In-process JSON parsing for web resources on iOS

ios/chrome/browser/web_resource/ios_web_resource_service.cc

+// Copyright 2015 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 "ios/chrome/browser/web_resource/ios_web_resource_service.h"
+
+#include "base/bind.h"
+#include "base/json/json_reader.h"
+#include "base/values.h"
+#include "ios/chrome/browser/application_context.h"
+#include "ios/web/public/web_thread.h"
+
+namespace {
+
+const char kInvalidDataTypeError[] =
+    "Data from web resource server is missing or not valid JSON.";
+
+const char kUnexpectedJSONFormatError[] =
+    "Data from web resource server does not have expected format.";
+
+// Helper method to run a closure.
+void RunClosure(const base::Closure& closure) {
+  closure.Run();
+}
+
+}  // namespace
+
+IOSWebResourceService::IOSWebResourceService(
+    PrefService* prefs,
+    const GURL& web_resource_server,
+    bool apply_locale_to_url,
+    const char* last_update_time_pref_name,
+    int start_fetch_delay_ms,
+    int cache_update_delay_ms)
+    : web_resource::WebResourceService(
+          prefs,
+          web_resource_server,
+          apply_locale_to_url ? GetApplicationContext()->GetApplicationLocale()
+                              : std::string(),
+          last_update_time_pref_name,
+          start_fetch_delay_ms,
+          cache_update_delay_ms,
+          nullptr) {
+}
+
+IOSWebResourceService::~IOSWebResourceService() {
+}
+
+// static
+base::Closure IOSWebResourceService::ParseJSONOnBackgroundThread(
+    scoped_ptr<std::string> data,
+    const SuccessCallback& success_callback,
+    const ErrorCallback& error_callback) {
+  if (data->empty())
+    return base::Bind(error_callback, std::string(kInvalidDataTypeError));
+
+  scoped_ptr<base::Value> value(base::JSONReader::Read(*data));
+  if (!value.get()) {
+    // Page information not properly read, or corrupted.
+    return base::Bind(error_callback, std::string(kInvalidDataTypeError));
+  }
+
+  if (!value->IsType(base::Value::TYPE_DICTIONARY))
+    return base::Bind(error_callback, std::string(kUnexpectedJSONFormatError));
+
+  return base::Bind(success_callback, base::Passed(&value));
+}
+
+void IOSWebResourceService::ParseJSON(const std::string& data,
+                                      const SuccessCallback& success_callback,
+                                      const ErrorCallback& error_callback) {
+  scoped_ptr<std::string> data_copy(new std::string(data));
+  base::PostTaskAndReplyWithResult(
+      web::WebThread::GetBlockingPool(), FROM_HERE,
+      base::Bind(&IOSWebResourceService::ParseJSONOnBackgroundThread,
+                 base::Passed(&data_copy), success_callback, error_callback),

[Bernhard Bauer, 2015/01/26 12:05:43]

Could you just pass the data directly?

[droger, 2015/01/26 12:14:23]

I used base::Passed to avoid making a copy. I am not sure what would be the
benefits of that, is it to make the code clearer?

[Bernhard Bauer, 2015/01/26 12:22:49]

Yeah, pretty much. You do already make a copy right before that :)

[droger, 2015/01/26 12:28:19]

Done.

+      base::Bind(&RunClosure));
+}
+
+net::URLRequestContextGetter* IOSWebResourceService::GetRequestContext() {
+  return GetApplicationContext()->GetSystemURLRequestContext();
+}