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1 // Copyright (c) 2014 Google Inc.
2 //
3 // Use of this source code is governed by a BSD-style license that can be
4 // found in the LICENSE file.
5 
6 // This header file defines implementation details of how the trace macros in
7 // SkTraceEventCommon.h collect and store trace events. Anything not
8 // implementation-specific should go in SkTraceEventCommon.h instead of here.
9 
10 #ifndef SkTraceEvent_DEFINED
11 #define SkTraceEvent_DEFINED
12 
13 #include "SkAtomics.h"
14 #include "SkEventTracer.h"
15 #include "SkTraceEventCommon.h"
16 
17 ////////////////////////////////////////////////////////////////////////////////
18 // Implementation specific tracing API definitions.
19 
20 // By default, const char* argument values are assumed to have long-lived scope
21 // and will not be copied. Use this macro to force a const char* to be copied.
22 #define TRACE_STR_COPY(str) \
23     skia::tracing_internals::TraceStringWithCopy(str)
24 
25 // By default, uint64 ID argument values are not mangled with the Process ID in
26 // TRACE_EVENT_ASYNC macros. Use this macro to force Process ID mangling.
27 #define TRACE_ID_MANGLE(id) \
28     skia::tracing_internals::TraceID::ForceMangle(id)
29 
30 // By default, pointers are mangled with the Process ID in TRACE_EVENT_ASYNC
31 // macros. Use this macro to prevent Process ID mangling.
32 #define TRACE_ID_DONT_MANGLE(id) \
33     skia::tracing_internals::TraceID::DontMangle(id)
34 
35 // Sets the current sample state to the given category and name (both must be
36 // constant strings). These states are intended for a sampling profiler.
37 // Implementation note: we store category and name together because we don't
38 // want the inconsistency/expense of storing two pointers.
39 // |thread_bucket| is [0..2] and is used to statically isolate samples in one
40 // thread from others.
41 #define TRACE_EVENT_SET_SAMPLING_STATE_FOR_BUCKET( \
42     bucket_number, category, name)                 \
43         skia::tracing_internals::                     \
44         TraceEventSamplingStateScope<bucket_number>::Set(category "\0" name)
45 
46 // Returns a current sampling state of the given bucket.
47 #define TRACE_EVENT_GET_SAMPLING_STATE_FOR_BUCKET(bucket_number) \
48     skia::tracing_internals::TraceEventSamplingStateScope<bucket_number>::Current()
49 
50 // Creates a scope of a sampling state of the given bucket.
51 //
52 // {  // The sampling state is set within this scope.
53 //    TRACE_EVENT_SAMPLING_STATE_SCOPE_FOR_BUCKET(0, "category", "name");
54 //    ...;
55 // }
56 #define TRACE_EVENT_SCOPED_SAMPLING_STATE_FOR_BUCKET(                   \
57     bucket_number, category, name)                                      \
58     skia::tracing_internals::TraceEventSamplingStateScope<bucket_number>   \
59         traceEventSamplingScope(category "\0" name);
60 
61 
62 #define INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE() \
63     *INTERNAL_TRACE_EVENT_UID(category_group_enabled) & \
64         (SkEventTracer::kEnabledForRecording_CategoryGroupEnabledFlags | \
65          SkEventTracer::kEnabledForEventCallback_CategoryGroupEnabledFlags)
66 
67 // Get a pointer to the enabled state of the given trace category. Only
68 // long-lived literal strings should be given as the category group. The
69 // returned pointer can be held permanently in a local static for example. If
70 // the unsigned char is non-zero, tracing is enabled. If tracing is enabled,
71 // TRACE_EVENT_API_ADD_TRACE_EVENT can be called. It's OK if tracing is disabled
72 // between the load of the tracing state and the call to
73 // TRACE_EVENT_API_ADD_TRACE_EVENT, because this flag only provides an early out
74 // for best performance when tracing is disabled.
75 // const uint8_t*
76 //     TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(const char* category_group)
77 #define TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED \
78     SkEventTracer::GetInstance()->getCategoryGroupEnabled
79 
80 // Get the number of times traces have been recorded. This is used to implement
81 // the TRACE_EVENT_IS_NEW_TRACE facility.
