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BLT/include/blt/std/allocator.h

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/*
* <Short Description>
* Copyright (C) 2023 Brett Terpstra
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#ifndef BLT_ALLOCATOR_H
#include <optional>
#include <limits>
#include <vector>
#include <blt/std/ranges.h>
#include <blt/std/utility.h>
#include <blt/std/types.h>
#include <blt/compatibility.h>
#include <stdexcept>
#include "logging.h"
#include <cstdlib>
#ifdef __unix__
#include <sys/mman.h>
#endif
namespace blt
{
template<typename value_type, typename pointer, typename const_pointer>
class allocator_base
{
public:
template<class U, class... Args>
inline void construct(U* p, Args&& ... args)
{
::new((void*) p) U(std::forward<Args>(args)...);
}
template<class U>
inline void destroy(U* p)
{
if (p != nullptr)
p->~U();
}
[[nodiscard]] inline size_t max_size() const
{
return std::numeric_limits<size_t>::max();
}
inline const_pointer address(const value_type& val)
{
return std::addressof(val);
}
inline pointer address(value_type& val)
{
return std::addressof(val);
}
};
template<typename T, size_t BLOCK_SIZE = 8192>
class area_allocator : public allocator_base<T, T*, const T*>
{
public:
using value = T;
using type = T;
using value_type = type;
using pointer = type*;
using const_pointer = const type*;
using void_pointer = void*;
using const_void_pointer = const void*;
using reference = value_type&;
using const_reference = const value_type&;
using size_type = size_t;
using difference_type = size_t;
using propagate_on_container_move_assignment = std::false_type;
template<class U>
struct rebind
{
typedef blt::area_allocator<U, BLOCK_SIZE> other;
};
using allocator_base<value_type, pointer, const_pointer>::allocator_base;
private:
/**
* Stores a view to a region of memory that has been deallocated
* This is a non-owning reference to the memory block
*
* pointer p is the pointer to the beginning of the block of memory
* size_t n is the number of elements that this block can hold
*/
struct pointer_view
{
pointer p;
size_t n;
};
/**
* Stores the actual data for allocated blocks. Since we would like to be able to allocate an arbitrary number of items
* we need a way of storing that data. The block storage holds an owning pointer to a region of memory with used elements
* Only up to used has to have their destructors called, which should be handled by the deallocate function
* it is UB to not deallocate memory allocated by this allocator
*
* an internal vector is used to store the regions of memory which have been deallocated. the allocate function will search for
* free blocks with sufficient size in order to maximize memory usage. In the future more advanced methods should be used
* for both faster access to deallocated blocks of sufficient size and to ensure coherent memory.
*/
struct block_storage
{
pointer data;
size_t used = 0;
// TODO: b-tree?
std::vector<pointer_view> unallocated_blocks;
};
/**
* Stores an index to a pointer_view along with the amount of memory leftover after the allocation
* it also stores the block being allocated to in question. The new inserted leftover should start at old_ptr + size
*/
struct block_view
{
block_storage* blk;
size_t index;
size_t leftover;
block_view(block_storage* blk, size_t index, size_t leftover): blk(blk), index(index), leftover(leftover)
{}
};
/**
* Allocate a new block of memory and push it to the back of blocks.
*/
inline void allocate_block()
{
//BLT_INFO("Allocating a new block of size %d", BLOCK_SIZE);
auto* blk = new block_storage();
blk->data = static_cast<pointer>(malloc(sizeof(T) * BLOCK_SIZE));
blocks.push_back(blk);
}
/**
* Searches for a free block inside the block storage with sufficient space and returns an optional view to it
* The optional will be empty if no open block can be found.
*/
inline std::optional<block_view> search_for_block(block_storage* blk, size_t n)
{
for (auto kv : blt::enumerate(blk->unallocated_blocks))
{
if (kv.second.n >= n)
return block_view{blk, kv.first, kv.second.n - n};
}
return {};
}
/**
* removes the block of memory from the unallocated_blocks storage in the underlying block, inserting a new unallocated block if
* there was any leftover. Returns a pointer to the beginning of the new block.
