src/vendor/rand/src/isaac.rs

   1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! The ISAAC random number generator.
  12
  13 #![allow(non_camel_case_types)]
  14
  15 use std::slice;
  16 use std::iter::repeat;
  17 use std::num::Wrapping as w;
  18 use std::fmt;
  19
  20 use {Rng, SeedableRng, Rand, w32, w64};
  21
  22 const RAND_SIZE_LEN: usize = 8;
  23 const RAND_SIZE: u32 = 1 << RAND_SIZE_LEN;
  24 const RAND_SIZE_USIZE: usize = 1 << RAND_SIZE_LEN;
  25
  26 /// A random number generator that uses the ISAAC algorithm[1].
  27 ///
  28 /// The ISAAC algorithm is generally accepted as suitable for
  29 /// cryptographic purposes, but this implementation has not be
  30 /// verified as such. Prefer a generator like `OsRng` that defers to
  31 /// the operating system for cases that need high security.
  32 ///
  33 /// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
  34 /// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
  35 #[derive(Copy)]
  36 pub struct IsaacRng {
  37     cnt: u32,
  38     rsl: [w32; RAND_SIZE_USIZE],
  39     mem: [w32; RAND_SIZE_USIZE],
  40     a: w32,
  41     b: w32,
  42     c: w32,
  43 }
  44
  45 static EMPTY: IsaacRng = IsaacRng {
  46     cnt: 0,
  47     rsl: [w(0); RAND_SIZE_USIZE],
  48     mem: [w(0); RAND_SIZE_USIZE],
  49     a: w(0), b: w(0), c: w(0),
  50 };
  51
  52 impl IsaacRng {
  53
  54     /// Create an ISAAC random number generator using the default
  55     /// fixed seed.
  56     pub fn new_unseeded() -> IsaacRng {
  57         let mut rng = EMPTY;
  58         rng.init(false);
  59         rng
  60     }
  61
  62     /// Initialises `self`. If `use_rsl` is true, then use the current value
  63     /// of `rsl` as a seed, otherwise construct one algorithmically (not
  64     /// randomly).
  65     fn init(&mut self, use_rsl: bool) {
  66         let mut a = w(0x9e3779b9);
  67         let mut b = a;
  68         let mut c = a;
  69         let mut d = a;
  70         let mut e = a;
  71         let mut f = a;
  72         let mut g = a;
  73         let mut h = a;
  74
  75         macro_rules! mix {
  76             () => {{
  77                 a=a^(b<<11); d=d+a; b=b+c;
  78                 b=b^(c>>2);  e=e+b; c=c+d;
  79                 c=c^(d<<8);  f=f+c; d=d+e;
  80                 d=d^(e>>16); g=g+d; e=e+f;
  81                 e=e^(f<<10); h=h+e; f=f+g;
  82                 f=f^(g>>4);  a=a+f; g=g+h;
  83                 g=g^(h<<8);  b=b+g; h=h+a;
  84                 h=h^(a>>9);  c=c+h; a=a+b;
  85             }}
  86         }
  87
  88         for _ in 0..4 {
  89             mix!();
  90         }
  91
  92         if use_rsl {
  93             macro_rules! memloop {
  94                 ($arr:expr) => {{
  95                     for i in (0..RAND_SIZE_USIZE/8).map(|i| i * 8) {
  96                         a=a+$arr[i  ]; b=b+$arr[i+1];
  97                         c=c+$arr[i+2]; d=d+$arr[i+3];
  98                         e=e+$arr[i+4]; f=f+$arr[i+5];
  99                         g=g+$arr[i+6]; h=h+$arr[i+7];
 100                         mix!();
 101                         self.mem[i  ]=a; self.mem[i+1]=b;
 102                         self.mem[i+2]=c; self.mem[i+3]=d;
 103                         self.mem[i+4]=e; self.mem[i+5]=f;
 104                         self.mem[i+6]=g; self.mem[i+7]=h;
 105                     }
 106                 }}
 107             }
 108
 109             memloop!(self.rsl);
 110             memloop!(self.mem);
 111         } else {
 112             for i in (0..RAND_SIZE_USIZE/8).map(|i| i * 8) {
 113                 mix!();
 114                 self.mem[i  ]=a; self.mem[i+1]=b;
