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fast-realloc-vector.h
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fast-realloc-vector.h
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//-----------------------------------------------------------------------------
// Author: Christoph Mayer
// Gropiusweg 13
// 44801 Bochum
//
// Copyright: Christoph Mayer
//
// Description:
// A fast vector class for objects which do not require their constructors
// or destructors to be called.
// This class uses malloc, realloc and free to allocate and
// free dynamic memory for the "vector". Especially the efficient
// realloc has no C++ equivalent - the major drawback of new and
// delete.
// Disadvantage: No constructors and destructors are called for
// objects in the vector. This limits is applicability.
// The fastvector-nd.h uses new and delete and does not use
// memcpy. It is therefore well suited for all classes.
// Unfortunately, its less efficient.
//
#ifndef FASTVECTOR_H
#define FASTVECTOR_H
#include <iostream>
#include <cstdlib>
#include <cstring>
#include <cctype>
// #include <iomanip>
#define _MINBUFFER_CAPACITY 4
template<typename T>
class fastvector
{
// Possibly even more efficient:
// Use pointer _end, _capacity_end instead of _len, _capacity
private:
T *_buf;
unsigned _len;
unsigned _capacity; // Capacity of container, i.e number of bytes availible
// for writing. If a capacity is requested by the user,
// an additional byte is reserved in order to be able to append
// the additional \0 which is appended by some function calls.
// Consequently, the capacity reported to user is _capacity-1.
protected:
public:
~fastvector ()
{
if (_buf)
// delete [] _buf;
std::free(_buf);
}
fastvector ():_buf(NULL), _len(0), _capacity(0)
{
}
fastvector (const T *v, unsigned len)
{
// std::cout << "New fastvector 2" << std::endl;
_len = len;
_capacity = len;
if (len)
{
_buf = (T *) malloc(_capacity*sizeof(T));
//_buf = new T [_capacity];
memcpy(_buf, v, len*sizeof(T));
}
else
{
_buf = NULL;
}
}
fastvector (const T *v_begin, const T *v_end)
{
// std::cout << "New fastvector 3" << std::endl;
_len = (v_end - v_begin);
_capacity = _len;
if (_len)
{
_buf = (T *)malloc(_capacity*sizeof(T));
// _buf = new T [_capacity];
memcpy(_buf, v_begin, _len*sizeof(T));
}
else
{
_buf = NULL;
}
}
fastvector (const fastvector &a):_len(a._len),_capacity(a._len)
{
if (_len)
{
_buf = (T *)malloc(_capacity*sizeof(T));
memcpy(_buf, a._buf, _len*sizeof(T));
}
else
{
_buf = NULL;
}
}
void push_back(const T &c)
{
if (_capacity == _len)
{
if (_buf == NULL)
{
_capacity = _MINBUFFER_CAPACITY;
_buf = (T *)malloc(_capacity*sizeof(T));
}
else
{
T *tmp;
_capacity <<= 1;
tmp = (T *)realloc(_buf, _capacity*sizeof(T));
if (tmp == NULL)
{
std::cout << "Program aborded due to failed realloc!" << std::endl;
exit(0);
}
_buf = tmp;
}
}
_buf[_len] = c;
++_len;
}
T *begin() const
{
return _buf;
}
T *end() const
{
return _buf+_len;
}
T *rbegin() const
{
return _buf + (_len - 1);
}
T *rend() const
{
return _buf - 1;
}
void assign(const T *v, int len)
{
_len = len;
reserve(len);
memcpy(_buf, v, len*sizeof(T));
}
void assign(const T *v_begin, const T *v_end)
{
_len = v_end - v_begin;
reserve(_len);
memcpy(_buf, v_begin, _len*sizeof(T));
}
void assign(const fastvector &a)
{
_len = a._len;
reserve(_len);
memcpy(_buf, a._buf, _len*sizeof(T));
}
void reserve(unsigned s)
{
// std::cout << "reserve" << std::endl;
if (_capacity < s)
{
if (_buf == NULL)
{
//_buf = new T [s];
_buf = (T *)malloc(s*sizeof(T));
}
else
{
T *tmp;
tmp = (T *)realloc(_buf, s*sizeof(T));
if (tmp == NULL)
{
std::cout << "Program aborded due to failed realloc!" << std::endl;
exit(0);
}
_buf = tmp;
}
_capacity = s;
}
}
bool empty() const
{
return _len == 0;
}
unsigned size() const
{
return _len;
}
unsigned capacity() const
{
return _capacity; // One char is reserved for the \0 at end of string
}
void clear()
{
// std::cout << "clear" << std::endl;
_len = 0;
}
void reset()
{
// std::cout << "reset" << std::endl;
if (_buf)
{
// delete [] _buf;
free(_buf);
_buf = NULL;
_capacity = 0;
_len = 0;
}
}
bool check_pos(unsigned pos)
{
return (pos < _len);
}
void set_unckecked(unsigned pos, const T &c)
{
_buf[pos] = c;
}
bool set(unsigned pos, const T &c)
{
if ( check_pos(pos) )
{
_buf[pos] = c;
return true;
}
else
{
return false;
}
}
void get_unckecked(unsigned pos, T &c)
{
c = _buf[pos];
}
T get_unckecked(unsigned pos)
{
return _buf[pos];
}
bool get(unsigned pos, T &c)
{
if ( check_pos(pos) )
{
c = _buf[pos];
return true;
}
else
{
return false;
}
}
fastvector &operator=(const fastvector &a)
{
_len = a._len;
if (_len)
{
reserve(_len);
memcpy(_buf, a._buf, _len*sizeof(T));
}
return *this;
}
void swap(fastvector &a)
{
T *_tmpbuf = _buf; _buf = a._buf; a._buf = _tmpbuf;
unsigned _tmplen = _len; _len = a._len; a._len = _tmplen;
unsigned _tmpcapacity = _capacity; _capacity = a._capacity; a._capacity = _tmpcapacity;
}
};
#endif