TraceEvent.h   [plain text]

/*
 * Copyright (C) 2011 Google Inc. All rights reserved.
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 *
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// Trace events are for tracking application performance and resource usage.
// Macros are provided to track:
//    Begin and end of function calls
//    Counters
//
// Events are issued against categories. Whereas LOG's
// categories are statically defined, TRACE categories are created
// implicitly with a string. For example:
//   TRACE_EVENT_INSTANT0("MY_SUBSYSTEM", "SomeImportantEvent")
//
// Events can be INSTANT, or can be pairs of BEGIN and END in the same scope:
//   TRACE_EVENT_BEGIN0("MY_SUBSYSTEM", "SomethingCostly")
//   doSomethingCostly()
//   TRACE_EVENT_END0("MY_SUBSYSTEM", "SomethingCostly")
// Note: our tools can't always determine the correct BEGIN/END pairs unless
// these are used in the same scope. Use ASYNC_BEGIN/ASYNC_END macros if you need them
// to be in separate scopes.
//
// A common use case is to trace entire function scopes. This
// issues a trace BEGIN and END automatically:
//   void doSomethingCostly() {
//     TRACE_EVENT0("MY_SUBSYSTEM", "doSomethingCostly");
//     ...
//   }
//
// Additional parameters can be associated with an event:
//   void doSomethingCostly2(int howMuch) {
//     TRACE_EVENT1("MY_SUBSYSTEM", "doSomethingCostly",
//         "howMuch", howMuch);
//     ...
//   }
//
// The trace system will automatically add to this information the
// current process id, thread id, and a timestamp in microseconds.
//
// To trace an asynchronous procedure such as an IPC send/receive, use ASYNC_BEGIN and
// ASYNC_END:
//   [single threaded sender code]
//     static int send_count = 0;
//     ++send_count;
//     TRACE_EVENT_ASYNC_BEGIN0("ipc", "message", send_count);
//     Send(new MyMessage(send_count));
//   [receive code]
//     void OnMyMessage(send_count) {
//       TRACE_EVENT_ASYNC_END0("ipc", "message", send_count);
//     }
// The third parameter is a unique ID to match ASYNC_BEGIN/ASYNC_END pairs.
// ASYNC_BEGIN and ASYNC_END can occur on any thread of any traced process. Pointers can
// be used for the ID parameter, and they will be mangled internally so that
// the same pointer on two different processes will not match. For example:
//   class MyTracedClass {
//    public:
//     MyTracedClass() {
//       TRACE_EVENT_ASYNC_BEGIN0("category", "MyTracedClass", this);
//     }
//     ~MyTracedClass() {
//       TRACE_EVENT_ASYNC_END0("category", "MyTracedClass", this);
//     }
//   }
//
// Trace event also supports counters, which is a way to track a quantity
// as it varies over time. Counters are created with the following macro:
//   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter", g_myCounterValue);
//
// Counters are process-specific. The macro itself can be issued from any
// thread, however.
//
// Sometimes, you want to track two counters at once. You can do this with two
// counter macros:
//   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter0", g_myCounterValue[0]);
//   TRACE_COUNTER1("MY_SUBSYSTEM", "myCounter1", g_myCounterValue[1]);
// Or you can do it with a combined macro:
//   TRACE_COUNTER2("MY_SUBSYSTEM", "myCounter",
//       "bytesPinned", g_myCounterValue[0],
//       "bytesAllocated", g_myCounterValue[1]);
// This indicates to the tracing UI that these counters should be displayed
// in a single graph, as a summed area chart.
//
// Since counters are in a global namespace, you may want to disembiguate with a
// unique ID, by using the TRACE_COUNTER_ID* variations.
//
// By default, trace collection is compiled in, but turned off at runtime.
// Collecting trace data is the responsibility of the embedding
// application. In Chrome's case, navigating to about:tracing will turn on
// tracing and display data collected across all active processes.
//
//
// Memory scoping note:
// Tracing copies the pointers, not the string content, of the strings passed
// in for category, name, and arg_names. Thus, the following code will
// cause problems:
//     char* str = strdup("impprtantName");
//     TRACE_EVENT_INSTANT0("SUBSYSTEM", str);  // BAD!
//     free(str);                   // Trace system now has dangling pointer
//
// To avoid this issue with the |name| and |arg_name| parameters, use the
// TRACE_EVENT_COPY_XXX overloads of the macros at additional runtime overhead.
// Notes: The category must always be in a long-lived char* (i.e. static const).
//        The |arg_values|, when used, are always deep copied with the _COPY
//        macros.
//
// When are string argument values copied:
// const char* arg_values are only referenced by default:
//     TRACE_EVENT1("category", "name",
//                  "arg1", "literal string is only referenced");
// Use TRACE_STR_COPY to force copying of a const char*:
//     TRACE_EVENT1("category", "name",
//                  "arg1", TRACE_STR_COPY("string will be copied"));
// std::string arg_values are always copied:
//     TRACE_EVENT1("category", "name",
//                  "arg1", std::string("string will be copied"));
//
//
// Thread Safety:
// A thread safe singleton and mutex are used for thread safety. Category
// enabled flags are used to limit the performance impact when the system
// is not enabled.
//
// TRACE_EVENT macros first cache a pointer to a category. The categories are
// statically allocated and safe at all times, even after exit. Fetching a
// category is protected by the TraceLog::lock_. Multiple threads initializing
// the static variable is safe, as they will be serialized by the lock and
// multiple calls will return the same pointer to the category.
//
// Then the category_enabled flag is checked. This is a unsigned char, and
// not intended to be multithread safe. It optimizes access to addTraceEvent
// which is threadsafe internally via TraceLog::lock_. The enabled flag may
// cause some threads to incorrectly call or skip calling addTraceEvent near
// the time of the system being enabled or disabled. This is acceptable as
// we tolerate some data loss while the system is being enabled/disabled and
// because addTraceEvent is threadsafe internally and checks the enabled state
// again under lock.
//
// Without the use of these static category pointers and enabled flags all
// trace points would carry a significant performance cost of aquiring a lock
// and resolving the category.

