blt-gp/include/blt/gp/stack.h

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#pragma once
/*
* Copyright (C) 2024 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_GP_STACK_H
#define BLT_GP_STACK_H
#include <blt/std/types.h>
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#include <blt/std/assert.h>
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#include <blt/std/logging.h>
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#include <blt/gp/fwdecl.h>
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#include <utility>
#include <stdexcept>
#include <cstdlib>
#include <memory>
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#include <type_traits>
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#include <cstring>
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namespace blt::gp
{
class stack_allocator
{
constexpr static blt::size_t PAGE_SIZE = 0x1000;
constexpr static blt::size_t MAX_ALIGNMENT = 8;
public:
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struct size_data_t
{
blt::size_t total_size_bytes = 0;
blt::size_t total_used_bytes = 0;
blt::size_t total_remaining_bytes = 0;
blt::size_t total_no_meta_bytes = 0;
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blt::size_t blocks = 0;
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};
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/**
* Pushes an instance of an object on to the stack
* @tparam T type to push
* @param value universal reference to the object to push
*/
template<typename T>
void push(T&& value)
{
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using NO_REF_T = std::remove_reference_t<T>;
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static_assert(std::is_trivially_copyable_v<NO_REF_T> && "Type must be bitwise copyable!");
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auto ptr = allocate_bytes<T>();
head->metadata.offset = static_cast<blt::u8*>(ptr) + aligned_size<T>();
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new(ptr) NO_REF_T(std::forward<T>(value));
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}
template<typename T>
T pop()
{
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using NO_REF_T = std::remove_reference_t<T>;
static_assert(std::is_trivially_copyable_v<NO_REF_T> && "Type must be bitwise copyable!");
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constexpr static auto TYPE_SIZE = aligned_size<T>();
if (head == nullptr)
throw std::runtime_error("Silly boi the stack is empty!");
if (head->used_bytes_in_block() < static_cast<blt::ptrdiff_t>(aligned_size<T>()))
throw std::runtime_error((std::string("Mismatched Types! Not enough space left in block! Bytes: ") += std::to_string(
head->used_bytes_in_block()) += " Size: " + std::to_string(sizeof(T))).c_str());
if (head->used_bytes_in_block() == 0)
move_back();
// make copy
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T t = *reinterpret_cast<T*>(head->metadata.offset - TYPE_SIZE);
// call destructor
reinterpret_cast<T*>(head->metadata.offset - TYPE_SIZE)->~T();
// move offset back
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head->metadata.offset -= TYPE_SIZE;
return t;
}
template<typename T>
T& from(blt::size_t bytes)
{
constexpr static auto TYPE_SIZE = aligned_size<T>();
auto remaining_bytes = static_cast<blt::i64>(bytes);
blt::i64 bytes_into_block = 0;
block* blk = head;
while (remaining_bytes > 0)
{
if (blk == nullptr)
throw std::runtime_error("Requested size is beyond the scope of this stack!");
auto bytes_available = blk->used_bytes_in_block() - remaining_bytes;
bytes_into_block = remaining_bytes;
if (bytes_available < 0)
{
remaining_bytes = -bytes_available;
blk = head->metadata.prev;
} else
break;
}
if (blk == nullptr)
throw std::runtime_error("Some nonsense is going on. This function already smells");
if (blk->used_bytes_in_block() < static_cast<blt::ptrdiff_t>(aligned_size<T>()))
throw std::runtime_error((std::string("Mismatched Types! Not enough space left in block! Bytes: ") += std::to_string(
blk->used_bytes_in_block()) += " Size: " + std::to_string(sizeof(T))).c_str());
return *reinterpret_cast<T*>((blk->metadata.offset - bytes_into_block) - TYPE_SIZE);
}
void pop_bytes(blt::ptrdiff_t bytes)
{
#if BLT_DEBUG_LEVEL >= 3
blt::size_t counter = 0;
#endif
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while (bytes > 0)
{
#if BLT_DEBUG_LEVEL > 0
if (head == nullptr)
{
BLT_WARN("Head is nullptr, unable to pop bytes!");
BLT_WARN("This error is normally caused by an invalid tree!");
#if BLT_DEBUG_LEVEL >= 3
BLT_WARN("Made it to %ld iterations", counter);
#endif
return;
}
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#if BLT_DEBUG_LEVEL >= 3
counter++;
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#endif
#endif
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auto diff = head->used_bytes_in_block() - bytes;
// if there is not enough room left to pop completely off the block, then move to the next previous block
// and pop from it, update the amount of bytes to reflect the amount removed from the current block
if (diff <= 0)
{
bytes -= head->used_bytes_in_block();
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if (diff == 0)
break;
move_back();
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} else
{
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// otherwise update the offset pointer
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head->metadata.offset -= bytes;
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break;
}
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}
}
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/**
* Warning this function should be used to transfer types, not arrays of types! It will produce an error if you attempt to pass more
* than one type # of bytes at a time~!
* @param to stack to push to
* @param bytes number of bytes to transfer out.
*/
void transfer_bytes(stack_allocator& to, blt::size_t bytes)
{
if (empty())
throw std::runtime_error("This stack is empty!");
if (head->used_bytes_in_block() < static_cast<blt::ptrdiff_t>(bytes))
BLT_ABORT("This stack doesn't contain enough data for this type! This is an invalid runtime state!");
if (head->used_bytes_in_block() == 0)
move_back();
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auto type_size = aligned_size(bytes);
auto ptr = to.allocate_bytes(bytes);
to.head->metadata.offset = static_cast<blt::u8*>(ptr) + type_size;
std::memcpy(ptr, head->metadata.offset - type_size, type_size);
head->metadata.offset -= type_size;
}
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template<typename... Args>
void call_destructors()
{
blt::size_t offset = 0;
((from<Args>(offset).~Args(), offset += stack_allocator::aligned_size<Args>()), ...);
}
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[[nodiscard]] bool empty() const
{
if (head == nullptr)
return true;
if (head->metadata.prev != nullptr)
return false;
return head->used_bytes_in_block() == 0;
}
[[nodiscard]] blt::ptrdiff_t bytes_in_head() const
{
if (head == nullptr)
return 0;
return head->used_bytes_in_block();
}
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/**
* Warning this function is slow!
