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authorcvs2svn <cvs2svn@FreeBSD.org>2004-06-16 09:47:30 +0000
committercvs2svn <cvs2svn@FreeBSD.org>2004-06-16 09:47:30 +0000
commitc80b93884dd45451a0849ddd0de0c7b0b1d145fb (patch)
tree244abd899a44b3482eeb9d9def6b010029e66471
parent87aef775a7551631bcce0760ae2f4228511faa64 (diff)
downloadsrc-c80b93884dd45451a0849ddd0de0c7b0b1d145fb.tar.gz
src-c80b93884dd45451a0849ddd0de0c7b0b1d145fb.zip
This commit was manufactured by cvs2svn to create branch 'RELENG_4_9'.
Notes
Notes: svn path=/releng/4.9/; revision=130589
-rw-r--r--contrib/cvs/lib/xsize.h108
1 files changed, 108 insertions, 0 deletions
diff --git a/contrib/cvs/lib/xsize.h b/contrib/cvs/lib/xsize.h
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+/* xsize.h -- Checked size_t computations.
+
+ Copyright (C) 2003 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2, or (at your option)
+ any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software Foundation,
+ Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+
+#ifndef _XSIZE_H
+#define _XSIZE_H
+
+/* Get size_t. */
+#include <stddef.h>
+
+/* Get SIZE_MAX. */
+#include <limits.h>
+#if HAVE_STDINT_H
+# include <stdint.h>
+#endif
+
+/* The size of memory objects is often computed through expressions of
+ type size_t. Example:
+ void* p = malloc (header_size + n * element_size).
+ These computations can lead to overflow. When this happens, malloc()
+ returns a piece of memory that is way too small, and the program then
+ crashes while attempting to fill the memory.
+ To avoid this, the functions and macros in this file check for overflow.
+ The convention is that SIZE_MAX represents overflow.
+ malloc (SIZE_MAX) is not guaranteed to fail -- think of a malloc
+ implementation that uses mmap --, it's recommended to use size_overflow_p()
+ or size_in_bounds_p() before invoking malloc().
+ The example thus becomes:
+ size_t size = xsum (header_size, xtimes (n, element_size));
+ void *p = (size_in_bounds_p (size) ? malloc (size) : NULL);
+*/
+
+/* Convert an arbitrary value >= 0 to type size_t. */
+#define xcast_size_t(N) \
+ ((N) <= SIZE_MAX ? (size_t) (N) : SIZE_MAX)
+
+/* Sum of two sizes, with overflow check. */
+static inline size_t
+#if __GNUC__ >= 3
+__attribute__ ((__pure__))
+#endif
+xsum (size_t size1, size_t size2)
+{
+ size_t sum = size1 + size2;
+ return (sum >= size1 ? sum : SIZE_MAX);
+}
+
+/* Sum of three sizes, with overflow check. */
+static inline size_t
+#if __GNUC__ >= 3
+__attribute__ ((__pure__))
+#endif
+xsum3 (size_t size1, size_t size2, size_t size3)
+{
+ return xsum (xsum (size1, size2), size3);
+}
+
+/* Sum of four sizes, with overflow check. */
+static inline size_t
+#if __GNUC__ >= 3
+__attribute__ ((__pure__))
+#endif
+xsum4 (size_t size1, size_t size2, size_t size3, size_t size4)
+{
+ return xsum (xsum (xsum (size1, size2), size3), size4);
+}
+
+/* Maximum of two sizes, with overflow check. */
+static inline size_t
+#if __GNUC__ >= 3
+__attribute__ ((__pure__))
+#endif
+xmax (size_t size1, size_t size2)
+{
+ /* No explicit check is needed here, because for any n:
+ max (SIZE_MAX, n) == SIZE_MAX and max (n, SIZE_MAX) == SIZE_MAX. */
+ return (size1 >= size2 ? size1 : size2);
+}
+
+/* Multiplication of a count with an element size, with overflow check.
+ The count must be >= 0 and the element size must be > 0.
+ This is a macro, not an inline function, so that it works correctly even
+ when N is of a wider tupe and N > SIZE_MAX. */
+#define xtimes(N, ELSIZE) \
+ ((N) <= SIZE_MAX / (ELSIZE) ? (size_t) (N) * (ELSIZE) : SIZE_MAX)
+
+/* Check for overflow. */
+#define size_overflow_p(SIZE) \
+ ((SIZE) == SIZE_MAX)
+/* Check against overflow. */
+#define size_in_bounds_p(SIZE) \
+ ((SIZE) != SIZE_MAX)
+
+#endif /* _XSIZE_H */