82 // unsigned int TRACE_EVENT_API_GET_NUM_TRACES_RECORDED()
83 #define TRACE_EVENT_API_GET_NUM_TRACES_RECORDED \
84     SkEventTracer::GetInstance()->getNumTracesRecorded
85 
86 // Add a trace event to the platform tracing system.
87 // SkEventTracer::Handle TRACE_EVENT_API_ADD_TRACE_EVENT(
88 //                    char phase,
89 //                    const uint8_t* category_group_enabled,
90 //                    const char* name,
91 //                    uint64_t id,
92 //                    int num_args,
93 //                    const char** arg_names,
94 //                    const uint8_t* arg_types,
95 //                    const uint64_t* arg_values,
96 //                    unsigned char flags)
97 #define TRACE_EVENT_API_ADD_TRACE_EVENT \
98     SkEventTracer::GetInstance()->addTraceEvent
99 
100 // Set the duration field of a COMPLETE trace event.
101 // void TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
102 //     const uint8_t* category_group_enabled,
103 //     const char* name,
104 //     SkEventTracer::Handle id)
105 #define TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION \
106     SkEventTracer::GetInstance()->updateTraceEventDuration
107 
108 #define TRACE_EVENT_API_ATOMIC_WORD intptr_t
109 #define TRACE_EVENT_API_ATOMIC_LOAD(var) sk_atomic_load(&var, sk_memory_order_relaxed)
110 #define TRACE_EVENT_API_ATOMIC_STORE(var, value) \
111     sk_atomic_store(&var, value, sk_memory_order_relaxed)
112 
113 // Defines visibility for classes in trace_event.h
114 #define TRACE_EVENT_API_CLASS_EXPORT SK_API
115 
116 // The thread buckets for the sampling profiler.
117 TRACE_EVENT_API_CLASS_EXPORT extern \
118     TRACE_EVENT_API_ATOMIC_WORD g_trace_state[3];
119 
120 #define TRACE_EVENT_API_THREAD_BUCKET(thread_bucket)                           \
121     g_trace_state[thread_bucket]
122 
123 ////////////////////////////////////////////////////////////////////////////////
124 
125 // Implementation detail: trace event macros create temporary variables
126 // to keep instrumentation overhead low. These macros give each temporary
127 // variable a unique name based on the line number to prevent name collisions.
128 #define INTERNAL_TRACE_EVENT_UID3(a,b) \
129     trace_event_unique_##a##b
130 #define INTERNAL_TRACE_EVENT_UID2(a,b) \
131     INTERNAL_TRACE_EVENT_UID3(a,b)
132 #define INTERNAL_TRACE_EVENT_UID(name_prefix) \
133     INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)
134 
135 // Implementation detail: internal macro to create static category.
136 // No barriers are needed, because this code is designed to operate safely
137 // even when the unsigned char* points to garbage data (which may be the case
138 // on processors without cache coherency).
139 #define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES( \
140     category_group, atomic, category_group_enabled) \
141     category_group_enabled = \
142         reinterpret_cast<const uint8_t*>(TRACE_EVENT_API_ATOMIC_LOAD( \
143             atomic)); \
144     if (!category_group_enabled) { \
145       category_group_enabled = \
146           TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(category_group); \
147       TRACE_EVENT_API_ATOMIC_STORE(atomic, \
148           reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>( \
149               category_group_enabled)); \
150     }
151 
152 #define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group) \
153     static TRACE_EVENT_API_ATOMIC_WORD INTERNAL_TRACE_EVENT_UID(atomic) = 0; \
154     const uint8_t* INTERNAL_TRACE_EVENT_UID(category_group_enabled); \
155     INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES(category_group, \
156         INTERNAL_TRACE_EVENT_UID(atomic), \
157         INTERNAL_TRACE_EVENT_UID(category_group_enabled));
158 
159 // Implementation detail: internal macro to create static category and add
160 // event if the category is enabled.
161 #define INTERNAL_TRACE_EVENT_ADD(phase, category_group, name, flags, ...) \
162     do { \
163       INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
164       if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
165         skia::tracing_internals::AddTraceEvent( \
166             phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
167             skia::tracing_internals::kNoEventId, flags, ##__VA_ARGS__); \
168       } \
169     } while (0)
170 
171 // Implementation detail: internal macro to create static category and add begin
172 // event if the category is enabled. Also adds the end event when the scope
173 // ends.
