Add a ProxyScriptFetcher class for doing asynch downloads of PAC scripts....

net/proxy/proxy_script_fetcher.cc

+// Copyright (c) 2008 The Chromium Authors. All rights reserved.  Use of this
+// source code is governed by a BSD-style license that can be found in the
+// LICENSE file.
+
+#include "net/proxy/proxy_script_fetcher.h"
+
+#include "base/compiler_specific.h"
+#include "base/message_loop.h"
+#include "base/string_util.h"
+#include "net/base/load_flags.h"
+#include "net/url_request/url_request.h"
+
+// TODO(eroman): 
+//   - Support auth-prompts.
+
+namespace net {
+
+namespace {
+
+// The maximum size (in bytes) allowed for a PAC script. Responses exceeding
+// this will fail with ERR_FILE_TOO_BIG.
+int max_response_bytes = 1048576;  // 1 megabyte
+
+// The maximum duration (in milliseconds) allowed for fetching the PAC script.
+// Responses exceeding this will fail with ERR_TIMED_OUT.
+int max_duration_ms = 300000;  // 5 minutes
+
+}  // namespace
+
+class ProxyScriptFetcherImpl : public ProxyScriptFetcher,
+                               public URLRequest::Delegate {
+ public:
+  // Creates a ProxyScriptFetcher that issues requests through
+  // |url_request_context|. |url_request_context| must remain valid for the
+  // lifetime of ProxyScriptFetcherImpl.
+  explicit ProxyScriptFetcherImpl(URLRequestContext* url_request_context);
+
+  virtual ~ProxyScriptFetcherImpl();
+
+  // ProxyScriptFetcher methods:
+
+  virtual void Fetch(const GURL& url, std::string* bytes,
+                     CompletionCallback* callback);
+  virtual void Cancel();
+
+  // URLRequest::Delegate methods:
+
+  virtual void OnAuthRequired(URLRequest* request,
+                              AuthChallengeInfo* auth_info);
+  virtual void OnSSLCertificateError(URLRequest* request, int cert_error,
+                                     X509Certificate* cert);
+  virtual void OnReceivedRedirect(URLRequest* request, const GURL& to_url);
+  virtual void OnResponseStarted(URLRequest* request);
+  virtual void OnReadCompleted(URLRequest* request, int num_bytes);
+  virtual void OnResponseCompleted(URLRequest* request);
+
+ private:
+  // Read more bytes from the response.
+  void ReadBody(URLRequest* request);
+
+  // Called once the request has completed to notify the caller of
+  // |response_code_| and |response_bytes_|.
+  void FetchCompleted();
+
+  // Clear out the state for the current request.
+  void ResetCurRequestState();
+
+  // Callback for time-out task of request with id |id|.
+  void OnTimeout(int id);
+
+  // Factory for creating the time-out task. This takes care of revoking
+  // outstanding tasks when |this| is deleted.
+  ScopedRunnableMethodFactory<ProxyScriptFetcherImpl> task_factory_;
+
+  // The context used for making network requests.
+  URLRequestContext* url_request_context_;
+
+  // Buffer that URLRequest writes into.
+  enum { kBufSize = 4096 };
+  char buf_[kBufSize];
+
+  // The next ID to use for |cur_request_| (monotonically increasing).
+  int next_id_;
+
+  // The current (in progress) request, or NULL.
+  scoped_ptr<URLRequest> cur_request_;
+
+  // State for current request (only valid when |cur_request_| is not NULL):
+
+  // Unique ID for the current request.
+  int cur_request_id_;
+
+  // Callback to invoke on completion of the fetch.
+  CompletionCallback* callback_;
+
+  // Holds the error condition that was hit on the current request, or OK.
+  int result_code_;
+
+  // Holds the bytes read so far. Will not exceed |max_response_bytes|. This
+  // buffer is owned by the owner of |callback|.
+  std::string* result_bytes_;
+};
+
+ProxyScriptFetcherImpl::ProxyScriptFetcherImpl(
+    URLRequestContext* url_request_context)
+    : ALLOW_THIS_IN_INITIALIZER_LIST(task_factory_(this)),
+      url_request_context_(url_request_context),
+      next_id_(0),
+      cur_request_(NULL),
+      cur_request_id_(0),
+      callback_(NULL),
+      result_code_(OK),
+      result_bytes_(NULL) {
+  DCHECK(url_request_context);
+}
+
+ProxyScriptFetcherImpl::~ProxyScriptFetcherImpl() {
+  // The URLRequest's destructor will cancel the outstanding request, and
+  // ensure that the delegate (this) is not called again.
+}
+
+void ProxyScriptFetcherImpl::Fetch(const GURL& url,
+                                   std::string* bytes,
+                                   CompletionCallback* callback) {
+  // It is invalid to call Fetch() while a request is already in progress.
+  DCHECK(!cur_request_.get());
+
+  DCHECK(callback);
+  DCHECK(bytes);
+
+  cur_request_.reset(new URLRequest(url, this));
+  cur_request_->set_context(url_request_context_);
+  cur_request_->set_method("GET");
+
+  // Make sure that the PAC script is downloaded using a direct connection,
+  // to avoid circular dependencies (fetching is a part of proxy resolution).
+  cur_request_->set_load_flags(LOAD_BYPASS_PROXY);
+
+  // Save the caller's info for notification on completion.
+  callback_ = callback;
+  result_bytes_ = bytes;
+  result_bytes_->clear();
+
+  // Post a task to timeout this request if it takes too long.
