tracing: Introduce API for composite IDs

base/trace_event/trace_event.h

 // 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.
 
 #ifndef BASE_TRACE_EVENT_TRACE_EVENT_H_
 #define BASE_TRACE_EVENT_TRACE_EVENT_H_
 
 // This header file defines implementation details of how the trace macros in
 // trace_event_common.h collect and store trace events. Anything not
 // implementation-specific should go in trace_event_common.h instead of here.
@@ skipping 25 matching lines @@
 #define TRACE_ID_MANGLE(id) \
     trace_event_internal::TraceID::ForceMangle(id)
 
 // DEPRECATED: do not use: Consider using TRACE_ID_{GLOBAL, LOCAL} macros,
 // instead. By default, pointers are mangled with the Process ID in
 // TRACE_EVENT_ASYNC macros. Use this macro to prevent Process ID mangling.
 #define TRACE_ID_DONT_MANGLE(id) \
     trace_event_internal::TraceID::DontMangle(id)
 
 // By default, trace IDs are eventually converted to a single 64-bit number. Use
-// this macro to add a scope string.
-#define TRACE_ID_WITH_SCOPE(scope, id) \
-    trace_event_internal::TraceID::WithScope(scope, id)
+// this macro to add a scope string. For example,
+//
+// TRACE_EVENT_NESTABLE_ASYNC_BEGIN0(
+//     "network", "ResourceLoad",
+//     TRACE_ID_WITH_SCOPE("BlinkResourceID", resourceID));
+//
+// Also, it is possible to prepend the ID with another number, like the process
+// ID. This is useful in creatin IDs that are unique among all processes. To do
+// that, pass two numbers after the scope string instead of one. For example,
+//
+// TRACE_EVENT_NESTABLE_ASYNC_BEGIN0(
+//     "network", "ResourceLoad",
+//     TRACE_ID_WITH_SCOPE("BlinkResourceID", pid, resourceID));
+#define TRACE_ID_WITH_SCOPE(scope, ...) \
+  trace_event_internal::TraceID::WithScope(scope, ##__VA_ARGS__)
 
 #define TRACE_ID_GLOBAL(id) trace_event_internal::TraceID::GlobalId(id)
 #define TRACE_ID_LOCAL(id) trace_event_internal::TraceID::LocalId(id)
 
 #define TRACE_EVENT_API_CURRENT_THREAD_ID \
   static_cast<int>(base::PlatformThread::CurrentId())
 
 #define INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE() \
   UNLIKELY(*INTERNAL_TRACE_EVENT_UID(category_group_enabled) &           \
            (base::trace_event::TraceCategory::ENABLED_FOR_RECORDING |    \
@@ skipping 364 matching lines @@
     WithScope(const char* scope, unsigned long long raw_id)
         : scope_(scope), raw_id_(raw_id) {}
     WithScope(const char* scope, LocalId local_id)
         : scope_(scope), raw_id_(local_id.raw_id()) {
       id_flags_ = TRACE_EVENT_FLAG_HAS_LOCAL_ID;
     }
     WithScope(const char* scope, GlobalId global_id)
         : scope_(scope), raw_id_(global_id.raw_id()) {
       id_flags_ = TRACE_EVENT_FLAG_HAS_GLOBAL_ID;
     }
+    WithScope(const char* scope,
+              unsigned long long prefix,
+              unsigned long long raw_id)
+        : scope_(scope), has_prefix_(true), prefix_(prefix), raw_id_(raw_id) {}
+    WithScope(const char* scope, unsigned long long prefix, GlobalId global_id)
+        : scope_(scope),
+          has_prefix_(true),
+          prefix_(prefix),
+          raw_id_(global_id.raw_id()) {
+      id_flags_ = TRACE_EVENT_FLAG_HAS_GLOBAL_ID;
+    }
     unsigned long long raw_id() const { return raw_id_; }
     const char* scope() const { return scope_; }
+    bool has_prefix() const { return has_prefix_; }
+    unsigned long long prefix() const { return prefix_; }
     unsigned int id_flags() const { return id_flags_; }
+
    private:
     const char* scope_ = nullptr;
+    bool has_prefix_ = false;
+    unsigned long long prefix_;
     unsigned long long raw_id_;
     unsigned int id_flags_ = TRACE_EVENT_FLAG_HAS_ID;
   };
 
   // DEPRECATED: consider using LocalId or GlobalId, instead.
   class DontMangle {
    public:
     explicit DontMangle(const void* raw_id)
         : raw_id_(static_cast<unsigned long long>(
               reinterpret_cast<uintptr_t>(raw_id))) {}
@@ skipping 62 matching lines @@
   TraceID(short raw_id)
       : raw_id_(static_cast<unsigned long long>(raw_id)) {}
   TraceID(signed char raw_id)
       : raw_id_(static_cast<unsigned long long>(raw_id)) {}
   TraceID(LocalId raw_id) : raw_id_(raw_id.raw_id()) {
     id_flags_ = TRACE_EVENT_FLAG_HAS_LOCAL_ID;
   }
   TraceID(GlobalId raw_id) : raw_id_(raw_id.raw_id()) {
     id_flags_ = TRACE_EVENT_FLAG_HAS_GLOBAL_ID;
   }
-  TraceID(WithScope scoped_id) : scope_(scoped_id.scope()),
-      raw_id_(scoped_id.raw_id()), id_flags_(scoped_id.id_flags()) {}
+  TraceID(WithScope scoped_id)
+      : scope_(scoped_id.scope()),
+        has_prefix_(scoped_id.has_prefix()),
+        prefix_(scoped_id.prefix()),
+        raw_id_(scoped_id.raw_id()),
+        id_flags_(scoped_id.id_flags()) {}
 
   unsigned long long raw_id() const { return raw_id_; }
   const char* scope() const { return scope_; }
+  bool has_prefix() const { return has_prefix_; }
+  unsigned long long prefix() const { return prefix_; }
   unsigned int id_flags() const { return id_flags_; }
 
   std::unique_ptr<base::trace_event::ConvertableToTraceFormat>
   AsConvertableToTraceFormat() const;
 
  private:
   const char* scope_ = nullptr;
+  bool has_prefix_ = false;
+  unsigned long long prefix_;
   unsigned long long raw_id_;
   unsigned int id_flags_ = TRACE_EVENT_FLAG_HAS_ID;
 };
 
 // Simple union to store various types as unsigned long long.
 union TraceValueUnion {
   bool as_bool;
   unsigned long long as_uint;
   long long as_int;
   double as_double;
@@ skipping 531 matching lines @@
   const char* name_;
   IDType id_;
 
   DISALLOW_COPY_AND_ASSIGN(TraceScopedTrackableObject);
 };
 
 }  // namespace trace_event
 }  // namespace base
 
 #endif  // BASE_TRACE_EVENT_TRACE_EVENT_H_