*/
inline pointer swap_pop_resize_if(const block_view& view, size_t n)
{
pointer_view ptr = view.blk->unallocated_blocks[view.index];
std::iter_swap(view.blk->unallocated_blocks.begin() + view.index, view.blk->unallocated_blocks.end() - 1);
view.blk->unallocated_blocks.pop_back();
if (view.leftover > 0)
view.blk->unallocated_blocks.push_back({ptr.p + n, view.leftover});
return ptr.p;
}
/**
* Finds the next available unallocated block of memory, or empty if there is none which meet size requirements
*/
inline std::optional<pointer> find_available_block(size_t n)
{
for (auto* blk : blocks)
{
if (auto view = search_for_block(blk, n))
return swap_pop_resize_if(view.value(), n);
}
return {};
}
/**
* returns a pointer to a block of memory along with an offset into that pointer that the requested block can be found at
*/
inline std::pair<pointer, size_t> getBlock(size_t n)
{
if (auto blk = find_available_block(n))
return {blk.value(), 0};
if (blocks.back()->used + n > BLOCK_SIZE)
allocate_block();
auto ptr = std::pair<pointer, size_t>{blocks.back()->data, blocks.back()->used};
blocks.back()->used += n;
return ptr;
}
/**
* Calls the constructor on elements if they require construction, otherwise constructor will not be called and this function is useless
*
* ALLOCATORS RETURN UNINIT STORAGE!! THIS HAS BEEN DISABLED.
*/
inline void allocate_in_block(pointer, size_t)
{
// if constexpr (std::is_default_constructible_v<T> && !std::is_trivially_default_constructible_v<T>)
// {
// for (size_t i = 0; i < n; i++)
// new(&begin[i]) T();
// }
}
public:
area_allocator()
{
allocate_block();
}
area_allocator(const area_allocator& copy) = delete;
area_allocator(area_allocator&& move) noexcept
{
blocks = move.blocks;
}
area_allocator& operator=(const area_allocator& copy) = delete;
area_allocator& operator=(area_allocator&& move) noexcept
{
std::swap(move.blocks, blocks);
}
[[nodiscard]] pointer allocate(size_t n)
{
if (n > BLOCK_SIZE)
throw std::runtime_error("Requested allocation is too large!");
auto block_info = getBlock(n);
auto* ptr = &block_info.first[block_info.second];
// call constructors on the objects if they require it
allocate_in_block(ptr, n);
return ptr;
}
void deallocate(pointer p, size_t n) noexcept
{
if (p == nullptr)
return;
// for (size_t i = 0; i < n; i++)
// p[i].~T();
for (auto*& blk : blocks)
{
if (p >= blk->data && p <= (blk->data + BLOCK_SIZE))
{
blk->unallocated_blocks.push_back(pointer_view{p, n});
break;
}
}
}
~area_allocator()
{
for (auto*& blk : blocks)
{
free(blk->data);
delete blk;
}
}
private:
std::vector<block_storage*> blocks;
};
// template<typename T>
// class bump_allocator : public allocator_base<T, T*, const T*>
// {
// public:
// using value = T;
// using type = T;
// using value_type = type;
// using pointer = type*;
// using const_pointer = const type*;
// using void_pointer = void*;
// using const_void_pointer = const void*;
// using reference = value_type&;
// using const_reference = const value_type&;
// using size_type = size_t;
// using difference_type = size_t;
// using propagate_on_container_move_assignment = std::false_type;
// template<class U>
// struct rebind
// {
// typedef blt::bump_allocator<U> other;
// };
// using allocator_base<value_type, pointer, const_pointer>::allocator_base;
// private:
// pointer buffer_;
// blt::size_t offset_;
// blt::size_t size_;
// public:
// explicit bump_allocator(blt::size_t size): buffer_(static_cast<pointer>(malloc(size * sizeof(T)))), offset_(0), size_(size)
// {}
//
// template<typename... Args>
// explicit bump_allocator(blt::size_t size, Args&& ... defaults):
// buffer_(static_cast<pointer>(malloc(size * sizeof(type)))), offset_(0), size_(size)
// {
// for (blt::size_t i = 0; i < size_; i++)
// ::new(&buffer_[i]) T(std::forward<Args>(defaults)...);
// }
//
// bump_allocator(pointer buffer, blt::size_t size): buffer_(buffer), offset_(0), size_(size)
// {}
//
// bump_allocator(const bump_allocator& copy) = delete;
//
// bump_allocator(bump_allocator&& move) noexcept
// {
// buffer_ = move.buffer_;
// size_ = move.size_;
// offset_ = move.offset_;
// }
//
// bump_allocator& operator=(const bump_allocator& copy) = delete;
//
// bump_allocator& operator=(bump_allocator&& move) noexcept
// {
// std::swap(move.buffer_, buffer_);
// std::swap(move.size_, size_);
// std::swap(move.offset_, offset_);
// }
//
// pointer allocate(blt::size_t n)
// {
// auto nv = offset_ + n;
// if (nv > size_)
// throw std::bad_alloc();
// pointer b = &buffer_[offset_];
// offset_ = nv;
// return b;
// }
//
// void deallocate(pointer, blt::size_t)
// {}
//
// ~bump_allocator()
// {
// free(buffer_);
// }
// };
/**
* The bump allocator is meant to be a faster area allocator which will only allocate forward through either a supplied buffer or size
* or will create a linked list type data structure of buffered blocks.
