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	zrand.c - libzahl - big integer library
	git clone git://git.suckless.org/libzahl
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	---
	zrand.c (3981B)
	---
	1 /* See LICENSE file for copyright and license details. */
	2 #include "internals.h"
	3
	4 #include <fcntl.h>
	5 #include <stdlib.h>
	6 #include <time.h>
	7 #include <unistd.h>
	8
	9 #ifndef FAST_RANDOM_PATHNAME
	10 # define FAST_RANDOM_PATHNAME "/dev/urandom"
	11 #endif
	12
	13 #ifndef SECURE_RANDOM_PATHNAME
	14 # define SECURE_RANDOM_PATHNAME "/dev/random"
	15 #endif
	16
	17
	18 static void
	19 zrand_libc_rand(void out, size_t n, void statep)
	20 {
	21 static char inited = 0;
	22
	23 unsigned int ri;
	24 double rd;
	25 unsigned char *buf = out;
	26
	27 if (!inited) {
	28 inited = 1;
	29 srand((unsigned)((intptr_t)out \| time(NULL)));
	30 }
	31
	32 while (n--) {
	33 ri = (unsigned)rand();
	34 rd = (double)ri / ((double)RAND_MAX + 1);
	35 #ifdef GOOD_RAND
	36 rd = 256 256;
	37 ri = (unsigned int)rd;
	38 buf[n] = (unsigned char)((ri >> 0) & 255);
	39 if (!n--) break;
	40 buf[n] = (unsigned char)((ri >> 8) & 255);
	41 #else
	42 rd *= 256;
	43 buf[n] = (unsigned char)rd;
	44 #endif
	45 }
	46
	47 (void) statep;
	48 }
	49
	50 static void
	51 zrand_libc_rand48(void out, size_t n, void statep)
	52 {
	53 static char inited = 0;
	54
	55 long int r0, r1;
	56 unsigned char *buf = out;
	57
	58 if (!inited) {
	59 inited = 1;
	60 srand48((intptr_t)out \| time(NULL));
	61 }
	62
	63 while (n--) {
	64 r0 = lrand48() & 15;
	65 r1 = lrand48() & 15;
	66 buf[n] = (unsigned char)((r0 << 4) \| r1);
	67 }
	68
	69 (void) statep;
	70 }
	71
	72 static void
	73 zrand_libc_random(void out, size_t n, void statep)
	74 {
	75 static char inited = 0;
	76
	77 long int ri;
	78 unsigned char *buf = out;
	79
	80 if (!inited) {
	81 inited = 1;
	82 srandom((unsigned)((intptr_t)out \| time(NULL)));
	83 }
	84
	85 while (n--) {
	86 ri = random();
	87 buf[n] = (unsigned char)((ri >> 0) & 255);
	88 if (!n--) break;
	89 buf[n] = (unsigned char)((ri >> 8) & 255);
	90 if (!n--) break;
	91 buf[n] = (unsigned char)((ri >> 16) & 255);
	92 }
	93
	94 (void) statep;
	95 }
	96
	97 static void
	98 zrand_fd(void out, size_t n, void statep)
	99 {
	100 int fd = (int )statep;
	101 ssize_t read_just;
	102 size_t read_total = 0;
	103 char *buf = out;
	104
	105 while (n) {
	106 read_just = read(fd, buf + read_total, n);
	107 if (check(read_just < 0))
	108 libzahl_failure(errno);
	109 read_total += (size_t)read_just;
	110 n -= (size_t)read_just;
	111 }
	112 }
	113
	114 static void
	115 zrand_get_random_bits(z_t r, size_t bits, void (fun)(void , size_t, vo…
	116 {
	117 size_t n, chars = CEILING_BITS_TO_CHARS(bits);
	118 zahl_char_t mask = 1;
	119
	120 ENSURE_SIZE(r, chars);
	121
	122 fun(r->chars, chars * sizeof(zahl_char_t), statep);
	123
	124 bits = BITS_IN_LAST_CHAR(bits);
	125 mask <<= bits;
	126 mask -= 1;
	127
	128 r->chars[chars - 1] &= mask;
	129 for (n = chars; n--;) {
	130 if (likely(r->chars[n])) {
	131 r->used = n + 1;
	132 SET_SIGNUM(r, 1);
	133 return;
	134 }
	135 }
	136 SET_SIGNUM(r, 0);
	137 }
	138
	139 void
	140 zrand(z_t r, enum zranddev dev, enum zranddist dist, z_t n)
	141 {
	142 #define RANDOM_UNIFORM(RETRY)\
	143 do {\
	144 if (check(znegative(n)))\
	145 libzahl_failure(-ZERROR_NEGATIVE);\
	146 bits = zbits(n);\
	147 do\
	148 zrand_get_random_bits(r, bits, random_fun, state…
	149 while (RETRY && unlikely(zcmpmag(r, n) > 0));\
	150 } while (0)
	151
	152
	153 const char *pathname = 0;
	154 size_t bits;
	155 int fd = -1;
	156 void *statep = 0;
	157 void (random_fun)(void , size_t, void *) = &zrand_fd;
	158
	159 switch (dev) {
	160 case FAST_RANDOM:
	161 pathname = FAST_RANDOM_PATHNAME;
	162 break;
	163 case SECURE_RANDOM:
	164 pathname = SECURE_RANDOM_PATHNAME;
	165 break;
	166 case LIBC_RAND_RANDOM:
	167 random_fun = &zrand_libc_rand;
	168 break;
	169 case DEFAULT_RANDOM:
	170 case FASTEST_RANDOM:
	171 case LIBC_RANDOM_RANDOM:
	172 random_fun = &zrand_libc_random;
	173 break;
	174 case LIBC_RAND48_RANDOM:
	175 random_fun = &zrand_libc_rand48;
	176 break;
	177 default:
	178 libzahl_failure(EINVAL);
	179 }
	180
	181 if (unlikely(zzero(n))) {
	182 SET_SIGNUM(r, 0);
	183 return;
	184 }
	185
	186 if (pathname) {
	187 fd = open(pathname, O_RDONLY);
	188 if (check(fd < 0))
	189 libzahl_failure(errno);
	190 statep = &fd;
	191 }
	192
	193 switch (dist) {
	194 case QUASIUNIFORM:
	195 RANDOM_UNIFORM(0);
	196 zadd(r, r, libzahl_const_1);
	197 zmul(r, r, n);
	198 zrsh(r, r, bits);
	199 break;
	200
	201 case UNIFORM:
	202 RANDOM_UNIFORM(1);
	203 break;
	204
	205 case MODUNIFORM:
	206 RANDOM_UNIFORM(0);
	207 if (unlikely(zcmpmag(r, n) > 0))
	208 zsub(r, r, n);
	209 break;
	210
	211 default:
	212 #if !defined(ZAHL_UNSAFE)
	213 libzahl_failure(EINVAL);
	214 #endif
	215 break;
	216 }
	217
	218 if (fd >= 0)
	219 close(fd);
	220 }