 115                 self.mem[i+2]=c; self.mem[i+3]=d;
 116                 self.mem[i+4]=e; self.mem[i+5]=f;
 117                 self.mem[i+6]=g; self.mem[i+7]=h;
 118             }
 119         }
 120
 121         self.isaac();
 122     }
 123
 124     /// Refills the output buffer (`self.rsl`)
 125     #[inline]
 126     fn isaac(&mut self) {
 127         self.c = self.c + w(1);
 128         // abbreviations
 129         let mut a = self.a;
 130         let mut b = self.b + self.c;
 131
 132         const MIDPOINT: usize = RAND_SIZE_USIZE / 2;
 133
 134         macro_rules! ind {
 135             ($x:expr) => ( self.mem[($x >> 2usize).0 as usize & (RAND_SIZE_USIZE - 1)] )
 136         }
 137
 138         let r = [(0, MIDPOINT), (MIDPOINT, 0)];
 139         for &(mr_offset, m2_offset) in r.iter() {
 140
 141             macro_rules! rngstepp {
 142                 ($j:expr, $shift:expr) => {{
 143                     let base = $j;
 144                     let mix = a << $shift;
 145
 146                     let x = self.mem[base  + mr_offset];
 147                     a = (a ^ mix) + self.mem[base + m2_offset];
 148                     let y = ind!(x) + a + b;
 149                     self.mem[base + mr_offset] = y;
 150
 151                     b = ind!(y >> RAND_SIZE_LEN) + x;
 152                     self.rsl[base + mr_offset] = b;
 153                 }}
 154             }
 155
 156             macro_rules! rngstepn {
 157                 ($j:expr, $shift:expr) => {{
 158                     let base = $j;
 159                     let mix = a >> $shift;
 160
 161                     let x = self.mem[base  + mr_offset];
 162                     a = (a ^ mix) + self.mem[base + m2_offset];
 163                     let y = ind!(x) + a + b;
 164                     self.mem[base + mr_offset] = y;
 165
 166                     b = ind!(y >> RAND_SIZE_LEN) + x;
 167                     self.rsl[base + mr_offset] = b;
 168                 }}
 169             }
 170
 171             for i in (0..MIDPOINT/4).map(|i| i * 4) {
 172                 rngstepp!(i + 0, 13);
 173                 rngstepn!(i + 1, 6);
 174                 rngstepp!(i + 2, 2);
 175                 rngstepn!(i + 3, 16);
 176             }
 177         }
 178
 179         self.a = a;
 180         self.b = b;
 181         self.cnt = RAND_SIZE;
 182     }
 183 }
 184
 185 // Cannot be derived because [u32; 256] does not implement Clone
 186 impl Clone for IsaacRng {
 187     fn clone(&self) -> IsaacRng {
 188         *self
 189     }
 190 }
 191
 192 impl Rng for IsaacRng {
 193     #[inline]
 194     fn next_u32(&mut self) -> u32 {
 195         if self.cnt == 0 {
 196             // make some more numbers
 197             self.isaac();
 198         }
 199         self.cnt -= 1;
 200
 201         // self.cnt is at most RAND_SIZE, but that is before the
 202         // subtraction above. We want to index without bounds
 203         // checking, but this could lead to incorrect code if someone
 204         // misrefactors, so we check, sometimes.
 205         //
 206         // (Changes here should be reflected in Isaac64Rng.next_u64.)
 207         debug_assert!(self.cnt < RAND_SIZE);
 208
 209         // (the % is cheaply telling the optimiser that we're always
 210         // in bounds, without unsafe. NB. this is a power of two, so
 211         // it optimises to a bitwise mask).
 212         self.rsl[(self.cnt % RAND_SIZE) as usize].0
 213     }
 214 }
 215
 216 impl<'a> SeedableRng<&'a [u32]> for IsaacRng {
 217     fn reseed(&mut self, seed: &'a [u32]) {
 218         // make the seed into [seed[0], seed[1], ..., seed[seed.len()
 219         // - 1], 0, 0, ...], to fill rng.rsl.
