1/*
2 * Copyright (c) 2000-2004,2011,2014 Apple 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//
40namespace Security {
41namespace LowLevelMemoryUtilities {
42
43
44//
45// The default system alignment.
46//
47static const size_t systemAlignment = 4;
48
49
50//
51// Get the local alignment for a type, as used by the acting compiler.
52//
53template <class T>
54inline 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//
62template <class Type, class Field>
63inline 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//
74inline size_t alignUp(size_t size, size_t alignment = systemAlignment)
75{
76	return ((size - 1) & ~(alignment - 1)) + alignment;
77}
78
79inline void *alignUp(void *p, size_t alignment = systemAlignment)
80{
81	return reinterpret_cast<void *>(alignUp(uintptr_t(p), alignment));
82}
83
84inline const void *alignUp(const void *p, size_t alignment = systemAlignment)
85{
86	return reinterpret_cast<const void *>(alignUp(uintptr_t(p), alignment));
87}
88
89template <class T>
90inline const T *increment(const void *p, ptrdiff_t offset)
91{ return reinterpret_cast<const T *>(uintptr_t(p) + offset); }
92
93template <class T>
94inline T *increment(void *p, ptrdiff_t offset)
95{ return reinterpret_cast<T *>(uintptr_t(p) + offset); }
96
97inline const void *increment(const void *p, ptrdiff_t offset)
98{ return increment<const void>(p, offset); }
99
100inline void *increment(void *p, ptrdiff_t offset)
101{ return increment<void>(p, offset); }
102
103template <class T>
104inline const T *increment(const void *p, ptrdiff_t offset, size_t alignment)
105{ return increment<const T>(alignUp(p, alignment), offset); }
106
107template <class T>
108inline T *increment(void *p, ptrdiff_t offset, size_t alignment)
109{ return increment<T>(alignUp(p, alignment), offset); }
110
111inline const void *increment(const void *p, ptrdiff_t offset, size_t alignment)
112{ return increment<const void>(p, offset, alignment); }
113
114inline void *increment(void *p, ptrdiff_t offset, size_t alignment)
115{ return increment<void>(p, offset, alignment); }
116
117inline 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
125