174 #define INTERNAL_TRACE_EVENT_ADD_SCOPED(category_group, name, ...) \
175     INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
176     skia::tracing_internals::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer); \
177     if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
178       SkEventTracer::Handle h = skia::tracing_internals::AddTraceEvent( \
179           TRACE_EVENT_PHASE_COMPLETE, \
180           INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
181           name, skia::tracing_internals::kNoEventId, \
182           TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
183       INTERNAL_TRACE_EVENT_UID(tracer).Initialize( \
184           INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, h); \
185     }
186 
187 // Implementation detail: internal macro to create static category and add
188 // event if the category is enabled.
189 #define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category_group, name, id, \
190                                          flags, ...) \
191     do { \
192       INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
193       if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
194         unsigned char trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID; \
195         skia::tracing_internals::TraceID trace_event_trace_id( \
196             id, &trace_event_flags); \
197         skia::tracing_internals::AddTraceEvent( \
198             phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
199             name, trace_event_trace_id.data(), trace_event_flags, \
200             ##__VA_ARGS__); \
201       } \
202     } while (0)
203 
204 // Implementation detail: internal macro to create static category and add
205 // event if the category is enabled.
206 #define INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP(phase, \
207         category_group, name, id, thread_id, flags, ...) \
208     do { \
209       INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
210       if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
211         unsigned char trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID; \
212         skia::tracing_internals::TraceID trace_event_trace_id( \
213             id, &trace_event_flags); \
214         skia::tracing_internals::AddTraceEventWithThreadIdAndTimestamp( \
215             phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
216             name, trace_event_trace_id.data(), \
217             thread_id, base::TimeTicks::FromInternalValue(timestamp), \
218             trace_event_flags, ##__VA_ARGS__); \
219       } \
220     } while (0)
221 
222 #define INTERNAL_TRACE_MEMORY(category, name)
223 
224 namespace skia {
225 namespace tracing_internals {
226 
227 // Specify these values when the corresponding argument of AddTraceEvent is not
228 // used.
229 const int kZeroNumArgs = 0;
230 const uint64_t kNoEventId = 0;
231 
232 // TraceID encapsulates an ID that can either be an integer or pointer. Pointers
233 // are by default mangled with the Process ID so that they are unlikely to
234 // collide when the same pointer is used on different processes.
235 class TraceID {
236  public:
237   class DontMangle {
238    public:
DontMangle(const void * id)239     explicit DontMangle(const void* id)
240         : data_(static_cast<uint64_t>(
241               reinterpret_cast<uintptr_t>(id))) {}
DontMangle(uint64_t id)242     explicit DontMangle(uint64_t id) : data_(id) {}
DontMangle(unsigned int id)243     explicit DontMangle(unsigned int id) : data_(id) {}
DontMangle(unsigned short id)244     explicit DontMangle(unsigned short id) : data_(id) {}
DontMangle(unsigned char id)245     explicit DontMangle(unsigned char id) : data_(id) {}
DontMangle(long long id)246     explicit DontMangle(long long id)
247         : data_(static_cast<uint64_t>(id)) {}
DontMangle(long id)248     explicit DontMangle(long id)
249         : data_(static_cast<uint64_t>(id)) {}
DontMangle(int id)250     explicit DontMangle(int id)
251         : data_(static_cast<uint64_t>(id)) {}
DontMangle(short id)252     explicit DontMangle(short id)
253         : data_(static_cast<uint64_t>(id)) {}
DontMangle(signed char id)254     explicit DontMangle(signed char id)
255         : data_(static_cast<uint64_t>(id)) {}
data()256     uint64_t data() const { return data_; }
257    private:
258     uint64_t data_;
259   };
260 
