/* Copyright (C) 1995, 2004 Free Software Foundation
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/* Copyright (C) 1995, 2004 Free Software Foundation
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The GNU C Library is free software; you can redistribute it and/or
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, write to the Free
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License along with the GNU C Library; if not, write to the Free
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Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA. */
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02110-1301 USA. */
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/*
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/*
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* This is derived from the Berkeley source:
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* This is derived from the Berkeley source:
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* @(#)random.c 5.5 (Berkeley) 7/6/88
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* @(#)random.c 5.5 (Berkeley) 7/6/88
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* It was reworked for the GNU C Library by Roland McGrath.
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* It was reworked for the GNU C Library by Roland McGrath.
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* Rewritten to use reentrant functions by Ulrich Drepper, 1995.
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* Rewritten to use reentrant functions by Ulrich Drepper, 1995.
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*/
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*/
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/*
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/*
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Copyright (C) 1983 Regents of the University of California.
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Copyright (C) 1983 Regents of the University of California.
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All rights reserved.
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions
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modification, are permitted provided that the following conditions
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are met:
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are met:
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1. Redistributions of source code must retain the above copyright
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1. Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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notice, this list of conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright
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2. Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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documentation and/or other materials provided with the distribution.
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4. Neither the name of the University nor the names of its contributors
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4. Neither the name of the University nor the names of its contributors
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may be used to endorse or promote products derived from this software
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may be used to endorse or promote products derived from this software
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without specific prior written permission.
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without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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SUCH DAMAGE.*/
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SUCH DAMAGE.*/
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#include <limits.h>
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#include <limits.h>
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#include <stdlib.h>
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#include <stdlib.h>
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#include "generate-random.h"
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#include "generate-random.h"
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/* An improved random number generation package. In addition to the standard
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/* An improved random number generation package. In addition to the standard
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rand()/srand() like interface, this package also has a special state info
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rand()/srand() like interface, this package also has a special state info
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interface. The initstate() routine is called with a seed, an array of
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interface. The initstate() routine is called with a seed, an array of
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bytes, and a count of how many bytes are being passed in; this array is
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bytes, and a count of how many bytes are being passed in; this array is
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then initialized to contain information for random number generation with
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then initialized to contain information for random number generation with
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that much state information. Good sizes for the amount of state
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that much state information. Good sizes for the amount of state
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information are 32, 64, 128, and 256 bytes. The state can be switched by
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information are 32, 64, 128, and 256 bytes. The state can be switched by
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calling the setstate() function with the same array as was initialized
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calling the setstate() function with the same array as was initialized
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with initstate(). By default, the package runs with 128 bytes of state
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with initstate(). By default, the package runs with 128 bytes of state
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information and generates far better random numbers than a linear
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information and generates far better random numbers than a linear
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congruential generator. If the amount of state information is less than
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congruential generator. If the amount of state information is less than
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32 bytes, a simple linear congruential R.N.G. is used. Internally, the
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32 bytes, a simple linear congruential R.N.G. is used. Internally, the
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state information is treated as an array of longs; the zeroth element of
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state information is treated as an array of longs; the zeroth element of
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the array is the type of R.N.G. being used (small integer); the remainder
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the array is the type of R.N.G. being used (small integer); the remainder
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of the array is the state information for the R.N.G. Thus, 32 bytes of
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of the array is the state information for the R.N.G. Thus, 32 bytes of
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state information will give 7 longs worth of state information, which will
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state information will give 7 longs worth of state information, which will
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allow a degree seven polynomial. (Note: The zeroth word of state
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allow a degree seven polynomial. (Note: The zeroth word of state
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information also has some other information stored in it; see setstate
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information also has some other information stored in it; see setstate
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for details). The random number generation technique is a linear feedback
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for details). The random number generation technique is a linear feedback
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shift register approach, employing trinomials (since there are fewer terms
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shift register approach, employing trinomials (since there are fewer terms
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to sum up that way). In this approach, the least significant bit of all
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to sum up that way). In this approach, the least significant bit of all
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the numbers in the state table will act as a linear feedback shift register,
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the numbers in the state table will act as a linear feedback shift register,
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and will have period 2^deg - 1 (where deg is the degree of the polynomial
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and will have period 2^deg - 1 (where deg is the degree of the polynomial
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being used, assuming that the polynomial is irreducible and primitive).
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being used, assuming that the polynomial is irreducible and primitive).