#ifndef TraceEvent_h
#define TraceEvent_h

#include "PlatformSupport.h"

#include <wtf/DynamicAnnotations.h>
#include <wtf/text/CString.h>

// Issues begin trace event here and end trace event when the current scope ends.
#define TRACE_EVENT(name, id, extra) TRACE_EVENT2("webkit", name, "id", id, "extra", extra)

// 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) \
    WebCore::TraceEvent::TraceStringWithCopy(str)

// Records a pair of begin and end events called "name" for the current
// scope, with 0, 1 or 2 associated arguments. If the category is not
// enabled, then this does nothing.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
#define TRACE_EVENT0(category, name) \
    INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name)
#define TRACE_EVENT1(category, name, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, arg1_name, arg1_val)
#define TRACE_EVENT2(category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, arg1_name, arg1_val, \
        arg2_name, arg2_val)

// Records a single event called "name" immediately, with 0, 1 or 2
// associated arguments. If the category is not enabled, then this
// does nothing.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
#define TRACE_EVENT_INSTANT0(category, name) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
        category, name, TRACE_EVENT_FLAG_NONE)
#define TRACE_EVENT_INSTANT1(category, name, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
#define TRACE_EVENT_INSTANT2(category, name, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
        arg2_name, arg2_val)
#define TRACE_EVENT_COPY_INSTANT0(category, name) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
        category, name, TRACE_EVENT_FLAG_COPY)
#define TRACE_EVENT_COPY_INSTANT1(category, name, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
#define TRACE_EVENT_COPY_INSTANT2(category, name, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_INSTANT, \
        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
        arg2_name, arg2_val)

// Records a single BEGIN event called "name" immediately, with 0, 1 or 2
// associated arguments. If the category is not enabled, then this
// does nothing.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
#define TRACE_EVENT_BEGIN0(category, name) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
        category, name, TRACE_EVENT_FLAG_NONE)
#define TRACE_EVENT_BEGIN1(category, name, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
#define TRACE_EVENT_BEGIN2(category, name, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
        arg2_name, arg2_val)
#define TRACE_EVENT_COPY_BEGIN0(category, name) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
        category, name, TRACE_EVENT_FLAG_COPY)
#define TRACE_EVENT_COPY_BEGIN1(category, name, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
#define TRACE_EVENT_COPY_BEGIN2(category, name, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_BEGIN, \
        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
        arg2_name, arg2_val)

