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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_CATEGORY_REGISTRY_H_
#define BASE_TRACE_EVENT_CATEGORY_REGISTRY_H_
#include <stddef.h>
#include <stdint.h>
#include "base/base_export.h"
#include "base/logging.h"
namespace base {
namespace trace_event {
struct TraceCategory;
class TraceCategoryTest;
class TraceLog;
// Allows fast and thread-safe acces to the state of all tracing categories.
// All the methods in this class can be concurrently called on multiple threads,
// unless otherwise noted (e.g., GetOrCreateCategoryLocked).
// The reason why this is a fully static class with global state is to allow to
// statically define known categories as global linker-initialized structs,
// without requiring static initializers.
class BASE_EXPORT CategoryRegistry {
public:
// Allows for-each iterations over a slice of the categories array.
class Range {
public:
Range(TraceCategory* begin, TraceCategory* end) : begin_(begin), end_(end) {
DCHECK_LE(begin, end);
}
TraceCategory* begin() const { return begin_; }
TraceCategory* end() const { return end_; }
private:
TraceCategory* const begin_;
TraceCategory* const end_;
};
// Known categories.
static TraceCategory* const kCategoryExhausted;
static TraceCategory* const kCategoryMetadata;
static TraceCategory* const kCategoryAlreadyShutdown;
// Returns a category entry from the Category.state_ptr() pointer.
// TODO(primiano): trace macros should just keep a pointer to the entire
// TraceCategory, not just the enabled state pointer. That would remove the
// need for this function and make everything cleaner at no extra cost (as
// long as the |state_| is the first field of the struct, which can be
// guaranteed via static_assert, see TraceCategory ctor).
static const TraceCategory* GetCategoryByStatePtr(
const uint8_t* category_state);
// Returns a category from its name or nullptr if not found.
// The output |category| argument is an undefinitely lived pointer to the
// TraceCategory owned by the registry. TRACE_EVENTx macros will cache this
// pointer and use it for checks in their fast-paths.
static TraceCategory* GetCategoryByName(const char* category_name);
static bool IsBuiltinCategory(const TraceCategory*);
private:
friend class TraceCategoryTest;
friend class TraceLog;
using CategoryInitializerFn = void (*)(TraceCategory*);
// Only for debugging/testing purposes, is a no-op on release builds.
static void Initialize();
// Resets the state of all categories, to clear up the state between tests.
static void ResetForTesting();
// Used to get/create a category in the slow-path. If the category exists
// already, this has the same effect of GetCategoryByName and returns false.
// If not, a new category is created and the CategoryInitializerFn is invoked
// before retuning true. The caller must guarantee serialization: either call
// this method from a single thread or hold a lock when calling this.
static bool GetOrCreateCategoryLocked(const char* category_name,
CategoryInitializerFn,
TraceCategory**);
// Allows to iterate over the valid categories in a for-each loop.
// This includes builtin categories such as __metadata.
static Range GetAllCategories();
};
} // namespace trace_event
} // namespace base
#endif // BASE_TRACE_EVENT_CATEGORY_REGISTRY_H_
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