1: /*2: * code for when the good (berkeley) random number generator is around3: */4:5: rnd(num)6: {7: return (random() % num);8: }9:10: srnd(num)11: {12: srandom(num);13: }14:15: #ifdef NO_RANDOM16:17: #ifndef lint18: static char sccsid[] = "@(#)random.c 4.2 (Berkeley) 83/01/02";19: #endif20:21: #include <stdio.h>22:23: /*24: * random.c:25: * An improved random number generation package. In addition to the standard26: * rand()/srand() like interface, this package also has a special state info27: * interface. The initstate() routine is called with a seed, an array of28: * bytes, and a count of how many bytes are being passed in; this array is then29: * initialized to contain information for random number generation with that30: * much state information. Good sizes for the amount of state information are31: * 32, 64, 128, and 256 bytes. The state can be switched by calling the32: * setstate() routine with the same array as was initiallized with initstate().33: * By default, the package runs with 128 bytes of state information and34: * generates far better random numbers than a linear congruential generator.35: * If the amount of state information is less than 32 bytes, a simple linear36: * congruential R.N.G. is used.37: * Internally, the state information is treated as an array of longs; the38: * zeroeth element of the array is the type of R.N.G. being used (small39: * integer); the remainder of the array is the state information for the40: * R.N.G. Thus, 32 bytes of state information will give 7 longs worth of41: * state information, which will allow a degree seven polynomial. (Note: the42: * zeroeth word of state information also has some other information stored43: * in it -- see setstate() for details).44: * The random number generation technique is a linear feedback shift register45: * approach, employing trinomials (since there are fewer terms to sum up that46: * way). In this approach, the least significant bit of all the numbers in47: * the state table will act as a linear feedback shift register, and will have48: * period 2^deg - 1 (where deg is the degree of the polynomial being used,49: * assuming that the polynomial is irreducible and primitive). The higher50: * order bits will have longer periods, since their values are also influenced51: * by pseudo-random carries out of the lower bits. The total period of the52: * generator is approximately deg*(2**deg - 1); thus doubling the amount of53: * state information has a vast influence on the period of the generator.54: * Note: the deg*(2**deg - 1) is an approximation only good for large deg,55: * when the period of the shift register is the dominant factor. With deg56: * equal to seven, the period is actually much longer than the 7*(2**7 - 1)57: * predicted by this formula.58: */59:60:61:62: /*63: * For each of the currently supported random number generators, we have a64: * break value on the amount of state information (you need at least this65: * many bytes of state info to support this random number generator), a degree66: * for the polynomial (actually a trinomial) that the R.N.G. is based on, and67: * the separation between the two lower order coefficients of the trinomial.68: */69:70: #define TYPE_0 0 /* linear congruential */71: #define BREAK_0 872: #define DEG_0 073: #define SEP_0 074:75: #define TYPE_1 1 /* x**7 + x**3 + 1 */76: #define BREAK_1 3277: #define DEG_1 778: #define SEP_1 379:80: #define TYPE_2 2 /* x**15 + x + 1 */81: #define BREAK_2 6482: #define DEG_2 1583: #define SEP_2 184:85: #define TYPE_3 3 /* x**31 + x**3 + 1 */86: #define BREAK_3 12887: #define DEG_3 3188: #define SEP_3 389:90: #define TYPE_4 4 /* x**63 + x + 1 */91: #define BREAK_4 25692: #define DEG_4 6393: #define SEP_4 194:95:96: /*97: * Array versions of the above information to make code run faster -- relies98: * on fact that TYPE_i == i.99: */100:101: #define MAX_TYPES 5 /* max number of types above */102:103: static int degrees[ MAX_TYPES ] = { DEG_0, DEG_1, DEG_2,104: DEG_3, DEG_4 };105:106: static int seps[ MAX_TYPES ] = { SEP_0, SEP_1, SEP_2,107: SEP_3, SEP_4 };108:109:110:111: /*112: * Initially, everything is set up as if from :113: * initstate( 1, &randtbl, 128 );114: * Note that this initialization takes advantage of the fact that srandom()115: * advances the front and rear