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small_vector.hh
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small_vector.hh
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// Copyright (c) 2013 Austin T. Clements. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
#ifndef _DWARFPP_SMALL_VECTOR_HH_
#define _DWARFPP_SMALL_VECTOR_HH_
DWARFPP_BEGIN_NAMESPACE
#if 1
#include <vector>
template <class T, unsigned Min>
class small_vector : public ::std::vector<T> {
typedef T value_type;
typedef value_type &reference;
typedef const value_type &const_reference;
typedef size_t size_type;
public:
reference revat(size_type i) { return *(::std::vector<T>::end() - (i + 1)); }
const_reference revat(size_type i) const { return *(::std::vector<T>::end() - (i + 1)); }
};
#else
/**
* A vector-like class that only heap allocates above a specified
* size.
*/
template <class T, unsigned Min>
class small_vector {
public:
typedef T value_type;
typedef value_type &reference;
typedef const value_type &const_reference;
typedef size_t size_type;
small_vector() : base((T *)buf), end(base), cap((T *)&buf[sizeof(T[Min])]) {}
small_vector(const small_vector<T, Min> &o) : base((T *)buf), end(base), cap((T *)&buf[sizeof(T[Min])]) {
*this = o;
}
small_vector(small_vector<T, Min> &&o) : base((T *)buf), end(base), cap((T *)&buf[sizeof(T[Min])]) {
if ((char *)o.base == o.buf) {
// Elements are inline; have to copy them
base = (T *)buf;
end = base;
cap = (T *)&buf[sizeof(T[Min])];
*this = o;
o.clear();
} else {
// Elements are external; swap pointers
base = o.base;
end = o.end;
cap = o.cap;
o.base = (T *)o.buf;
o.end = o.base;
o.cap = (T *)&o.buf[sizeof(T[Min])];
}
}
~small_vector() {
clear();
if ((char *)base != buf) delete[](char *) base;
}
small_vector &operator=(const small_vector<T, Min> &o) {
size_type osize = o.size();
clear();
reserve(osize);
for (size_type i = 0; i < osize; i++) new (&base[i]) T(o[i]);
end = base + osize;
return *this;
}
size_type size() const { return end - base; }
bool empty() const { return base == end; }
void reserve(size_type n) {
if (n <= (size_type)(cap - base)) return;
size_type target = cap - base;
if (target == 0) target = 1;
while (target < n) target <<= 1;
char *newbuf = new char[sizeof(T) * target];
T *src = base, *dest = (T *)newbuf;
for (; src < end; src++, dest++) {
new (dest) T(*src);
dest->~T();
}
if ((char *)base != buf) delete[](char *) base;
base = (T *)newbuf;
end = dest;
cap = base + target;
}
reference operator[](size_type n) { return base[n]; }
const_reference operator[](size_type n) const { return base[n]; }
reference at(size_type n) { return base[n]; }
const_reference at(size_type n) const { return base[n]; }
/**
* "Reverse at". revat(0) is equivalent to back(). revat(1)
* is the element before back. Etc.
*/
reference revat(size_type n) { return *(end - 1 - n); }
const_reference revat(size_type n) const { return *(end - 1 - n); }
reference front() { return base[0]; }
const_reference front() const { return base[0]; }
reference back() { return *(end - 1); }
const_reference back() const { return *(end - 1); }
void push_back(const T &x) {
reserve(size() + 1);
new (end) T(x);
end++;
}
void push_back(T &&x) {
reserve(size() + 1);
new (end) T(std::move(x));
end++;
}
void pop_back() {
end--;
end->~T();
}
void clear() {
for (T *p = base; p < end; ++p) p->~T();
end = base;
}
private:
char buf[sizeof(T[Min])];
T *base, *end, *cap;
};
#endif
DWARFPP_END_NAMESPACE
#endif