Internalize JSON chunk management to trace_event.h API.

base/debug/trace_event.cc

 // Copyright (c) 2011 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 "base/debug/trace_event.h"
 
 #include <algorithm>
 
 #if defined(OS_WIN)
 #include "base/debug/trace_event_win.h"
@@ skipping 206 matching lines @@
   }
 }
 
 TraceEvent::~TraceEvent() {
 }
 
 void TraceEvent::AppendEventsAsJSON(const std::vector<TraceEvent>& events,
                                     size_t start,
                                     size_t count,
                                     std::string* out) {
-  *out += "[";
   for (size_t i = 0; i < count && start + i < events.size(); ++i) {
     if (i > 0)
       *out += ",";
     events[i + start].AppendAsJSON(out);
   }
-  *out += "]";
 }
 
 void TraceEvent::AppendAsJSON(std::string* out) const {
   const char* phase_str = GetPhaseStr(phase_);
   int64 time_int64 = timestamp_.ToInternalValue();
   // Category name checked at category creation time.
   DCHECK(!strchr(name_, '"'));
   StringAppendF(out,
       "{\"cat\":\"%s\",\"pid\":%i,\"tid\":%i,\"ts\":%lld,"
       "\"ph\":\"%s\",\"name\":\"%s\",\"args\":{",
@@ skipping 11 matching lines @@
     *out += "\"";
     *out += arg_names_[i];
     *out += "\":";
     arg_values_[i].AppendAsJSON(out);
   }
   *out += "}}";
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 //
+// TraceResultBuffer
+//
+////////////////////////////////////////////////////////////////////////////////
+
+TraceResultBuffer::TraceResultBuffer() {
+}
+
+TraceResultBuffer::~TraceResultBuffer() {
+}
+
+void TraceResultBuffer::AddFragment(const std::string& trace_fragment) {
+  fragments_.push_back(trace_fragment);
+}
+
+void TraceResultBuffer::GetJSON(std::string* json_trace_output) {
+  *json_trace_output = "[";
+  for (size_t i = 0; i < fragments_.size(); ++i) {

[nduca, 2011/10/20 00:28:03]

Algorithmically, I see a bit too many strdups. I'd <3 to see this do:

std::string result_; bool terminated_;
constructor: result_("["), terminated_(false);
addfragment: DCHECK(!terminated_); result_ += trace_fragment; result_ += ",";
getJSON() {
  if(!terminated_) {
    terminated_ = true;
    result += "]";
  }
  return result_;
}

bonus points for unterminating instead of dchecking.

Less strduping == good, yes?

[jbates, 2011/10/20 22:18:49]

Similar optimizations occurred to me, but I thought performance was not
important here so not worth the design complication / code maintenance. Ah well!
Done.

+    if (i > 0)
+      *json_trace_output += ",";
+    *json_trace_output += fragments_[i];
+  }
+  *json_trace_output += "]";
+}
+
+////////////////////////////////////////////////////////////////////////////////
+//
 // TraceLog
 //
 ////////////////////////////////////////////////////////////////////////////////
 
 // static
 TraceLog* TraceLog::GetInstance() {
   return Singleton<TraceLog, StaticMemorySingletonTraits<TraceLog> >::get();
 }
 
 TraceLog::TraceLog()
@@ skipping 335 matching lines @@
         NULL, 0, NULL, 0,
         p_data_->threshold_begin_id, p_data_->threshold,
         TraceLog::EVENT_FLAG_NONE);
   }
 }
 
 }  // namespace internal
 
 }  // namespace debug
 }  // namespace base