pointers 10*rand_deg times, and hence the116: * rear pointer which starts at 0 will also end up at zero; thus the zeroeth117: * element of the state information, which contains info about the current118: * position of the rear pointer is just119: * MAX_TYPES*(rptr - state) + TYPE_3 == TYPE_3.120: */121:122: static long randtbl[ DEG_3 + 1 ] = { TYPE_3,123: 0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342,124: 0xde3b81e0, 0xdf0a6fb5, 0xf103bc02, 0x48f340fb,125: 0x7449e56b, 0xbeb1dbb0, 0xab5c5918, 0x946554fd,126: 0x8c2e680f, 0xeb3d799f, 0xb11ee0b7, 0x2d436b86,127: 0xda672e2a, 0x1588ca88, 0xe369735d, 0x904f35f7,128: 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc,129: 0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b,130: 0xf5ad9d0e, 0x8999220b, 0x27fb47b9 };131:132: /*133: * fptr and rptr are two pointers into the state info, a front and a rear134: * pointer. These two pointers are always rand_sep places aparts, as they cycle135: * cyclically through the state information. (Yes, this does mean we could get136: * away with just one pointer, but the code for random() is more efficient this137: * way). The pointers are left positioned as they would be from the call138: * initstate( 1, randtbl, 128 )139: * (The position of the rear pointer, rptr, is really 0 (as explained above140: * in the initialization of randtbl) because the state table pointer is set141: * to point to randtbl[1] (as explained below).142: */143:144: static long *fptr = &randtbl[ SEP_3 + 1 ];145: static long *rptr = &randtbl[ 1 ];146:147:148:149: /*150: * The following things are the pointer to the state information table,151: * the type of the current generator, the degree of the current polynomial152: * being used, and the separation between the two pointers.153: * Note that for efficiency of random(), we remember the first location of154: * the state information, not the zeroeth. Hence it is valid to access155: * state[-1], which is used to store the type of the R.N.G.156: * Also, we remember the last location, since this is more efficient than157: * indexing every time to find the address of the last element to see if158: * the front and rear pointers have wrapped.159: */160:161: static long *state = &randtbl[ 1 ];162:163: static int rand_type = TYPE_3;164: static int rand_deg = DEG_3;165: static int rand_sep = SEP_3;166:167: static long *end_ptr = &randtbl[ DEG_3 + 1 ];168:169:170:171: /*172: * srandom:173: * Initialize the random number generator based on the given seed. If the174: * type is the trivial no-state-information type, just remember the seed.175: * Otherwise, initializes state[] based on the given "seed" via a linear176: * congruential generator. Then, the pointers are set to known locations177: * that are exactly rand_sep places apart. Lastly, it cycles the state178: * information a given number of times to get rid of any initial dependencies179: * introduced by the L.C.R.N.G.180: * Note that the initialization of randtbl[] for default usage relies on181: * values produced by this routine.182: */183:184: srandom( x )185:186: unsigned x;187: {188: register int i, j;189:190: if( rand_type == TYPE_0 ) {191: state[ 0 ] = x;192: }193: else {194: j = 1;195: state[ 0 ] = x;196: for( i = 1; i < rand_deg; i++ ) {197: state[i] = 1103515245*state[i - 1] + 12345;198: }199: fptr = &state[ rand_sep ];200: rptr = &state[ 0 ];201: for( i = 0; i < 10*rand_deg; i++ ) random();202: }203: }204:205:206:207: /*208: * initstate:209: * Initialize the state information in the given array of n bytes for210: * future random number generation. Based on the number of bytes we211: * are given, and the break values for the different R.N.G.'s, we choose212: * the best (largest) one we can and set things up for it. srandom() is213: * then called to initialize the state information.214: * Note that on return from srandom(), we set state[-1] to be the type215: * multiplexed with the current value of the rear pointer; this is so216: * successive calls to initstate() won't lose this information and will217: * be able to restart with setstate().218: * Note: the first thing we do is save the current state, if any, just like219: * setstate() so that it doesn't matter when initstate is called.220: * Returns a pointer to the old state.221: */222:223: char *224: initstate( seed, arg_state, n )225:226: unsigned seed; /* seed for R. N. G. */227: char *arg_state; /* pointer to state array */228: int n; /* # bytes of state info */229: {230: register char *ostate = (char *)( &state[ -1 ] );231:232: if( rand_type == TYPE_0 ) state[ -1 ] = rand_type;233: else state[ -1 ] = MAX_TYPES*(rptr - state) + rand_type;234: if( n < BREAK_1 ) {235: if( n < BREAK_0 ) {236: fprintf( stderr, "initstate: not enough state (%d bytes) with which to do jack; ignored.