// Records a single END event for "name" immediately. If the category
// is not enabled, then this does nothing.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
#define TRACE_EVENT_END0(category, name) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
        category, name, TRACE_EVENT_FLAG_NONE)
#define TRACE_EVENT_END1(category, name, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
#define TRACE_EVENT_END2(category, name, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
        category, name, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val, \
        arg2_name, arg2_val)
#define TRACE_EVENT_COPY_END0(category, name) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
        category, name, TRACE_EVENT_FLAG_COPY)
#define TRACE_EVENT_COPY_END1(category, name, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val)
#define TRACE_EVENT_COPY_END2(category, name, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_END, \
        category, name, TRACE_EVENT_FLAG_COPY, arg1_name, arg1_val, \
        arg2_name, arg2_val)

// Time threshold event:
// Only record the event if the duration is greater than the specified
// threshold_us (time in microseconds).
// Records a pair of begin and end events called "name" for the current
// scope, with 0, 1 or 2 associated arguments. If the category is not
// enabled, then this does nothing.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
#define TRACE_EVENT_IF_LONGER_THAN0(threshold_us, category, name) \
    INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN(threshold_us, category, name)
#define TRACE_EVENT_IF_LONGER_THAN1( \
    threshold_us, category, name, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN( \
        threshold_us, category, name, arg1_name, arg1_val)
#define TRACE_EVENT_IF_LONGER_THAN2( \
    threshold_us, category, name, arg1_name, arg1_val, arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN( \
        threshold_us, category, name, arg1_name, arg1_val, arg2_name, arg2_val)

// Records the value of a counter called "name" immediately. Value
// must be representable as a 32 bit integer.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
#define TRACE_COUNTER1(category, name, value) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
        category, name, TRACE_EVENT_FLAG_NONE, \
        "value", static_cast<int>(value))
#define TRACE_COPY_COUNTER1(category, name, value) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
        category, name, TRACE_EVENT_FLAG_COPY, \
        "value", static_cast<int>(value))

// Records the values of a multi-parted counter called "name" immediately.
// The UI will treat value1 and value2 as parts of a whole, displaying their
// values as a stacked-bar chart.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
#define TRACE_COUNTER2(category, name, value1_name, value1_val, \
        value2_name, value2_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
        category, name, TRACE_EVENT_FLAG_NONE, \
        value1_name, static_cast<int>(value1_val), \
        value2_name, static_cast<int>(value2_val))
#define TRACE_COPY_COUNTER2(category, name, value1_name, value1_val, \
        value2_name, value2_val) \
    INTERNAL_TRACE_EVENT_ADD(TRACE_EVENT_PHASE_COUNTER, \
        category, name, TRACE_EVENT_FLAG_COPY, \
        value1_name, static_cast<int>(value1_val), \
        value2_name, static_cast<int>(value2_val))

// Records the value of a counter called "name" immediately. Value
// must be representable as a 32 bit integer.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
// - |id| is used to disambiguate counters with the same name. It must either
//   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
//   will be xored with a hash of the process ID so that the same pointer on
//   two different processes will not collide.
#define TRACE_COUNTER_ID1(category, name, id, value) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
        category, name, id, TRACE_EVENT_FLAG_NONE, \
        "value", static_cast<int>(value))
#define TRACE_COPY_COUNTER_ID1(category, name, id, value) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
        category, name, id, TRACE_EVENT_FLAG_COPY, \
        "value", static_cast<int>(value))

