68 lines
1.9 KiB
C
68 lines
1.9 KiB
C
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/*
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* Copyright 2015-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 <cstddef>
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#include <type_traits>
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namespace folly {
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namespace detail {
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// Shortcut, so we don't have to use enable_if everywhere
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struct FormatTraitsBase {
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typedef void enabled;
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};
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// Traits that define enabled, value_type, and at() for anything
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// indexable with integral keys: pointers, arrays, vectors, and maps
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// with integral keys
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template <class T, class Enable = void>
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struct IndexableTraits;
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// Base class for sequences (vectors, deques)
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template <class C>
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struct IndexableTraitsSeq : public FormatTraitsBase {
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typedef C container_type;
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typedef typename C::value_type value_type;
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static const value_type& at(const C& c, int idx) {
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return c.at(idx);
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}
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static const value_type& at(const C& c, int idx, const value_type& dflt) {
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return (idx >= 0 && size_t(idx) < c.size()) ? c.at(idx) : dflt;
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}
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};
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// Base class for associative types (maps)
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template <class C>
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struct IndexableTraitsAssoc : public FormatTraitsBase {
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typedef typename C::value_type::second_type value_type;
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static const value_type& at(const C& c, int idx) {
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return c.at(static_cast<typename C::key_type>(idx));
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}
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static const value_type& at(const C& c, int idx, const value_type& dflt) {
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auto pos = c.find(static_cast<typename C::key_type>(idx));
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return pos != c.end() ? pos->second : dflt;
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}
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};
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} // namespace detail
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} // namespace folly
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