main.cpp

#include "perf.h"

int main(int argc, const char *argv[])
{
    PerfElapsed elapsed;

    elapsed.begin();
    elapsed.end();
    elapsed.print();

    PerfCounter count;

    count.count();
    count.print();

    count.count();
    count.count();
    count.count();
    count.count();
    count.print();

    return 0;
}

perf.cpp

#include "perf.h"

#include <stdio.h>
#include <inttypes.h>

class PerfCounterPriv {
public:
    void foo();

    uint32_t count = 0;
};

void PerfCounterPriv::foo()
{
    printf("private counter foo()\n");
}

class PerfElapsedPriv {
public:
    void bar();

    uint32_t start = 0;
    uint32_t end = 0;
};

void PerfElapsedPriv::bar()
{
    printf("private elapsed bar()\n");
}

// ---------------------
// Public implementation

PerfCounter::PerfCounter()
{
    p = new PerfCounterPriv();
    p->foo();
}

PerfCounter::~PerfCounter()
{
    delete p;
}

void PerfCounter::print()
{
    printf("%" PRIu32 "\n", p->count);
}

void PerfCounter::count()
{
    p->count++;
}

PerfElapsed::PerfElapsed()
{
    p = new PerfElapsedPriv();
    p->bar();
}

PerfElapsed::~PerfElapsed()
{
    delete p;
}

void PerfElapsed::print()
{
    printf("%" PRIu32 "\n", p->end - p->start);
}

void PerfElapsed::begin()
{
    p->start = 0;
}

void PerfElapsed::end()
{
    p->end = 20;
}

perf.h

#pragma once

class Perf {
public:
    virtual void print() = 0;
};

class PerfCounterPriv;
class PerfElapsedPriv;

class PerfCounter : public Perf {
public:
    PerfCounter();
    ~PerfCounter();

    void print() override;
    void count();

private:
    PerfCounterPriv *p;
};

class PerfElapsed : public Perf {
public:
    PerfElapsed();
    ~PerfElapsed();

    void print() override;
    void begin();
    void end();
private:
    PerfElapsedPriv *p;
};