// Records the values of a multi-parted counter called "name" immediately.
// The UI will treat value1 and value2 as parts of a whole, displaying their
// values as a stacked-bar chart.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
// - |id| is used to disambiguate counters with the same name. It must either
//   be a pointer or an integer value up to 64 bits. If it's a pointer, the bits
//   will be xored with a hash of the process ID so that the same pointer on
//   two different processes will not collide.
#define TRACE_COUNTER_ID2(category, name, id, value1_name, value1_val, \
        value2_name, value2_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
        category, name, id, TRACE_EVENT_FLAG_NONE, \
        value1_name, static_cast<int>(value1_val), \
        value2_name, static_cast<int>(value2_val))
#define TRACE_COPY_COUNTER_ID2(category, name, id, value1_name, value1_val, \
        value2_name, value2_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_COUNTER, \
        category, name, id, TRACE_EVENT_FLAG_COPY, \
        value1_name, static_cast<int>(value1_val), \
        value2_name, static_cast<int>(value2_val))

// Records a single ASYNC_BEGIN event called "name" immediately, with 0, 1 or 2
// associated arguments. If the category is not enabled, then this
// does nothing.
// - category and name strings must have application lifetime (statics or
//   literals). They may not include " chars.
// - |id| is used to match the ASYNC_BEGIN event with the ASYNC_END event. ASYNC
//   events are considered to match if their category, name and id values all
//   match. |id| must either be a pointer or an integer value up to 64 bits. If
//   it's a pointer, the bits will be xored with a hash of the process ID so
//   that the same pointer on two different processes will not collide.
// An asynchronous operation can consist of multiple phases. The first phase is
// defined by the ASYNC_BEGIN calls. Additional phases can be defined using the
// ASYNC_STEP_BEGIN macros. When the operation completes, call ASYNC_END.
// An async operation can span threads and processes, but all events in that
// operation must use the same |name| and |id|. Each event can have its own
// args.
#define TRACE_EVENT_ASYNC_BEGIN0(category, name, id) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
        category, name, id, TRACE_EVENT_FLAG_NONE)
#define TRACE_EVENT_ASYNC_BEGIN1(category, name, id, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
        category, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
#define TRACE_EVENT_ASYNC_BEGIN2(category, name, id, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
        category, name, id, TRACE_EVENT_FLAG_NONE, \
        arg1_name, arg1_val, arg2_name, arg2_val)
#define TRACE_EVENT_COPY_ASYNC_BEGIN0(category, name, id) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
        category, name, id, TRACE_EVENT_FLAG_COPY)
#define TRACE_EVENT_COPY_ASYNC_BEGIN1(category, name, id, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
        category, name, id, TRACE_EVENT_FLAG_COPY, \
        arg1_name, arg1_val)
#define TRACE_EVENT_COPY_ASYNC_BEGIN2(category, name, id, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_BEGIN, \
        category, name, id, TRACE_EVENT_FLAG_COPY, \
        arg1_name, arg1_val, arg2_name, arg2_val)

// Records a single ASYNC_STEP event for |step| immediately. If the category
// is not enabled, then this does nothing. The |name| and |id| must match the
// ASYNC_BEGIN event above. The |step| param identifies this step within the
// async event. This should be called at the beginning of the next phase of an
// asynchronous operation.
#define TRACE_EVENT_ASYNC_BEGIN_STEP0(category, name, id, step) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP, \
        category, name, id, TRACE_EVENT_FLAG_NONE, "step", step)
#define TRACE_EVENT_ASYNC_BEGIN_STEP1(category, name, id, step, \
                                      arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP, \
        category, name, id, TRACE_EVENT_FLAG_NONE, "step", step, \
        arg1_name, arg1_val)
#define TRACE_EVENT_COPY_ASYNC_BEGIN_STEP0(category, name, id, step) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP, \
        category, name, id, TRACE_EVENT_FLAG_COPY, "step", step)
#define TRACE_EVENT_COPY_ASYNC_BEGIN_STEP1(category, name, id, step, \
        arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_STEP, \
        category, name, id, TRACE_EVENT_FLAG_COPY, "step", step, \
        arg1_name, arg1_val)

