diff options
Diffstat (limited to 'stdlib/drand48-iter.c')
| -rw-r--r-- | stdlib/drand48-iter.c | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/stdlib/drand48-iter.c b/stdlib/drand48-iter.c new file mode 100644 index 0000000000..013dbe792f --- /dev/null +++ b/stdlib/drand48-iter.c @@ -0,0 +1,102 @@ +/* Copyright (C) 1995 Free Software Foundation, Inc. +This file is part of the GNU C Library. +Contributed by Ulrich Drepper <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 Library General Public License as +published by the Free Software Foundation; either version 2 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 +Library General Public License for more details. + +You should have received a copy of the GNU Library General Public +License along with the GNU C Library; see the file COPYING.LIB. 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> + + +/* Global state for non-reentrent functions. */ +struct drand48_data __libc_drand48_data; + + +int +__drand48_iterate (xsubi, buffer) + unsigned short int xsubi[3]; + struct drand48_data *buffer; +{ + /* Be generous for the arguments, detect some errors. */ + if (xsubi == NULL || buffer == NULL) + { + errno = EFAULT; + return -1; + } + + /* Initialize buffer, if not yet done. */ + if (!buffer->init) + { + if (sizeof (unsigned short int) == 2) + { + buffer->a[2] = 0x5; + buffer->a[1] = 0xdeec; + buffer->a[0] = 0xe66d; + } + else + { + buffer->a[2] = 0x5deec; + buffer->a[1] = 0xe66d0000; + buffer->a[0] = 0; + } + 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. */ + + if (sizeof (long int) >= 6) + { + /* The `long' data type is sufficent. */ + unsigned long int X, a, result; + +#define ONE_STEP \ + if (sizeof (unsigned short int) == 2) \ + { \ + X = (xsubi[2] << 16 | xsubi[1]) << 16 | xsubi[0]; \ + a = (buffer->a[2] << 16 | buffer->a[1]) << 16 | buffer->a[0]; \ + \ + result = X * a + buffer->c; \ + \ + xsubi[0] = result & 0xffff; \ + result >>= 16; \ + xsubi[1] = result & 0xffff; \ + result >>= 16; \ + xsubi[2] = result & 0xffff; \ + } \ + else \ + { \ + X = xsubi[2] << 16 | xsubi[1] >> 16; \ + a = buffer->a[2] << 16 | buffer->a[1] >> 16; \ + \ + result = X * a + buffer->c; \ + \ + xsubi[0] = result >> 16 & 0xffffffffl; \ + xsubi[1] = result << 16 & 0xffff0000l; \ + } + ONE_STEP; + } + else + { + /* We have to use the `long long' data type. */ + unsigned long long int X, a, result; + ONE_STEP; + } + + return 0; +} |