godot/core/cowdata.h
Hein-Pieter van Braam 4240e3d668 Optimizations for trivial types
Relying on various compiler primitives we can reduce the work done
in our memory allocators and CowData. For types with trivial ctors or
dtors we can skip looping over all elements when creating, resizing,
and destroying lists of objects.

These primitives are supported by clang, msvc, and GCC. However, once
we've moved to C++11 we can rely on several std:: primitives that do
the same thing and are standardized.

In my testing the extra conditionals introduced here get removed from
the generated program entirely as the results for these primitives is
known at compile time.
2019-01-03 08:47:34 +01:00

353 lines
8.4 KiB
C++

/*************************************************************************/
/* cowdata.h */
/*************************************************************************/
/* This file is part of: */
/* GODOT ENGINE */
/* https://godotengine.org */
/*************************************************************************/
/* Copyright (c) 2007-2019 Juan Linietsky, Ariel Manzur. */
/* Copyright (c) 2014-2019 Godot Engine contributors (cf. AUTHORS.md) */
/* */
/* Permission is hereby granted, free of charge, to any person obtaining */
/* a copy of this software and associated documentation files (the */
/* "Software"), to deal in the Software without restriction, including */
/* without limitation the rights to use, copy, modify, merge, publish, */
/* distribute, sublicense, and/or sell copies of the Software, and to */
/* permit persons to whom the Software is furnished to do so, subject to */
/* the following conditions: */
/* */
/* The above copyright notice and this permission notice shall be */
/* included in all copies or substantial portions of the Software. */
/* */
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
/*************************************************************************/
#ifndef COWDATA_H_
#define COWDATA_H_
#include <string.h>
#include "core/os/memory.h"
#include "core/safe_refcount.h"
template <class T>
class Vector;
class String;
class CharString;
template <class T, class V>
class VMap;
template <class T>
class CowData {
template <class TV>
friend class Vector;
friend class String;
friend class CharString;
template <class TV, class VV>
friend class VMap;
private:
mutable T *_ptr;
// internal helpers
_FORCE_INLINE_ uint32_t *_get_refcount() const {
if (!_ptr)
return NULL;
return reinterpret_cast<uint32_t *>(_ptr) - 2;
}
_FORCE_INLINE_ uint32_t *_get_size() const {
if (!_ptr)
return NULL;
return reinterpret_cast<uint32_t *>(_ptr) - 1;
}
_FORCE_INLINE_ T *_get_data() const {
if (!_ptr)
return NULL;
return reinterpret_cast<T *>(_ptr);
}
_FORCE_INLINE_ size_t _get_alloc_size(size_t p_elements) const {
//return nearest_power_of_2_templated(p_elements*sizeof(T)+sizeof(SafeRefCount)+sizeof(int));
return next_power_of_2(p_elements * sizeof(T));
}
_FORCE_INLINE_ bool _get_alloc_size_checked(size_t p_elements, size_t *out) const {
#if defined(_add_overflow) && defined(_mul_overflow)
size_t o;
size_t p;
if (_mul_overflow(p_elements, sizeof(T), &o)) {
*out = 0;
return false;
}
*out = next_power_of_2(o);
if (_add_overflow(o, static_cast<size_t>(32), &p)) return false; //no longer allocated here
return true;
#else
// Speed is more important than correctness here, do the operations unchecked
// and hope the best
*out = _get_alloc_size(p_elements);
return true;
#endif
}
void _unref(void *p_data);
void _ref(const CowData *p_from);
void _ref(const CowData &p_from);
void _copy_on_write();
public:
void operator=(const CowData<T> &p_from) { _ref(p_from); }
_FORCE_INLINE_ T *ptrw() {
_copy_on_write();
return (T *)_get_data();
}
_FORCE_INLINE_ const T *ptr() const {
return _get_data();
}
_FORCE_INLINE_ int size() const {
uint32_t *size = (uint32_t *)_get_size();
if (size)
return *size;
else
return 0;
}
_FORCE_INLINE_ void clear() { resize(0); }
