// // Random.cpp // // $Id: //poco/1.3/Foundation/src/Random.cpp#3 $ // // Library: Foundation // Package: Crypt // Module: Random // // Definition of class Random. // // Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH. // and Contributors. // // Permission is hereby granted, free of charge, to any person or organization // obtaining a copy of the software and accompanying documentation covered by // this license (the "Software") to use, reproduce, display, distribute, // execute, and transmit the Software, and to prepare derivative works of the // Software, and to permit third-parties to whom the Software is furnished to // do so, all subject to the following: // // The copyright notices in the Software and this entire statement, including // the above license grant, this restriction and the following disclaimer, // must be included in all copies of the Software, in whole or in part, and // all derivative works of the Software, unless such copies or derivative // works are solely in the form of machine-executable object code generated by // a source language processor. // // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, // FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT // SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE // FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE, // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER // DEALINGS IN THE SOFTWARE. // // // Based on the FreeBSD random number generator. // src/lib/libc/stdlib/random.c,v 1.25 // // Copyright (c) 1983, 1993 // The Regents of the University of California. All rights reserved. // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions // are met: // 1. Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // 2. Redistributions in binary form must reproduce the above copyright // notice, this list of conditions and the following disclaimer in the // documentation and/or other materials provided with the distribution. // 4. Neither the name of the University nor the names of its contributors // may be used to endorse or promote products derived from this software // without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE // ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE // FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL // DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS // OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) // HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT // LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY // OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF // SUCH DAMAGE. // #include "Poco/Random.h" #include "Poco/RandomStream.h" #include <ctime> /* * random.c: * * An improved random number generation package. In addition to the standard * rand()/srand() like interface, this package also has a special state info * interface. The initstate() routine is called with a seed, an array of * bytes, and a count of how many bytes are being passed in; this array is * then initialized to contain information for random number generation with * that much state information. Good sizes for the amount of state * information are 32, 64, 128, and 256 bytes. The state can be switched by * calling the setstate() routine with the same array as was initiallized * with initstate(). By default, the package runs with 128 bytes of state * information and generates far better random numbers than a linear * congruential generator. If the amount of state information is less than * 32 bytes, a simple linear congruential R.N.G. is used. * * Internally, the state information is treated as an array of uint32_t's; the * zeroeth element of the array is the type of R.N.G. being used (small * integer); the remainder of the array is the state information for the * R.N.G. Thus, 32 bytes of state information will give 7 ints worth of * state information, which will allow a degree seven polynomial. (Note: * the zeroeth word of state information also has some other information * stored in it -- see setstate() for details). * * The random number generation technique is a linear feedback shift register * approach, employing trinomials (since there are fewer terms to sum up that * way). In this approach, the least significant bit of all the numbers in * the state table will act as a linear feedback shift register, and will * have period 2^deg - 1 (where deg is the degree of the polynomial being * used, assuming that the polynomial is irreducible and primitive). The * higher order bits will have longer periods, since their values are also * influenced by pseudo-random carries out of the lower bits. The total * period of the generator is approximately deg*(2**deg - 1); thus doubling * the amount of state information has a vast influence on the period of the * generator. Note: the deg*(2**deg - 1) is an approximation only good for * large deg, when the period of the shift is the dominant factor. * With deg equal to seven, the period is actually much longer than the * 7*(2**7 - 1) predicted by this formula. * * Modified 28 December 1994 by Jacob S. Rosenberg. * The following changes have been made: * All references to the type u_int have been changed to unsigned long. * All references to type int have been changed to type long. Other * cleanups have been made as well. A warning for both initstate and * setstate has been inserted to the effect that on Sparc platforms * the 'arg_state' variable must be forced to begin on word boundaries. * This can be easily done by casting a long integer array to char *. * The overall logic has been left STRICTLY alone. This software was * tested on both a VAX and Sun SpacsStation with exactly the same * results. The new version and the original give IDENTICAL results. * The new version is somewhat faster than the original. As the * documentation says: "By default, the package runs with 128 bytes of * state information and generates far better random numbers than a linear * congruential generator. If the amount of state information is less than * 32 bytes, a simple linear congruential R.N.G. is used." For a buffer of * 128 bytes, this new version runs about 19 