[thirdparty/glibc.git] / stdlib / drand48-iter.c

/* Copyright (C) 1995, 1996 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>
#include <limits.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 (USHRT_MAX == 0xffffU)
      buffer->a[2] = 0x5;
      buffer->a[1] = 0xdeec;
      buffer->a[0] = 0xe66d;
#else
      buffer->a[2] = 0x5deecUL;
      buffer->a[1] = 0xe66d0000UL;
      buffer->a[0] = 0;
#endif
      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;
}
Commit	Line	Data
1d8dc429	1	/* Copyright (C) 1995, 1996 Free Software Foundation, Inc.
60478656 RM	2	This file is part of the GNU C Library.
	3	Contributed by Ulrich Drepper <drepper@gnu.ai.mit.edu>, August 1995.
	4
	5	The GNU C Library is free software; you can redistribute it and/or
	6	modify it under the terms of the GNU Library General Public License as
	7	published by the Free Software Foundation; either version 2 of the
	8	License, or (at your option) any later version.
	9
	10	The GNU C Library is distributed in the hope that it will be useful,
	11	but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	13	Library General Public License for more details.
	14
	15	You should have received a copy of the GNU Library General Public
	16	License along with the GNU C Library; see the file COPYING.LIB. If
	17	not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
	18	Boston, MA 02111-1307, USA. */
	19
	20	#include <errno.h>
	21	#include <stdlib.h>
1d8dc429	22	#include <limits.h>
60478656 RM	23
	24
	25	/* Global state for non-reentrent functions. */
	26	struct drand48_data __libc_drand48_data;
	27
	28
	29	int
	30	__drand48_iterate (xsubi, buffer)
	31	unsigned short int xsubi[3];
	32	struct drand48_data *buffer;
	33	{
	34	/* Be generous for the arguments, detect some errors. */
	35	if (xsubi == NULL \|\| buffer == NULL)
	36	{
	37	errno = EFAULT;
	38	return -1;
	39	}
	40
	41	/* Initialize buffer, if not yet done. */
	42	if (!buffer->init)
	43	{
1d8dc429 RM	44	#if (USHRT_MAX == 0xffffU)
	45	buffer->a[2] = 0x5;
	46	buffer->a[1] = 0xdeec;
	47	buffer->a[0] = 0xe66d;
	48	#else
	49	buffer->a[2] = 0x5deecUL;
	50	buffer->a[1] = 0xe66d0000UL;
	51	buffer->a[0] = 0;
	52	#endif
60478656 RM	53	buffer->c = 0xb;
	54	buffer->init = 1;
	55	}
	56
	57	/* Do the real work. We choose a data type which contains at least
	58	48 bits. Because we compute the modulus it does not care how
	59	many bits really are computed. */
	60
	61	if (sizeof (long int) >= 6)
	62	{
	63	/* The `long' data type is sufficent. */
	64	unsigned long int X, a, result;
	65
	66	#define ONE_STEP \
	67	if (sizeof (unsigned short int) == 2) \
	68	{ \
	69	X = (xsubi[2] << 16 \| xsubi[1]) << 16 \| xsubi[0]; \
	70	a = (buffer->a[2] << 16 \| buffer->a[1]) << 16 \| buffer->a[0]; \
	71	\
	72	result = X * a + buffer->c; \
	73	\
	74	xsubi[0] = result & 0xffff; \
	75	result >>= 16; \
	76	xsubi[1] = result & 0xffff; \
	77	result >>= 16; \
	78	xsubi[2] = result & 0xffff; \
	79	} \
	80	else \
	81	{ \
	82	X = xsubi[2] << 16 \| xsubi[1] >> 16; \
	83	a = buffer->a[2] << 16 \| buffer->a[1] >> 16; \
	84	\
	85	result = X * a + buffer->c; \
	86	\
	87	xsubi[0] = result >> 16 & 0xffffffffl; \
	88	xsubi[1] = result << 16 & 0xffff0000l; \
	89	}
	90	ONE_STEP;
	91	}
	92	else
	93	{
	94	/* We have to use the `long long' data type. */
	95	unsigned long long int X, a, result;
	96	ONE_STEP;
	97	}
	98
	99	return 0;
	100	}