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- // 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>
- #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<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.
- constexpr 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
- // 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_
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