// Records a single ASYNC_END event for "name" immediately. If the category
// is not enabled, then this does nothing.
#define TRACE_EVENT_ASYNC_END0(category, name, id) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
        category, name, id, TRACE_EVENT_FLAG_NONE)
#define TRACE_EVENT_ASYNC_END1(category, name, id, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
        category, name, id, TRACE_EVENT_FLAG_NONE, arg1_name, arg1_val)
#define TRACE_EVENT_ASYNC_END2(category, name, id, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
        category, name, id, TRACE_EVENT_FLAG_NONE, \
        arg1_name, arg1_val, arg2_name, arg2_val)
#define TRACE_EVENT_COPY_ASYNC_END0(category, name, id) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
        category, name, id, TRACE_EVENT_FLAG_COPY)
#define TRACE_EVENT_COPY_ASYNC_END1(category, name, id, arg1_name, arg1_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
        category, name, id, TRACE_EVENT_FLAG_COPY, \
        arg1_name, arg1_val)
#define TRACE_EVENT_COPY_ASYNC_END2(category, name, id, arg1_name, arg1_val, \
        arg2_name, arg2_val) \
    INTERNAL_TRACE_EVENT_ADD_WITH_ID(TRACE_EVENT_PHASE_ASYNC_END, \
        category, name, id, TRACE_EVENT_FLAG_COPY, \
        arg1_name, arg1_val, arg2_name, arg2_val)

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

// Get a pointer to the enabled state of the given trace category. Only
// long-lived literal strings should be given as the category name. 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 unsigned char*
//     TRACE_EVENT_API_GET_CATEGORY_ENABLED(const char* category_name)
#define TRACE_EVENT_API_GET_CATEGORY_ENABLED \
    WebCore::PlatformSupport::getTraceCategoryEnabledFlag

// Add a trace event to the platform tracing system. Returns thresholdBeginId
// for use in a corresponding end TRACE_EVENT_API_ADD_TRACE_EVENT call.
// int TRACE_EVENT_API_ADD_TRACE_EVENT(
//                    char phase,
//                    const unsigned char* category_enabled,
//                    const char* name,
//                    unsigned long long id,
//                    int num_args,
//                    const char** arg_names,
//                    const unsigned char* arg_types,
//                    const unsigned long long* arg_values,
//                    int thresholdBeginID,
//                    long long threshold,
//                    unsigned char flags)
#define TRACE_EVENT_API_ADD_TRACE_EVENT \
    WebCore::PlatformSupport::addTraceEvent

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

// 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 collissions.
#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 INTERNALTRACEEVENTUID(name_prefix) \
    INTERNAL_TRACE_EVENT_UID2(name_prefix, __LINE__)

// Implementation detail: internal macro to create static category.
// - WTF_ANNOTATE_BENIGN_RACE, see Thread Safety above.
#define INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category) \
    static const unsigned char* INTERNALTRACEEVENTUID(catstatic) = 0; \
    WTF_ANNOTATE_BENIGN_RACE(&INTERNALTRACEEVENTUID(catstatic), \
                             "trace_event category"); \
    if (!INTERNALTRACEEVENTUID(catstatic)) \
      INTERNALTRACEEVENTUID(catstatic) = \
          TRACE_EVENT_API_GET_CATEGORY_ENABLED(category);

// Implementation detail: internal macro to create static category and add
// event if the category is enabled.
#if COMPILER(MSVC7_OR_LOWER)
#define INTERNAL_TRACE_EVENT_ADD(ignore) ((void)0)
#else
#define INTERNAL_TRACE_EVENT_ADD(phase, category, name, flags, ...) \
    do { \
        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
        if (*INTERNALTRACEEVENTUID(catstatic)) { \
            WebCore::TraceEvent::addTraceEvent( \
                phase, INTERNALTRACEEVENTUID(catstatic), name, \
                WebCore::TraceEvent::noEventId, flags, ##__VA_ARGS__); \
        } \
    } while (0)
#endif

