AU: MultiHttpFetcher cleanup/rewrite

multi_range_http_fetcher.h

Index: multi_range_http_fetcher.h
diff --git a/multi_range_http_fetcher.h b/multi_range_http_fetcher.h
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+// Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROMEOS_PLATFORM_UPDATE_ENGINE_MULTI_RANGE_HTTP_FETCHER_H__
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_MULTI_RANGE_HTTP_FETCHER_H__
+
+#include <deque>
+#include <utility>
+#include <vector>
+
+#include <base/scoped_ptr.h>
+
+#include "update_engine/http_fetcher.h"
+
+// This class is a simple wrapper around an HttpFetcher. The client
+// specifies a vector of byte ranges. MultiRangeHTTPFetcher will fetch bytes
+// from those offsets, using the same bash fetcher for all ranges. Thus, the
+// fetcher must support beginning a transfter after one has stopped. Pass -1
+// as a length to specify unlimited length. It really only would make sense
+// for the last range specified to have unlimited length, tho it is legal for
+// other entries to have unlimited length.
+
+// There are three states a MultiRangeHTTPFetcher object will be in:
+// - Stopped (start state)
+// - Downloading
+// - Pending transfer ended
+// Various functions below that might change state indicate possible
+// state changes.
+
+namespace chromeos_update_engine {
+
+class MultiRangeHTTPFetcher : public HttpFetcher, public HttpFetcherDelegate {
+ public:
+  // Takes ownership of the passed in fetcher.
+  explicit MultiRangeHTTPFetcher(HttpFetcher* base_fetcher)
+      : HttpFetcher(base_fetcher->proxy_resolver()),
+        base_fetcher_(base_fetcher),
+        base_fetcher_active_(false),
+        pending_transfer_ended_(false),
+        terminating_(false),
+        current_index_(0),
+        bytes_received_this_range_(0) {}
+  ~MultiRangeHTTPFetcher() {}
+
+  void ClearRanges() { ranges_.clear(); }
+
+  void AddRange(off_t offset, off_t size) {
+    ranges_.push_back(std::make_pair(offset, size));
+  }
+
+  virtual void SetOffset(off_t offset) {}  // for now, doesn't support this
+
+  // Begins the transfer to the specified URL.
+  // State change: Stopped -> Downloading
+  // (corner case: Stopped -> Stopped for an empty request)
+  virtual void BeginTransfer(const std::string& url);
+
+  // State change: Downloading -> Pending transfer ended
+  virtual void TerminateTransfer();
+
+  virtual void Pause() { base_fetcher_->Pause(); }
+
+  virtual void Unpause() { base_fetcher_->Unpause(); }
+
+  // These functions are overloaded in LibcurlHttp fetcher for testing purposes.
+  virtual void set_idle_seconds(int seconds) {
+    base_fetcher_->set_idle_seconds(seconds);
+  }
+  virtual void set_retry_seconds(int seconds) {
+    base_fetcher_->set_retry_seconds(seconds);
+  }
+  virtual void SetConnectionAsExpensive(bool is_expensive) {
+    base_fetcher_->SetConnectionAsExpensive(is_expensive);
+  }
+  virtual void SetBuildType(bool is_official) {
+    base_fetcher_->SetBuildType(is_official);
+  }
+  virtual void SetProxies(const std::deque<std::string>& proxies) {
+    base_fetcher_->SetProxies(proxies);
+  }
+
+ private:
+  // pair<offset, length>:
+  typedef std::vector<std::pair<off_t, off_t> > RangesVect;
+  
+  // State change: Stopped or Downloading -> Downloading
+  void StartTransfer();
+
+// State change: Downloading -> Downloading or Pending transfer ended
+  virtual void ReceivedBytes(HttpFetcher* fetcher,
+                             const char* bytes,
+                             int length);
+
+  // State change: Pending transfer ended -> Stopped
+  void TransferEnded(HttpFetcher* fetcher, bool successful);
+  // These two call TransferEnded():
+  virtual void TransferComplete(HttpFetcher* fetcher, bool successful);
+  virtual void TransferTerminated(HttpFetcher* fetcher);
+
+  void Reset();
+
+  scoped_ptr<HttpFetcher> base_fetcher_;
+
+  // If true, do not send any more data or TransferComplete to the delegate.
+  bool base_fetcher_active_;
+
+  // If true, the next fetcher needs to be started when TransferTerminated is
+  // received from the current fetcher.
+  bool pending_transfer_ended_;
+  
+  // True if we are waiting for base fetcher to terminate b/c we are
+  // ourselves terminating.
+  bool terminating_;
+
+  RangesVect ranges_;
+
+  RangesVect::size_type current_index_;  // index into ranges_
+  off_t bytes_received_this_range_;
+
+  DISALLOW_COPY_AND_ASSIGN(MultiRangeHTTPFetcher);
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_MULTI_RANGE_HTTP_FETCHER_H__