Ichthyostega
bad4827b34
Only minor rearrangements necessary to make that possible with C++20
And while at this change (which requires a full rebuild of Lumiera)
- simplify the defined comparison operators, as C++20 can infer most variations
- also mark various usages of `const char*` either as Literal or CStr
Remark: regarding copyright, up to now this is entirely my work,
with two major creation steps in 2008 (conception) and
in 2017 (introduction of a symbol table)
108 lines
2.8 KiB
C++
108 lines
2.8 KiB
C++
/*
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Symbol(impl) - helpers for working with literal string IDs
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Copyright (C)
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2009,2017 Hermann Vosseler <Ichthyostega@web.de>
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**Lumiera** is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2 of the License, or (at your
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option) any later version. See the file COPYING for further details.
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* *****************************************************************/
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/** @file symbol-impl.cpp
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** Implementation functionality to support definition of lib::Symbol.
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** @see lib::Symbol
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** @see control::CommandRegistry for usage example of the hash function.
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** @see symbol-table.hpp for the implementation of _interned strings_
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*/
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#include "lib/symbol.hpp"
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#include "lib/symbol-table.hpp"
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#include <boost/functional/hash.hpp>
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#include <cstddef>
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#include <cstring>
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#include <string>
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using std::size_t;
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using std::string;
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using std::forward;
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using boost::hash_combine;
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namespace lib {
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const size_t STRING_MAX_RELEVANT = LUMIERA_IDSTRING_MAX_RELEVANT;
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namespace { // global symbol table
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SymbolTable&
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symbolTable()
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{
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static SymbolTable theSymbolTable;
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return theSymbolTable; // Meyer's Singleton
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}
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}
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/**
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* create Symbol by symbol table lookup.
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* @note identical strings will be mapped to the same Symbol (embedded pointer)
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* @warning potential lock contention, since each ctor call needs to do a lookup
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* @remark since lumiera::LifecycleHook entries use a Symbol, the symbol table is
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* implemented as Meyer's singleton and pulled up early, way before main()
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*/
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Symbol::Symbol (string&& definition)
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: Literal{symbolTable().internedString (forward<string> (definition))}
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{ }
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/* == predefined marker Symbols == */
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Symbol Symbol::ANY = "*";
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Symbol Symbol::EMPTY = "";
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Symbol Symbol::BOTTOM = "⟂";
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Symbol Symbol::FAILURE = "↯";
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// see also: lib/format-obj.cpp
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// We can not share these definitions due to undefined static init order
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/** generate hash value based on the Literal's contents.
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* This function is intended to be picked up by ADL, and should be usable
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* both with `std::hash` and `<boost/functional/hash.hpp>`. It is implemented
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* similar as the boost::hash specialisation for std::string */
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HashVal
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hash_value (Literal literal)
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{
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size_t hash=0;
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if (literal)
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{
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size_t cnt = 1;
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CStr pos = literal;
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for ( ; cnt <= STRING_MAX_RELEVANT and *pos ; ++cnt, ++pos )
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hash_combine (hash, *pos);
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}
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return hash;
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}
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/** hash value for Symbols is directly based on the symbol table entry */
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HashVal
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hash_value (Symbol sym)
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{
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return sym? boost::hash_value (sym.c())
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: 0;
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}
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} // namespace lib
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