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