Index: base/trace_event/trace_category.h |
diff --git a/base/trace_event/trace_category.h b/base/trace_event/trace_category.h |
new file mode 100644 |
index 0000000000000000000000000000000000000000..5a7915ac03866af8881307ea06985530fc0aaad4 |
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+++ b/base/trace_event/trace_category.h |
@@ -0,0 +1,109 @@ |
+// Copyright 2016 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_CATEGORY_H_ |
+#define BASE_TRACE_EVENT_TRACE_CATEGORY_H_ |
+ |
+#include <stdint.h> |
+ |
+namespace base { |
+namespace trace_event { |
+ |
+// Captures the state of an invidivual trace category. Nothing except tracing |
+// internals (e.g., TraceLog) is supposed to have non-const Category pointers. |
+struct TraceCategory { |
+ // The TRACE_EVENT macros should only use this value as a bool. |
+ // These enum values are effectively a public API and third_party projects |
+ // depend on their value. Hence, never remove or recycle existing bits, unless |
+ // you are sure that all the third-party projects that depend on this have |
+ // been updated. |
+ enum StateFlags : uint8_t { |
+ ENABLED_FOR_RECORDING = 1 << 0, |
+ |
+ // Not used anymore. |
+ DEPRECATED_ENABLED_FOR_MONITORING = 1 << 1, |
+ DEPRECATED_ENABLED_FOR_EVENT_CALLBACK = 1 << 2, |
+ |
+ ENABLED_FOR_ETW_EXPORT = 1 << 3, |
+ ENABLED_FOR_FILTERING = 1 << 4 |
+ }; |
+ |
+ static const TraceCategory* FromStatePtr(const uint8_t* state_ptr) { |
+ static_assert( |
+ offsetof(TraceCategory, state_) == 0, |
+ "|state_| must be the first field of the TraceCategory class."); |
+ return reinterpret_cast<const TraceCategory*>(state_ptr); |
+ } |
+ |
+ bool is_valid() const { return name_ != nullptr; } |
+ void set_name(const char* name) { name_ = name; } |
+ const char* name() const { |
+ DCHECK(is_valid()); |
+ return name_; |
+ } |
+ |
+ // TODO(primiano): This is an intermediate solution to deal with the fact that |
+ // today TRACE_EVENT* macros cache the state ptr. They should just cache the |
+ // full TraceCategory ptr, which is immutable, and use these helper function |
+ // here. This will get rid of the need of this awkward ptr getter completely. |
+ const uint8_t* state_ptr() const { |
+ return const_cast<const uint8_t*>(&state_); |
+ } |
+ |
+ uint8_t state() const { |
+ return *const_cast<volatile const uint8_t*>(&state_); |
+ } |
+ |
+ bool is_enabled() const { return state() != 0; } |
+ |
+ void set_state(uint8_t state) { |
+ *const_cast<volatile uint8_t*>(&state_) = state; |
+ } |
+ |
+ void clear_state_flag(StateFlags flag) { set_state(state() & (~flag)); } |
+ void set_state_flag(StateFlags flag) { set_state(state() | flag); } |
+ |
+ uint32_t enabled_filters() const { |
+ return *const_cast<volatile const uint32_t*>(&enabled_filters_); |
+ } |
+ |
+ bool is_filter_enabled(size_t index) const { |
+ DCHECK(index < sizeof(enabled_filters_) * 8); |
+ return (enabled_filters() & (1 << index)) != 0; |
+ } |
+ |
+ void set_enabled_filters(uint32_t enabled_filters) { |
+ *const_cast<volatile uint32_t*>(&enabled_filters_) = enabled_filters; |
+ } |
+ |
+ void reset_for_testing() { |
+ set_state(0); |
+ set_enabled_filters(0); |
+ } |
+ |
+ // These fields should not be accessed directly, not even by tracing code. |
+ // The only reason why these are not private is because it makes it impossible |
+ // to have a global array of TraceCategory in category_registry.cc without |
+ // creating initializers. See discussion on goo.gl/qhZN94 and |
+ // crbug.com/{660967,660828}. |
+ |
+ // The enabled state. TRACE_EVENT* macros will capture events if any of the |
+ // flags here are set. Since TRACE_EVENTx macros are used in a lot of |
+ // fast-paths, accesses to this field are non-barriered and racy by design. |
+ // This field is mutated when starting/stopping tracing and we don't care |
+ // about missing some events. |
+ uint8_t state_; |
+ |
+ // When ENABLED_FOR_FILTERING is set, this contains a bitmap to the |
+ // coressponding filter (see event_filters.h). |
+ uint32_t enabled_filters_; |
+ |
+ // TraceCategory group names are long lived static strings. |
+ const char* name_; |
+}; |
+ |
+} // namespace trace_event |
+} // namespace base |
+ |
+#endif // BASE_TRACE_EVENT_TRACE_CATEGORY_H_ |