127 lines
3.2 KiB
C++
127 lines
3.2 KiB
C++
/*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*
|
|
* Copyright 2015-2016 Danny Robson <danny@nerdcruft.net>
|
|
*/
|
|
|
|
#include "./stack.hpp"
|
|
|
|
#include "../debug.hpp"
|
|
#include "../pointer.hpp"
|
|
#include "../cast.hpp"
|
|
|
|
using util::alloc::stack;
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
stack::stack (void *begin, void *end):
|
|
m_begin (reinterpret_cast<char*> (begin)),
|
|
m_end (reinterpret_cast<char*> (end)),
|
|
m_cursor (reinterpret_cast<char*> (begin))
|
|
{
|
|
CHECK_LE (m_begin, m_end);
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
union record {
|
|
using offset_t = uint32_t;
|
|
|
|
char *as_bytes;
|
|
offset_t *as_uint32;
|
|
};
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
constexpr auto MIN_ALIGNMENT = sizeof (record::offset_t);
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
void*
|
|
stack::allocate (size_t bytes, size_t alignment)
|
|
{
|
|
alignment = util::max (MIN_ALIGNMENT, alignment);
|
|
|
|
// 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
|
|
ptr = align (ptr, alignment);
|
|
|
|
// ensure we haven't overrun our allocated segment
|
|
if (ptr + bytes > m_end)
|
|
throw std::bad_alloc ();
|
|
|
|
// store the total size and record the new stack head
|
|
record record;
|
|
record.as_bytes = ptr - sizeof (record::offset_t);
|
|
*record.as_uint32 = trunc_cast<uint32_t> (ptr - m_cursor);
|
|
|
|
m_cursor = ptr + bytes;
|
|
|
|
return ptr;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
void
|
|
stack::deallocate (void *_ptr, size_t bytes, size_t alignment)
|
|
{
|
|
(void)bytes;
|
|
|
|
alignment = util::max (MIN_ALIGNMENT, alignment);
|
|
|
|
auto ptr = reinterpret_cast<char*> (_ptr);
|
|
|
|
record record;
|
|
record.as_bytes = ptr - sizeof (record::offset_t);
|
|
|
|
CHECK_LE (bytes, *record.as_uint32);
|
|
CHECK_GE (m_cursor - *record.as_uint32, m_begin);
|
|
|
|
m_cursor -= *record.as_uint32 + bytes;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
void
|
|
stack::reset (void)
|
|
{
|
|
m_cursor = m_begin;
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
size_t
|
|
stack::capacity (void) const
|
|
{
|
|
return m_end - m_begin;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
size_t
|
|
stack::used (void) const
|
|
{
|
|
return m_cursor - m_begin;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
size_t
|
|
stack::remain (void) const
|
|
{
|
|
return capacity () - used ();
|
|
}
|