ChromeTracingTracer.h

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/*
 * Copyright 2017 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
#ifndef ChromeTracingTracer_DEFINED
#define ChromeTracingTracer_DEFINED
 
#include "include/core/SkString.h"
#include "include/utils/SkEventTracer.h"
#include "src/base/SkSpinlock.h"
#include "src/core/SkTHash.h"
#include "tools/trace/EventTracingPriv.h"
 
class SkJSONWriter;
 
/**
 * A SkEventTracer implementation that logs events to JSON for viewing with chrome://tracing.
 */
class ChromeTracingTracer : public SkEventTracer {
public:
    ChromeTracingTracer(const char* filename);
    ~ChromeTracingTracer() override;
 
    SkEventTracer::Handle addTraceEvent(char            phase,
                                        const uint8_t*  categoryEnabledFlag,
                                        const char*     name,
                                        uint64_t        id,
                                        int             numArgs,
                                        const char**    argNames,
                                        const uint8_t*  argTypes,
                                        const uint64_t* argValues,
                                        uint8_t         flags) override;
 
    void updateTraceEventDuration(const uint8_t*        categoryEnabledFlag,
                                  const char*           name,
                                  SkEventTracer::Handle handle) override;
 
    const uint8_t* getCategoryGroupEnabled(const char* name) override {
        return fCategories.getCategoryGroupEnabled(name);
    }
 
    const char* getCategoryGroupName(const uint8_t* categoryEnabledFlag) override {
        return fCategories.getCategoryGroupName(categoryEnabledFlag);
    }
 
    // The Chrome tracer does not yet support splitting up trace output into sections.
    void newTracingSection(const char* name) override {}
 
private:
    void flush();
 
    enum {
        // Events are variable size, but most commonly 48 bytes, assuming 64-bit pointers and
        // reasonable packing. This is a first guess at a number that balances memory usage vs.
        // time overhead of allocating blocks.
        kBlockSize = 512 * 1024,
    };
 
    typedef std::unique_ptr<uint8_t[]> BlockPtr;
    struct TraceEventBlock {
        BlockPtr fBlock;
        int      fEventsInBlock;
    };
 
    void createBlock();
 
    Handle appendEvent(const void* data, size_t size);
 
    SkString                 fFilename;
    SkSpinlock               fMutex;
    SkEventTracingCategories fCategories;
 
    TraceEventBlock fCurBlock;
    size_t          fCurBlockUsed;
 
    skia_private::TArray<TraceEventBlock> fBlocks;
};
 
#endif