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#pragma once
#include <array>
#include <vector>
#include <algorithm>
// Fast memory storage on the stack when possible or in std::vector
namespace c11log
{
namespace details
{
template<unsigned short STACK_SIZE = 128>
class stack_buf
{
public:
using bufpair_t = std::pair<const char*, std::size_t>;
using iterator = char const*;
static constexpr unsigned short stack_size = STACK_SIZE;
stack_buf() :_v(), _stack_size(0) {}
~stack_buf() = default;
stack_buf& operator=(const stack_buf& other) = delete;
stack_buf(const stack_buf& other):stack_buf(other, delegate_copy_move{})
{}
stack_buf(stack_buf&& other):stack_buf(other, delegate_copy_move{})
{
other.clear();
}
void append(const char* buf, std::size_t buf_size)
{
//If we are aleady using _v, forget about the stack
if (vector_used())
{
_v.insert(_v.end(), buf, buf + buf_size);
}
//Try use the stack
else
{
if (_stack_size + buf_size <= STACK_SIZE)
{
std::memcpy(&_stack_array[_stack_size], buf, buf_size);
_stack_size += buf_size;
}
//Not enough stack space. Copy all to _v
else
{
_v.reserve(_stack_size + buf_size);
_v.insert(_v.end(), _stack_array.begin(), _stack_array.begin() + _stack_size);
_v.insert(_v.end(), buf, buf + buf_size);
}
}
}
void clear()
{
_stack_size = 0;
_v.clear();
}
bufpair_t get() const
{
if (vector_used())
return bufpair_t(_v.data(), _v.size());
else
return bufpair_t(_stack_array.data(), _stack_size);
}
iterator begin() const
{
return get().first;
}
iterator end() const
{
bufpair_t bpair = get();
return bpair.first + bpair.second;
}
std::size_t size() const
{
return get().second;
}
private:
struct delegate_copy_move {};
template<class T1>
stack_buf(T1&& other, delegate_copy_move)
{
_stack_size = other._stack_size;
if (other.vector_used())
_v = std::forward<T1>(other)._v;
else
std::copy_n(other._stack_array.begin(), other._stack_size, _stack_array.begin());
}
bool vector_used() const
{
return !(_v.empty());
}
std::vector<char> _v;
std::array<char, STACK_SIZE> _stack_array;
std::size_t _stack_size;
};
}
} //namespace c11log { namespace details {