// 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 #include "base/check.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(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. constexpr const uint8_t* state_ptr() const { return const_cast(&state_); } uint8_t state() const { return *const_cast(&state_); } bool is_enabled() const { return state() != 0; } void set_state(uint8_t state) { *const_cast(&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(&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(&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 // corresponding 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_