Mercurial > hg > octave-lyh > gnulib-hg
changeset 15954:dc9665de5e48
New module 'integer_length_l'.
* lib/integer_length_l.c: New file.
* modules/integer_length_l: New file.
author | Bruno Haible <bruno@clisp.org> |
---|---|
date | Sat, 15 Oct 2011 02:15:31 +0200 |
parents | 3d1d9a55be68 |
children | 1eff9504e1dc |
files | ChangeLog lib/integer_length_l.c modules/integer_length_l |
diffstat | 3 files changed, 112 insertions(+), 0 deletions(-) [+] |
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--- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2011-10-14 Bruno Haible <bruno@clisp.org> + + New module 'integer_length_l'. + * lib/integer_length_l.c: New file. + * modules/integer_length_l: New file. + 2011-10-14 Bruno Haible <bruno@clisp.org> Tests for module 'integer_length'.
new file mode 100644 --- /dev/null +++ b/lib/integer_length_l.c @@ -0,0 +1,81 @@ +/* integer_length_l - find most significant bit in an 'unsigned long'. + Copyright (C) 2011 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 3 of the License, 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 <http://www.gnu.org/licenses/>. */ + +/* Written by Bruno Haible <bruno@clisp.org>, 2011. */ + +#include <config.h> + +/* Specification. */ +#include "integer_length.h" + +#include <limits.h> +#include <stddef.h> + +#undef MIN +#define MIN(a,b) ((a) < (b) ? (a) : (b)) + +#ifdef USE_LONG_LONG +# define FUNC integer_length_ll +# define TYPE unsigned long long +# define GCC_BUILTIN __builtin_clzll +#else +# define FUNC integer_length_l +# define TYPE unsigned long +# define GCC_BUILTIN __builtin_clzl +#endif + +#define NBITS (sizeof (TYPE) * CHAR_BIT) + +/* Modify shift count to be in bounds, even in dead code, otherwise GCC + emits warnings "right shift count >= width of type". */ +#define MSC(i) MIN (i, NBITS - 1) + +int +FUNC (TYPE x) +{ +#if __GNUC__ > 3 || (__GNUC__ == 3 && __GNUC_MINOR__ >= 4) + if (x == 0) + return 0; + else + return NBITS - GCC_BUILTIN (x); +#else + /* Split x into chunks, and look at one chunk after the other. */ + if (sizeof (TYPE) > 2 * sizeof (unsigned int)) + { + /* Generic loop. */ + size_t i; + + for (i = (sizeof (TYPE) - 1) / sizeof (unsigned int); i >= 2; i--) + { + unsigned int y = x >> (i * sizeof (unsigned int) * CHAR_BIT); + if (y != 0) + return i * sizeof (unsigned int) * CHAR_BIT + integer_length (y); + } + } + + /* Unrolled the last 2 loop rounds. */ + /* i = 1 */ + if (sizeof (TYPE) > 1 * sizeof (unsigned int)) + { + unsigned int y = x >> MSC (1 * sizeof (unsigned int) * CHAR_BIT); + if (y != 0) + return 1 * sizeof (unsigned int) * CHAR_BIT + integer_length (y); + } + + /* i = 0 */ + return integer_length ((unsigned int) x); +#endif +}
new file mode 100644 --- /dev/null +++ b/modules/integer_length_l @@ -0,0 +1,25 @@ +Description: +Finds the most significant bit in an 'unsigned long'. + +Files: +lib/integer_length.h +lib/integer_length_l.c +m4/longlong.m4 + +Depends-on: +integer_length + +configure.ac: +AC_REQUIRE([AC_TYPE_UNSIGNED_LONG_LONG_INT]) + +Makefile.am: +lib_SOURCES += integer_length_l.c + +Include: +"integer_length.h" + +License: +LGPLv2+ + +Maintainer: +Bruno Haible