mirror of
https://github.com/DCC-EX/CommandStation-EX.git
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57 lines
2.0 KiB
C++
57 lines
2.0 KiB
C++
/*
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* © 2024 Vincent Hamp and Chris Harlow
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* All rights reserved.
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*
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* This file is part of CommandStation-EX
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*
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* This is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* It is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with CommandStation. If not, see <https://www.gnu.org/licenses/>.
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*/
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/* Reader be aware:
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This function implements the _hk data type so that a string keyword
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is hashed to the same value as the DCCEXParser uses to hash incoming
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keywords.
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Thus "MAIN"_hk generates exactly the same run time vakue
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as const int16_t HASH_KEYWORD_MAIN=11339
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*/
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#ifndef KeywordHAsher_h
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#define KeywordHasher_h
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#include <Arduino.h>
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constexpr uint16_t CompiletimeKeywordHasher(const char * sv, uint16_t running=0) {
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return (*sv==0) ? running : CompiletimeKeywordHasher(sv+1,
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(*sv >= '0' && *sv <= '9')
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? (10*running+*sv-'0') // Numeric hash
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: ((running << 5) + running) ^ *sv
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); //
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}
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constexpr int16_t operator""_hk(const char * keyword, size_t len)
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{
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return (int16_t) CompiletimeKeywordHasher(keyword,len*0);
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}
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/* Some historical values for testing:
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const int16_t HASH_KEYWORD_MAIN = 11339;
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const int16_t HASH_KEYWORD_SLOW = -17209;
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const int16_t HASH_KEYWORD_SPEED28 = -17064;
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const int16_t HASH_KEYWORD_SPEED128 = 25816;
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*/
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static_assert("MAIN"_hk == 11339,"Keyword hasher error");
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static_assert("SLOW"_hk == -17209,"Keyword hasher error");
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static_assert("SPEED28"_hk == -17064,"Keyword hasher error");
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static_assert("SPEED128"_hk == 25816,"Keyword hasher error");
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#endif |