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88 lines
3.0 KiB
C
88 lines
3.0 KiB
C
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/*
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* Copyright 2016 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 <algorithm>
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#include <string>
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#include <glog/logging.h>
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#include <folly/Likely.h>
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namespace folly {
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namespace detail {
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/***
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* The qfind_first_byte_of_* functions are declared here, before Range.h, so
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* they cannot take StringPiece values. But they're there to operate on
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* StringPiece values. Dependency cycles: fun.
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*
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* StringPieceLite is here to break that dependency cycle.
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*/
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class StringPieceLite {
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public:
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StringPieceLite(const char* b, const char* e) : b_(b), e_(e) {}
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template <typename Range>
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/* implicit */ StringPieceLite(const Range& r) :
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StringPieceLite(r.data(), r.data() + r.size()) {}
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const char* data() const { return b_; }
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const char* begin() const { return b_; }
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const char* end() const { return e_; }
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size_t size() const { return e_ - b_; }
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bool empty() const { return size() == 0; }
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const char& operator[](size_t i) const { DCHECK_GT(size(), i); return b_[i]; }
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template <typename Range>
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explicit operator Range() const { return Range(begin(), end()); }
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private:
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const char* b_;
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const char* e_;
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};
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inline size_t qfind_first_byte_of_std(const StringPieceLite haystack,
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const StringPieceLite needles) {
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auto ret = std::find_first_of(haystack.begin(), haystack.end(),
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needles.begin(), needles.end(),
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[](char a, char b) { return a == b; });
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return ret == haystack.end() ? std::string::npos : ret - haystack.begin();
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}
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size_t qfind_first_byte_of_bitset(const StringPieceLite haystack,
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const StringPieceLite needles);
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size_t qfind_first_byte_of_byteset(const StringPieceLite haystack,
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const StringPieceLite needles);
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inline size_t qfind_first_byte_of_nosse(const StringPieceLite haystack,
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const StringPieceLite needles) {
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if (UNLIKELY(needles.empty() || haystack.empty())) {
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return std::string::npos;
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}
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// The thresholds below were empirically determined by benchmarking.
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// This is not an exact science since it depends on the CPU, the size of
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// needles, and the size of haystack.
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if ((needles.size() >= 4 && haystack.size() <= 10) ||
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(needles.size() >= 16 && haystack.size() <= 64) ||
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needles.size() >= 32) {
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return qfind_first_byte_of_byteset(haystack, needles);
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}
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return qfind_first_byte_of_std(haystack, needles);
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}
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}
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}
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