// 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.
#if COMPILER(MSVC7_OR_LOWER)
#define INTERNAL_TRACE_EVENT_ADD_SCOPED(ignore) ((void)0)
#else
#define INTERNAL_TRACE_EVENT_ADD_SCOPED(category, name, ...) \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
    WebCore::TraceEvent::TraceEndOnScopeClose \
        INTERNALTRACEEVENTUID(profileScope); \
    if (*INTERNALTRACEEVENTUID(catstatic)) { \
      WebCore::TraceEvent::addTraceEvent( \
          TRACE_EVENT_PHASE_BEGIN, \
          INTERNALTRACEEVENTUID(catstatic), \
          name, WebCore::TraceEvent::noEventId, \
          TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
      INTERNALTRACEEVENTUID(profileScope).initialize( \
          INTERNALTRACEEVENTUID(catstatic), name); \
    }
#endif

// 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. If the elapsed time is < threshold time, the begin/end pair is erased.
#if COMPILER(MSVC7_OR_LOWER)
#define INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN(ignore) ((void)0)
#else
#define INTERNAL_TRACE_EVENT_ADD_SCOPED_IF_LONGER_THAN(threshold, \
        category, name, ...) \
    INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
    WebCore::TraceEvent::TraceEndOnScopeCloseThreshold \
        INTERNALTRACEEVENTUID(profileScope); \
    if (*INTERNALTRACEEVENTUID(catstatic)) { \
      int INTERNALTRACEEVENTUID(begin_event_id) = \
        WebCore::TraceEvent::addTraceEvent( \
            TRACE_EVENT_PHASE_BEGIN, \
            INTERNALTRACEEVENTUID(catstatic), \
            name, WebCore::TraceEvent::noEventId, \
            TRACE_EVENT_FLAG_NONE, ##__VA_ARGS__); \
      INTERNALTRACEEVENTUID(profileScope).initialize( \
          INTERNALTRACEEVENTUID(catstatic), name, \
          INTERNALTRACEEVENTUID(begin_event_id), threshold); \
    }
#endif

// Implementation detail: internal macro to create static category and add
// event if the category is enabled.
#if COMPILER(MSVC7_OR_LOWER)
#define INTERNAL_TRACE_EVENT_ADD_WITH_ID(ignore) ((void)0)
#else
#define INTERNAL_TRACE_EVENT_ADD_WITH_ID(phase, category, name, id, flags, \
                                         ...) \
    do { \
        INTERNAL_TRACE_EVENT_GET_CATEGORY_INFO(category); \
        if (*INTERNALTRACEEVENTUID(catstatic)) { \
            unsigned char traceEventFlags = flags | TRACE_EVENT_FLAG_HAS_ID; \
            WebCore::TraceEvent::TraceID traceEventTraceID( \
                id, &traceEventFlags); \
            WebCore::TraceEvent::addTraceEvent( \
                phase, INTERNALTRACEEVENTUID(catstatic), \
                name, traceEventTraceID.data(), traceEventFlags, \
                ##__VA_ARGS__); \
        } \
    } while (0)
#endif

// Notes regarding the following definitions:
// New values can be added and propagated to third party libraries, but existing
// definitions must never be changed, because third party libraries may use old
// definitions.

// Phase indicates the nature of an event entry. E.g. part of a begin/end pair.
#define TRACE_EVENT_PHASE_BEGIN    ('B')
#define TRACE_EVENT_PHASE_END      ('E')
#define TRACE_EVENT_PHASE_INSTANT  ('I')
#define TRACE_EVENT_PHASE_ASYNC_BEGIN ('S')
#define TRACE_EVENT_PHASE_ASYNC_STEP  ('T')
#define TRACE_EVENT_PHASE_ASYNC_END   ('F')
#define TRACE_EVENT_PHASE_METADATA ('M')
#define TRACE_EVENT_PHASE_COUNTER  ('C')

// Flags for changing the behavior of TRACE_EVENT_API_ADD_TRACE_EVENT.
#define TRACE_EVENT_FLAG_NONE        (static_cast<unsigned char>(0))
#define TRACE_EVENT_FLAG_COPY        (static_cast<unsigned char>(1 << 0))
#define TRACE_EVENT_FLAG_HAS_ID      (static_cast<unsigned char>(1 << 1))
#define TRACE_EVENT_FLAG_MANGLE_ID   (static_cast<unsigned char>(1 << 2))