* @tparam ALLOC allocator to use for any allocations. In the case of the non-linked variant, this will be used if a size is supplied. The supplied buffer must be allocated with this allocator!
* @tparam linked use a linked list to allocate with the allocator or just use the supplied buffer and throw an exception of we cannot allocate
*/
template<bool linked, template<typename> typename ALLOC = std::allocator>
class bump_allocator_old;
template<template<typename> typename ALLOC>
class bump_allocator_old<false, ALLOC>
{
private:
ALLOC<blt::u8> allocator;
blt::u8* buffer_;
blt::u8* offset_;
blt::size_t size_;
public:
explicit bump_allocator_old(blt::size_t size): buffer_(static_cast<blt::u8*>(allocator.allocate(size))), offset_(buffer_), size_(size)
{}
explicit bump_allocator_old(blt::u8* buffer, blt::size_t size): buffer_(buffer), offset_(buffer), size_(size)
{}
template<typename T>
[[nodiscard]] T* allocate()
{
size_t remaining_num_bytes = size_ - static_cast<size_t>(buffer_ - offset_);
auto pointer = static_cast<void*>(offset_);
const auto aligned_address = std::align(alignof(T), sizeof(T), pointer, remaining_num_bytes);
if (aligned_address == nullptr)
throw std::bad_alloc{};
offset_ = static_cast<blt::u8*>(aligned_address) + sizeof(T);
return static_cast<T*>(aligned_address);
}
template<typename T, typename... Args>
[[nodiscard]] T* emplace(Args&& ... args)
{
const auto allocated_memory = allocate<T>();
return new(allocated_memory) T{std::forward<Args>(args)...};
}
template<class U, class... Args>
inline void construct(U* p, Args&& ... args)
{
::new((void*) p) U(std::forward<Args>(args)...);
}
template<class U>
inline void destroy(U* p)
{
if (p != nullptr)
p->~U();
}
~bump_allocator_old()
{
allocator.deallocate(buffer_, size_);
}
};
template<template<typename> typename ALLOC>
class bump_allocator_old<true, ALLOC>
{
private:
struct block
{
blt::size_t allocated_objects = 0;
blt::u8* buffer = nullptr;
blt::u8* offset = nullptr;
explicit block(blt::u8* buffer): buffer(buffer), offset(buffer)
{}
};
ALLOC<blt::u8> allocator;
std::vector<block, ALLOC<block>> blocks;
blt::size_t size_;
blt::size_t allocations = 0;
blt::size_t deallocations = 0;
void expand()
{
auto ptr = static_cast<blt::u8*>(allocator.allocate(size_));
blocks.push_back(block{ptr});
allocations++;
}
template<typename T>
T* allocate_back()
{
auto& back = blocks.back();
size_t remaining_bytes = size_ - static_cast<size_t>(back.offset - back.buffer);
auto pointer = static_cast<void*>(back.offset);
const auto aligned_address = std::align(alignof(T), sizeof(T), pointer, remaining_bytes);
if (aligned_address != nullptr)
{
back.offset = static_cast<blt::u8*>(aligned_address) + sizeof(T);
back.allocated_objects++;
}
return static_cast<T*>(aligned_address);
}
public:
/**
* @param size of the list blocks
*/
explicit bump_allocator_old(blt::size_t size): size_(size)
{
expand();
}
template<typename T>
[[nodiscard]] T* allocate()
{
if (auto ptr = allocate_back<T>(); ptr == nullptr)
expand();
else
return ptr;
if (auto ptr = allocate_back<T>(); ptr == nullptr)
throw std::bad_alloc();
else
return ptr;
}
template<typename T>
void deallocate(T* p)
{
auto* ptr = reinterpret_cast<blt::u8*>(p);
for (auto e : blt::enumerate(blocks))
{
auto& block = e.second;
if (ptr >= block.buffer && ptr <= block.offset)
{
block.allocated_objects--;
if (block.allocated_objects == 0)
{
std::iter_swap(blocks.begin() + e.first, blocks.end() - 1);
allocator.deallocate(blocks.back().buffer, size_);
blocks.pop_back();
deallocations++;
}
return;
}
}
}
template<typename T, typename... Args>
[[nodiscard]] T* emplace(Args&& ... args)
{
const auto allocated_memory = allocate<T>();
return new(allocated_memory) T{std::forward<Args>(args)...};
}
template<class U, class... Args>
inline void construct(U* p, Args&& ... args)
{
::new((void*) p) U(std::forward<Args>(args)...);
}
template<class U>
inline void destroy(U* p)
{
if (p != nullptr)
p->~U();
}
~bump_allocator_old()
{
if (allocations != deallocations)
BLT_WARN("Allocator has blocks which have not been deallocated! Destructors might not have been called!");
for (auto& v : blocks)
allocator.deallocate(v.buffer, size_);
}
};
// size of 2mb in bytes
inline constexpr blt::size_t BLT_2MB_SIZE = 4096 * 512;
/**
* blt::bump_allocator. Allocates blocks of BLOCK_SIZE with zero reuse. When all objects from a block are fully deallocated the block will be freed
* @tparam BLOCK_SIZE size of block to use. recommended to be multiple of page size or huge page size.
