intrusive ptr

intrusive1.cc

#include <string>
#include <unordered_set>

#include <boost/intrusive_ptr.hpp>
#include <boost/noncopyable.hpp>

#include <gperftools/malloc_extension.h>

#include <assert.h>
#include <string.h>

class Item : boost::noncopyable
{
 public:
  Item(const char* key,
       uint32_t flags,
       int valuelen,
       uint64_t cas)
    : keylen_(strlen(key)),
      valuelen_(valuelen),
      cas_(cas)
  {
    char buf[64];
    flaglen_ = snprintf(buf, sizeof buf, " %u %d\r\n", flags, valuelen);
    data_ = static_cast<char*>(::malloc(totalLen()));
    memcpy(data_, key, keylen_);
    memcpy(data_ + keylen_, buf, flaglen_);
    data_[totalLen() - 2] = '\r';
    data_[totalLen() - 1] = '\n';
  }

  ~Item()
  {
    ::free(data_);
  }

  void assign(const char* value, int valuelen)
  {
    assert(valuelen <= valuelen_);
    memcpy(data_ + keylen_ + flaglen_, value, valuelen);
  }

  size_t hash() const
  {
    return std::_Hash_impl::hash(data_, keylen_);
  }

  bool equals(const Item& rhs) const
  {
    return keylen_ == rhs.keylen_ && memcmp(data_, rhs.data_, keylen_) == 0;
  }

  int inc_ref() const
  {
    return ++refcount_;
  }

  int dec_ref() const
  {
    return --refcount_;
  }

 private:

  int totalLen() const
  {
    return keylen_ + flaglen_ + valuelen_ + 2;
  }

  const uint8_t keylen_;
  uint8_t flaglen_ = 0;
  mutable uint16_t refcount_ = 0;
  const int valuelen_;
  const uint64_t cas_;
  char* data_ = nullptr;
};

typedef boost::intrusive_ptr<const Item> ConstItemPtr;

void intrusive_ptr_add_ref(const Item* p)
{
  if (p->inc_ref() == 0)
    assert(false && "refcount overflow");
}

void intrusive_ptr_release(const Item* p)
{
  if (p->dec_ref() == 0)
    delete p;
}

struct Hash
{
  size_t operator()(const ConstItemPtr& x) const
  {
    return x->hash();
  }
};

struct Equal
{
  bool operator()(const ConstItemPtr& x, const ConstItemPtr& y) const
  {
    return x->equals(*y);
  }
};

typedef std::unordered_set<ConstItemPtr, Hash, Equal> Map;

int main(int argc, char* argv[])
{
  MallocExtension::Initialize();

  int items = argc > 1 ? atoi(argv[1]) : 1000 * 1000;
  int keylen = 10;
  int valuelen = 100;
  char key[256] = { 0 };
  std::string value;
  Map theMap;
  for (int i = 0; i < items; ++i)
  {
    snprintf(key, sizeof key, "%0*d", keylen, i);
    value.assign(valuelen, "0123456789"[i % 10]);
    boost::intrusive_ptr<Item> item(new Item(key, 0, valuelen, 1));
    item->assign(value.data(), value.size());
    auto result = theMap.insert(std::move(item));
    assert(result.second);
  }

  printf("sizeof Item = %zd\n", sizeof(Item));
  printf("sizeof intrusive_ptr = %zd\n", sizeof(boost::intrusive_ptr<Item>));
  printf("items = %zd\n", theMap.size());

  char buf[65536] = "";
  MallocExtension::instance()->GetStats(buf, sizeof buf);
  printf("%s\n", buf);
}

intrusive2.cc

#include <string>
#include <unordered_set>

#include <boost/intrusive_ptr.hpp>
#include <boost/noncopyable.hpp>

#include <gperftools/malloc_extension.h>

#include <assert.h>
#include <string.h>

class Item : boost::noncopyable
{
 public:
  Item(const char* key,
       uint32_t flags,
       int valuelen,
       uint64_t cas)
    : keylen_(strlen(key)),
      valuelen_(valuelen),
      hash_(std::_Hash_impl::hash(key, keylen_)),
      cas_(cas)
  {
    char buf[64];
    flaglen_ = snprintf(buf, sizeof buf, " %u %d\r\n", flags, valuelen);
    data_ = static_cast<char*>(::malloc(totalLen()));
    memcpy(data_, key, keylen_);
    memcpy(data_ + keylen_, buf, flaglen_);
    data_[totalLen() - 2] = '\r';
    data_[totalLen() - 1] = '\n';
  }

  ~Item()
  {
    ::free(data_);
  }

  void assign(const char* value, int valuelen)
  {
    assert(valuelen <= valuelen_);
    memcpy(data_ + keylen_ + flaglen_, value, valuelen);
  }

  size_t hash() const
  {
    return hash_;
  }

  bool equals(const Item& rhs) const
  {
    return keylen_ == rhs.keylen_ && memcmp(data_, rhs.data_, keylen_) == 0;
  }

  int inc_ref() const
  {
    return ++refcount_;
  }

  int dec_ref() const
  {
    return --refcount_;
  }

 private:

  int totalLen() const
  {
    return keylen_ + flaglen_ + valuelen_ + 2;
  }

  const uint8_t keylen_;
  uint8_t flaglen_ = 0;
  mutable uint16_t refcount_ = 0;
  const int valuelen_;
  const size_t hash_;
  const uint64_t cas_;
  char* data_ = nullptr;
};

typedef boost::intrusive_ptr<const Item> ConstItemPtr;

void intrusive_ptr_add_ref(const Item* p)
{
  if (p->inc_ref() == 0)
    assert(false && "refcount overflow");
}

void intrusive_ptr_release(const Item* p)
{
  if (p->dec_ref() == 0)
    delete p;
}

struct Hash
{
  size_t operator()(const ConstItemPtr& x) const noexcept  // noexcept is the key
  {
    return x->hash();
  }
};

struct Equal
{
  bool operator()(const ConstItemPtr& x, const ConstItemPtr& y) const
  {
    return x->equals(*y);
  }
};

typedef std::unordered_set<ConstItemPtr, Hash, Equal> Map;

int main(int argc, char* argv[])
{
  MallocExtension::Initialize();

  int items = argc > 1 ? atoi(argv[1]) : 1000 * 1000;
  int keylen = 10;
  int valuelen = 100;
  char key[256] = { 0 };
  std::string value;
  Map theMap;
  for (int i = 0; i < items; ++i)
  {
    snprintf(key, sizeof key, "%0*d", keylen, i);
    value.assign(valuelen, "0123456789"[i % 10]);
    boost::intrusive_ptr<Item> item(new Item(key, 0, valuelen, 1));
    item->assign(value.data(), value.size());
    auto result = theMap.insert(std::move(item));
    assert(result.second);
  }

  printf("sizeof Item = %zd\n", sizeof(Item));
  printf("sizeof intrusive_ptr = %zd\n", sizeof(boost::intrusive_ptr<Item>));
  printf("items = %zd\n", theMap.size());

  char buf[65536] = "";
  MallocExtension::instance()->GetStats(buf, sizeof buf);
  printf("%s\n", buf);
}