ACE/ace/OS_Errno.h

   1 // -*- C++ -*-
   2
   3 //=============================================================================
   4 /**
   5  *  @file   OS_Errno.h
   6  *
   7  *  @author Doug Schmidt <d.schmidt@vanderbilt.edu>
   8  */
   9 //=============================================================================
  10
  11 #ifndef ACE_OS_ERRNO_H
  12 #define ACE_OS_ERRNO_H
  13 #include /**/ "ace/pre.h"
  14
  15 #include /**/ "ace/ACE_export.h"
  16
  17 #if !defined (ACE_LACKS_PRAGMA_ONCE)
  18 # pragma once
  19 #endif /* ACE_LACKS_PRAGMA_ONCE */
  20
  21 #include "ace/OS_NS_errno.h"
  22
  23 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  24
  25 /**
  26  * @class ACE_Errno_Guard
  27  *
  28  * @brief Provides a wrapper to improve performance when thread-specific
  29  * errno must be saved and restored in a block of code.
  30  *
  31  * The typical use-case for this is the following:
  32  * int error = errno;
  33  * call_some_function_that_might_change_errno ();
  34  * errno = error;
  35  * This can be replaced with
  36  * {
  37  * ACE_Errno_Guard guard (errno);
  38  * call_some_function_that_might_change_errno ();
  39  * }
  40  * This implementation is more elegant and more efficient since it
  41  * avoids an unnecessary second access to thread-specific storage
  42  * by caching a pointer to the value of errno in TSS.
  43  */
  44 class ACE_Export ACE_Errno_Guard
  45 {
  46 public:
  47   ///  Stash the value of @a error into @c error_ and initialize the
  48   ///  @c errno_ptr_ to the address of @a errno_ref.
  49   ACE_Errno_Guard (ACE_ERRNO_TYPE &errno_ref,
  50                    int error);
  51
  52   ///  Initialize the @c errno_ptr_ to the address of @a errno_ref.
  53   ACE_Errno_Guard (ACE_ERRNO_TYPE &errno_ref);
  54
  55   /// Reset the value of @c errno to <error>.
  56   ~ACE_Errno_Guard ();
  57
  58   /// Assign @a erro> to error_.
  59   int operator= (int error);
  60
  61   /// Compare @a error with error_ for equality.
  62   bool operator== (int error);
  63
  64   /// Compare @a error with error_ for inequality.
  65   bool operator!= (int error);
  66
  67 private:
  68   ACE_Errno_Guard (const ACE_Errno_Guard &) = delete;
  69   ACE_Errno_Guard &operator= (const ACE_Errno_Guard &) = delete;
  70
  71 #if defined (ACE_MT_SAFE)
  72   ACE_ERRNO_TYPE *errno_ptr_;
  73 #endif /* ACE_MT_SAFE */
  74   int error_;
  75 };
  76
  77 ACE_END_VERSIONED_NAMESPACE_DECL
  78
  79 // Inlining this class on debug builds with can cause
  80 // deadlocks during static initialization. On non debug builds it
  81 // causes compilation errors.
  82 #if defined (ACE_HAS_INLINED_OSCALLS)
  83 # if defined (ACE_INLINE)
  84 #  undef ACE_INLINE
  85 # endif /* ACE_INLINE */
  86 # define ACE_INLINE inline
  87 # include "ace/OS_Errno.inl"
  88 #endif /* ACE_HAS_INLINED_OSCALLS */
  89
  90 #include /**/ "ace/post.h"
  91 #endif /* ACE_OS_ERRNO_H */