// Type values for identifying types in the TraceValue union.
#define TRACE_VALUE_TYPE_BOOL         (static_cast<unsigned char>(1))
#define TRACE_VALUE_TYPE_UINT         (static_cast<unsigned char>(2))
#define TRACE_VALUE_TYPE_INT          (static_cast<unsigned char>(3))
#define TRACE_VALUE_TYPE_DOUBLE       (static_cast<unsigned char>(4))
#define TRACE_VALUE_TYPE_POINTER      (static_cast<unsigned char>(5))
#define TRACE_VALUE_TYPE_STRING       (static_cast<unsigned char>(6))
#define TRACE_VALUE_TYPE_COPY_STRING  (static_cast<unsigned char>(7))


namespace WebCore {

namespace TraceEvent {

// Specify these values when the corresponding argument of addTraceEvent is not
// used.
const int zeroNumArgs = 0;
const int noThresholdBeginId = -1;
const long long noThresholdValue = 0;
const unsigned long long noEventId = 0;

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

    unsigned long long data() const { return m_data; }

private:
    unsigned long long m_data;
};

// Simple union to store various types as unsigned long long.
union TraceValueUnion {
    bool m_bool;
    unsigned long long m_uint;
    long long m_int;
    double m_double;
    const void* m_pointer;
    const char* m_string;
};

// Simple container for const char* that should be copied instead of retained.
class TraceStringWithCopy {
public:
    explicit TraceStringWithCopy(const char* str) : m_str(str) { }
    operator const char* () const { return m_str; }
private:
    const char* m_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, \
                                     unsigned long long* value) { \
        TraceValueUnion typeValue; \
        typeValue.union_member = arg; \
        *type = value_type_id; \
        *value = typeValue.m_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, \
                                     unsigned long long* value) { \
        *type = value_type_id; \
        *value = static_cast<unsigned long long>(arg); \
    }

INTERNAL_DECLARE_SET_TRACE_VALUE_INT(unsigned long long, 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(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, m_bool, TRACE_VALUE_TYPE_BOOL)
INTERNAL_DECLARE_SET_TRACE_VALUE(double, m_double, TRACE_VALUE_TYPE_DOUBLE)
INTERNAL_DECLARE_SET_TRACE_VALUE(const void*, m_pointer,
                                 TRACE_VALUE_TYPE_POINTER)
INTERNAL_DECLARE_SET_TRACE_VALUE(const char*, m_string,
                                 TRACE_VALUE_TYPE_STRING)
INTERNAL_DECLARE_SET_TRACE_VALUE(const TraceStringWithCopy&, m_string,
                                 TRACE_VALUE_TYPE_COPY_STRING)

#undef INTERNAL_DECLARE_SET_TRACE_VALUE
#undef INTERNAL_DECLARE_SET_TRACE_VALUE_INT

// WTF::String version of setTraceValue so that trace arguments can be strings.
static inline void setTraceValue(const WTF::CString& arg,
                                 unsigned char* type,
                                 unsigned long long* value) {
    TraceValueUnion typeValue;
    typeValue.m_string = arg.data();
    *type = TRACE_VALUE_TYPE_COPY_STRING;
    *value = typeValue.m_uint;
}

// These addTraceEvent template functions are defined here instead of in the
// macro, because the arg values could be temporary string objects. 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 int addTraceEvent(char phase,
                                const unsigned char* categoryEnabled,
                                const char* name,
                                unsigned long long id,
                                unsigned char flags) {
    return TRACE_EVENT_API_ADD_TRACE_EVENT(
        phase, categoryEnabled, name, id,
        zeroNumArgs, 0, 0, 0,
        noThresholdBeginId, noThresholdValue, flags);
}

template<class ARG1_TYPE>
static inline int addTraceEvent(char phase,
                                const unsigned char* categoryEnabled,
                                const char* name,
                                unsigned long long id,
                                unsigned char flags,
                                const char* arg1Name,
                                const ARG1_TYPE& arg1Val) {
    const int numArgs = 1;
    unsigned char argTypes[1];
    unsigned long long argValues[1];
    setTraceValue(arg1Val, &argTypes[0], &argValues[0]);
    return TRACE_EVENT_API_ADD_TRACE_EVENT(
        phase, categoryEnabled, name, id,
        numArgs, &arg1Name, argTypes, argValues,
        noThresholdBeginId, noThresholdValue, flags);
}

