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/*
* Copyright (C) 2011 Apple Inc. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of Apple Inc. ("Apple") nor the names of
* its contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef SamplingCounter_h
#define SamplingCounter_h
#include <stdint.h>
#include <wtf/Assertions.h>
namespace JSC {
// AbstractSamplingCounter:
//
// Implements a named set of counters, printed on exit if ENABLE(SAMPLING_COUNTERS).
// See subclasses below, SamplingCounter, GlobalSamplingCounter and DeletableSamplingCounter.
class AbstractSamplingCounter {
friend class DeletableSamplingCounter;
public:
void count(uint32_t count = 1)
{
m_counter += count;
}
JS_EXPORT_PRIVATE static void dump();
int64_t* addressOfCounter() { return &m_counter; }
protected:
// Effectively the contructor, however called lazily in the case of GlobalSamplingCounter.
void init(const char* name)
{
m_counter = 0;
m_name = name;
// Set m_next to point to the head of the chain, and inform whatever is
// currently at the head that this node will now hold the pointer to it.
m_next = s_abstractSamplingCounterChain;
s_abstractSamplingCounterChain->m_referer = &m_next;
// Add this node to the head of the list.
s_abstractSamplingCounterChain = this;
m_referer = &s_abstractSamplingCounterChain;
}
int64_t m_counter;
const char* m_name;
AbstractSamplingCounter* m_next;
// This is a pointer to the pointer to this node in the chain; used to
// allow fast linked list deletion.
AbstractSamplingCounter** m_referer;
// Null object used to detect end of static chain.
static AbstractSamplingCounter s_abstractSamplingCounterChainEnd;
JS_EXPORTDATA static AbstractSamplingCounter* s_abstractSamplingCounterChain;
static bool s_completed;
};
#if ENABLE(SAMPLING_COUNTERS)
// SamplingCounter:
//
// This class is suitable and (hopefully!) convenient for cases where a counter is
// required within the scope of a single function. It can be instantiated as a
// static variable since it contains a constructor but not a destructor (static
// variables in WebKit cannot have destructors).
//
// For example:
//
// void someFunction()
// {
// static SamplingCounter countMe("This is my counter. There are many like it, but this one is mine.");
// countMe.count();
// // ...
// }
//
class SamplingCounter : public AbstractSamplingCounter {
public:
SamplingCounter(const char* name) { init(name); }
};
// GlobalSamplingCounter:
//
// This class is suitable for use where a counter is to be declared globally,
// since it contains neither a constructor nor destructor. Instead, ensure
// that 'name()' is called to provide the counter with a name (and also to
// allow it to be printed out on exit).
//
// GlobalSamplingCounter globalCounter;
//
// void firstFunction()
// {
// // Put this within a function that is definitely called!
// // (Or alternatively alongside all calls to 'count()').
// globalCounter.name("I Name You Destroyer.");
// globalCounter.count();
// // ...
// }
//
// void secondFunction()
// {
// globalCounter.count();
// // ...
// }
//
class GlobalSamplingCounter : public AbstractSamplingCounter {
public:
void name(const char* name)
{
// Global objects should be mapped in zero filled memory, so this should
// be a safe (albeit not necessarily threadsafe) check for 'first call'.
if (!m_next)
init(name);
}
};
// DeletableSamplingCounter:
//
// The above classes (SamplingCounter, GlobalSamplingCounter), are intended for
// use within a global or static scope, and as such cannot have a destructor.
// This means there is no convenient way for them to remove themselves from the
// static list of counters, and should an instance of either class be freed
// before 'dump()' has walked over the list it will potentially walk over an
// invalid pointer.
//
// This class is intended for use where the counter may possibly be deleted before
// the program exits. Should this occur, the counter will print it's value to
// stderr, and remove itself from the static list. Example:
//
// DeletableSamplingCounter* counter = new DeletableSamplingCounter("The Counter With No Name");
// counter->count();
// delete counter;
//
class DeletableSamplingCounter : public AbstractSamplingCounter {
public:
DeletableSamplingCounter(const char* name) { init(name); }
~DeletableSamplingCounter()
{
if (!s_completed)
dataFile("DeletableSamplingCounter \"%s\" deleted early (with count %lld)\n", m_name, m_counter);
// Our m_referer pointer should know where the pointer to this node is,
// and m_next should know that this node is the previous node in the list.
ASSERT(*m_referer == this);
ASSERT(m_next->m_referer == &m_next);
// Remove this node from the list, and inform m_next that we have done so.
m_next->m_referer = m_referer;
*m_referer = m_next;
}
};
#endif
} // namespace JSC
#endif // SamplingCounter_h
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