* @tparam USE_HUGE allocate using mmap and huge pages. If this fails it will use mmap to allocate normally. defaults to off because linux has parent huge pages.
* @tparam HUGE_PAGE_SIZE size the system allows huge pages to be. defaults to 2mb
* @tparam WARN_ON_FAIL print warning messages if allocating huge pages fail
*/
template<blt::size_t BLOCK_SIZE = BLT_2MB_SIZE, bool USE_HUGE = false, blt::size_t HUGE_PAGE_SIZE = BLT_2MB_SIZE, bool WARN_ON_FAIL = false>
class bump_allocator
{
// ensure power of two
static_assert(((BLOCK_SIZE & (BLOCK_SIZE - 1)) == 0) && "Must be a power of two!");
public:
/**
* convert any pointer back into a pointer its block
*/
template<typename T>
static inline auto to_block(T* p)
{
return reinterpret_cast<block*>(reinterpret_cast<std::uintptr_t>(p) & static_cast<std::uintptr_t>(~(BLOCK_SIZE - 1)));
}
private:
/**
* Logging function used for handling mmap errors. call after a failed mmap call.
* @param LOG_FUNC function to log with, must be a BLT_*_STREAM
*/
template<typename LOG_FUNC>
static void handle_mmap_error(LOG_FUNC func = BLT_ERROR_STREAM)
{
#define BLT_WRITE(arg) func << arg << '\n';
switch (errno)
{
case EACCES:
BLT_WRITE("fd not set to open!");
break;
case EAGAIN:
BLT_WRITE("The file has been locked, or too much memory has been locked");
break;
case EBADF:
BLT_WRITE("fd is not a valid file descriptor");
break;
case EEXIST:
BLT_WRITE("MAP_FIXED_NOREPLACE was specified in flags, and the range covered "
"by addr and length clashes with an existing mapping.");
break;
case EINVAL:
BLT_WRITE("We don't like addr, length, or offset (e.g., they are too large, or not aligned on a page boundary).");
BLT_WRITE("Or length was 0");
BLT_WRITE("Or flags contained none of MAP_PRIVATE, MAP_SHARED, or MAP_SHARED_VALIDATE.");
break;
case ENFILE:
BLT_WRITE("The system-wide limit on the total number of open files has been reached.");
break;
case ENODEV:
BLT_WRITE("The underlying filesystem of the specified file does not support memory mapping.");
break;
case ENOMEM:
BLT_WRITE("No memory is available.");
BLT_WRITE("Or The process's maximum number of mappings would have been exceeded. "
"This error can also occur for munmap(), when unmapping a region in the middle of an existing mapping, "
"since this results in two smaller mappings on either side of the region being unmapped.");
BLT_WRITE("Or The process's RLIMIT_DATA limit, described in getrlimit(2), would have been exceeded.");
BLT_WRITE("Or We don't like addr, because it exceeds the virtual address space of the CPU.");
break;
case EOVERFLOW:
BLT_WRITE("On 32-bit architecture together with the large file extension (i.e., using 64-bit off_t): "
"the number of pages used for length plus number of "
"pages used for offset would overflow unsigned long (32 bits).");
break;
case EPERM:
BLT_WRITE("The prot argument asks for PROT_EXEC but the mapped area "
"belongs to a file on a filesystem that was mounted no-exec.");
BLT_WRITE("Or The operation was prevented by a file seal");
BLT_WRITE("Or The MAP_HUGETLB flag was specified, but the caller "
"was not privileged (did not have the CAP_IPC_LOCK capability) "
"and is not a member of the sysctl_hugetlb_shm_group group; "
"see the description of /proc/sys/vm/sysctl_hugetlb_shm_group");
break;
case ETXTBSY:
BLT_WRITE("MAP_DENYWRITE was set but the object specified by fd is open for writing.");
break;
}
}
struct block
{
struct block_metadata_t
{
blt::size_t allocated_objects = 0;
block* next = nullptr;
block* prev = nullptr;
blt::u8* offset = nullptr;
} metadata;
blt::u8 buffer[BLOCK_SIZE - sizeof(metadata)]{};
block()
{
metadata.offset = buffer;
}
};
// remaining space inside the block after accounting for the metadata
static constexpr blt::size_t BLOCK_REMAINDER = BLOCK_SIZE - sizeof(typename block::block_metadata_t);
block* base = nullptr;
block* head = nullptr;
/**
* Handles the allocation of the bytes for the block.
