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      1 /*
      2  * Copyright 2014 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include "SkAtomics.h"
      9 #include "SkEventTracer.h"
     10 #include "SkOnce.h"
     11 
     12 #include <stdlib.h>
     13 
     14 class SkDefaultEventTracer : public SkEventTracer {
     15     SkEventTracer::Handle
     16         addTraceEvent(char phase,
     17                       const uint8_t* categoryEnabledFlag,
     18                       const char* name,
     19                       uint64_t id,
     20                       int numArgs,
     21                       const char** argNames,
     22                       const uint8_t* argTypes,
     23                       const uint64_t* argValues,
     24                       uint8_t flags) override { return 0; }
     25 
     26     void
     27         updateTraceEventDuration(const uint8_t* categoryEnabledFlag,
     28                                  const char* name,
     29                                  SkEventTracer::Handle handle) override {}
     30 
     31     const uint8_t* getCategoryGroupEnabled(const char* name) override {
     32         static uint8_t no = 0;
     33         return &no;
     34     }
     35     const char* getCategoryGroupName(
     36       const uint8_t* categoryEnabledFlag) override {
     37         static const char* dummy = "dummy";
     38         return dummy;
     39     }
     40 };
     41 
     42 // We prefer gUserTracer if it's been set, otherwise we fall back on a default tracer;
     43 static SkEventTracer* gUserTracer = nullptr;
     44 
     45 void SkEventTracer::SetInstance(SkEventTracer* tracer) {
     46     SkASSERT(nullptr == sk_atomic_load(&gUserTracer, sk_memory_order_acquire));
     47     sk_atomic_store(&gUserTracer, tracer, sk_memory_order_release);
     48     // An atomic load during process shutdown is probably overkill, but safe overkill.
     49     atexit([]() { delete sk_atomic_load(&gUserTracer, sk_memory_order_acquire); });
     50 }
     51 
     52 SkEventTracer* SkEventTracer::GetInstance() {
     53     if (SkEventTracer* tracer = sk_atomic_load(&gUserTracer, sk_memory_order_acquire)) {
     54         return tracer;
     55     }
     56     static SkOnce once;
     57     static SkDefaultEventTracer* defaultTracer;
     58     once([] { defaultTracer = new SkDefaultEventTracer; });
     59     return defaultTracer;
     60 }
     61