bsnes/nall/string/allocator/copy-on-write.hpp

93 lines
2.0 KiB
C++
Executable File

#pragma once
namespace nall {
string::string() : _data(nullptr), _refs(nullptr), _capacity(0), _size(0) {
}
template<typename T>
auto string::get() -> T* {
static char _null[] = "";
if(!_data) return (T*)_null;
if(*_refs > 1) _data = _copy(); //make unique for write operations
return (T*)_data;
}
template<typename T>
auto string::data() const -> const T* {
static const char _null[] = "";
if(!_data) return (const T*)_null;
return (const T*)_data;
}
auto string::reset() -> type& {
if(_data && !--*_refs) {
memory::free(_data);
_data = nullptr; //_refs = nullptr; is unnecessary
}
_capacity = 0;
_size = 0;
return *this;
}
auto string::reserve(uint capacity) -> type& {
if(capacity > _capacity) {
_capacity = bit::round(max(31u, capacity) + 1) - 1;
_data = _data ? _copy() : _allocate();
}
return *this;
}
auto string::resize(uint size) -> type& {
reserve(size);
get()[_size = size] = 0;
return *this;
}
auto string::operator=(const string& source) -> string& {
if(&source == this) return *this;
reset();
if(source._data) {
_data = source._data;
_refs = source._refs;
_capacity = source._capacity;
_size = source._size;
++*_refs;
}
return *this;
}
auto string::operator=(string&& source) -> string& {
if(&source == this) return *this;
reset();
_data = source._data;
_refs = source._refs;
_capacity = source._capacity;
_size = source._size;
source._data = nullptr;
source._refs = nullptr;
source._capacity = 0;
source._size = 0;
return *this;
}
auto string::_allocate() -> char* {
auto _temp = memory::allocate<char>(_capacity + 1 + sizeof(uint));
*_temp = 0;
_refs = (uint*)(_temp + _capacity + 1); //this will always be aligned by 32 via reserve()
*_refs = 1;
return _temp;
}
auto string::_copy() -> char* {
auto _temp = memory::allocate<char>(_capacity + 1 + sizeof(uint));
memory::copy(_temp, _data, _size = min(_capacity, _size));
_temp[_size] = 0;
--*_refs;
_refs = (uint*)(_temp + _capacity + 1);
*_refs = 1;
return _temp;
}
}