ACE/ace/Env_Value_T.h

   1 // -*- C++ -*-
   2
   3 //=============================================================================
   4 /**
   5  *  @file    Env_Value_T.h
   6  *
   7  *  Template to encapsulate getting a value from an environment variable
   8  *  and using a supplied default value if not in the environment.
   9  *
  10  *  @author Chris Cleeland (derived from work by Carlos O'Ryan)
  11  */
  12 //=============================================================================
  13
  14 #ifndef ACE_ENV_VALUE_T_H
  15 #define ACE_ENV_VALUE_T_H
  16
  17 #include /**/ "ace/pre.h"
  18
  19 #include /**/ "ace/config-all.h"
  20 #include "ace/Global_Macros.h"
  21 #include "ace/OS_NS_stdlib.h"
  22 #include "ace/Copy_Disabled.h"
  23
  24 #if !defined (ACE_LACKS_PRAGMA_ONCE)
  25 # pragma once
  26 #endif /* ACE_LACKS_PRAGMA_ONCE */
  27
  28 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  29
  30 /**
  31  * @class ACE_Env_Value
  32  *
  33  * @brief Environment Variable Value
  34  *
  35  * Reads a variable from the user environment, providing a default
  36  * value.
  37  */
  38 template <class T>
  39 class ACE_Env_Value : private ACE_Copy_Disabled
  40 {
  41 public:
  42   /**
  43    * Default constructor which isn't bound to a specific environment
  44    * variable name or a default value.  Before being useful it must
  45    * open()'d.
  46    */
  47   ACE_Env_Value ();
  48
  49   /// Constructor that calls open().
  50   ACE_Env_Value (const ACE_TCHAR *varname, const T &vardefault);
  51
  52   /// Destroy the value.
  53   ~ACE_Env_Value ();
  54
  55   /// Returns the value as type T.
  56   operator T ();
  57
  58   /// The constructor, read @a varname from the environment, using
  59   /// @a defval as its value if it is not defined.
  60   void open (const ACE_TCHAR *varname, const T &defval);
  61
  62   /// Returns the name of the variable being tracked.
  63   const ACE_TCHAR *varname () const;
  64
  65 private:
  66   void fetch_value ();
  67
  68   const ACE_TCHAR *varname_;
  69   T value_;
  70 };
  71
  72 /// Function to convert a string @a s into type @c T.
  73 template <class T> void ACE_Convert (const ACE_TCHAR *s, T &t);
  74
  75 ACE_END_VERSIONED_NAMESPACE_DECL
  76
  77 #if defined (__ACE_INLINE__)
  78 #include "ace/Env_Value_T.inl"
  79 #endif /* __ACE_INLINE__ */
  80
  81 #include "ace/Env_Value_T.cpp"
  82
  83 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  84
  85 template <> inline void
  86 ACE_Convert (const ACE_TCHAR *s, ACE_TCHAR *&v)
  87 {
  88   v = (ACE_TCHAR *) s;
  89 }
  90
  91 template <> inline void
  92 ACE_Convert (const ACE_TCHAR *s, const ACE_TCHAR *&v)
  93 {
  94   v = (const ACE_TCHAR *) s;
  95 }
  96
  97 template <> inline void
  98 ACE_Convert (const ACE_TCHAR *s, short &si)
  99 {
 100   si = static_cast<short> (ACE_OS::strtol (s, 0, 10));
 101 }
 102
 103 template <> inline void
 104 ACE_Convert (const ACE_TCHAR *s, u_short &us)
 105 {
 106   us = static_cast <u_short> (ACE_OS::strtol (s, 0, 10));
 107 }
 108
 109 template <> inline void
 110 ACE_Convert (const ACE_TCHAR *s, u_int &i)
 111 {
 112   i = static_cast<u_int> (ACE_OS::strtol (s, 0, 10));
 113 }
 114
 115 template <> inline void
 116 ACE_Convert (const ACE_TCHAR *s, long &l)
 117 {
 118   l = ACE_OS::strtol (s, 0, 10);
 119 }
 120
 121 template <> inline void
 122 ACE_Convert (const ACE_TCHAR *s, int &i)
 123 {
 124   i = static_cast<int> (ACE_OS::strtol (s, 0, 10));
 125 }
 126
 127 template <> inline void
 128 ACE_Convert (const ACE_TCHAR *s, u_long &ul)
 129 {
 130   ul = ACE_OS::strtoul (s, 0, 10);
 131 }
 132
 133 template <> inline void
 134 ACE_Convert (const ACE_TCHAR *s, double &d)
 135 {
 136   d = ACE_OS::strtod (s, 0);
 137 }
 138
 139 // Default calls a CTOR on type T of the form 'T::T(const char*)', but
 140 // users can feel free to create their own specialized conversion
 141 // functions if necessary, as shown above.  Note that for 'char*' the
 142 // default is used because a simple cast will be performed and no
 143 // conversion will be necessary.
 144 template <class T> inline void
 145 ACE_Convert (const ACE_TCHAR *s, T &t)
 146 {
 147   t = T (s);
 148 }
 149
 150 ACE_END_VERSIONED_NAMESPACE_DECL
 151
 152 #include /**/ "ace/post.h"
 153 #endif /* ACE_ENV_VALUE_T_H */