261   class ForceMangle {
262    public:
ForceMangle(uint64_t id)263     explicit ForceMangle(uint64_t id) : data_(id) {}
ForceMangle(unsigned int id)264     explicit ForceMangle(unsigned int id) : data_(id) {}
ForceMangle(unsigned short id)265     explicit ForceMangle(unsigned short id) : data_(id) {}
ForceMangle(unsigned char id)266     explicit ForceMangle(unsigned char id) : data_(id) {}
ForceMangle(long long id)267     explicit ForceMangle(long long id)
268         : data_(static_cast<uint64_t>(id)) {}
ForceMangle(long id)269     explicit ForceMangle(long id)
270         : data_(static_cast<uint64_t>(id)) {}
ForceMangle(int id)271     explicit ForceMangle(int id)
272         : data_(static_cast<uint64_t>(id)) {}
ForceMangle(short id)273     explicit ForceMangle(short id)
274         : data_(static_cast<uint64_t>(id)) {}
ForceMangle(signed char id)275     explicit ForceMangle(signed char id)
276         : data_(static_cast<uint64_t>(id)) {}
data()277     uint64_t data() const { return data_; }
278    private:
279     uint64_t data_;
280   };
281 
TraceID(const void * id,unsigned char * flags)282   TraceID(const void* id, unsigned char* flags)
283       : data_(static_cast<uint64_t>(
284               reinterpret_cast<uintptr_t>(id))) {
285     *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
286   }
TraceID(ForceMangle id,unsigned char * flags)287   TraceID(ForceMangle id, unsigned char* flags) : data_(id.data()) {
288     *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
289   }
TraceID(DontMangle id,unsigned char * flags)290   TraceID(DontMangle id, unsigned char* flags) : data_(id.data()) {
291   }
TraceID(uint64_t id,unsigned char * flags)292   TraceID(uint64_t id, unsigned char* flags)
293       : data_(id) { (void)flags; }
TraceID(unsigned int id,unsigned char * flags)294   TraceID(unsigned int id, unsigned char* flags)
295       : data_(id) { (void)flags; }
TraceID(unsigned short id,unsigned char * flags)296   TraceID(unsigned short id, unsigned char* flags)
297       : data_(id) { (void)flags; }
TraceID(unsigned char id,unsigned char * flags)298   TraceID(unsigned char id, unsigned char* flags)
299       : data_(id) { (void)flags; }
TraceID(long long id,unsigned char * flags)300   TraceID(long long id, unsigned char* flags)
301       : data_(static_cast<uint64_t>(id)) { (void)flags; }
TraceID(long id,unsigned char * flags)302   TraceID(long id, unsigned char* flags)
303       : data_(static_cast<uint64_t>(id)) { (void)flags; }
TraceID(int id,unsigned char * flags)304   TraceID(int id, unsigned char* flags)
305       : data_(static_cast<uint64_t>(id)) { (void)flags; }
TraceID(short id,unsigned char * flags)306   TraceID(short id, unsigned char* flags)
307       : data_(static_cast<uint64_t>(id)) { (void)flags; }
TraceID(signed char id,unsigned char * flags)308   TraceID(signed char id, unsigned char* flags)
309       : data_(static_cast<uint64_t>(id)) { (void)flags; }
310 
data()311   uint64_t data() const { return data_; }
312 
313  private:
314   uint64_t data_;
315 };
316 
317 // Simple union to store various types as uint64_t.
318 union TraceValueUnion {
319   bool as_bool;
320   uint64_t as_uint;
321   long long as_int;
322   double as_double;
323   const void* as_pointer;
324   const char* as_string;
325 };
326 
327 // Simple container for const char* that should be copied instead of retained.
328 class TraceStringWithCopy {
329  public:
TraceStringWithCopy(const char * str)330   explicit TraceStringWithCopy(const char* str) : str_(str) {}
331   operator const char* () const { return str_; }
332  private:
333   const char* str_;
334 };
335 
336 // Define SetTraceValue for each allowed type. It stores the type and
337 // value in the return arguments. This allows this API to avoid declaring any
338 // structures so that it is portable to third_party libraries.
339 #define INTERNAL_DECLARE_SET_TRACE_VALUE(actual_type, \
340                                          union_member, \
341                                          value_type_id) \
342     static inline void SetTraceValue( \
343         actual_type arg, \
344         unsigned char* type, \
345         uint64_t* value) { \
346       TraceValueUnion type_value; \
347       type_value.union_member = arg; \
348       *type = value_type_id; \
349       *value = type_value.as_uint; \
350     }
351 // Simpler form for int types that can be safely casted.
