src/base/LookupTable.h

   1 /*
   2  * Copyright (C) 1996-2015 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 #ifndef SQUID_LOOKUPTABLE_H_
  10 #define SQUID_LOOKUPTABLE_H_
  11
  12 #include "SBuf.h"
  13
  14 #include <map>
  15
  16 /**
  17  * a record in the initializer list for a LookupTable
  18  *
  19  * In case it is wished to extend the structure of a LookupTable's initializer
  20  * list, it can be done by using a custom struct which must match
  21  * LookupTableRecord's signature plus any extra custom fields the user may
  22  * wish to add; the extended record type must then be passed as RecordType
  23  * template parameter to LookupTable.
  24  */
  25 template <typename EnumType>
  26 struct LookupTableRecord
  27 {
  28     const char *name;
  29     EnumType id;
  30 };
  31
  32 /**
  33  * SBuf -> case-insensitive enum lookup table
  34  *
  35  * How to use:
  36  * enum enum_type { ... };
  37  * static const LookupTable<enum_type>::Record initializerTable[] = {
  38  *   {"key1", ENUM_1}, {"key2", ENUM_2}, ... {nullptr, ENUM_INVALID_VALUE}
  39  * };
  40  * LookupTable<enum_type> lookupTableInstance(ENUM_INVALID_VALUE, initializerTable);
  41  *
  42  * then in the code:
  43  * SBuf s(string_to_lookup);
  44  * enum_type item = lookupTableInstance.lookup(s);
  45  * if (item != ENUM_INVALID_VALUE) { // do stuff }
  46  *
  47  */
  48
  49 struct SBufCaseInsensitiveLess : public std::binary_function<SBuf, SBuf, bool> {
  50     bool operator() (const SBuf &x, const SBuf &y) const {
  51         return x.caseCmp(y) < 0;
  52     }
  53 };
  54 template<typename EnumType, typename RecordType = LookupTableRecord<EnumType> >
  55 class LookupTable
  56 {
  57 public:
  58     /// element of the lookup table initialization list
  59     typedef RecordType Record;
  60
  61     LookupTable(const EnumType theInvalid, const Record data[]) :
  62         invalidValue(theInvalid)
  63     {
  64         for (auto i = 0; data[i].name != nullptr; ++i) {
  65             lookupTable[SBuf(data[i].name)] = data[i].id;
  66         }
  67     }
  68
  69     EnumType lookup(const SBuf &key) const {
  70         auto r = lookupTable.find(key);
  71         if (r == lookupTable.end())
  72             return invalidValue;
  73         return r->second;
  74     }
  75
  76 private:
  77     typedef std::map<const SBuf, EnumType, SBufCaseInsensitiveLess> lookupTable_t;
  78     lookupTable_t lookupTable;
  79     EnumType invalidValue;
  80 };
  81
  82 #endif /* SQUID_LOOKUPTABLE_H_ */
  83