diff options
Diffstat (limited to 'libc/stdlib/drand48-iter.c')
-rw-r--r-- | libc/stdlib/drand48-iter.c | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/libc/stdlib/drand48-iter.c b/libc/stdlib/drand48-iter.c new file mode 100644 index 000000000..7ccc2fbc9 --- /dev/null +++ b/libc/stdlib/drand48-iter.c @@ -0,0 +1,59 @@ +/* Copyright (C) 1995, 1996, 2001 Free Software Foundation, Inc. + This file is part of the GNU C Library. + Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu <mailto:drepper@gnu.ai.mit.edu>>, August 1995. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, write to the Free + Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + 02111-1307 USA. */ + +#include <errno.h> +#include <stdlib.h> +#include <limits.h> +#include <stdint.h> +#include <sys/types.h> + +/* Global state for non-reentrant functions. */ +struct drand48_data __libc_drand48_data; + + +int +__drand48_iterate (xsubi, buffer) + unsigned short int xsubi[3]; + struct drand48_data *buffer; +{ + uint64_t X; + uint64_t result; + + /* Initialize buffer, if not yet done. */ + if (unlikely(!buffer->__init)) + { + buffer->__a = 0x5deece66dull; + buffer->__c = 0xb; + buffer->__init = 1; + } + + /* Do the real work. We choose a data type which contains at least + 48 bits. Because we compute the modulus it does not care how + many bits really are computed. */ + + X = (uint64_t) xsubi[2] << 32 | (uint32_t) xsubi[1] << 16 | xsubi[0]; + + result = X * buffer->__a + buffer->__c; + + xsubi[0] = result & 0xffff; + xsubi[1] = (result >> 16) & 0xffff; + xsubi[2] = (result >> 32) & 0xffff; + + return 0; +} |