src/core/SkTraceEvent.h

// Copyright (c) 2014 Google Inc.
//
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This header file defines implementation details of how the trace macros in
// SkTraceEventCommon.h collect and store trace events. Anything not
// implementation-specific should go in SkTraceEventCommon.h instead of here.

#ifndef SkTraceEvent_DEFINED
#define SkTraceEvent_DEFINED

#include "SkEventTracer.h"
#include "SkTraceEventCommon.h"
#include <atomic>

////////////////////////////////////////////////////////////////////////////////
// Implementation specific tracing API definitions.

// Makes it easier to add traces with a simple TRACE_EVENT0("skia", TRACE_FUNC).
#if defined(_MSC_VER)
    #define TRACE_FUNC __FUNCSIG__
#else
    #define TRACE_FUNC __PRETTY_FUNCTION__
#endif

// By default, const char* argument values are assumed to have long-lived scope
// and will not be copied. Use this macro to force a const char* to be copied.
#define TRACE_STR_COPY(str) \
    skia::tracing_internals::TraceStringWithCopy(str)


#define INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE() \
    *INTERNAL_TRACE_EVENT_UID(category_group_enabled) & \
        (SkEventTracer::kEnabledForRecording_CategoryGroupEnabledFlags | \
         SkEventTracer::kEnabledForEventCallback_CategoryGroupEnabledFlags)

// Get a pointer to the enabled state of the given trace category. Only
// long-lived literal strings should be given as the category group. The
// returned pointer can be held permanently in a local static for example. If
// the unsigned char is non-zero, tracing is enabled. If tracing is enabled,
// TRACE_EVENT_API_ADD_TRACE_EVENT can be called. It's OK if tracing is disabled
// between the load of the tracing state and the call to
// TRACE_EVENT_API_ADD_TRACE_EVENT, because this flag only provides an early out
// for best performance when tracing is disabled.
// const uint8_t*
//     TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(const char* category_group)
#define TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED \
    SkEventTracer::GetInstance()->getCategoryGroupEnabled

// Add a trace event to the platform tracing system.
// SkEventTracer::Handle TRACE_EVENT_API_ADD_TRACE_EVENT(
//                    char phase,
//                    const uint8_t* category_group_enabled,
//                    const char* name,
//                    uint64_t id,
//                    int num_args,
//                    const char** arg_names,
//                    const uint8_t* arg_types,
//                    const uint64_t* arg_values,
//                    unsigned char flags)
#define TRACE_EVENT_API_ADD_TRACE_EVENT \
    SkEventTracer::GetInstance()->addTraceEvent

// Set the duration field of a COMPLETE trace event.
// void TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
//     const uint8_t* category_group_enabled,
//     const char* name,
//     SkEventTracer::Handle id)
#define TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION \
    SkEventTracer::GetInstance()->updateTraceEventDuration

// Defines visibility for classes in trace_event.h
#define TRACE_EVENT_API_CLASS_EXPORT SK_API

// We prepend this string to all category names, so that ALL Skia trace events are
// disabled by default when tracing in Chrome.
#define TRACE_CATEGORY_PREFIX "disabled-by-default-"

////////////////////////////////////////////////////////////////////////////////

// Implementation detail: trace event macros create temporary variables
// to keep instrumentation overhead low. These macros give each temporary
// variable a unique name based on the line number to prevent name collisions.
#define INTERNAL_TRACE_EVENT_UID3(a,b) \
    trace_event_unique_##a##b
#define INTERNAL_TRACE_EVENT_UID2(a,b) \
    INTERNAL_TRACE_EVENT_UID3(a,b)
#define INTERNAL_TRACE_EVENT_UID(name_prefix) \
    INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)

// Implementation detail: internal macro to create static category.
// No barriers are needed, because this code is designed to operate safely
// even when the unsigned char* points to garbage data (which may be the case
// on processors without cache coherency).
#define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES( \
    category_group, atomic, category_group_enabled) \
    category_group_enabled = \
        reinterpret_cast<const uint8_t*>(atomic.load(std::memory_order_relaxed)); \
    if (!category_group_enabled) { \
      category_group_enabled = TRACE_EVENT_API_GET_CATEGORY_GROUP_ENABLED(category_group); \
      atomic.store(reinterpret_cast<intptr_t>(category_group_enabled), \
                   std::memory_order_relaxed); \
    }

