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/*
* Copyright 2017 Facebook, Inc.
*
* 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.
*/
#pragma once
#include <stddef.h>
namespace folly {
template <typename T>
class GroupVarint;
namespace detail {
template <typename T>
struct GroupVarintTraits;
template <>
struct GroupVarintTraits<uint32_t> {
enum : uint32_t {
kGroupSize = 4,
kHeaderSize = 1,
};
};
template <>
struct GroupVarintTraits<uint64_t> {
enum : uint32_t {
kGroupSize = 5,
kHeaderSize = 2,
};
};
template <typename T>
class GroupVarintBase {
protected:
typedef GroupVarintTraits<T> Traits;
enum : uint32_t { kHeaderSize = Traits::kHeaderSize };
public:
typedef T type;
/**
* Number of integers encoded / decoded in one pass.
*/
enum : uint32_t { kGroupSize = Traits::kGroupSize };
/**
* Maximum encoded size.
*/
enum : uint32_t { kMaxSize = kHeaderSize + sizeof(type) * kGroupSize };
/**
* Maximum size for n values.
*/
static size_t maxSize(size_t n) {
// Full groups
size_t total = (n / kGroupSize) * kFullGroupSize;
// Incomplete last group, if any
n %= kGroupSize;
if (n) {
total += kHeaderSize + n * sizeof(type);
}
return total;
}
/**
* Size of n values starting at p.
*/
static size_t totalSize(const T* p, size_t n) {
size_t size = 0;
for (; n >= kGroupSize; n -= kGroupSize, p += kGroupSize) {
size += Derived::size(p);
}
if (n) {
size += Derived::partialSize(p, n);
}
return size;
}
private:
typedef GroupVarint<T> Derived;
enum { kFullGroupSize = kHeaderSize + kGroupSize * sizeof(type) };
};
} // namespace detail
} // namespace folly