libsecurity_utilities/lib/memutils.h

   1 /*
   2  * Copyright (c) 2000-2004 Apple Computer, Inc. All Rights Reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. Please obtain a copy of the License at
  10  * http://www.opensource.apple.com/apsl/ and read it before using this
  11  * file.
  12  *
  13  * The Original Code and all software distributed under the License are
  14  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  15  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  16  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  18  * Please see the License for the specific language governing rights and
  19  * limitations under the License.
  20  *
  21  * @APPLE_LICENSE_HEADER_END@
  22  */
  23
  24
  25 //
  26 // memutils - memory-related low-level utilities for easier living
  27 //
  28 #ifndef _H_MEMUTILS
  29 #define _H_MEMUTILS
  30
  31 #include <security_utilities/utilities.h>
  32 #include <sys/types.h>
  33 #include <stdlib.h>
  34 #include <algorithm>
  35
  36
  37 //
  38 // Encapsulate these very sharp tools in a separate (ugly-named) namespace
  39 //
  40 namespace Security {
  41 namespace LowLevelMemoryUtilities {
  42
  43
  44 //
  45 // The default system alignment.
  46 //
  47 static const size_t systemAlignment = 4;
  48
  49
  50 //
  51 // Get the local alignment for a type, as used by the acting compiler.
  52 //
  53 template <class T>
  54 inline size_t alignof() { struct { char c; T t; } s; return sizeof(s) - sizeof(T); }
  55
  56
  57 //
  58 // Get the local offset of a field in a (struct or class) type, as layed out
  59 // by the acting compiler.
  60 // NB: "offsetof" is a standard-defined macro. Don't use that.
  61 //
  62 template <class Type, class Field>
  63 inline size_t fieldOffsetOf(Field (Type::*field))
  64 {
  65         Type *object = 0;       // we don't REALLY need this, but it's easier to read
  66         return uintptr_t(&(object->*field)) - uintptr_t(object);
  67 }
  68
  69
  70 //
  71 // Round up a size or pointer to an alignment boundary.
  72 // Alignment must be a power of two; default is default alignment.
  73 //
  74 inline size_t alignUp(size_t size, size_t alignment = systemAlignment)
  75 {
  76         return ((size - 1) & ~(alignment - 1)) + alignment;
  77 }
  78
  79 inline void *alignUp(void *p, size_t alignment = systemAlignment)
  80 {
  81         return reinterpret_cast<void *>(alignUp(uintptr_t(p), alignment));
  82 }
  83
  84 inline const void *alignUp(const void *p, size_t alignment = systemAlignment)
  85 {
  86         return reinterpret_cast<const void *>(alignUp(uintptr_t(p), alignment));
  87 }
  88
  89 template <class T>
  90 inline const T *increment(const void *p, ptrdiff_t offset)
  91 { return reinterpret_cast<const T *>(uintptr_t(p) + offset); }
  92
  93 template <class T>
  94 inline T *increment(void *p, ptrdiff_t offset)
  95 { return reinterpret_cast<T *>(uintptr_t(p) + offset); }
  96
  97 inline const void *increment(const void *p, ptrdiff_t offset)
  98 { return increment<const void>(p, offset); }
  99
 100 inline void *increment(void *p, ptrdiff_t offset)
 101 { return increment<void>(p, offset); }
 102
 103 template <class T>
 104 inline const T *increment(const void *p, ptrdiff_t offset, size_t alignment)
 105 { return increment<const T>(alignUp(p, alignment), offset); }
 106
 107 template <class T>
 108 inline T *increment(void *p, ptrdiff_t offset, size_t alignment)
 109 { return increment<T>(alignUp(p, alignment), offset); }
 110
 111 inline const void *increment(const void *p, ptrdiff_t offset, size_t alignment)
 112 { return increment<const void>(p, offset, alignment); }
 113
 114 inline void *increment(void *p, ptrdiff_t offset, size_t alignment)
 115 { return increment<void>(p, offset, alignment); }
 116
 117 inline ptrdiff_t difference(const void *p1, const void *p2)
 118 { return uintptr_t(p1) - uintptr_t(p2); }
 119
 120
 121 } // end namespace LowLevelMemoryUtilities
 122 } // end namespace Security
 123
 124 #endif //_H_MEMUTILS