#define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group) \
    static std::atomic<intptr_t> INTERNAL_TRACE_EVENT_UID(atomic){0}; \
    const uint8_t* INTERNAL_TRACE_EVENT_UID(category_group_enabled); \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO_CUSTOM_VARIABLES( \
        TRACE_CATEGORY_PREFIX category_group, \
        INTERNAL_TRACE_EVENT_UID(atomic), \
        INTERNAL_TRACE_EVENT_UID(category_group_enabled));

// Implementation detail: internal macro to create static category and add
// event if the category is enabled.
#define INTERNAL_TRACE_EVENT_ADD(phase, category_group, name, flags, ...) \
    do { \
      INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
      if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
        skia::tracing_internals::AddTraceEvent( \
            phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, \
            skia::tracing_internals::kNoEventId, flags, ##__VA_ARGS__); \
      } \
    } while (0)

// Implementation detail: internal macro to create static category and add
// event if the category is enabled.
#define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category_group, name, id, \
                                         flags, ...) \
    do { \
      INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
      if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
        unsigned char trace_event_flags = flags | TRACE_EVENT_FLAG_HAS_ID; \
        skia::tracing_internals::TraceID trace_event_trace_id( \
            id, &trace_event_flags); \
        skia::tracing_internals::AddTraceEvent( \
            phase, INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
            name, trace_event_trace_id.data(), trace_event_flags, \
            ##__VA_ARGS__); \
      } \
    } while (0)

// Implementation detail: internal macro to create static category and add begin
// event if the category is enabled. Also adds the end event when the scope
// ends.
#define INTERNAL_TRACE_EVENT_ADD_SCOPED(category_group, name, ...) \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category_group); \
    skia::tracing_internals::ScopedTracer INTERNAL_TRACE_EVENT_UID(tracer); \
    do { \
        if (INTERNAL_TRACE_EVENT_CATEGORY_GROUP_ENABLED_FOR_RECORDING_MODE()) { \
          SkEventTracer::Handle h = skia::tracing_internals::AddTraceEvent( \
              TRACE_EVENT_PHASE_COMPLETE, \
              INTERNAL_TRACE_EVENT_UID(category_group_enabled), \
              name, skia::tracing_internals::kNoEventId, \
              TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
          INTERNAL_TRACE_EVENT_UID(tracer).Initialize( \
              INTERNAL_TRACE_EVENT_UID(category_group_enabled), name, h); \
        } \
    } while (0)

namespace skia {
namespace tracing_internals {

// Specify these values when the corresponding argument of AddTraceEvent is not
// used.
const int kZeroNumArgs = 0;
const uint64_t kNoEventId = 0;

// TraceID encapsulates an ID that can either be an integer or pointer. Pointers
// are by default mangled with the Process ID so that they are unlikely to
// collide when the same pointer is used on different processes.
class TraceID {
public:
    TraceID(const void* id, unsigned char* flags)
            : data_(static_cast<uint64_t>(reinterpret_cast<uintptr_t>(id))) {
        *flags |= TRACE_EVENT_FLAG_MANGLE_ID;
    }
    TraceID(uint64_t id, unsigned char* flags)
        : data_(id) { (void)flags; }
    TraceID(unsigned int id, unsigned char* flags)
        : data_(id) { (void)flags; }
    TraceID(unsigned short id, unsigned char* flags)
        : data_(id) { (void)flags; }
    TraceID(unsigned char id, unsigned char* flags)
        : data_(id) { (void)flags; }
    TraceID(long long id, unsigned char* flags)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
    TraceID(long id, unsigned char* flags)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
    TraceID(int id, unsigned char* flags)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
    TraceID(short id, unsigned char* flags)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }
    TraceID(signed char id, unsigned char* flags)
        : data_(static_cast<uint64_t>(id)) { (void)flags; }

    uint64_t data() const { return data_; }

private:
    uint64_t data_;
};

// Simple union to store various types as uint64_t.
union TraceValueUnion {
  bool as_bool;
  uint64_t as_uint;
  long long as_int;
  double as_double;
  const void* as_pointer;
  const char* as_string;
};

// Simple container for const char* that should be copied instead of retained.
class TraceStringWithCopy {
 public:
  explicit TraceStringWithCopy(const char* str) : str_(str) {}
  operator const char* () const { return str_; }
 private:
  const char* str_;
};

