Parse out XSSI guards in Suggestion JSON response

chrome/browser/autocomplete/search_provider.cc

 // Copyright 2012 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 "chrome/browser/autocomplete/search_provider.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/callback.h"
@@ skipping 582 matching lines @@
 
   if (clear_cached_results)
     ClearAllResults();
 }
 
 void SearchProvider::OnURLFetchComplete(const net::URLFetcher* source) {
   DCHECK(!done_);
   suggest_results_pending_--;
   LogOmniboxSuggestRequest(REPLY_RECEIVED);
   DCHECK_GE(suggest_results_pending_, 0);  // Should never go negative.
-  const net::HttpResponseHeaders* const response_headers =
-      source->GetResponseHeaders();
-  std::string json_data;
-  source->GetResponseAsString(&json_data);
-  // JSON is supposed to be UTF-8, but some suggest service providers send JSON
-  // files in non-UTF-8 encodings.  The actual encoding is usually specified in
-  // the Content-Type header field.
-  if (response_headers) {
-    std::string charset;
-    if (response_headers->GetCharset(&charset)) {
-      string16 data_16;
-      // TODO(jungshik): Switch to CodePageToUTF8 after it's added.
-      if (base::CodepageToUTF16(json_data, charset.c_str(),
-                                base::OnStringConversionError::FAIL,
-                                &data_16))
-        json_data = UTF16ToUTF8(data_16);
-    }
-  }
 
   const bool is_keyword = (source == keyword_fetcher_.get());
   // Ensure the request succeeded and that the provider used is still available.
   // A verbatim match cannot be generated without this provider, causing errors.
   const bool request_succeeded =
       source->GetStatus().is_success() && (source->GetResponseCode() == 200) &&
       (is_keyword ?
           providers_.GetKeywordProviderURL() :
           providers_.GetDefaultProviderURL());
 
@@ skipping 10 matching lines @@
       UMA_HISTOGRAM_TIMES("Omnibox.SuggestRequest.Success.GoogleResponseTime",
                           elapsed_time);
     } else {
       UMA_HISTOGRAM_TIMES("Omnibox.SuggestRequest.Failure.GoogleResponseTime",
                           elapsed_time);
     }
   }
 
   bool results_updated = false;
   if (request_succeeded) {
-    JSONStringValueSerializer deserializer(json_data);
-    deserializer.set_allow_trailing_comma(true);
-    scoped_ptr<Value> data(deserializer.Deserialize(NULL, NULL));
-    results_updated = data.get() && ParseSuggestResults(data.get(), is_keyword);
+    const net::HttpResponseHeaders* const response_headers =
+        source->GetResponseHeaders();
+    std::string json_data;
+    source->GetResponseAsString(&json_data);
+    // JSON is supposed to be UTF-8, but some suggest service providers send
+    // JSON files in non-UTF-8 encodings.  The actual encoding is usually
+    // specified in the Content-Type header field.
+    if (response_headers) {
+      std::string charset;
+      if (response_headers->GetCharset(&charset)) {
+        string16 data_16;
+        // TODO(jungshik): Switch to CodePageToUTF8 after it's added.
+        if (base::CodepageToUTF16(json_data, charset.c_str(),
+                                  base::OnStringConversionError::FAIL,
+                                  &data_16))
+          json_data = UTF16ToUTF8(data_16);
+      }
+    }
+
+    int error_code = 0;

[Peter Kasting, 2013/10/29 19:03:57]

This doesn't need to be declared outside the loop.  Declare it where it's used.

[Anuj, 2013/10/29 19:10:35]

Done.

+    int lookup_start_index = 0;
+    while (true) {
+      // The JSON response should be an array.
+      size_t response_start_index = json_data.find("[", lookup_start_index);

[Peter Kasting, 2013/10/29 19:03:57]

Just use a for loop to avoid this temp and write things more clearly and
compactly:

    for (size_t response_start_index = json_data.find("[");
         response_start_index != std::string::npos;
         response_start_index = json_data.find("[", 1)) {
      // Remove any XSSI guards to allow for JSON parsing.
      if (response_start_index > 0)
      ...

[Anuj, 2013/10/29 19:10:35]

Done.

+
+      if (response_start_index == std::string::npos)
+        break;
+
+      // Remove any XSSI guards to allow for JSON parsing.
+      if (response_start_index > 0)
+        json_data.erase(0, response_start_index - 1);
+
+      lookup_start_index = 1;
+
+      JSONStringValueSerializer deserializer(json_data);
+      deserializer.set_allow_trailing_comma(true);
+      scoped_ptr<Value> data(deserializer.Deserialize(&error_code, NULL));
+      if (error_code == 0) {
+        results_updated = data.get() &&
+            ParseSuggestResults(data.get(), is_keyword);
+        break;
+      }
+    }
   }
 
   UpdateMatches();
   if (done_ || results_updated)
     listener_->OnProviderUpdate(results_updated);
 }
 
 void SearchProvider::Run() {
   // Start a new request with the current input.
   suggest_results_pending_ = 0;
@@ skipping 1098 matching lines @@
     it->set_relevance(max_query_relevance);
     it->set_relevance_from_server(relevance_from_server);
   }
 }
 
 void SearchProvider::UpdateDone() {
   // We're done when the timer isn't running, there are no suggest queries
   // pending, and we're not waiting on Instant.
   done_ = !timer_.IsRunning() && (suggest_results_pending_ == 0);
 }