Mercurial > hg > octave-jordi > gnulib-hg
annotate lib/xsize.h @ 5848:a48fb0e98c8c
*** empty log message ***
| author | Paul Eggert <eggert@cs.ucla.edu> |
|---|---|
| date | Sat, 14 May 2005 06:03:57 +0000 |
| parents | 1ca4f3678daf |
| children | 7ebb4a06fabd |
| rev | line source |
|---|---|
| 4852 | 1 /* xsize.h -- Checked size_t computations. |
| 2 | |
| 3 Copyright (C) 2003 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 2, 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, | |
|
5848
a48fb0e98c8c
*** empty log message ***
Paul Eggert <eggert@cs.ucla.edu>
parents:
4870
diff
changeset
|
17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ |
| 4852 | 18 |
| 19 #ifndef _XSIZE_H | |
| 20 #define _XSIZE_H | |
| 21 | |
| 22 /* Get size_t. */ | |
| 23 #include <stddef.h> | |
| 24 | |
| 25 /* Get SIZE_MAX. */ | |
|
4855
21b00e0426f7
Solaris portability problem.
Bruno Haible <bruno@clisp.org>
parents:
4852
diff
changeset
|
26 #include <limits.h> |
| 4852 | 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 | |
| 4870 | 40 implementation that uses mmap --, it's recommended to use size_overflow_p() |
| 41 or size_in_bounds_p() before invoking malloc(). | |
| 4852 | 42 The example thus becomes: |
| 43 size_t size = xsum (header_size, xtimes (n, element_size)); | |
| 4870 | 44 void *p = (size_in_bounds_p (size) ? malloc (size) : NULL); |
| 4852 | 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 | |
| 4870 | 53 #if __GNUC__ >= 3 |
| 54 __attribute__ ((__pure__)) | |
| 55 #endif | |
| 4852 | 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 | |
| 4870 | 64 #if __GNUC__ >= 3 |
| 65 __attribute__ ((__pure__)) | |
| 66 #endif | |
| 4852 | 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 | |
| 4870 | 74 #if __GNUC__ >= 3 |
| 75 __attribute__ ((__pure__)) | |
| 76 #endif | |
| 4852 | 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 | |
| 4870 | 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 | |
| 4852 | 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 tupe 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 */ |