* This function will either use mmap to allocate huge pages if requested
* or use std::align_alloc to create an aligned allocation
* @return pointer to a constructed block
*/
block* allocate_block()
{
block* buffer;
#ifdef __unix__
if constexpr (USE_HUGE)
{
static_assert((BLOCK_SIZE & (HUGE_PAGE_SIZE - 1)) == 0 && "Must be multiple of the huge page size!");
buffer = static_cast<block*>(mmap(nullptr, BLOCK_SIZE, PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_HUGETLB | MAP_POPULATE, -1, 0));
// if we fail to allocate a huge page we can try to allocate normally
if (buffer == MAP_FAILED)
{
if constexpr (WARN_ON_FAIL)
{
BLT_WARN_STREAM << "We failed to allocate huge pages\n";
handle_mmap_error(BLT_WARN_STREAM);
BLT_WARN_STREAM << "\033[1;31mYou should attempt to enable "
"huge pages as this will allocate normal pages and double the memory usage!\033[22m\n";
}
blt::size_t bytes = BLOCK_SIZE * 2;
buffer = static_cast<block*>(mmap(nullptr, bytes, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_POPULATE, -1, 0));
if (buffer == MAP_FAILED)
{
BLT_ERROR_STREAM << "Failed to allocate normal pages\n";
handle_mmap_error(BLT_ERROR_STREAM);
throw std::bad_alloc();
}
if constexpr (WARN_ON_FAIL)
{
if (((size_t) buffer & (HUGE_PAGE_SIZE - 1)) != 0)
BLT_ERROR("Pointer is not aligned! %p", buffer);
}
auto* ptr = static_cast<void*>(buffer);
auto ptr_size = reinterpret_cast<blt::size_t>(ptr);
buffer = static_cast<block*>(std::align(BLOCK_SIZE, BLOCK_SIZE, ptr, bytes));
if constexpr (WARN_ON_FAIL)
BLT_ERROR("Offset by %ld pages, resulting: %p", (reinterpret_cast<blt::size_t>(buffer) - ptr_size) / 4096, buffer);
}
} else
buffer = reinterpret_cast<block*>(std::aligned_alloc(BLOCK_SIZE, BLOCK_SIZE));
#else
buffer = reinterpret_cast<block*>(std::aligned_alloc(BLOCK_SIZE, BLOCK_SIZE));
#endif
construct(buffer);
return buffer;
}
/**
* Allocates a new block and pushes it to the front of the linked listed
*/
void allocate_forward()
{
auto* block = allocate_block();
if (head == nullptr)
{
base = head = block;
return;
}
block->metadata.prev = head;
head->metadata.next = block;
head = block;
}
/**
* handles the actual allocation and alignment of memory
* @param bytes number of bytes to allocate
* @param alignment alignment required
* @return aligned pointer
*/
void* allocate_bytes(blt::size_t bytes, blt::size_t alignment)
{
if (head == nullptr)
return nullptr;
blt::size_t remaining_bytes = BLOCK_REMAINDER - static_cast<blt::size_t>(head->metadata.offset - head->buffer);
auto pointer = static_cast<void*>(head->metadata.offset);
return std::align(alignment, bytes, pointer, remaining_bytes);
}
/**
* allocate an object starting from the next available address
* @tparam T type to allocate for
* @param count number of elements to allocate
* @return nullptr if the object could not be allocated, pointer to the object if it could, pointer to the start if count != 1
*/
template<typename T>
T* allocate_object(blt::size_t count)
{
blt::size_t bytes = sizeof(T) * count;
const auto aligned_address = allocate_bytes(bytes, alignof(T));
if (aligned_address != nullptr)
{
head->metadata.allocated_objects++;
head->metadata.offset = static_cast<blt::u8*>(aligned_address) + bytes;
}
return static_cast<T*>(aligned_address);
}
/**
* Frees a block
* @param p pointer to the block to free
*/
inline void delete_block(block* p)
{
if constexpr (USE_HUGE)
{
if (munmap(p, BLOCK_SIZE))
{
BLT_ERROR_STREAM << "FAILED TO DEALLOCATE BLOCK\n";
