66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
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/*
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* Copyright (c) Facebook, Inc. and its affiliates.
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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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/**
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* @author Giuseppe Ottaviano <ott@fb.com>
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*
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* Shared utils for BitVectorCoding.h and EliasFanoCoding.h.
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*/
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#pragma once
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#include <stddef.h>
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namespace folly {
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namespace compression {
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namespace detail {
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/**
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* Helpers to store pointers to forward and skip pointer arrays only
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* if they are used, that is, the quantum is nonzero. If it is 0, the
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* class is empty, and the member is static to keep the syntax valid,
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* thus it will take no space in a derived class thanks to empty base
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* class optimization.
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*/
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template <size_t>
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class ForwardPointers {
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protected:
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explicit ForwardPointers(const unsigned char* ptr) : forwardPointers_(ptr) {}
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const unsigned char* const forwardPointers_;
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};
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template <>
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class ForwardPointers<0> {
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protected:
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explicit ForwardPointers(const unsigned char*) {}
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constexpr static const unsigned char* const forwardPointers_{};
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};
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template <size_t>
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class SkipPointers {
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protected:
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explicit SkipPointers(const unsigned char* ptr) : skipPointers_(ptr) {}
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const unsigned char* const skipPointers_;
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};
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template <>
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class SkipPointers<0> {
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protected:
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explicit SkipPointers(const unsigned char*) {}
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constexpr static const unsigned char* const skipPointers_{};
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};
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} // namespace detail
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} // namespace compression
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} // namespace folly
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