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The higher order bits will have longer periods, since their values are
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The higher order bits will have longer periods, since their values are
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also influenced by pseudo-random carries out of the lower bits. The
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also influenced by pseudo-random carries out of the lower bits. The
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total period of the generator is approximately deg*(2**deg - 1); thus
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total period of the generator is approximately deg*(2**deg - 1); thus
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doubling the amount of state information has a vast influence on the
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doubling the amount of state information has a vast influence on the
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period of the generator. Note: The deg*(2**deg - 1) is an approximation
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period of the generator. Note: The deg*(2**deg - 1) is an approximation
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only good for large deg, when the period of the shift register is the
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only good for large deg, when the period of the shift register is the
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dominant factor. With deg equal to seven, the period is actually much
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dominant factor. With deg equal to seven, the period is actually much
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longer than the 7*(2**7 - 1) predicted by this formula. */
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longer than the 7*(2**7 - 1) predicted by this formula. */
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/* For each of the currently supported random number generators, we have a
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/* For each of the currently supported random number generators, we have a
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break value on the amount of state information (you need at least this many
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break value on the amount of state information (you need at least this many
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bytes of state info to support this random number generator), a degree for
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bytes of state info to support this random number generator), a degree for
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the polynomial (actually a trinomial) that the R.N.G. is based on, and
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the polynomial (actually a trinomial) that the R.N.G. is based on, and
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separation between the two lower order coefficients of the trinomial. */
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separation between the two lower order coefficients of the trinomial. */
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/* Linear congruential. */
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/* Linear congruential. */
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#define TYPE_0 0
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#define TYPE_0 0
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#define BREAK_0 8
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#define BREAK_0 8
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#define DEG_0 0
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#define DEG_0 0
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#define SEP_0 0
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#define SEP_0 0
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/* x**7 + x**3 + 1. */
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/* x**7 + x**3 + 1. */
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#define TYPE_1 1
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#define TYPE_1 1
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#define BREAK_1 32
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#define BREAK_1 32
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#define DEG_1 7
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#define DEG_1 7
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#define SEP_1 3
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#define SEP_1 3
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/* x**15 + x + 1. */
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/* x**15 + x + 1. */
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#define TYPE_2 2
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#define TYPE_2 2
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#define BREAK_2 64
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#define BREAK_2 64
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#define DEG_2 15
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#define DEG_2 15
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#define SEP_2 1
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#define SEP_2 1
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/* x**31 + x**3 + 1. */
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/* x**31 + x**3 + 1. */
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#define TYPE_3 3
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#define TYPE_3 3
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#define BREAK_3 128
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#define BREAK_3 128
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#define DEG_3 31
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#define DEG_3 31
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#define SEP_3 3
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#define SEP_3 3
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/* x**63 + x + 1. */
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/* x**63 + x + 1. */
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#define TYPE_4 4
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#define TYPE_4 4
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#define BREAK_4 256
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#define BREAK_4 256
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#define DEG_4 63
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#define DEG_4 63
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#define SEP_4 1
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#define SEP_4 1
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/* Array versions of the above information to make code run faster.
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/* Array versions of the above information to make code run faster.
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Relies on fact that TYPE_i == i. */
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Relies on fact that TYPE_i == i. */
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#define MAX_TYPES 5 /* Max number of types above. */
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#define MAX_TYPES 5 /* Max number of types above. */
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/* Initially, everything is set up as if from:
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/* Initially, everything is set up as if from:
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initstate(1, randtbl, 128);
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initstate(1, randtbl, 128);
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Note that this initialization takes advantage of the fact that srandom
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Note that this initialization takes advantage of the fact that srandom
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advances the front and rear pointers 10*rand_deg times, and hence the
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advances the front and rear pointers 10*rand_deg times, and hence the
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rear pointer which starts at 0 will also end up at zero; thus the zeroth
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rear pointer which starts at 0 will also end up at zero; thus the zeroth
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element of the state information, which contains info about the current
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element of the state information, which contains info about the current
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position of the rear pointer is just
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position of the rear pointer is just
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(MAX_TYPES * (rptr - state)) + TYPE_3 == TYPE_3. */
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(MAX_TYPES * (rptr - state)) + TYPE_3 == TYPE_3. */
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static int randtbl[DEG_3 + 1] =
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static int randtbl[DEG_3 + 1] =
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{
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{
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TYPE_3,
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TYPE_3,
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-1726662223, 379960547, 1735697613, 1040273694, 1313901226,
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-1726662223, 379960547, 1735697613, 1040273694, 1313901226,
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1627687941, -179304937, -2073333483, 1780058412, -1989503057,
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1627687941, -179304937, -2073333483, 1780058412, -1989503057,
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-615974602, 344556628, 939512070, -1249116260, 1507946756,
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-615974602, 344556628, 939512070, -1249116260, 1507946756,
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-812545463, 154635395, 1388815473, -1926676823, 525320961,
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-812545463, 154635395, 1388815473, -1926676823, 525320961,
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-1009028674, 968117788, -123449607, 1284210865, 435012392,
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-1009028674, 968117788, -123449607, 1284210865, 435012392,
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-2017506339, -911064859, -370259173, 1132637927, 1398500161,
