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comparison lib/xsize.h @ 398:7987ee447833 3.0-beta1
Added generated files for release
author | lost@l-w.ca |
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date | Fri, 23 Jul 2010 17:18:52 -0600 |
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1 /* xsize.h -- Checked size_t computations. | |
2 | |
3 Copyright (C) 2003, 2008, 2009, 2010 Free Software Foundation, Inc. | |
4 | |
5 This program is free software; you can redistribute it and/or modify | |
6 it under the terms of the GNU General Public License as published by | |
7 the Free Software Foundation; either version 3, or (at your option) | |
8 any later version. | |
9 | |
10 This program is distributed in the hope that it will be useful, | |
11 but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 GNU General Public License for more details. | |
14 | |
15 You should have received a copy of the GNU General Public License | |
16 along with this program; if not, write to the Free Software Foundation, | |
17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ | |
18 | |
19 #ifndef _XSIZE_H | |
20 #define _XSIZE_H | |
21 | |
22 /* Get size_t. */ | |
23 #include <stddef.h> | |
24 | |
25 /* Get SIZE_MAX. */ | |
26 #include <limits.h> | |
27 #if HAVE_STDINT_H | |
28 # include <stdint.h> | |
29 #endif | |
30 | |
31 /* The size of memory objects is often computed through expressions of | |
32 type size_t. Example: | |
33 void* p = malloc (header_size + n * element_size). | |
34 These computations can lead to overflow. When this happens, malloc() | |
35 returns a piece of memory that is way too small, and the program then | |
36 crashes while attempting to fill the memory. | |
37 To avoid this, the functions and macros in this file check for overflow. | |
38 The convention is that SIZE_MAX represents overflow. | |
39 malloc (SIZE_MAX) is not guaranteed to fail -- think of a malloc | |
40 implementation that uses mmap --, it's recommended to use size_overflow_p() | |
41 or size_in_bounds_p() before invoking malloc(). | |
42 The example thus becomes: | |
43 size_t size = xsum (header_size, xtimes (n, element_size)); | |
44 void *p = (size_in_bounds_p (size) ? malloc (size) : NULL); | |
45 */ | |
46 | |
47 /* Convert an arbitrary value >= 0 to type size_t. */ | |
48 #define xcast_size_t(N) \ | |
49 ((N) <= SIZE_MAX ? (size_t) (N) : SIZE_MAX) | |
50 | |
51 /* Sum of two sizes, with overflow check. */ | |
52 static inline size_t | |
53 #if __GNUC__ >= 3 | |
54 __attribute__ ((__pure__)) | |
55 #endif | |
56 xsum (size_t size1, size_t size2) | |
57 { | |
58 size_t sum = size1 + size2; | |
59 return (sum >= size1 ? sum : SIZE_MAX); | |
60 } | |
61 | |
62 /* Sum of three sizes, with overflow check. */ | |
63 static inline size_t | |
64 #if __GNUC__ >= 3 | |
65 __attribute__ ((__pure__)) | |
66 #endif | |
67 xsum3 (size_t size1, size_t size2, size_t size3) | |
68 { | |
69 return xsum (xsum (size1, size2), size3); | |
70 } | |
71 | |
72 /* Sum of four sizes, with overflow check. */ | |
73 static inline size_t | |
74 #if __GNUC__ >= 3 | |
75 __attribute__ ((__pure__)) | |
76 #endif | |
77 xsum4 (size_t size1, size_t size2, size_t size3, size_t size4) | |
78 { | |
79 return xsum (xsum (xsum (size1, size2), size3), size4); | |
80 } | |
81 | |
82 /* Maximum of two sizes, with overflow check. */ | |
83 static inline size_t | |
84 #if __GNUC__ >= 3 | |
85 __attribute__ ((__pure__)) | |
86 #endif | |
87 xmax (size_t size1, size_t size2) | |
88 { | |
89 /* No explicit check is needed here, because for any n: | |
90 max (SIZE_MAX, n) == SIZE_MAX and max (n, SIZE_MAX) == SIZE_MAX. */ | |
91 return (size1 >= size2 ? size1 : size2); | |
92 } | |
93 | |
94 /* Multiplication of a count with an element size, with overflow check. | |
95 The count must be >= 0 and the element size must be > 0. | |
96 This is a macro, not an inline function, so that it works correctly even | |
97 when N is of a wider type and N > SIZE_MAX. */ | |
98 #define xtimes(N, ELSIZE) \ | |
99 ((N) <= SIZE_MAX / (ELSIZE) ? (size_t) (N) * (ELSIZE) : SIZE_MAX) | |
100 | |
101 /* Check for overflow. */ | |
102 #define size_overflow_p(SIZE) \ | |
103 ((SIZE) == SIZE_MAX) | |
104 /* Check against overflow. */ | |
105 #define size_in_bounds_p(SIZE) \ | |
106 ((SIZE) != SIZE_MAX) | |
107 | |
108 #endif /* _XSIZE_H */ |