\n" );237: return;238: }239: rand_type = TYPE_0;240: rand_deg = DEG_0;241: rand_sep = SEP_0;242: }243: else {244: if( n < BREAK_2 ) {245: rand_type = TYPE_1;246: rand_deg = DEG_1;247: rand_sep = SEP_1;248: }249: else {250: if( n < BREAK_3 ) {251: rand_type = TYPE_2;252: rand_deg = DEG_2;253: rand_sep = SEP_2;254: }255: else {256: if( n < BREAK_4 ) {257: rand_type = TYPE_3;258: rand_deg = DEG_3;259: rand_sep = SEP_3;260: }261: else {262: rand_type = TYPE_4;263: rand_deg = DEG_4;264: rand_sep = SEP_4;265: }266: }267: }268: }269: state = &( ( (long *)arg_state )[1] ); /* first location */270: end_ptr = &state[ rand_deg ]; /* must set end_ptr before srandom */271: srandom( seed );272: if( rand_type == TYPE_0 ) state[ -1 ] = rand_type;273: else state[ -1 ] = MAX_TYPES*(rptr - state) + rand_type;274: return( ostate );275: }276:277:278:279: /*280: * setstate:281: * Restore the state from the given state array.282: * Note: it is important that we also remember the locations of the pointers283: * in the current state information, and restore the locations of the pointers284: * from the old state information. This is done by multiplexing the pointer285: * location into the zeroeth word of the state information.286: * Note that due to the order in which things are done, it is OK to call287: * setstate() with the same state as the current state.288: * Returns a pointer to the old state information.289: */290:291: char *292: setstate( arg_state )293:294: char *arg_state;295: {296: register long *new_state = (long *)arg_state;297: register int type = new_state[0]%MAX_TYPES;298: register int rear = new_state[0]/MAX_TYPES;299: char *ostate = (char *)( &state[ -1 ] );300:301: if( rand_type == TYPE_0 ) state[ -1 ] = rand_type;302: else state[ -1 ] = MAX_TYPES*(rptr - state) + rand_type;303: switch( type ) {304: case TYPE_0:305: case TYPE_1:306: case TYPE_2:307: case TYPE_3:308: case TYPE_4:309: rand_type = type;310: rand_deg = degrees[ type ];311: rand_sep = seps[ type ];312: break;313:314: default:315: fprintf( stderr, "setstate: state info has been munged; not changed.\n" );316: }317: state = &new_state[ 1 ];318: if( rand_type != TYPE_0 ) {319: rptr = &state[ rear ];320: fptr = &state[ (rear + rand_sep)%rand_deg ];321: }322: end_ptr = &state[ rand_deg ]; /* set end_ptr too */323: return( ostate );324: }325:326:327:328: /*329: * random:330: * If we are using the trivial TYPE_0 R.N.G., just do the old linear331: * congruential bit. Otherwise, we do our fancy trinomial stuff, which is the332: * same in all ther other cases due to all the global variables that have been333: * set up. The basic operation is to add the number at the rear pointer into334: * the one at the front pointer. Then both pointers are advanced to the next335: * location cyclically in the table. The value returned is the sum generated,336: * reduced to 31 bits by throwing away the "least random" low bit.337: * Note: the code takes advantage of the fact that both the front and338: * rear pointers can't wrap on the same call by not testing the rear339: * pointer if the front one has wrapped.340: * Returns a 31-bit random number.341: */342:343: long344: random()345: {346: long i;347:348: if( rand_type == TYPE_0 ) {349: i = state[0] = ( state[0]*1103515245 + 12345 )&0x7fffffff;350: }351: else {352: *fptr += *rptr;353: i = (*fptr >> 1)&0x7fffffff; /* chucking least random bit */354: if( ++fptr >= end_ptr ) {355: fptr = state;356: ++rptr;357: }358: else {359: if( ++rptr >= end_ptr ) rptr = state;360: }361: }362: return( i );363: }364:365: #endif NO_RANDOM

rnd
defined in line 5; used 3 times

- in /usr/src/games/fortune/fortune.c line 187, 219
- in /usr/src/games/fortune/strfile.c line 388

srnd
defined in line 10; used 2 times

- in /usr/src/games/fortune/fortune.c line 185
- in /usr/src/games/fortune/strfile.c line 361