_FORCE_INLINE_ bool empty() const { return _ptr == 0; }
_FORCE_INLINE_ void set(int p_index, const T &p_elem) {
CRASH_BAD_INDEX(p_index, size());
_copy_on_write();
_get_data()[p_index] = p_elem;
}
_FORCE_INLINE_ T &get_m(int p_index) {
CRASH_BAD_INDEX(p_index, size());
_copy_on_write();
return _get_data()[p_index];
}
_FORCE_INLINE_ const T &get(int p_index) const {
CRASH_BAD_INDEX(p_index, size());
return _get_data()[p_index];
}
Error resize(int p_size);
_FORCE_INLINE_ void remove(int p_index) {
ERR_FAIL_INDEX(p_index, size());
T *p = ptrw();
int len = size();
for (int i = p_index; i < len - 1; i++) {
p[i] = p[i + 1];
};
resize(len - 1);
};
Error insert(int p_pos, const T &p_val) {
ERR_FAIL_INDEX_V(p_pos, size() + 1, ERR_INVALID_PARAMETER);
resize(size() + 1);
for (int i = (size() - 1); i > p_pos; i--)
set(i, get(i - 1));
set(p_pos, p_val);
return OK;
};
_FORCE_INLINE_ CowData();
_FORCE_INLINE_ ~CowData();
_FORCE_INLINE_ CowData(CowData<T> &p_from) { _ref(p_from); };
};
template <class T>
void CowData<T>::_unref(void *p_data) {
if (!p_data)
return;
uint32_t *refc = _get_refcount();
if (atomic_decrement(refc) > 0)
return; // still in use
// clean up
if (!__has_trivial_destructor(T)) {
uint32_t *count = _get_size();
T *data = (T *)(count + 1);
for (uint32_t i = 0; i < *count; ++i) {
// call destructors
data[i].~T();
}
}
// free mem
Memory::free_static((uint8_t *)p_data, true);
}
template <class T>
void CowData<T>::_copy_on_write() {
if (!_ptr)
return;
uint32_t *refc = _get_refcount();
if (unlikely(*refc > 1)) {
/* in use by more than me */
uint32_t current_size = *_get_size();
uint32_t *mem_new = (uint32_t *)Memory::alloc_static(_get_alloc_size(current_size), true);
*(mem_new - 2) = 1; //refcount
*(mem_new - 1) = current_size; //size
T *_data = (T *)(mem_new);
// initialize new elements
if (__has_trivial_copy(T)) {
memcpy(mem_new, _ptr, current_size * sizeof(T));
} else {
for (uint32_t i = 0; i < current_size; i++) {
memnew_placement(&_data[i], T(_get_data()[i]));
}
}
_unref(_ptr);
_ptr = _data;
}
}
template <class T>
Error CowData<T>::resize(int p_size) {
ERR_FAIL_COND_V(p_size < 0, ERR_INVALID_PARAMETER);
if (p_size == size())
return OK;
if (p_size == 0) {
// wants to clean up
_unref(_ptr);
_ptr = NULL;
return OK;
}
// possibly changing size, copy on write
_copy_on_write();
size_t alloc_size;
ERR_FAIL_COND_V(!_get_alloc_size_checked(p_size, &alloc_size), ERR_OUT_OF_MEMORY);
if (p_size > size()) {
if (size() == 0) {
// alloc from scratch
uint32_t *ptr = (uint32_t *)Memory::alloc_static(alloc_size, true);
ERR_FAIL_COND_V(!ptr, ERR_OUT_OF_MEMORY);
*(ptr - 1) = 0; //size, currently none
*(ptr - 2) = 1; //refcount
_ptr = (T *)ptr;
} else {
void *_ptrnew = (T *)Memory::realloc_static(_ptr, alloc_size, true);
ERR_FAIL_COND_V(!_ptrnew, ERR_OUT_OF_MEMORY);
_ptr = (T *)(_ptrnew);
}
// construct the newly created elements
if (!__has_trivial_constructor(T)) {
T *elems = _get_data();
for (int i = *_get_size(); i < p_size; i++) {
memnew_placement(&elems[i], T);
}
}
*_get_size() = p_size;
} else if (p_size < size()) {
if (!__has_trivial_destructor(T)) {
// deinitialize no longer needed elements
for (uint32_t i = p_size; i < *_get_size(); i++) {
T *t = &_get_data()[i];
t->~T();
}
}
void *_ptrnew = (T *)Memory::realloc_static(_ptr, alloc_size, true);
ERR_FAIL_COND_V(!_ptrnew, ERR_OUT_OF_MEMORY);
_ptr = (T *)(_ptrnew);
*_get_size() = p_size;
}
return OK;
}
template <class T>
void CowData<T>::_ref(const CowData *p_from) {
_ref(*p_from);
}
template <class T>
void CowData<T>::_ref(const CowData &p_from) {
if (_ptr == p_from._ptr)
return; // self assign, do nothing.
_unref(_ptr);
_ptr = NULL;
if (!p_from._ptr)
return; //nothing to do
if (atomic_conditional_increment(p_from._get_refcount()) > 0) { // could reference
_ptr = p_from._ptr;
}
}
template <class T>
CowData<T>::CowData() {
_ptr = NULL;
}
template <class T>
CowData<T>::~CowData() {
_unref(_ptr);
}
#endif /* COW_H_ */