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-2017506339, -911064859, -370259173, 1132637927, 1398500161,
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-205601318,
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-205601318,
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};
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};
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static struct generate_random_data unsafe_state =
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static struct generate_random_data unsafe_state =
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{
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{
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/* FPTR and RPTR are two pointers into the state info, a front and a rear
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/* FPTR and RPTR are two pointers into the state info, a front and a rear
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pointer. These two pointers are always rand_sep places aparts, as they
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pointer. These two pointers are always rand_sep places aparts, as they
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cycle through the state information. (Yes, this does mean we could get
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cycle through the state information. (Yes, this does mean we could get
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away with just one pointer, but the code for random is more efficient
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away with just one pointer, but the code for random is more efficient
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this way). The pointers are left positioned as they would be from the call:
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this way). The pointers are left positioned as they would be from the call:
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initstate(1, randtbl, 128);
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initstate(1, randtbl, 128);
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(The position of the rear pointer, rptr, is really 0 (as explained above
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(The position of the rear pointer, rptr, is really 0 (as explained above
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in the initialization of randtbl) because the state table pointer is set
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in the initialization of randtbl) because the state table pointer is set
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to point to randtbl[1] (as explained below).) */
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to point to randtbl[1] (as explained below).) */
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&randtbl[SEP_3 + 1], /* fptr */
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&randtbl[SEP_3 + 1], /* fptr */
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&randtbl[1], /* rptr */
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&randtbl[1], /* rptr */
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/* The following things are the pointer to the state information table,
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/* The following things are the pointer to the state information table,
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the type of the current generator, the degree of the current polynomial
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the type of the current generator, the degree of the current polynomial
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being used, and the separation between the two pointers.
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being used, and the separation between the two pointers.
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Note that for efficiency of random, we remember the first location of
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Note that for efficiency of random, we remember the first location of
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the state information, not the zeroth. Hence it is valid to access
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the state information, not the zeroth. Hence it is valid to access
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state[-1], which is used to store the type of the R.N.G.
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state[-1], which is used to store the type of the R.N.G.
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Also, we remember the last location, since this is more efficient than
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Also, we remember the last location, since this is more efficient than
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indexing every time to find the address of the last element to see if
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indexing every time to find the address of the last element to see if
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the front and rear pointers have wrapped. */
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the front and rear pointers have wrapped. */
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&randtbl[1], /* state */
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&randtbl[1], /* state */
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TYPE_3, /* rand_type */
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TYPE_3, /* rand_type */
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DEG_3, /* rand_deg */
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DEG_3, /* rand_deg */
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SEP_3, /* rand_sep */
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SEP_3, /* rand_sep */
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&randtbl[sizeof (randtbl) / sizeof (randtbl[0])] /* end_ptr */
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&randtbl[sizeof (randtbl) / sizeof (randtbl[0])] /* end_ptr */
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};
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};
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/* Initialize the random number generator based on the given seed. If the
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/* Initialize the random number generator based on the given seed. If the
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type is the trivial no-state-information type, just remember the seed.
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type is the trivial no-state-information type, just remember the seed.
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Otherwise, initializes state[] based on the given "seed" via a linear
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Otherwise, initializes state[] based on the given "seed" via a linear
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congruential generator. Then, the pointers are set to known locations
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congruential generator. Then, the pointers are set to known locations
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that are exactly rand_sep places apart. Lastly, it cycles the state
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that are exactly rand_sep places apart. Lastly, it cycles the state
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information a given number of times to get rid of any initial dependencies
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information a given number of times to get rid of any initial dependencies
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introduced by the L.C.R.N.G. Note that the initialization of randtbl[]
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introduced by the L.C.R.N.G. Note that the initialization of randtbl[]
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for default usage relies on values produced by this routine. */
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for default usage relies on values produced by this routine. */
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void
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void
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generate_srandom (unsigned int x)
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generate_srandom (unsigned int x)
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{
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{
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(void) generate_srandom_r (x, &unsafe_state);
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(void) generate_srandom_r (x, &unsafe_state);
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}
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}
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/* Initialize the state information in the given array of N bytes for
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/* Initialize the state information in the given array of N bytes for
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future random number generation. Based on the number of bytes we
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future random number generation. Based on the number of bytes we
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are given, and the break values for the different R.N.G.'s, we choose
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are given, and the break values for the different R.N.G.'s, we choose
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the best (largest) one we can and set things up for it. srandom is
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the best (largest) one we can and set things up for it. srandom is
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then called to initialize the state information. Note that on return
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then called to initialize the state information. Note that on return
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from srandom, we set state[-1] to be the type multiplexed with the current
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from srandom, we set state[-1] to be the type multiplexed with the current
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value of the rear pointer; this is so successive calls to initstate won't
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value of the rear pointer; this is so successive calls to initstate won't
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lose this information and will be able to restart with setstate.