percent faster and for a 16 * byte buffer it is about 5 percent faster. */ /* * For each of the currently supported random number generators, we have a * break value on the amount of state information (you need at least this * many bytes of state info to support this random number generator), a degree * for the polynomial (actually a trinomial) that the R.N.G. is based on, and * the separation between the two lower order coefficients of the trinomial. */ #define TYPE_0 0 /* linear congruential */ #define BREAK_0 8 #define DEG_0 0 #define SEP_0 0 #define TYPE_1 1 /* x**7 + x**3 + 1 */ #define BREAK_1 32 #define DEG_1 7 #define SEP_1 3 #define TYPE_2 2 /* x**15 + x + 1 */ #define BREAK_2 64 #define DEG_2 15 #define SEP_2 1 #define TYPE_3 3 /* x**31 + x**3 + 1 */ #define BREAK_3 128 #define DEG_3 31 #define SEP_3 3 #define TYPE_4 4 /* x**63 + x + 1 */ #define BREAK_4 256 #define DEG_4 63 #define SEP_4 1 namespace Poco { Random::Random(int stateSize) { poco_assert (BREAK_0 <= stateSize && stateSize <= BREAK_4); _pBuffer = new char[stateSize]; initState((UInt32) std::time(NULL), _pBuffer, stateSize); } 00179 Random::~Random() { delete [] _pBuffer; } /* * Compute x = (7^5 * x) mod (2^31 - 1) * wihout overflowing 31 bits: * (2^31 - 1) = 127773 * (7^5) + 2836 * From "Random number generators: good ones are hard to find", * Park and Miller, Communications of the ACM, vol. 31, no. 10, * October 1988, p. 1195. */ inline UInt32 Random::goodRand(Int32 x) { Int32 hi, lo; if (x == 0) x = 123459876; hi = x / 127773; lo = x % 127773; x = 16807 * lo - 2836 * hi; if (x < 0) x += 0x7FFFFFFF; return x; } /* * Initialize the random number generator based on the given seed. If the * type is the trivial no-state-information type, just remember the seed. * Otherwise, initializes state[] based on the given "seed" via a linear * congruential generator. Then, the pointers are set to known locations * that are exactly rand_sep places apart. Lastly, it cycles the state * information a given number of times to get rid of any initial dependencies * introduced by the L.C.R.N.G. Note that the initialization of randtbl[] * for default usage relies on values produced by this routine. */ 00217 void Random::seed(UInt32 x) { int i, lim; _state[0] = x; if (_randType == TYPE_0) lim = NSHUFF; else { for (i = 1; i < _randDeg; i++) _state[i] = goodRand(_state[i - 1]); _fptr = &_state[_randSep]; _rptr = &_state[0]; lim = 10 * _randDeg; } for (i = 0; i < lim; i++) next(); } /* * Many programs choose the seed value in a totally predictable manner. * This often causes problems. We seed the generator using the much more * secure random(4) interface. Note that this particular seeding * procedure can generate states which are impossible to reproduce by * calling srandom() with any value, since the succeeding terms in the * state buffer are no longer derived from the LC algorithm applied to * a fixed seed. */ 00246 void Random::seed() { std::streamsize len; if (_randType == TYPE_0) len = sizeof _state[0]; else len = _randDeg * sizeof _state[0]; RandomInputStream rstr; rstr.read((char*) _state, len); } /* * Initialize the state information in the given array of n bytes for future * random number generation. Based on the number of bytes we are given, and * the break values for the different R.N.G.'s, we choose the best (largest) * one we can and set things up for it. srandom() is then called to * initialize the state information. * * Note that on return from srandom(), we set state[-1] to be the type * multiplexed with the current value of the rear pointer; this is so * successive calls to initstate() won't lose this information and will be * able to restart with setstate(). * * Note: the first thing we do is save the current state, if any, just like * setstate() so that it doesn't matter when initstate is called. * * Returns a pointer to the old state. * * Note: The Sparc platform requires that arg_state begin on an int * word boundary; otherwise a bus error will occur. Even so, lint will * complain about mis-alignment, but you should disregard these messages. */ 00281 void Random::initState(UInt32 s, char* argState, Int32 n) { UInt32* intArgState = (UInt32*) argState; if (n < BREAK_0) { poco_bugcheck_msg("not enough state"); return; } if (n < BREAK_1) { _randType = TYPE_0; _randDeg = DEG_0; _randSep = SEP_0; } else if (n < BREAK_2) { _randType = TYPE_1; _randDeg = DEG_1; _randSep = SEP_1; } else if (n < BREAK_3) { _randType = TYPE_2; _randDeg = DEG_2; _randSep = SEP_2; } else if (n < BREAK_4) { _randType = TYPE_3; _randDeg = DEG_3; _randSep = SEP_3; } else { _randType = TYPE_4; _randDeg = DEG_4; _randSep = SEP_4; } _state = intArgState + 1; /* first location */ _endPtr = &_state[_randDeg]; /* must set end_ptr before seed */ seed(s); if (_randType == TYPE_0) intArgState[0] = _randType; else intArgState[0] = MAX_TYPES * (int) (_rptr - _state) + _randType; } /* * Next: * * If we are using the trivial TYPE_0 R.N.G., just do the old linear * congruential bit. Otherwise, we do our fancy trinomial stuff, which is * the same in all the other cases due to all the global variables that have * been set up. The basic operation is to add the number at the rear pointer * into the one at the front pointer. Then both pointers are advanced to * the next location cyclically in the table. The value returned is the sum * generated, reduced to 31 bits by throwing away the "least random" low bit. * * Note: the code takes advantage of the fact that both the front and * rear pointers can't wrap on the same call by not testing the rear * pointer if the front one has wrapped. * * Returns a 31-bit random number. */ 00347 UInt32 Random::next() { UInt32 i; UInt32 *f, *r; if (_randType == TYPE_0) { i = _state[0]; _state[0] = i = goodRand(i) & 0x7FFFFFFF; } else { /* * Use local variables rather than static variables for speed. */ f = _fptr; r = _rptr; *f += *r; i = (*f >> 1) & 0x7FFFFFFF; /* chucking least random bit */ if (++f >= _endPtr) { f = _state; ++r; } else if (++r >= _endPtr) { r = _state; } _fptr = f; _rptr = r; } return i; } } // namespace Poco

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