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 
EqualsnsID47   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:
nsIDToCString(const nsID & aID)105   explicit nsIDToCString(const nsID& aID) {
106     aID.ToProvidedString(mStringBytes);
107   }
108 
get()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
183