352 #define INTERNAL_DECLARE_SET_TRACE_VALUE_INT(actual_type, \
353                                              value_type_id) \
354     static inline void SetTraceValue( \
355         actual_type arg, \
356         unsigned char* type, \
357         uint64_t* value) { \
358       *type = value_type_id; \
359       *value = static_cast<uint64_t>(arg); \
360     }
361 
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(uint64_t,TRACE_VALUE_TYPE_UINT)362 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(uint64_t, TRACE_VALUE_TYPE_UINT)
363 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned int, TRACE_VALUE_TYPE_UINT)
364 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned short, TRACE_VALUE_TYPE_UINT)
365 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned char, TRACE_VALUE_TYPE_UINT)
366 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long long, TRACE_VALUE_TYPE_INT)
367 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long, TRACE_VALUE_TYPE_INT)
368 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int, TRACE_VALUE_TYPE_INT)
369 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(short, TRACE_VALUE_TYPE_INT)
370 INTERNAL_DECLARE_SET_TRACE_VALUE_INT(signed char, TRACE_VALUE_TYPE_INT)
371 INTERNAL_DECLARE_SET_TRACE_VALUE(bool, as_bool, TRACE_VALUE_TYPE_BOOL)
372 INTERNAL_DECLARE_SET_TRACE_VALUE(double, as_double, TRACE_VALUE_TYPE_DOUBLE)
373 INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, as_pointer,
374                                  TRACE_VALUE_TYPE_POINTER)
375 INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, as_string,
376                                  TRACE_VALUE_TYPE_STRING)
377 INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&, as_string,
378                                  TRACE_VALUE_TYPE_COPY_STRING)
379 
380 #undef INTERNAL_DECLARE_SET_TRACE_VALUE
381 #undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT
382 
383 // These AddTraceEvent and AddTraceEvent template
384 // functions are defined here instead of in the macro, because the arg_values
385 // could be temporary objects, such as std::string. In order to store
386 // pointers to the internal c_str and pass through to the tracing API,
387 // the arg_values must live throughout these procedures.
388 
389 static inline SkEventTracer::Handle
390 AddTraceEvent(
391     char phase,
392     const uint8_t* category_group_enabled,
393     const char* name,
394     uint64_t id,
395     unsigned char flags) {
396   return TRACE_EVENT_API_ADD_TRACE_EVENT(
397       phase, category_group_enabled, name, id,
398       kZeroNumArgs, nullptr, nullptr, nullptr, flags);
399 }
400 
401 template<class ARG1_TYPE>
402 static inline SkEventTracer::Handle
AddTraceEvent(char phase,const uint8_t * category_group_enabled,const char * name,uint64_t id,unsigned char flags,const char * arg1_name,const ARG1_TYPE & arg1_val)403 AddTraceEvent(
404     char phase,
405     const uint8_t* category_group_enabled,
406     const char* name,
407     uint64_t id,
408     unsigned char flags,
409     const char* arg1_name,
410     const ARG1_TYPE& arg1_val) {
411   const int num_args = 1;
412   uint8_t arg_types[1];
413   uint64_t arg_values[1];
414   SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
415   return TRACE_EVENT_API_ADD_TRACE_EVENT(
416       phase, category_group_enabled, name, id,
417       num_args, &arg1_name, arg_types, arg_values, flags);
418 }
419 
420 template<class ARG1_TYPE, class ARG2_TYPE>
421 static inline SkEventTracer::Handle
AddTraceEvent(char phase,const uint8_t * category_group_enabled,const char * name,uint64_t id,unsigned char flags,const char * arg1_name,const ARG1_TYPE & arg1_val,const char * arg2_name,const ARG2_TYPE & arg2_val)422 AddTraceEvent(
423     char phase,
424     const uint8_t* category_group_enabled,
425     const char* name,
426     uint64_t id,
427     unsigned char flags,
428     const char* arg1_name,
429     const ARG1_TYPE& arg1_val,
430     const char* arg2_name,
431     const ARG2_TYPE& arg2_val) {
432   const int num_args = 2;
433   const char* arg_names[2] = { arg1_name, arg2_name };
434   unsigned char arg_types[2];
435   uint64_t arg_values[2];
436   SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
437   SetTraceValue(arg2_val, &arg_types[1], &arg_values[1]);
438   return TRACE_EVENT_API_ADD_TRACE_EVENT(
439       phase, category_group_enabled, name, id,
440       num_args, arg_names, arg_types, arg_values, flags);
441 }
442 
443 // Used by TRACE_EVENTx macros. Do not use directly.
