xpcom/base/nsID.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef nsID_h__
   8 #define nsID_h__
   9
  10 #include <string.h>
  11
  12 #include "nscore.h"
  13
  14 #define NSID_LENGTH 39
  15
  16 /**
  17  * A "unique identifier". This is modeled after OSF DCE UUIDs.
  18  */
  19
  20 struct nsID {
  21   /**
  22    * @name Identifier values
  23    */
  24
  25   //@{
  26   uint32_t m0;
  27   uint16_t m1;
  28   uint16_t m2;
  29   uint8_t m3[8];
  30   //@}
  31
  32   /**
  33    * @name Methods
  34    */
  35
  36   //@{
  37   /**
  38    * Ensures everything is zeroed out.
  39    */
  40   void Clear();
  41
  42   /**
  43    * Equivalency method. Compares this nsID with another.
  44    * @return <b>true</b> if they are the same, <b>false</b> if not.
  45    */
  46
  47   inline bool Equals(const nsID& aOther) const {
  48     // At the time of this writing, modern compilers (namely Clang) inline this
  49     // memcmp call into a single SIMD operation on x86/x86-64 architectures (as
  50     // long as we compare to zero rather than returning the full integer return
  51     // value), which is measurably more efficient to any manual comparisons we
  52     // can do directly.
  53 #if defined(__x86_64__) || defined(__i386__)
  54     return !memcmp(this, &aOther, sizeof *this);
  55 #else
  56     // However, on ARM architectures, compilers still tend to generate a direct
  57     // memcmp call, which we'd like to avoid.
  58     return (((uint32_t*)&m0)[0] == ((uint32_t*)&aOther.m0)[0]) &&
  59            (((uint32_t*)&m0)[1] == ((uint32_t*)&aOther.m0)[1]) &&
  60            (((uint32_t*)&m0)[2] == ((uint32_t*)&aOther.m0)[2]) &&
  61            (((uint32_t*)&m0)[3] == ((uint32_t*)&aOther.m0)[3]);
  62 #endif
  63   }
  64
  65   inline bool operator==(const nsID& aOther) const { return Equals(aOther); }
  66
  67   /**
  68    * nsID Parsing method. Turns a {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
  69    * string into an nsID
  70    */
  71   bool Parse(const char* aIDStr);
  72
  73 #ifndef XPCOM_GLUE_AVOID_NSPR
  74   /**
  75    * nsID string encoder. Returns an allocated string in
  76    * {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} format. Caller should free string.
  77    * YOU SHOULD ONLY USE THIS IF YOU CANNOT USE ToProvidedString() BELOW.
  78    */
  79   char* ToString() const;
  80
  81   /**
  82    * nsID string encoder. Builds a string in
  83    * {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} format, into a char[NSID_LENGTH]
  84    * buffer provided by the caller (for instance, on the stack).
  85    */
  86   void ToProvidedString(char (&aDest)[NSID_LENGTH]) const;
  87
  88 #endif  // XPCOM_GLUE_AVOID_NSPR
  89
  90   // Infallibly duplicate an nsID. Must be freed with free().
  91   nsID* Clone() const;
  92
  93   //@}
  94 };
  95
  96 #ifndef XPCOM_GLUE_AVOID_NSPR
  97 /**
  98  * A stack helper class to convert a nsID to a string.  Useful
  99  * for printing nsIDs.  For example:
 100  *   nsID aID = ...;
 101  *   printf("%s", nsIDToCString(aID).get());
 102  */
 103 class nsIDToCString {
 104  public:
 105   explicit nsIDToCString(const nsID& aID) {
 106     aID.ToProvidedString(mStringBytes);
 107   }
 108
 109   const char* get() const { return mStringBytes; }
 110
 111  protected:
 112   char mStringBytes[NSID_LENGTH];
 113 };
 114 #endif
 115
 116 /*
 117  * Class IDs
 118  */
 119
 120 typedef nsID nsCID;
 121
 122 // Define an CID
 123 #define NS_DEFINE_CID(_name, _cidspec) const nsCID _name = _cidspec
 124
 125 #define NS_DEFINE_NAMED_CID(_name) static const nsCID k##_name = _name
 126
 127 #define REFNSCID const nsCID&
 128
 129 /**
 130  * An "interface id" which can be used to uniquely identify a given
 131  * interface.
 132  */
 133
 134 typedef nsID nsIID;
 135
 136 /**
 137  * A macro shorthand for <tt>const nsIID&<tt>
 138  */
 139
 140 #define REFNSIID const nsIID&
 141
 142 /**
 143  * Define an IID
 144  * obsolete - do not use this macro
 145  */
 146
 147 #define NS_DEFINE_IID(_name, _iidspec) const nsIID _name = _iidspec
 148
 149 /**
 150  * A macro to build the static const IID accessor method. The Dummy
 151  * template parameter only exists so that the kIID symbol will be linked
 152  * properly (weak symbol on linux, gnu_linkonce on mac, multiple-definitions
 153  * merged on windows). Dummy should always be instantiated as "void".
 154  */
 155
 156 #define NS_DECLARE_STATIC_IID_ACCESSOR(the_iid) \
 157   template <typename T, typename U>             \
 158   struct COMTypeInfo;
 159
 160 #define NS_DEFINE_STATIC_IID_ACCESSOR(the_interface, the_iid)                \
 161   template <typename T>                                                      \
 162   struct the_interface::COMTypeInfo<the_interface, T> {                      \
 163     static const nsIID kIID NS_HIDDEN;                                       \
 164   };                                                                         \
 165   template <typename T>                                                      \
 166   const nsIID the_interface::COMTypeInfo<the_interface, T>::kIID NS_HIDDEN = \
 167       the_iid;
 168
 169 /**
 170  * A macro to build the static const CID accessor method
 171  */
 172
 173 #define NS_DEFINE_STATIC_CID_ACCESSOR(the_cid) \
 174   static const nsID& GetCID() {                \
 175     static const nsID cid = the_cid;           \
 176     return cid;                                \
 177   }
 178
 179 #define NS_GET_IID(T) (T::COMTypeInfo<T, void>::kIID)
 180 #define NS_GET_TEMPLATE_IID(T) (T::template COMTypeInfo<T, void>::kIID)
 181
 182 #endif