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			95 lines
		
	
	
	
		
			2.3 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
			
		
		
	
	
			95 lines
		
	
	
	
		
			2.3 KiB
		
	
	
	
		
			C++
		
	
	
	
	
	
/*
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    This file is part of TON Blockchain Library.
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    TON Blockchain Library is free software: you can redistribute it and/or modify
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    it under the terms of the GNU Lesser General Public License as published by
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    the Free Software Foundation, either version 2 of the License, or
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    (at your option) any later version.
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    TON Blockchain Library is distributed in the hope that it will be useful,
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    but WITHOUT ANY WARRANTY; without even the implied warranty of
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    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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    GNU Lesser General Public License for more details.
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    You should have received a copy of the GNU Lesser General Public License
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    along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
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    Copyright 2017-2020 Telegram Systems LLP
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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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