444 class TRACE_EVENT_API_CLASS_EXPORT ScopedTracer {
445  public:
446   // Note: members of data_ intentionally left uninitialized. See Initialize.
ScopedTracer()447   ScopedTracer() : p_data_(nullptr) {}
448 
~ScopedTracer()449   ~ScopedTracer() {
450     if (p_data_ && *data_.category_group_enabled)
451       TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
452           data_.category_group_enabled, data_.name, data_.event_handle);
453   }
454 
Initialize(const uint8_t * category_group_enabled,const char * name,SkEventTracer::Handle event_handle)455   void Initialize(const uint8_t* category_group_enabled,
456                   const char* name,
457                   SkEventTracer::Handle event_handle) {
458     data_.category_group_enabled = category_group_enabled;
459     data_.name = name;
460     data_.event_handle = event_handle;
461     p_data_ = &data_;
462   }
463 
464  private:
465   // This Data struct workaround is to avoid initializing all the members
466   // in Data during construction of this object, since this object is always
467   // constructed, even when tracing is disabled. If the members of Data were
468   // members of this class instead, compiler warnings occur about potential
469   // uninitialized accesses.
470   struct Data {
471     const uint8_t* category_group_enabled;
472     const char* name;
473     SkEventTracer::Handle event_handle;
474   };
475   Data* p_data_;
476   Data data_;
477 };
478 
479 // Used by TRACE_EVENT_BINARY_EFFICIENTx macro. Do not use directly.
480 class TRACE_EVENT_API_CLASS_EXPORT ScopedTraceBinaryEfficient {
481  public:
482   ScopedTraceBinaryEfficient(const char* category_group, const char* name);
483   ~ScopedTraceBinaryEfficient();
484 
485  private:
486   const uint8_t* category_group_enabled_;
487   const char* name_;
488   SkEventTracer::Handle event_handle_;
489 };
490 
491 // This macro generates less code then TRACE_EVENT0 but is also
492 // slower to execute when tracing is off. It should generally only be
493 // used with code that is seldom executed or conditionally executed
494 // when debugging.
495 // For now the category_group must be "gpu".
496 #define TRACE_EVENT_BINARY_EFFICIENT0(category_group, name) \
497     skia::tracing_internals::ScopedTraceBinaryEfficient \
498         INTERNAL_TRACE_EVENT_UID(scoped_trace)(category_group, name);
499 
500 // TraceEventSamplingStateScope records the current sampling state
501 // and sets a new sampling state. When the scope exists, it restores
502 // the sampling state having recorded.
503 template<size_t BucketNumber>
504 class TraceEventSamplingStateScope {
505  public:
TraceEventSamplingStateScope(const char * category_and_name)506   TraceEventSamplingStateScope(const char* category_and_name) {
507     previous_state_ = TraceEventSamplingStateScope<BucketNumber>::Current();
508     TraceEventSamplingStateScope<BucketNumber>::Set(category_and_name);
509   }
510 
~TraceEventSamplingStateScope()511   ~TraceEventSamplingStateScope() {
512     TraceEventSamplingStateScope<BucketNumber>::Set(previous_state_);
513   }
514 
Current()515   static inline const char* Current() {
516     return reinterpret_cast<const char*>(TRACE_EVENT_API_ATOMIC_LOAD(
517       g_trace_state[BucketNumber]));
518   }
519 
Set(const char * category_and_name)520   static inline void Set(const char* category_and_name) {
521     TRACE_EVENT_API_ATOMIC_STORE(
522       g_trace_state[BucketNumber],
523       reinterpret_cast<TRACE_EVENT_API_ATOMIC_WORD>(
524         const_cast<char*>(category_and_name)));
525   }
526 
527  private:
528   const char* previous_state_;
529 };
530 
531 }  // namespace tracing_internals
532 }  // namespace skia
533 
534 #endif
535