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Diffstat (limited to 'grub-core/lib/gnulib/malloca.c')
-rw-r--r-- | grub-core/lib/gnulib/malloca.c | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/grub-core/lib/gnulib/malloca.c b/grub-core/lib/gnulib/malloca.c new file mode 100644 index 0000000..f60c5fb --- /dev/null +++ b/grub-core/lib/gnulib/malloca.c @@ -0,0 +1,105 @@ +/* Safe automatic memory allocation. + Copyright (C) 2003, 2006-2007, 2009-2019 Free Software Foundation, Inc. + Written by Bruno Haible <bruno@clisp.org>, 2003, 2018. + + 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 3, 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, see <https://www.gnu.org/licenses/>. */ + +#define _GL_USE_STDLIB_ALLOC 1 +#include <config.h> + +/* Specification. */ +#include "malloca.h" + +#include "verify.h" + +/* The speed critical point in this file is freea() applied to an alloca() + result: it must be fast, to match the speed of alloca(). The speed of + mmalloca() and freea() in the other case are not critical, because they + are only invoked for big memory sizes. + Here we use a bit in the address as an indicator, an idea by Ondřej Bílka. + malloca() can return three types of pointers: + - Pointers ≡ 0 mod 2*sa_alignment_max come from stack allocation. + - Pointers ≡ sa_alignment_max mod 2*sa_alignment_max come from heap + allocation. + - NULL comes from a failed heap allocation. */ + +/* Type for holding very small pointer differences. */ +typedef unsigned char small_t; +/* Verify that it is wide enough. */ +verify (2 * sa_alignment_max - 1 <= (small_t) -1); + +void * +mmalloca (size_t n) +{ +#if HAVE_ALLOCA + /* Allocate one more word, used to determine the address to pass to freea(), + and room for the alignment ≡ sa_alignment_max mod 2*sa_alignment_max. */ + size_t nplus = n + sizeof (small_t) + 2 * sa_alignment_max - 1; + + if (nplus >= n) + { + char *mem = (char *) malloc (nplus); + + if (mem != NULL) + { + char *p = + (char *)((((uintptr_t)mem + sizeof (small_t) + sa_alignment_max - 1) + & ~(uintptr_t)(2 * sa_alignment_max - 1)) + + sa_alignment_max); + /* Here p >= mem + sizeof (small_t), + and p <= mem + sizeof (small_t) + 2 * sa_alignment_max - 1 + hence p + n <= mem + nplus. + So, the memory range [p, p+n) lies in the allocated memory range + [mem, mem + nplus). */ + ((small_t *) p)[-1] = p - mem; + /* p ≡ sa_alignment_max mod 2*sa_alignment_max. */ + return p; + } + } + /* Out of memory. */ + return NULL; +#else +# if !MALLOC_0_IS_NONNULL + if (n == 0) + n = 1; +# endif + return malloc (n); +#endif +} + +#if HAVE_ALLOCA +void +freea (void *p) +{ + /* Check argument. */ + if ((uintptr_t) p & (sa_alignment_max - 1)) + { + /* p was not the result of a malloca() call. Invalid argument. */ + abort (); + } + /* Determine whether p was a non-NULL pointer returned by mmalloca(). */ + if ((uintptr_t) p & sa_alignment_max) + { + void *mem = (char *) p - ((small_t *) p)[-1]; + free (mem); + } +} +#endif + +/* + * Hey Emacs! + * Local Variables: + * coding: utf-8 + * End: + */ |