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tdlib-fork/tdutils/td/utils/StackAllocator.h

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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2020
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#pragma once
#include "td/utils/common.h"
#include "td/utils/MovableValue.h"
#include "td/utils/Slice.h"
#include <array>
#include <cstdlib>
#include <memory>
namespace td {
class StackAllocator {
class Deleter {
public:
void operator()(char *ptr) {
free_ptr(ptr);
}
};
// TODO: alloc memory with mmap and unload unused pages
// memory still can be corrupted, but it is better than explicit free function
// TODO: use pointer that can't be even copied
using PtrImpl = std::unique_ptr<char, Deleter>;
class Ptr {
public:
Ptr(char *ptr, size_t size) : ptr_(ptr), size_(size) {
}
MutableSlice as_slice() const {
return MutableSlice(ptr_.get(), size_.get());
}
private:
PtrImpl ptr_;
MovableValue<size_t> size_;
};
static void free_ptr(char *ptr) {
impl().free_ptr(ptr);
}
struct Impl {
static const size_t MEM_SIZE = 1024 * 1024;
std::array<char, MEM_SIZE> mem;
size_t pos{0};
char *alloc(size_t size) {
if (size == 0) {
size = 1;
}
char *res = mem.data() + pos;
size = (size + 7) & -8;
pos += size;
if (pos > MEM_SIZE) {
std::abort(); // memory is over
}
return res;
}
void free_ptr(char *ptr) {
size_t new_pos = ptr - mem.data();
if (new_pos >= pos) {
std::abort(); // shouldn't happen
}
pos = new_pos;
}
};
static Impl &impl();
public:
static Ptr alloc(size_t size) {
return Ptr(impl().alloc(size), size);
}
};
} // namespace td