handle_mmap_error(BLT_ERROR_STREAM);
}
} else
free(p);
}
public:
bump_allocator() = default;
/**
* Takes an unused size parameter. Purely used for compatibility with the old bump_allocator
*/
explicit bump_allocator(blt::size_t)
{}
/**
* Allocate bytes for a type
* @tparam T type to allocate
* @param count number of elements to allocate for
* @throws std::bad_alloc
* @return aligned pointer to the beginning of the allocated memory
*/
template<typename T>
[[nodiscard]] T* allocate(blt::size_t count = 1)
{
if constexpr (sizeof(T) > BLOCK_REMAINDER)
throw std::bad_alloc();
T* ptr = allocate_object<T>(count);
if (ptr != nullptr)
return ptr;
allocate_forward();
ptr = allocate_object<T>(count);
if (ptr == nullptr)
throw std::bad_alloc();
return ptr;
}
/**
* Deallocate a pointer, does not call the destructor
* @tparam T type of pointer
* @param p pointer to deallocate
*/
template<typename T>
void deallocate(T* p)
{
if (p == nullptr)
return;
auto blk = to_block(p);
if (--blk->metadata.allocated_objects == 0)
{
if (blk == base)
base = head = nullptr;
if (blk->metadata.prev != nullptr)
blk->metadata.prev->metadata.next = blk->metadata.next;
delete_block(blk);
}
}
/**
* allocate a type then call its constructor with arguments
* @tparam T type to construct
* @tparam Args type of args to construct with
* @param args args to construct with
* @return aligned pointer to the constructed type
*/
template<typename T, typename... Args>
[[nodiscard]] T* emplace(Args&& ... args)
{
const auto allocated_memory = allocate<T>();
return new(allocated_memory) T{std::forward<Args>(args)...};
}
/**
* allocate an array of count T with argument(s) args and call T's constructor
* @tparam T class to construct
* @tparam Args argument types to supply to construction
* @param count size of the array to allocate in number of elements. Note calling this with count = 0 is equivalent to calling emplace
* @param args the args to supply to construction
* @return aligned pointer to the beginning of the array of T
*/
template<typename T, typename... Args>
[[nodiscard]] T* emplace_many(blt::size_t count, Args&& ... args)
{
if (count == 0)
return nullptr;
const auto allocated_memory = allocate<T>(count);
for (blt::size_t i = 0; i < count; i++)
new(allocated_memory + i) T{std::forward<Args>(args)...};
return allocated_memory;
}
/**
* Used to construct a class U with parameters Args
* @tparam U class to construct
* @tparam Args args to use
* @param p pointer to non-constructed memory
* @param args list of arguments to build the class with
*/
template<class U, class... Args>
inline void construct(U* p, Args&& ... args)
{
::new((void*) p) U(std::forward<Args>(args)...);
}
/**
* Call the destructor for class U with pointer p
* @tparam U class to call destructor on, this will not do anything if the type is std::trivially_destructible
* @param p
*/
template<class U>
inline void destroy(U* p)
{
if constexpr (std::is_trivially_destructible_v<U>)
{
if (p != nullptr)
p->~U();
}
}
/**
* Calls destroy on pointer p
* Then calls deallocate on p
* @tparam U class to destroy
* @param p pointer to deallocate
*/
template<class U>
inline void destruct(U* p)
{
destroy(p);
deallocate(p);
}
~bump_allocator()
{
block* next = base;
while (next != nullptr)
{
auto* after = next->metadata.next;
delete_block(next);
next = after;
}
}
};
}
#define BLT_ALLOCATOR_H
#endif //BLT_ALLOCATOR_H
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