tracing: Introduce API for composite IDs

base/trace_event/trace_event_impl.cc

 // Copyright (c) 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 "base/trace_event/trace_event_impl.h"
 
 #include <stddef.h>
 
 #include "base/format_macros.h"
 #include "base/json/string_escape.h"
@@ skipping 440 matching lines @@
 }  // namespace base
 
 namespace trace_event_internal {
 
 std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
 TraceID::AsConvertableToTraceFormat() const {
   auto value = base::MakeUnique<base::trace_event::TracedValue>();
 
   if (scope_ != kGlobalScope)
     value->SetString("scope", scope_);
-  switch (id_flags_) {
-    case TRACE_EVENT_FLAG_HAS_ID:
-      value->SetString(
-          "id",
-          base::StringPrintf("0x%" PRIx64, static_cast<uint64_t>(raw_id_)));
-      break;
-    case TRACE_EVENT_FLAG_HAS_GLOBAL_ID:
-      value->BeginDictionary("id2");
-      value->SetString(
-          "global",
-          base::StringPrintf("0x%" PRIx64, static_cast<uint64_t>(raw_id_)));
-      value->EndDictionary();
-      break;
-    case TRACE_EVENT_FLAG_HAS_LOCAL_ID:
-      value->BeginDictionary("id2");
-      value->SetString(
-          "local",
-          base::StringPrintf("0x%" PRIx64, static_cast<uint64_t>(raw_id_)));
-      value->EndDictionary();
-      break;
-    default:
-      NOTREACHED() << "Unrecognized ID flag";
+
+  std::string id_field_name = "id";

[caseq, 2016/11/21 19:47:20]

looks like this could be const char* instead.

[chiniforooshan, 2016/11/21 21:12:15]

Done.

+  if (id_flags_ == TRACE_EVENT_FLAG_HAS_GLOBAL_ID) {
+    id_field_name = "global";
+    value->BeginDictionary("id2");
+  } else if (id_flags_ == TRACE_EVENT_FLAG_HAS_LOCAL_ID) {
+    id_field_name = "local";
+    value->BeginDictionary("id2");
+  } else if (id_flags_ != TRACE_EVENT_FLAG_HAS_ID) {
+    NOTREACHED() << "Unrecognized ID flag";
   }
 
+  if (has_prefix_) {
+    value->BeginArrayWithCopiedName(id_field_name);

[caseq, 2016/11/21 19:47:20]

... using const char* would let us get rid of coping here.

[chiniforooshan, 2016/11/21 21:12:15]

Done.

+    value->AppendString(
+        base::StringPrintf("0x%" PRIx64, static_cast<uint64_t>(prefix_)));
+    value->AppendString(
+        base::StringPrintf("0x%" PRIx64, static_cast<uint64_t>(raw_id_)));
+    value->EndArray();
+  } else {
+    value->SetStringWithCopiedName(
+        id_field_name,
+        base::StringPrintf("0x%" PRIx64, static_cast<uint64_t>(raw_id_)));
+  }
+
+  if (id_flags_ != TRACE_EVENT_FLAG_HAS_ID)
+    value->EndDictionary();
+
   return std::move(value);
 }
 
 }  // namespace trace_event_internal