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| 1 // Copyright 2016 The Chromium Authors. All rights reserved. |
| 2 // Use of this source code is governed by a BSD-style license that can be |
| 3 // found in the LICENSE file. |
| 4 |
| 5 #ifndef BASE_TRACE_EVENT_TRACE_CATEGORY_H_ |
| 6 #define BASE_TRACE_EVENT_TRACE_CATEGORY_H_ |
| 7 |
| 8 #include <stdint.h> |
| 9 |
| 10 namespace base { |
| 11 namespace trace_event { |
| 12 |
| 13 // Captures the state of an invidivual trace category. Nothing except tracing |
| 14 // internals (e.g., TraceLog) is supposed to have non-const Category pointers. |
| 15 struct TraceCategory { |
| 16 // The TRACE_EVENT macros should only use this value as a bool. |
| 17 // These enum values are effectively a public API and third_party projects |
| 18 // depend on their value. Hence, never remove or recycle existing bits, unless |
| 19 // you are sure that all the third-party projects that depend on this have |
| 20 // been updated. |
| 21 enum StateFlags : uint8_t { |
| 22 ENABLED_FOR_RECORDING = 1 << 0, |
| 23 |
| 24 // Not used anymore. |
| 25 DEPRECATED_ENABLED_FOR_MONITORING = 1 << 1, |
| 26 DEPRECATED_ENABLED_FOR_EVENT_CALLBACK = 1 << 2, |
| 27 |
| 28 ENABLED_FOR_ETW_EXPORT = 1 << 3, |
| 29 ENABLED_FOR_FILTERING = 1 << 4 |
| 30 }; |
| 31 |
| 32 static const TraceCategory* FromStatePtr(const uint8_t* state_ptr) { |
| 33 static_assert( |
| 34 offsetof(TraceCategory, state_) == 0, |
| 35 "|state_| must be the first field of the TraceCategory class."); |
| 36 return reinterpret_cast<const TraceCategory*>(state_ptr); |
| 37 } |
| 38 |
| 39 bool is_valid() const { return name_ != nullptr; } |
| 40 void set_name(const char* name) { name_ = name; } |
| 41 const char* name() const { |
| 42 DCHECK(is_valid()); |
| 43 return name_; |
| 44 } |
| 45 |
| 46 // TODO(primiano): This is an intermediate solution to deal with the fact that |
| 47 // today TRACE_EVENT* macros cache the state ptr. They should just cache the |
| 48 // full TraceCategory ptr, which is immutable, and use these helper function |
| 49 // here. This will get rid of the need of this awkward ptr getter completely. |
| 50 const uint8_t* state_ptr() const { |
| 51 return const_cast<const uint8_t*>(&state_); |
| 52 } |
| 53 |
| 54 uint8_t state() const { |
| 55 return *const_cast<volatile const uint8_t*>(&state_); |
| 56 } |
| 57 |
| 58 bool is_enabled() const { return state() != 0; } |
| 59 |
| 60 void set_state(uint8_t state) { |
| 61 *const_cast<volatile uint8_t*>(&state_) = state; |
| 62 } |
| 63 |
| 64 void clear_state_flag(StateFlags flag) { set_state(state() & (~flag)); } |
| 65 void set_state_flag(StateFlags flag) { set_state(state() | flag); } |
| 66 |
| 67 uint32_t enabled_filters() const { |
| 68 return *const_cast<volatile const uint32_t*>(&enabled_filters_); |
| 69 } |
| 70 |
| 71 bool is_filter_enabled(size_t index) const { |
| 72 DCHECK(index < sizeof(enabled_filters_) * 8); |
| 73 return (enabled_filters() & (1 << index)) != 0; |
| 74 } |
| 75 |
| 76 void set_enabled_filters(uint32_t enabled_filters) { |
| 77 *const_cast<volatile uint32_t*>(&enabled_filters_) = enabled_filters; |
| 78 } |
| 79 |
| 80 void reset_for_testing() { |
| 81 set_state(0); |
| 82 set_enabled_filters(0); |
| 83 } |
| 84 |
| 85 // These fields should not be accessed directly, not even by tracing code. |
| 86 // The only reason why these are not private is because it makes it impossible |
| 87 // to have a global array of TraceCategory in category_registry.cc without |
| 88 // creating initializers. See discussion on goo.gl/qhZN94 and |
| 89 // crbug.com/{660967,660828}. |
| 90 |
| 91 // The enabled state. TRACE_EVENT* macros will capture events if any of the |
| 92 // flags here are set. Since TRACE_EVENTx macros are used in a lot of |
| 93 // fast-paths, accesses to this field are non-barriered and racy by design. |
| 94 // This field is mutated when starting/stopping tracing and we don't care |
| 95 // about missing some events. |
| 96 uint8_t state_; |
| 97 |
| 98 // When ENABLED_FOR_FILTERING is set, this contains a bitmap to the |
| 99 // coressponding filter (see event_filters.h). |
| 100 uint32_t enabled_filters_; |
| 101 |
| 102 // TraceCategory group names are long lived static strings. |
| 103 const char* name_; |
| 104 }; |
| 105 |
| 106 } // namespace trace_event |
| 107 } // namespace base |
| 108 |
| 109 #endif // BASE_TRACE_EVENT_TRACE_CATEGORY_H_ |
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