+  cur_request_id_ = ++next_id_;
+  MessageLoop::current()->PostDelayedTask(FROM_HERE,
+      task_factory_.NewRunnableMethod(&ProxyScriptFetcherImpl::OnTimeout,
+                                      cur_request_id_),
+      static_cast<int>(max_duration_ms));
+
+  // Start the request.
+  cur_request_->Start();
+}
+
+void ProxyScriptFetcherImpl::Cancel() {
+  // ResetCurRequestState will free the URLRequest, which will cause
+  // cancellation.
+  ResetCurRequestState();
+}
+
+void ProxyScriptFetcherImpl::OnAuthRequired(URLRequest* request,
+                                            AuthChallengeInfo* auth_info) {
+  DCHECK(request == cur_request_.get());
+  // TODO(eroman):
+  result_code_ = ERR_NOT_IMPLEMENTED;
+  request->CancelAuth();
+}
+
+void ProxyScriptFetcherImpl::OnSSLCertificateError(URLRequest* request,
+                                                   int cert_error,
+                                                   X509Certificate* cert) {
+  DCHECK(request == cur_request_.get());
+  // Certificate errors are in same space as net errors.
+  result_code_ = cert_error;
+  request->Cancel();
+}
+
+void ProxyScriptFetcherImpl::OnReceivedRedirect(URLRequest* request,
+                                                const GURL& to_url) {
+  DCHECK(request == cur_request_.get());
+  // OK, thanks for telling.
+}
+
+void ProxyScriptFetcherImpl::OnResponseStarted(URLRequest* request) {
+  DCHECK(request == cur_request_.get());
+
+  if (!request->status().is_success()) {
+    OnResponseCompleted(request);
+    return;
+  }
+
+  // Require HTTP responses to have a success status code.
+  if (request->url().SchemeIs("http") || request->url().SchemeIs("https")) {
+    // NOTE about mime types: We do not enforce mime types on PAC files.
+    // This is for compatibility with {IE 7, Firefox 3, Opera 9.5}
+
+    // NOTE about status codes: We are like Firefox 3 in this respect. 
+    // {IE 7, Safari 3, Opera 9.5} do not care about the status code.
+    if (request->GetResponseCode() != 200) {
+      result_code_ = ERR_PAC_STATUS_NOT_OK;
+      request->Cancel();
+      return;
+    }
+  }
+
+  ReadBody(request);
+}
+
+void ProxyScriptFetcherImpl::OnReadCompleted(URLRequest* request,
+                                             int num_bytes) {
+  DCHECK(request == cur_request_.get());
+  if (num_bytes > 0) {
+    // Enforce maximum size bound.
+    if (num_bytes + result_bytes_->size() >
+        static_cast<size_t>(max_response_bytes)) {
+      result_code_ = ERR_FILE_TOO_BIG;
+      request->Cancel();
+      return;
+    }
+    result_bytes_->append(buf_, num_bytes);
+    ReadBody(request);
+  } else {  // Error while reading, or EOF
+    OnResponseCompleted(request);
+  }
+}
+
+void ProxyScriptFetcherImpl::OnResponseCompleted(URLRequest* request) {
+  DCHECK(request == cur_request_.get());
+
+  // Use |result_code_| as the request's error if we have already set it to
+  // something specific.
+  if (result_code_ == OK && !request->status().is_success())
+    result_code_ = request->status().os_error();
+
+  FetchCompleted();
+}
+
+void ProxyScriptFetcherImpl::ReadBody(URLRequest* request) {
+  int num_bytes;
+  if (request->Read(buf_, kBufSize, &num_bytes)) {
+    OnReadCompleted(request, num_bytes);
+  } else if (!request->status().is_io_pending()) {
+    // Read failed synchronously.
+    OnResponseCompleted(request);
+  }
+}
+
+void ProxyScriptFetcherImpl::FetchCompleted() {
+  // On error, the caller expects empty string for bytes.
+  if (result_code_ != OK)
+    result_bytes_->clear();
+
+  int result_code = result_code_;
+  CompletionCallback* callback = callback_;
+
+  ResetCurRequestState();
+
+  callback->Run(result_code);
+}
+
+void ProxyScriptFetcherImpl::ResetCurRequestState() {
+  cur_request_.reset();
+  cur_request_id_ = 0;
+  callback_ = NULL;
+  result_code_ = OK;
+  result_bytes_ = NULL;
+}
+
+void ProxyScriptFetcherImpl::OnTimeout(int id) {
+  // Timeout tasks may outlive the URLRequest they reference. Make sure it
+  // is still applicable.
+  if (cur_request_id_ != id)
+    return;
+
+  DCHECK(cur_request_.get());
+  result_code_ = ERR_TIMED_OUT;
+  cur_request_->Cancel();
+}
+
+// static
+ProxyScriptFetcher* ProxyScriptFetcher::Create(
+    URLRequestContext* url_request_context) {
+  return new ProxyScriptFetcherImpl(url_request_context);
+}
+
+// static
+int ProxyScriptFetcher::SetTimeoutConstraintForUnittest(
+    int timeout_ms) {
+  int prev = max_duration_ms;
+  max_duration_ms = timeout_ms;
+  return prev;
+}
+
+// static
+size_t ProxyScriptFetcher::SetSizeConstraintForUnittest(size_t size_bytes) {
+  size_t prev = max_response_bytes;
+  max_response_bytes = size_bytes;
+  return prev;
+}
+
+}  // namespace net