xpcom/glue/nsMemory.h

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  37
  38 #ifndef nsMemory_h__
  39 #define nsMemory_h__
  40
  41 #include "nsXPCOM.h"
  42 #include "nsIMemory.h"
  43
  44 #define NS_MEMORY_CONTRACTID "@mozilla.org/xpcom/memory-service;1"
  45 #define NS_MEMORY_CLASSNAME  "Global Memory Service"
  46 #define NS_MEMORY_CID                                \
  47 { /* 30a04e40-38e7-11d4-8cf5-0060b0fc14a3 */         \
  48     0x30a04e40,                                      \
  49     0x38e7,                                          \
  50     0x11d4,                                          \
  51     {0x8c, 0xf5, 0x00, 0x60, 0xb0, 0xfc, 0x14, 0xa3} \
  52 }
  53
  54
  55 /**
  56  * Static helper routines to manage memory. These routines allow easy access
  57  * to xpcom's built-in (global) nsIMemory implementation, without needing
  58  * to go through the service manager to get it. However this requires clients
  59  * to link with the xpcom DLL.
  60  *
  61  * This class is not threadsafe and is intented for use only on the main
  62  * thread.
  63  */
  64 class nsMemory
  65 {
  66 public:
  67     static NS_HIDDEN_(void*) Alloc(size_t size)
  68         { return NS_Alloc(size); }
  69
  70     static NS_HIDDEN_(void*) Realloc(void* ptr, PRSize size)
  71         { return NS_Realloc(ptr, size); }
  72
  73     static NS_HIDDEN_(void) Free(void* ptr)
  74         { NS_Free(ptr); }
  75
  76     static NS_COM_GLUE nsresult   HeapMinimize(PRBool aImmediate);
  77     static NS_COM_GLUE void*      Clone(const void* ptr, PRSize size);
  78     static NS_COM_GLUE nsIMemory* GetGlobalMemoryService();       // AddRefs
  79 };
  80
  81 /**
  82  * Macro to free all elements of an XPCOM array of a given size using
  83  * freeFunc, then frees the array itself using nsMemory::Free().
  84  *
  85  * Note that this macro (and its wrappers) can be used to deallocate a
  86  * partially- or completely-built array while unwinding an error
  87  * condition inside the XPCOM routine that was going to return the
  88  * array.  For this to work on a partially-built array, your code
  89  * needs to be building the array from index 0 upwards, and simply
  90  * pass the number of elements that have already been built (and thus
  91  * need to be freed) as |size|.
  92  *
  93  * Thanks to <alecf@netscape.com> for suggesting this form, which
  94  * allows the macro to be used with NS_RELEASE / NS_RELEASE_IF in
  95  * addition to nsMemory::Free.
  96  *
  97  * @param size      Number of elements in the array.  If not a constant, this
  98  *                  should be a PRInt32.  Note that this means this macro
  99  *                  will not work if size >= 2^31.
 100  * @param array     The array to be freed.
 101  * @param freeFunc  The function or macro to be used to free it.
 102  *                  For arrays of nsISupports (or any class derived
 103  *                  from it), NS_IF_RELEASE (or NS_RELEASE) should be
 104  *                  passed as freeFunc.  For most (all?) other pointer
 105  *                  types (including XPCOM strings and wstrings),
 106  *                  nsMemory::Free should be used, since the
 107  *                  shared-allocator (nsMemory) is what will have been
 108  *                  used to allocate the memory.
 109  */
 110 #define NS_FREE_XPCOM_POINTER_ARRAY(size, array, freeFunc)                    \
 111     PR_BEGIN_MACRO                                                            \
 112         PRInt32 iter_ = PRInt32(size);                                        \
 113         while (--iter_ >= 0)                                                  \
 114             freeFunc((array)[iter_]);                                         \
 115         NS_Free((array));                                                     \
 116     PR_END_MACRO
 117
 118 // convenience macros for commonly used calls.  mmmmm.  syntactic sugar.
 119
 120 /**
 121  * Macro to free arrays of non-refcounted objects allocated by the
 122  * shared allocator (nsMemory) such as strings and wstrings.  A
 123  * convenience wrapper around NS_FREE_XPCOM_POINTER_ARRAY.
 124  *
 125  * @param size      Number of elements in the array.  If not a constant, this
 126  *                  should be a PRInt32.  Note that this means this macro
 127  *                  will not work if size >= 2^31.
 128  * @param array     The array to be freed.
 129  */
 130 #define NS_FREE_XPCOM_ALLOCATED_POINTER_ARRAY(size, array)                    \
 131     NS_FREE_XPCOM_POINTER_ARRAY((size), (array), NS_Free)
 132
 133 /**
 134  * Macro to free an array of pointers to nsISupports (or classes
 135  * derived from it).  A convenience wrapper around
 136  * NS_FREE_XPCOM_POINTER_ARRAY.
 137  *
 138  * Note that if you know that none of your nsISupports pointers are
 139  * going to be 0, you can gain a bit of speed by calling
 140  * NS_FREE_XPCOM_POINTER_ARRAY directly and using NS_RELEASE as your
 141  * free function.
 142  *
 143  * @param size      Number of elements in the array.  If not a constant, this
 144  *                  should be a PRInt32.  Note that this means this macro
 145  *                  will not work if size >= 2^31.
 146  * @param array     The array to be freed.
 147  */
 148 #define NS_FREE_XPCOM_ISUPPORTS_POINTER_ARRAY(size, array)                    \
 149     NS_FREE_XPCOM_POINTER_ARRAY((size), (array), NS_IF_RELEASE)
 150
 151 /**
 152  * Helpful array length function for calculating the length of a
 153  * statically declared array.
 154  */
 155
 156 #define NS_ARRAY_LENGTH(array_) \
 157   (sizeof(array_)/sizeof(array_[0]))
 158
 159 /**
 160  * An enumeration type used to represent a method of assignment.
 161  */
 162 enum nsAssignmentType {
 163     NS_ASSIGNMENT_COPY,   // copy by value
 164     NS_ASSIGNMENT_DEPEND, // copy by reference
 165     NS_ASSIGNMENT_ADOPT   // copy by reference (take ownership of resource)
 166 };
 167
 168 #endif // nsMemory_h__
 169