template<class ARG1_TYPE, class ARG2_TYPE>
static inline int addTraceEvent(char phase,
                                const unsigned char* categoryEnabled,
                                const char* name,
                                unsigned long long id,
                                unsigned char flags,
                                const char* arg1Name,
                                const ARG1_TYPE& arg1Val,
                                const char* arg2Name,
                                const ARG2_TYPE& arg2Val) {
    const int numArgs = 2;
    const char* argNames[2] = { arg1Name, arg2Name };
    unsigned char argTypes[2];
    unsigned long long argValues[2];
    setTraceValue(arg1Val, &argTypes[0], &argValues[0]);
    setTraceValue(arg2Val, &argTypes[1], &argValues[1]);
    return TRACE_EVENT_API_ADD_TRACE_EVENT(
        phase, categoryEnabled, name, id,
        numArgs, argNames, argTypes, argValues,
        noThresholdBeginId, noThresholdValue, flags);
}

// Used by TRACE_EVENTx macro. Do not use directly.
class TraceEndOnScopeClose {
public:
    // Note: members of m_data intentionally left uninitialized. See initialize.
    TraceEndOnScopeClose() : m_pdata(0) { }
    ~TraceEndOnScopeClose()
    {
        if (m_pdata)
            addEventIfEnabled();
    }

    void initialize(const unsigned char* categoryEnabled,
                    const char* name)
    {
        m_data.categoryEnabled = categoryEnabled;
        m_data.name = name;
        m_pdata = &m_data;
    }

private:
    // Add the end event if the category is still enabled.
    void addEventIfEnabled()
    {
        // Only called when m_pdata is non-null.
        if (*m_pdata->categoryEnabled) {
            TRACE_EVENT_API_ADD_TRACE_EVENT(
                TRACE_EVENT_PHASE_END,
                m_pdata->categoryEnabled,
                m_pdata->name, noEventId,
                zeroNumArgs, 0, 0, 0,
                noThresholdBeginId, noThresholdValue, TRACE_EVENT_FLAG_NONE);
        }
    }

    // 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 unsigned char* categoryEnabled;
        const char* name;
    };
    Data* m_pdata;
    Data m_data;
};

// Used by TRACE_EVENTx macro. Do not use directly.
class TraceEndOnScopeCloseThreshold {
public:
    // Note: members of m_data intentionally left uninitialized. See initialize.
    TraceEndOnScopeCloseThreshold() : m_pdata(0) { }
    ~TraceEndOnScopeCloseThreshold()
    {
        if (m_pdata)
            addEventIfEnabled();
    }

    // Called by macros only when tracing is enabled at the point when the begin
    // event is added.
    void initialize(const unsigned char* categoryEnabled,
                    const char* name,
                    int thresholdBeginID,
                    long long threshold)
    {
        m_data.categoryEnabled = categoryEnabled;
        m_data.name = name;
        m_data.thresholdBeginID = thresholdBeginID;
        m_data.threshold = threshold;
        m_pdata = &m_data;
    }

private:
    // Add the end event if the category is still enabled.
    void addEventIfEnabled()
    {
        // Only called when m_pdata is non-null.
        if (*m_pdata->categoryEnabled) {
            TRACE_EVENT_API_ADD_TRACE_EVENT(
                TRACE_EVENT_PHASE_END,
                m_pdata->categoryEnabled,
                m_pdata->name, noEventId,
                zeroNumArgs, 0, 0, 0,
                m_pdata->thresholdBeginID, m_pdata->threshold,
                TRACE_EVENT_FLAG_NONE);
        }
    }

    // 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 {
        long long threshold;
        const unsigned char* categoryEnabled;
        const char* name;
        int thresholdBeginID;
    };
    Data* m_pdata;
    Data m_data;
};

} // namespace TraceEvent

} // namespace WebCore

#endif