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