src/base/YesNoNone.h

   1 /*
   2  * Copyright (C) 1996-2018 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_YESNONONE_H_
  10 #define SQUID_YESNONONE_H_
  11
  12 #include "base/TextException.h"
  13
  14 // TODO: generalize / template to non-boolean option types
  15 // and make YesNoNone the boolean instance of the template
  16
  17 /**
  18  * Used for boolean enabled/disabled options with complex default logic.
  19  * Allows Squid to compute the right default after configuration.
  20  * Checks that not-yet-defined option values are not used.
  21  * Allows for implicit default Yes/No values to be used by initialization
  22  * without configure() being called, but not dumped as squid.conf content.
  23  *
  24  * Use x.configure(bool) when the value is configured.
  25  * Use x.defaultTo(bool) to assign defaults.
  26  */
  27 class YesNoNone
  28 {
  29     enum SetHow : uint8_t { optUnspecified = 0, optImplicitly = 1, optConfigured = 2 };
  30
  31 public:
  32     // this constructor initializes to 'unspecified' state
  33     YesNoNone():
  34         setHow_(optUnspecified),
  35         option(false)
  36     {}
  37
  38     // this constructor initializes to 'implicit' state
  39     explicit YesNoNone(bool beSet):
  40         setHow_(optImplicitly),
  41         option(beSet)
  42     {}
  43
  44     /// the boolean equivalent of the value stored.
  45     /// asserts if the value has not been set.
  46     explicit operator bool() const {
  47         Must(setHow_ != optUnspecified);
  48         return option;
  49     }
  50
  51     /// enables or disables the option; updating to 'configured' state
  52     void configure(bool beSet) {
  53         setHow_ = optConfigured;
  54         option = beSet;
  55     }
  56
  57     /// enables or disables the option; updating to 'implicit' state
  58     void defaultTo(bool beSet) {
  59         Must(setHow_ != optConfigured);
  60         setHow_ = optImplicitly;
  61         option = beSet;
  62     }
  63
  64     /// whether the option was enabled or disabled,
  65     /// by squid.conf values resulting in explicit configure() usage.
  66     bool configured() const {return setHow_ == optConfigured;}
  67
  68 private:
  69     SetHow setHow_; ///< how the option was set
  70     bool option; ///< specified yes/no value; meaningless if optUnspecified
  71 };
  72
  73 #endif /* SQUID_YESNONONE_H_ */
  74