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