Cashew: implement backend usage API

src/libcurl_http_fetcher.h

Index: src/libcurl_http_fetcher.h
diff --git a/src/libcurl_http_fetcher.h b/src/libcurl_http_fetcher.h
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+// Copyright (c) 2009 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.
+
+// NOTE: lifted from src/platform/update_engine and tweaked for cashew
+// TODO(vlaviano): see http_fetcher.h
+
+#ifndef SRC_LIBCURL_HTTP_FETCHER_H_
+#define SRC_LIBCURL_HTTP_FETCHER_H_
+
+#include <curl/curl.h>
+#include <glib.h>
+
+#include <map>
+#include <string>
+
+#include <base/basictypes.h>  // NOLINT
+
+#include "src/http_fetcher.h"
+
+// This is a concrete implementation of HttpFetcher that uses libcurl to do the
+// http work.
+
+namespace cashew {
+
+class LibcurlHttpFetcher : public HttpFetcher {
+ public:
+  static const int kMaxRedirects = 10;
+
+  LibcurlHttpFetcher()
+      : curl_multi_handle_(NULL),
+        curl_handle_(NULL),
+        timeout_source_(NULL),
+        transfer_in_progress_(false),
+        retry_count_(0),
+        retry_seconds_(60),
+        idle_seconds_(1) {}
+
+  // Cleans up all internal state. Does not notify delegate
+  ~LibcurlHttpFetcher();
+
+  // Begins the transfer if it hasn't already begun.
+  virtual void BeginTransfer(const std::string& url);
+
+  // If the transfer is in progress, aborts the transfer early.
+  // The transfer cannot be resumed.
+  virtual void TerminateTransfer();
+
+  // Suspend the transfer by calling curl_easy_pause(CURLPAUSE_ALL).
+  virtual void Pause();
+
+  // Resume the transfer by calling curl_easy_pause(CURLPAUSE_CONT).
+  virtual void Unpause();
+
+  // Libcurl sometimes asks to be called back after some time while
+  // leaving that time unspecified. In that case, we pick a reasonable
+  // default of one second, but it can be overridden here. This is
+  // primarily useful for testing.
+  // From http://curl.haxx.se/libcurl/c/curl_multi_timeout.html:
+  //     if libcurl returns a -1 timeout here, it just means that libcurl
+  //     currently has no stored timeout value. You must not wait too long
+  //     (more than a few seconds perhaps) before you call
+  //     curl_multi_perform() again.
+  void set_idle_seconds(int seconds) { idle_seconds_ = seconds; }
+
+  // Sets the retry timeout. Useful for testing.
+  void set_retry_seconds(int seconds) { retry_seconds_ = seconds; }
+
+ private:
+  // Resumes a transfer where it left off. This will use the
+  // HTTP Range: header to make a new connection from where the last
+  // left off.
+  virtual void ResumeTransfer(const std::string& url);
+
+  // These two methods are for glib main loop callbacks. They are called
+  // when either a file descriptor is ready for work or when a timer
+  // has fired. The static versions are shims for libcurl which has a C API.
+  bool FDCallback(GIOChannel *source, GIOCondition condition);
+  static gboolean StaticFDCallback(GIOChannel *source,
+                                   GIOCondition condition,
+                                   gpointer data) {
+    return reinterpret_cast<LibcurlHttpFetcher*>(data)->FDCallback(source,
+                                                                   condition);
+  }
+  gboolean TimeoutCallback();
+  static gboolean StaticTimeoutCallback(gpointer data) {
+    return reinterpret_cast<LibcurlHttpFetcher*>(data)->TimeoutCallback();
+  }
+
+  gboolean RetryTimeoutCallback();
+  static gboolean StaticRetryTimeoutCallback(void* arg) {
+    return static_cast<LibcurlHttpFetcher*>(arg)->RetryTimeoutCallback();
+  }
+
+  // Calls into curl_multi_perform to let libcurl do its work. Returns after
+  // curl_multi_perform is finished, which may actually be after more than
+  // one call to curl_multi_perform. This method will set up the glib run
+  // loop with sources for future work that libcurl will do.
+  // This method will not block.
+  // Returns true if we should resume immediately after this call.
+  void CurlPerformOnce();
+
+  // Sets up glib main loop sources as needed by libcurl. This is generally
+  // the file descriptor of the socket and a timer in case nothing happens
+  // on the fds.
+  void SetupMainloopSources();
+
+  // Callback called by libcurl when new data has arrived on the transfer
+  size_t LibcurlWrite(void *ptr, size_t size, size_t nmemb);
+  static size_t StaticLibcurlWrite(void *ptr, size_t size,
+                                   size_t nmemb, void *stream) {
+    return reinterpret_cast<LibcurlHttpFetcher*>(stream)->
+        LibcurlWrite(ptr, size, nmemb);
+  }
+
+  // Cleans up the following if they are non-null:
+  // curl(m) handles, io_channels_, timeout_source_.
+  void CleanUp();
+
+  // Handles for the libcurl library
+  CURLM *curl_multi_handle_;
+  CURL *curl_handle_;
+
+  // a list of all file descriptors that we're waiting on from the
+  // glib main loop
+  typedef std::map<int, std::pair<GIOChannel*, guint> > IOChannels;
+  IOChannels io_channels_;
+
+  // if non-NULL, a timer we're waiting on. glib main loop will call us back
+  // when it fires.
+  GSource* timeout_source_;
+
+  bool transfer_in_progress_;
+
+  // The transfer size. -1 if not known.
+  off_t transfer_size_;
+
+  // How many bytes have been downloaded and sent to the delegate.
+  off_t bytes_downloaded_;
+
+  // If we resumed an earlier transfer, data offset that we used for the
+  // new connection.  0 otherwise.
+  off_t resume_offset_;
+
+  // Number of resumes performed.
+  int retry_count_;
+
+  // Seconds to wait before retrying a resume.
+  int retry_seconds_;
+
+  // Seconds to wait before asking libcurl to "perform".
+  int idle_seconds_;
+
+  DISALLOW_COPY_AND_ASSIGN(LibcurlHttpFetcher);
+};
+
+}  // namespace cashew
+
+#endif  // SRC_LIBCURL_HTTP_FETCHER_H_