mirror of https://github.com/axmolengine/axmol.git
68 lines
2.5 KiB
C
68 lines
2.5 KiB
C
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/*
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* Copyright 2021 Google Inc. All rights reserved.
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*
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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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#ifndef FLATBUFFERS_ALLOCATOR_H_
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#define FLATBUFFERS_ALLOCATOR_H_
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#include "flatbuffers/base.h"
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namespace flatbuffers {
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// Allocator interface. This is flatbuffers-specific and meant only for
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// `vector_downward` usage.
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class Allocator {
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public:
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virtual ~Allocator() {}
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// Allocate `size` bytes of memory.
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virtual uint8_t *allocate(size_t size) = 0;
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// Deallocate `size` bytes of memory at `p` allocated by this allocator.
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virtual void deallocate(uint8_t *p, size_t size) = 0;
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// Reallocate `new_size` bytes of memory, replacing the old region of size
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// `old_size` at `p`. In contrast to a normal realloc, this grows downwards,
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// and is intended specifcally for `vector_downward` use.
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// `in_use_back` and `in_use_front` indicate how much of `old_size` is
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// actually in use at each end, and needs to be copied.
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virtual uint8_t *reallocate_downward(uint8_t *old_p, size_t old_size,
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size_t new_size, size_t in_use_back,
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size_t in_use_front) {
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FLATBUFFERS_ASSERT(new_size > old_size); // vector_downward only grows
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uint8_t *new_p = allocate(new_size);
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memcpy_downward(old_p, old_size, new_p, new_size, in_use_back,
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in_use_front);
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deallocate(old_p, old_size);
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return new_p;
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}
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protected:
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// Called by `reallocate_downward` to copy memory from `old_p` of `old_size`
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// to `new_p` of `new_size`. Only memory of size `in_use_front` and
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// `in_use_back` will be copied from the front and back of the old memory
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// allocation.
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void memcpy_downward(uint8_t *old_p, size_t old_size, uint8_t *new_p,
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size_t new_size, size_t in_use_back,
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size_t in_use_front) {
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memcpy(new_p + new_size - in_use_back, old_p + old_size - in_use_back,
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in_use_back);
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memcpy(new_p, old_p, in_use_front);
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}
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};
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} // namespace flatbuffers
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#endif // FLATBUFFERS_ALLOCATOR_H_
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