// Define SetTraceValue for each allowed type. It stores the type and
// value in the return arguments. This allows this API to avoid declaring any
// structures so that it is portable to third_party libraries.
#define INTERNAL_DECLARE_SET_TRACE_VALUE(actual_type, \
                                         union_member, \
                                         value_type_id) \
    static inline void SetTraceValue( \
        actual_type arg, \
        unsigned char* type, \
        uint64_t* value) { \
      TraceValueUnion type_value; \
      type_value.union_member = arg; \
      *type = value_type_id; \
      *value = type_value.as_uint; \
    }
// Simpler form for int types that can be safely casted.
#define INTERNAL_DECLARE_SET_TRACE_VALUE_INT(actual_type, \
                                             value_type_id) \
    static inline void SetTraceValue( \
        actual_type arg, \
        unsigned char* type, \
        uint64_t* value) { \
      *type = value_type_id; \
      *value = static_cast<uint64_t>(arg); \
    }

INTERNAL_DECLARE_SET_TRACE_VALUE_INT(uint64_t, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned int, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned short, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned char, TRACE_VALUE_TYPE_UINT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long long, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(long, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(int, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(short, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE_INT(signed char, TRACE_VALUE_TYPE_INT)
INTERNAL_DECLARE_SET_TRACE_VALUE(bool, as_bool, TRACE_VALUE_TYPE_BOOL)
INTERNAL_DECLARE_SET_TRACE_VALUE(double, as_double, TRACE_VALUE_TYPE_DOUBLE)
INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, as_pointer, TRACE_VALUE_TYPE_POINTER)
INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, as_string, TRACE_VALUE_TYPE_STRING)
INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&, as_string,
                                 TRACE_VALUE_TYPE_COPY_STRING)

#undef INTERNAL_DECLARE_SET_TRACE_VALUE
#undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT

// These AddTraceEvent and AddTraceEvent template
// functions are defined here instead of in the macro, because the arg_values
// could be temporary objects, such as std::string. In order to store
// pointers to the internal c_str and pass through to the tracing API,
// the arg_values must live throughout these procedures.

static inline SkEventTracer::Handle
AddTraceEvent(
    char phase,
    const uint8_t* category_group_enabled,
    const char* name,
    uint64_t id,
    unsigned char flags) {
  return TRACE_EVENT_API_ADD_TRACE_EVENT(
      phase, category_group_enabled, name, id,
      kZeroNumArgs, nullptr, nullptr, nullptr, flags);
}

template<class ARG1_TYPE>
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 int num_args = 1;
  uint8_t arg_types[1];
  uint64_t arg_values[1];
  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
  return TRACE_EVENT_API_ADD_TRACE_EVENT(
      phase, category_group_enabled, name, id,
      num_args, &arg1_name, arg_types, arg_values, flags);
}

template<class ARG1_TYPE, class ARG2_TYPE>
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) {
  const int num_args = 2;
  const char* arg_names[2] = { arg1_name, arg2_name };
  unsigned char arg_types[2];
  uint64_t arg_values[2];
  SetTraceValue(arg1_val, &arg_types[0], &arg_values[0]);
  SetTraceValue(arg2_val, &arg_types[1], &arg_values[1]);
  return TRACE_EVENT_API_ADD_TRACE_EVENT(
      phase, category_group_enabled, name, id,
      num_args, arg_names, arg_types, arg_values, flags);
}

// Used by TRACE_EVENTx macros. Do not use directly.
class TRACE_EVENT_API_CLASS_EXPORT ScopedTracer {
 public:
  // Note: members of data_ intentionally left uninitialized. See Initialize.
  ScopedTracer() : p_data_(nullptr) {}

  ~ScopedTracer() {
    if (p_data_ && *data_.category_group_enabled)
      TRACE_EVENT_API_UPDATE_TRACE_EVENT_DURATION(
          data_.category_group_enabled, data_.name, data_.event_handle);
  }

  void Initialize(const uint8_t* category_group_enabled,
                  const char* name,
                  SkEventTracer::Handle event_handle) {
    data_.category_group_enabled = category_group_enabled;
    data_.name = name;
    data_.event_handle = event_handle;
    p_data_ = &data_;
  }

 private:
  // This Data struct workaround is to avoid initializing all the members
  // in Data during construction of this object, since this object is always
  // constructed, even when tracing is disabled. If the members of Data were
  // members of this class instead, compiler warnings occur about potential
  // uninitialized accesses.
  struct Data {
    const uint8_t* category_group_enabled;
    const char* name;
    SkEventTracer::Handle event_handle;
  };
  Data* p_data_;
  Data data_;
};

}  // namespace tracing_internals
}  // namespace skia

#endif