* @return the size of the stack allocator in bytes
*/
[[nodiscard]] size_data_t size()
{
size_data_t size_data;
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auto* next = head;
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while (next != nullptr)
{
size_data.total_size_bytes += next->metadata.size;
size_data.total_no_meta_bytes += next->storage_size();
size_data.total_remaining_bytes += next->remaining_bytes_in_block();
size_data.total_used_bytes += next->used_bytes_in_block();
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size_data.blocks++;
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next = next->metadata.next;
}
return size_data;
}
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stack_allocator() = default;
// TODO: cleanup this allocator!
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// if you keep track of type size information you can memcpy between stack allocators as you already only allow trivially copyable types
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stack_allocator(const stack_allocator& copy)
{
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if (copy.empty())
return;
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head = nullptr;
block* list_itr = nullptr;
// start at the beginning of the list
block* current = copy.head;
while (current != nullptr)
{
list_itr = current;
current = current->metadata.prev;
}
// copy all the blocks
while (list_itr != nullptr)
{
push_block(list_itr->metadata.size);
std::memcpy(head->buffer, list_itr->buffer, list_itr->storage_size());
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head->metadata.size = list_itr->metadata.size;
head->metadata.offset = head->buffer + list_itr->used_bytes_in_block();
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list_itr = list_itr->metadata.next;
}
}
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stack_allocator& operator=(const stack_allocator& copy) = delete;
stack_allocator(stack_allocator&& move) noexcept
{
head = move.head;
move.head = nullptr;
}
stack_allocator& operator=(stack_allocator&& move) noexcept
{
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move.head = std::exchange(head, move.head);
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return *this;
}
~stack_allocator()
{
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free_chain(head);
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}
template<typename T>
static inline constexpr blt::size_t aligned_size() noexcept
{
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return aligned_size(sizeof(T));
}
static inline constexpr blt::size_t aligned_size(blt::size_t size) noexcept
{
return (size + (MAX_ALIGNMENT - 1)) & ~(MAX_ALIGNMENT - 1);
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}
private:
struct block
{
struct block_metadata_t
{
blt::size_t size = 0;
block* next = nullptr;
block* prev = nullptr;
blt::u8* offset = nullptr;
} metadata;
blt::u8 buffer[8]{};
explicit block(blt::size_t size)
{
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#if BLT_DEBUG_LEVEL > 0
if (size < PAGE_SIZE)
{
BLT_WARN("Hey this block is too small, who allocated it?");
std::abort();
}
#endif
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metadata.size = size;
metadata.offset = buffer;
}
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void reset()
{
metadata.offset = buffer;
}
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[[nodiscard]] blt::ptrdiff_t storage_size() const
{
return static_cast<blt::ptrdiff_t>(metadata.size - sizeof(typename block::block_metadata_t));
}
[[nodiscard]] blt::ptrdiff_t used_bytes_in_block() const
{
return static_cast<blt::ptrdiff_t>(metadata.offset - buffer);
}
[[nodiscard]] blt::ptrdiff_t remaining_bytes_in_block() const
{
return storage_size() - used_bytes_in_block();
}
};
template<typename T>
void* allocate_bytes()
{
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return allocate_bytes(sizeof(T));
}
void* allocate_bytes(blt::size_t size)
{
auto ptr = get_aligned_pointer(size);
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if (ptr == nullptr)
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{
if (head != nullptr && head->metadata.next != nullptr)
{
head = head->metadata.next;
if (head != nullptr)
head->reset();
} else
push_block(aligned_size(size));
}
ptr = get_aligned_pointer(size);
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if (ptr == nullptr)
throw std::bad_alloc();
return ptr;
}
void* get_aligned_pointer(blt::size_t bytes)
{
if (head == nullptr)
return nullptr;
blt::size_t remaining_bytes = head->remaining_bytes_in_block();
auto* pointer = static_cast<void*>(head->metadata.offset);
return std::align(MAX_ALIGNMENT, bytes, pointer, remaining_bytes);
}
void push_block(blt::size_t size)
{
auto blk = allocate_block(size);
if (head == nullptr)
{
head = blk;
return;
}
head->metadata.next = blk;
blk->metadata.prev = head;
head = blk;
}
static size_t to_nearest_page_size(blt::size_t bytes)
{
constexpr static blt::size_t MASK = ~(PAGE_SIZE - 1);
return (bytes & MASK) + PAGE_SIZE;
}
static block* allocate_block(blt::size_t bytes)
{
auto size = to_nearest_page_size(bytes);
auto* data = std::aligned_alloc(PAGE_SIZE, size);
new(data) block{size};
return reinterpret_cast<block*>(data);
}
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static void free_chain(block* current)
{
while (current != nullptr)
{
block* ptr = current;
current = current->metadata.prev;
std::free(ptr);
}
}
inline void move_back()
{
auto old = head;
head = head->metadata.prev;
if (head == nullptr)
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head = old;
//free_chain(old);
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// required to prevent silly memory :3
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// if (head != nullptr)
// head->metadata.next = nullptr;
// std::free(old);
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}
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private:
block* head = nullptr;
};
}
#endif //BLT_GP_STACK_H