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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>
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_
|
