native_client_sdk/src/examples/api/url_loader/url_loader_handler.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef URL_LOADER_HANDLER_H_
   6 #define URL_LOADER_HANDLER_H_
   7
   8 #include <string>
   9 #include "ppapi/cpp/completion_callback.h"
  10 #include "ppapi/cpp/instance.h"
  11 #include "ppapi/cpp/url_loader.h"
  12 #include "ppapi/cpp/url_request_info.h"
  13 #include "ppapi/utility/completion_callback_factory.h"
  14 #define READ_BUFFER_SIZE 32768
  15
  16 // URLLoaderHandler is used to download data from |url|. When download is
  17 // finished or when an error occurs, it posts a message back to the browser
  18 // with the results encoded in the message as a string and self-destroys.
  19 //
  20 // pp::URLLoader.GetDownloadProgress() is used to to allocate the memory
  21 // required for url_response_body_ before the download starts.  (This is not so
  22 // much of a performance improvement, but it saves some memory since
  23 // std::string.insert() typically grows the string's capacity by somewhere
  24 // between 50% to 100% when it needs more memory, depending on the
  25 // implementation.)  Other performance improvements made as outlined in this
  26 // bug: http://code.google.com/p/chromium/issues/detail?id=103947
  27 //
  28 // EXAMPLE USAGE:
  29 // URLLoaderHandler* handler* = URLLoaderHandler::Create(instance,url);
  30 // handler->Start();
  31 //
  32 class URLLoaderHandler {
  33  public:
  34   // Creates instance of URLLoaderHandler on the heap.
  35   // URLLoaderHandler objects shall be created only on the heap (they
  36   // self-destroy when all data is in).
  37   static URLLoaderHandler* Create(pp::Instance* instance_,
  38                                   const std::string& url);
  39   // Initiates page (URL) download.
  40   void Start();
  41
  42  private:
  43   URLLoaderHandler(pp::Instance* instance_, const std::string& url);
  44   ~URLLoaderHandler();
  45
  46   // Callback for the pp::URLLoader::Open().
  47   // Called by pp::URLLoader when response headers are received or when an
  48   // error occurs (in response to the call of pp::URLLoader::Open()).
  49   // Look at <ppapi/c/ppb_url_loader.h> and
  50   // <ppapi/cpp/url_loader.h> for more information about pp::URLLoader.
  51   void OnOpen(int32_t result);
  52
  53   // Callback for the pp::URLLoader::ReadResponseBody().
  54   // |result| contains the number of bytes read or an error code.
  55   // Appends data from this->buffer_ to this->url_response_body_.
  56   void OnRead(int32_t result);
  57
  58   // Reads the response body (asynchronously) into this->buffer_.
  59   // OnRead() will be called when bytes are received or when an error occurs.
  60   void ReadBody();
  61
  62   // Append data bytes read from the URL onto the internal buffer.  Does
  63   // nothing if |num_bytes| is 0.
  64   void AppendDataBytes(const char* buffer, int32_t num_bytes);
  65
  66   // Post a message back to the browser with the download results.
  67   void ReportResult(const std::string& fname,
  68                     const std::string& text,
  69                     bool success);
  70   // Post a message back to the browser with the download results and
  71   // self-destroy.  |this| is no longer valid when this method returns.
  72   void ReportResultAndDie(const std::string& fname,
  73                           const std::string& text,
  74                           bool success);
  75
  76   pp::Instance* instance_;  // Weak pointer.
  77   std::string url_;         // URL to be downloaded.
  78   pp::URLRequestInfo url_request_;
  79   pp::URLLoader url_loader_;  // URLLoader provides an API to download URLs.
  80   char* buffer_;              // Temporary buffer for reads.
  81   std::string url_response_body_;  // Contains accumulated downloaded data.
  82   pp::CompletionCallbackFactory<URLLoaderHandler> cc_factory_;
  83
  84   URLLoaderHandler(const URLLoaderHandler&);
  85   void operator=(const URLLoaderHandler&);
  86 };
  87
  88 #endif  // URL_LOADER_HANDLER_H_