83 lines
2.2 KiB
C++
83 lines
2.2 KiB
C++
/*
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* Authored by Alex Hultman, 2018-2022.
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* Intellectual property of third-party.
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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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* http://www.apache.org/licenses/LICENSE-2.0
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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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#ifndef UWS_BLOOMFILTER_H
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#define UWS_BLOOMFILTER_H
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/* This filter has no false positives or collisions for the standard
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* and non-standard common request headers */
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#include <string_view>
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#include <bitset>
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namespace uWS {
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struct BloomFilter {
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private:
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std::bitset<256> filter;
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static inline uint32_t perfectHash(uint32_t features) {
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return features *= 1843993368;
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}
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union ScrambleArea {
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unsigned char p[4];
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uint32_t val;
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};
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ScrambleArea getFeatures(std::string_view key) {
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ScrambleArea s;
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s.p[0] = reinterpret_cast<const unsigned char&>(key[0]);
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s.p[1] = reinterpret_cast<const unsigned char&>(key[key.length() - 1]);
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s.p[2] = reinterpret_cast<const unsigned char&>(key[key.length() - 2]);
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s.p[3] = reinterpret_cast<const unsigned char&>(key[key.length() >> 1]);
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return s;
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}
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public:
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bool mightHave(std::string_view key) {
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if (key.length() < 2) {
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return true;
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}
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ScrambleArea s = getFeatures(key);
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s.val = perfectHash(s.val);
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return filter[s.p[0]] &&
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filter[s.p[1]] &&
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filter[s.p[2]] &&
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filter[s.p[3]];
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}
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void add(std::string_view key) {
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if (key.length() >= 2) {
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ScrambleArea s = getFeatures(key);
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s.val = perfectHash(s.val);
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filter[s.p[0]] = 1;
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filter[s.p[1]] = 1;
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filter[s.p[2]] = 1;
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filter[s.p[3]] = 1;
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}
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}
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void reset() {
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filter.reset();
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}
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};
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}
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#endif // UWS_BLOOMFILTER_H
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