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-rw-r--r--libc/stdlib/drand48-iter.c59
1 files changed, 59 insertions, 0 deletions
diff --git a/libc/stdlib/drand48-iter.c b/libc/stdlib/drand48-iter.c
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+++ b/libc/stdlib/drand48-iter.c
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+/* 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;
+}