Danny Robson
f6056153e3
This places, at long last, the core library code into the same namespace as the extended library code.
117 lines
3.4 KiB
C++
117 lines
3.4 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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*
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* Copyright 2015 Danny Robson <danny@nerdcruft.net>
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*/
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#ifndef CRUFT_UTIL_ALLOC_RAW_STACK_HPP
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#define CRUFT_UTIL_ALLOC_RAW_STACK_HPP
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#include "../../view.hpp"
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#include "../../pointer.hpp"
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#include <cstddef>
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namespace cruft::alloc::raw {
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// allocate memory from a buffer in a stacklike manner. deallocation that
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// is not correctly ordered has undefined (read 'bad') results.
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class stack {
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public:
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stack (const stack&) = delete;
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stack (stack&&) = delete;
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stack& operator= (const stack&) = delete;
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stack& operator= (stack&&) = delete;
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stack (cruft::view<std::byte*> _data);
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template <typename T>
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cruft::view<T*>
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allocate (size_t count, size_t alignment)
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{
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constexpr auto MIN_ALIGNMENT = sizeof (record::offset_t);
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const auto bytes = count * sizeof (T);
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// reserve space at the front of the allocation to record the total
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// allocation size so we can account for alignment if required.
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auto ptr = m_cursor + sizeof (record::offset_t);
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// align the outgoing pointer if required
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alignment = cruft::max (MIN_ALIGNMENT, alignment);
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ptr = cruft::align (ptr, alignment);
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// ensure we haven't overrun our allocated segment
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if (ptr + bytes > m_end)
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throw std::bad_alloc ();
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// use a 'record' struct as a window into the reserved space at the front
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// of the allocation and store the offset to the previous allocation head
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// (from the record struct). allows us to account for alignment.
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record r;
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r.as_bytes = ptr - sizeof (record::offset_t);
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*r.as_offset = cruft::cast::lossless <uint32_t> (ptr - m_cursor);
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m_cursor = ptr + bytes;
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return { cruft::cast::alignment<T*> (ptr), count };
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}
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template <typename T>
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cruft::view<T*>
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allocate (size_t count)
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{
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return allocate<T> (count, alignof (T));
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}
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template <typename T>
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void deallocate (cruft::view<T*> _ptr)
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{
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auto ptr = reinterpret_cast<std::byte*> (_ptr.data ());
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record r;
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r.as_bytes = ptr - sizeof (record::offset_t);
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//CHECK_LE (bytes, *record.as_offset);
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CHECK_GE (m_cursor - *r.as_offset, m_begin);
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m_cursor -= sizeof (T) * _ptr.size ();
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m_cursor -= *r.as_offset;
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}
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cruft::view<std::byte*> data (void);
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cruft::view<const std::byte*> data (void) const;
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std::byte* begin (void);
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const std::byte* begin (void) const;
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std::byte* end (void);
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const std::byte* end (void) const;
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size_t offset (const void*) const;
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void reset (void);
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size_t capacity (void) const;
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size_t used (void) const;
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size_t remain (void) const;
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private:
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union record {
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using offset_t = uint32_t;
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std::byte *as_bytes;
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offset_t *as_offset;
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};
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std::byte *const m_begin;
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std::byte *const m_end;
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std::byte *m_cursor;
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};
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}
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#endif
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