and OnReadErrorCallback() respectively.
+ void OnReadDoneCallback(size_t bytes_read);
+ void OnReadErrorCallback(const brillo::Error* error);
+
+ // Whether the transfer was started and didn't finish yet.
+ bool transfer_in_progress_{false};
+
+ // Whether the transfer is paused.
+ bool transfer_paused_{false};
+
+ // Whether there's an ongoing asynchronous read. When this value is true, the
+ // the |buffer_| is being used by the |stream_|.
+ bool ongoing_read_{false};
+
+ // Total number of bytes copied.
+ uint64_t bytes_copied_{0};
+
+ // The offset inside the file where the read should start.
+ uint64_t offset_{0};
+
+ // The length of the data or -1 if unknown (will read until EOF).
+ int64_t data_length_{-1};
+
+ brillo::StreamPtr stream_;
+
+ // The buffer used for reading from the stream.
+ brillo::Blob buffer_;
+
+ DISALLOW_COPY_AND_ASSIGN(FileFetcher);
+};
+
+} // namespace chromeos_update_engine
+
+#endif // UPDATE_ENGINE_COMMON_FILE_FETCHER_H_