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_CATEGORY_REGISTRY_H_ 6 #define BASE_TRACE_EVENT_CATEGORY_REGISTRY_H_ 7 8 #include <stddef.h> 9 #include <stdint.h> 10 11 #include "base/base_export.h" 12 #include "base/logging.h" 13 14 namespace base { 15 namespace trace_event { 16 17 struct TraceCategory; 18 class TraceCategoryTest; 19 class TraceLog; 20 21 // Allows fast and thread-safe acces to the state of all tracing categories. 22 // All the methods in this class can be concurrently called on multiple threads, 23 // unless otherwise noted (e.g., GetOrCreateCategoryLocked). 24 // The reason why this is a fully static class with global state is to allow to 25 // statically define known categories as global linker-initialized structs, 26 // without requiring static initializers. 27 class BASE_EXPORT CategoryRegistry { 28 public: 29 // Allows for-each iterations over a slice of the categories array. 30 class Range { 31 public: Range(TraceCategory * begin,TraceCategory * end)32 Range(TraceCategory* begin, TraceCategory* end) : begin_(begin), end_(end) { 33 DCHECK_LE(begin, end); 34 } begin()35 TraceCategory* begin() const { return begin_; } end()36 TraceCategory* end() const { return end_; } 37 38 private: 39 TraceCategory* const begin_; 40 TraceCategory* const end_; 41 }; 42 43 // Known categories. 44 static TraceCategory* const kCategoryExhausted; 45 static TraceCategory* const kCategoryMetadata; 46 static TraceCategory* const kCategoryAlreadyShutdown; 47 48 // Returns a category entry from the Category.state_ptr() pointer. 49 // TODO(primiano): trace macros should just keep a pointer to the entire 50 // TraceCategory, not just the enabled state pointer. That would remove the 51 // need for this function and make everything cleaner at no extra cost (as 52 // long as the |state_| is the first field of the struct, which can be 53 // guaranteed via static_assert, see TraceCategory ctor). 54 static const TraceCategory* GetCategoryByStatePtr( 55 const uint8_t* category_state); 56 57 // Returns a category from its name or nullptr if not found. 58 // The output |category| argument is an undefinitely lived pointer to the 59 // TraceCategory owned by the registry. TRACE_EVENTx macros will cache this 60 // pointer and use it for checks in their fast-paths. 61 static TraceCategory* GetCategoryByName(const char* category_name); 62 63 static bool IsBuiltinCategory(const TraceCategory*); 64 65 private: 66 friend class TraceCategoryTest; 67 friend class TraceLog; 68 using CategoryInitializerFn = void (*)(TraceCategory*); 69 70 // Only for debugging/testing purposes, is a no-op on release builds. 71 static void Initialize(); 72 73 // Resets the state of all categories, to clear up the state between tests. 74 static void ResetForTesting(); 75 76 // Used to get/create a category in the slow-path. If the category exists 77 // already, this has the same effect of GetCategoryByName and returns false. 78 // If not, a new category is created and the CategoryInitializerFn is invoked 79 // before retuning true. The caller must guarantee serialization: either call 80 // this method from a single thread or hold a lock when calling this. 81 static bool GetOrCreateCategoryLocked(const char* category_name, 82 CategoryInitializerFn, 83 TraceCategory**); 84 85 // Allows to iterate over the valid categories in a for-each loop. 86 // This includes builtin categories such as __metadata. 87 static Range GetAllCategories(); 88 }; 89 90 } // namespace trace_event 91 } // namespace base 92 93 #endif // BASE_TRACE_EVENT_CATEGORY_REGISTRY_H_ 94