102 lines
2.2 KiB
C++
102 lines
2.2 KiB
C++
/*
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* Copyright 2012-present Facebook, Inc.
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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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#pragma once
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#include <stddef.h>
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#include <stdint.h>
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namespace folly {
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template <typename T>
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class GroupVarint;
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namespace detail {
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template <typename T>
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struct GroupVarintTraits;
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template <>
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struct GroupVarintTraits<uint32_t> {
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enum : uint32_t {
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kGroupSize = 4,
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kHeaderSize = 1,
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};
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};
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template <>
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struct GroupVarintTraits<uint64_t> {
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enum : uint32_t {
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kGroupSize = 5,
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kHeaderSize = 2,
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};
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};
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template <typename T>
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class GroupVarintBase {
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protected:
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typedef GroupVarintTraits<T> Traits;
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enum : uint32_t { kHeaderSize = Traits::kHeaderSize };
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public:
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typedef T type;
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/**
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* Number of integers encoded / decoded in one pass.
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*/
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enum : uint32_t { kGroupSize = Traits::kGroupSize };
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/**
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* Maximum encoded size.
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*/
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enum : uint32_t { kMaxSize = kHeaderSize + sizeof(type) * kGroupSize };
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/**
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* Maximum size for n values.
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*/
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static size_t maxSize(size_t n) {
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// Full groups
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size_t total = (n / kGroupSize) * kFullGroupSize;
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// Incomplete last group, if any
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n %= kGroupSize;
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if (n) {
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total += kHeaderSize + n * sizeof(type);
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}
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return total;
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}
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/**
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* Size of n values starting at p.
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*/
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static size_t totalSize(const T* p, size_t n) {
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size_t size = 0;
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for (; n >= kGroupSize; n -= kGroupSize, p += kGroupSize) {
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size += Derived::size(p);
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}
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if (n) {
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size += Derived::partialSize(p, n);
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}
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return size;
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}
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private:
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typedef GroupVarint<T> Derived;
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enum { kFullGroupSize = kHeaderSize + kGroupSize * sizeof(type) };
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};
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} // namespace detail
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} // namespace folly
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