libc/stdlib/random.c

31 static char sccsid[] = "@(#)random.c	8.2 (Berkeley) 5/19/95";
45  * random.c:
47  * An improved random number generation package.  In addition to the standard
51  * then initialized to contain information for random number generation with
56  * information and generates far better random numbers than a linear
68  * The random number generation technique is a linear feedback shift register
75  * influenced by pseudo-random carries out of the lower bits.  The total
96  * state information and generates far better random numbers than a linear
104  * For each of the currently supported random number generators, we have a
106  * many bytes of state info to support this random number generator), a degree
168 /* The random sequences do not vary much with the seed */
189  * could get away with just one pointer, but the code for random() is more
206  * of random(), we remember the first location of the state information, not
224  * The random sequences do not vary much with the seed,
254  * Initialize the random number generator based on the given seed.  If the
279 		(void)random();
286  * This often causes problems.  We seed the generator using pseudo-random
319  * random number generation.  Based on the number of bytes we are given, and
350 		    "random: not enough state (%ld bytes); ignored.\n", n);
427 		    "random: state info corrupted; not changed.\n");
439  * random:
447  * generated, reduced to 31 bits by throwing away the "least random" low bit.
453  * Returns a 31-bit random number.
456 random(void)
470 		i = (*f >> 1) & 0x7fffffff;	/* chucking least random bit */