84 lines
1.8 KiB
C++
84 lines
1.8 KiB
C++
//
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// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#pragma once
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#include "td/utils/common.h"
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#include "td/utils/MovableValue.h"
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#include "td/utils/Slice.h"
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#include <array>
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#include <cstdlib>
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#include <memory>
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namespace td {
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class StackAllocator {
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class Deleter {
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public:
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void operator()(char *ptr) {
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free_ptr(ptr);
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}
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};
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// TODO: alloc memory with mmap and unload unused pages
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// memory still can be corrupted, but it is better than explicit free function
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// TODO: use pointer that can't be even copied
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using PtrImpl = std::unique_ptr<char, Deleter>;
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class Ptr {
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public:
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Ptr(char *ptr, size_t size) : ptr_(ptr), size_(size) {
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}
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MutableSlice as_slice() const {
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return MutableSlice(ptr_.get(), size_.get());
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}
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private:
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PtrImpl ptr_;
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MovableValue<size_t> size_;
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};
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static void free_ptr(char *ptr) {
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impl().free_ptr(ptr);
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}
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struct Impl {
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static const size_t MEM_SIZE = 1024 * 1024;
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std::array<char, MEM_SIZE> mem;
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size_t pos{0};
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char *alloc(size_t size) {
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if (size == 0) {
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size = 1;
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}
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char *res = mem.data() + pos;
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size = (size + 7) & -8;
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pos += size;
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if (pos > MEM_SIZE) {
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std::abort(); // memory is over
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}
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return res;
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}
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void free_ptr(char *ptr) {
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size_t new_pos = ptr - mem.data();
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if (new_pos >= pos) {
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std::abort(); // shouldn't happen
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}
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pos = new_pos;
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}
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};
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static Impl &impl();
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public:
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static Ptr alloc(size_t size) {
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return Ptr(impl().alloc(size), size);
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}
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};
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} // namespace td
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