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