1 | // |
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2 | // Cforall Version 1.0.0 Copyright (C) 2015 University of Waterloo |
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3 | // |
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4 | // The contents of this file are covered under the licence agreement in the |
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5 | // file "LICENCE" distributed with Cforall. |
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6 | // |
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7 | // InternedString.h -- |
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8 | // |
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9 | // Author : Aaron B. Moss |
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10 | // Created On : Thu Jun 14 11:15:00 2018 |
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11 | // Last Modified By : Aaron B. Moss |
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12 | // Last Modified On : Thu Jun 14 11:15:00 2018 |
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13 | // Update Count : 1 |
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14 | // |
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15 | |
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16 | #pragma once |
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17 | |
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18 | #include <functional> |
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19 | #include <string> |
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20 | #include <unordered_set> |
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21 | #include <utility> |
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22 | |
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23 | /// Keeps canonical copies of a std::string for quicker comparisons |
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24 | class interned_string { |
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25 | /// Shared map of canonical string representations |
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26 | static std::unordered_set< std::string > canonical; |
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27 | |
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28 | /// Canonical representation of empty string |
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29 | static const std::string* empty_string() { |
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30 | static const std::string* mt = [](){ |
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31 | return &*canonical.emplace( "" ).first; |
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32 | }(); |
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33 | return mt; |
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34 | } |
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35 | |
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36 | /// Canonicalize string |
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37 | template<typename S> |
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38 | static const std::string* intern( S&& s ) { |
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39 | return &*canonical.emplace( std::forward<S>(s) ).first; |
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40 | } |
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41 | |
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42 | /// Pointer to stored string |
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43 | const std::string* s; |
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44 | |
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45 | public: |
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46 | interned_string() : s{empty_string()} {} |
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47 | interned_string(const char* cs) : s{intern(cs)} {} |
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48 | interned_string(const std::string& ss) : s{intern(ss)} {} |
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49 | /// Invalid string |
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50 | interned_string(std::nullptr_t) : s{nullptr} {} |
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51 | |
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52 | operator const std::string& () const { return *s; } |
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53 | const std::string& str() const { return (const std::string&)*this; } |
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54 | |
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55 | bool operator== (const interned_string& o) const { return s == o.s; } |
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56 | bool operator!= (const interned_string& o) const { return s != o.s; } |
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57 | |
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58 | /// Check for invalid string |
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59 | explicit operator bool () { return s != nullptr; } |
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60 | }; |
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61 | |
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62 | inline std::ostream& operator<< (std::ostream& out, const interned_string& s) { |
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63 | return out << (const std::string&)s; |
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64 | } |
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65 | |
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66 | namespace std { |
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67 | template<> struct hash<interned_string> { |
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68 | std::size_t operator() (const interned_string& s) const { |
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69 | return std::hash<const std::string*>{}( &(const std::string&)s ); |
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70 | } |
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71 | }; |
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72 | } |
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73 | |
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74 | // Local Variables: // |
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75 | // tab-width: 4 // |
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76 | // mode: c++ // |
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77 | // compile-command: "make install" // |
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78 | // End: // |
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