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lose this information and will be able to restart with setstate.
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Note: The first thing we do is save the current state, if any, just like
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Note: The first thing we do is save the current state, if any, just like
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setstate so that it doesn't matter when initstate is called.
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setstate so that it doesn't matter when initstate is called.
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Returns a pointer to the old state. */
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Returns a pointer to the old state. */
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char *
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char *
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generate_initstate (unsigned int seed, char *arg_state, size_t n)
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generate_initstate (unsigned int seed, char *arg_state, size_t n)
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{
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{
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int *ostate;
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int *ostate;
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ostate = &unsafe_state.state[-1];
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ostate = &unsafe_state.state[-1];
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generate_initstate_r (seed, arg_state, n, &unsafe_state);
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generate_initstate_r (seed, arg_state, n, &unsafe_state);
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return (char *) ostate;
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return (char *) ostate;
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}
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}
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/* Restore the state from the given state array.
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/* Restore the state from the given state array.
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Note: It is important that we also remember the locations of the pointers
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Note: It is important that we also remember the locations of the pointers
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in the current state information, and restore the locations of the pointers
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in the current state information, and restore the locations of the pointers
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from the old state information. This is done by multiplexing the pointer
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from the old state information. This is done by multiplexing the pointer
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location into the zeroth word of the state information. Note that due
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location into the zeroth word of the state information. Note that due
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to the order in which things are done, it is OK to call setstate with the
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to the order in which things are done, it is OK to call setstate with the
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same state as the current state
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same state as the current state
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Returns a pointer to the old state information. */
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Returns a pointer to the old state information. */
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char *
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char *
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generate_setstate (char *arg_state)
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generate_setstate (char *arg_state)
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{
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{
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int *ostate;
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int *ostate;
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|
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ostate = &unsafe_state.state[-1];
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ostate = &unsafe_state.state[-1];
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if (generate_setstate_r (arg_state, &unsafe_state) < 0)
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if (generate_setstate_r (arg_state, &unsafe_state) < 0)
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ostate = NULL;
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ostate = NULL;
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return (char *) ostate;
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return (char *) ostate;
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}
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}
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/* If we are using the trivial TYPE_0 R.N.G., just do the old linear
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/* If we are using the trivial TYPE_0 R.N.G., just do the old linear
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congruential bit. Otherwise, we do our fancy trinomial stuff, which is the
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congruential bit. Otherwise, we do our fancy trinomial stuff, which is the
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same in all the other cases due to all the global variables that have been
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same in all the other cases due to all the global variables that have been
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set up. The basic operation is to add the number at the rear pointer into
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set up. The basic operation is to add the number at the rear pointer into
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the one at the front pointer. Then both pointers are advanced to the next
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the one at the front pointer. Then both pointers are advanced to the next
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location cyclically in the table. The value returned is the sum generated,
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location cyclically in the table. The value returned is the sum generated,
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reduced to 31 bits by throwing away the "least random" low bit.
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reduced to 31 bits by throwing away the "least random" low bit.
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Note: The code takes advantage of the fact that both the front and
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Note: The code takes advantage of the fact that both the front and
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rear pointers can't wrap on the same call by not testing the rear
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rear pointers can't wrap on the same call by not testing the rear
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pointer if the front one has wrapped. Returns a 31-bit random number. */
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pointer if the front one has wrapped. Returns a 31-bit random number. */
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|
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long int
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long int
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generate_random (void)
|
generate_random (void)
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{
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{
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int retval;
|
int retval;
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(void) generate_random_r (&unsafe_state, &retval);
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(void) generate_random_r (&unsafe_state, &retval);
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return retval;
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return retval;
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}
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}
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