 220         let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u32));
 221
 222         for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
 223             *rsl_elem = w(seed_elem);
 224         }
 225         self.cnt = 0;
 226         self.a = w(0);
 227         self.b = w(0);
 228         self.c = w(0);
 229
 230         self.init(true);
 231     }
 232
 233     /// Create an ISAAC random number generator with a seed. This can
 234     /// be any length, although the maximum number of elements used is
 235     /// 256 and any more will be silently ignored. A generator
 236     /// constructed with a given seed will generate the same sequence
 237     /// of values as all other generators constructed with that seed.
 238     fn from_seed(seed: &'a [u32]) -> IsaacRng {
 239         let mut rng = EMPTY;
 240         rng.reseed(seed);
 241         rng
 242     }
 243 }
 244
 245 impl Rand for IsaacRng {
 246     fn rand<R: Rng>(other: &mut R) -> IsaacRng {
 247         let mut ret = EMPTY;
 248         unsafe {
 249             let ptr = ret.rsl.as_mut_ptr() as *mut u8;
 250
 251             let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_USIZE * 4);
 252             other.fill_bytes(slice);
 253         }
 254         ret.cnt = 0;
 255         ret.a = w(0);
 256         ret.b = w(0);
 257         ret.c = w(0);
 258
 259         ret.init(true);
 260         return ret;
 261     }
 262 }
 263
 264 impl fmt::Debug for IsaacRng {
 265     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 266         write!(f, "IsaacRng {{}}")
 267     }
 268 }
 269
 270 const RAND_SIZE_64_LEN: usize = 8;
 271 const RAND_SIZE_64: usize = 1 << RAND_SIZE_64_LEN;
 272
 273 /// A random number generator that uses ISAAC-64[1], the 64-bit
 274 /// variant of the ISAAC algorithm.
 275 ///
 276 /// The ISAAC algorithm is generally accepted as suitable for
 277 /// cryptographic purposes, but this implementation has not be
 278 /// verified as such. Prefer a generator like `OsRng` that defers to
 279 /// the operating system for cases that need high security.
 280 ///
 281 /// [1]: Bob Jenkins, [*ISAAC: A fast cryptographic random number
 282 /// generator*](http://www.burtleburtle.net/bob/rand/isaacafa.html)
 283 #[derive(Copy)]
 284 pub struct Isaac64Rng {
 285     cnt: usize,
 286     rsl: [w64; RAND_SIZE_64],
 287     mem: [w64; RAND_SIZE_64],
 288     a: w64,
 289     b: w64,
 290     c: w64,
 291 }
 292
 293 static EMPTY_64: Isaac64Rng = Isaac64Rng {
 294     cnt: 0,
 295     rsl: [w(0); RAND_SIZE_64],
 296     mem: [w(0); RAND_SIZE_64],
 297     a: w(0), b: w(0), c: w(0),
 298 };
 299
 300 impl Isaac64Rng {
 301     /// Create a 64-bit ISAAC random number generator using the
 302     /// default fixed seed.
 303     pub fn new_unseeded() -> Isaac64Rng {
 304         let mut rng = EMPTY_64;
 305         rng.init(false);
 306         rng
 307     }
 308
 309     /// Initialises `self`. If `use_rsl` is true, then use the current value
 310     /// of `rsl` as a seed, otherwise construct one algorithmically (not
 311     /// randomly).
 312     fn init(&mut self, use_rsl: bool) {
 313         macro_rules! init {
 314             ($var:ident) => (
 315                 let mut $var = w(0x9e3779b97f4a7c13);
 316             )
 317         }
 318         init!(a); init!(b); init!(c); init!(d);
 319         init!(e); init!(f); init!(g); init!(h);
 320
 321         macro_rules! mix {
 322             () => {{
 323                 a=a-e; f=f^(h>>9);  h=h+a;
 324                 b=b-f; g=g^(a<<9);  a=a+b;
 325                 c=c-g; h=h^(b>>23); b=b+c;
 326                 d=d-h; a=a^(c<<15); c=c+d;
 327                 e=e-a; b=b^(d>>14); d=d+e;
 328                 f=f-b; c=c^(e<<20); e=e+f;
 329                 g=g-c; d=d^(f>>17); f=f+g;
 330                 h=h-d; e=e^(g<<14); g=g+h;
 331             }}
 332         }
 333
 334         for _ in 0..4 {
 335             mix!();
 336         }
 337
 338         if use_rsl {
 339             macro_rules! memloop {
 340                 ($arr:expr) => {{
 341                     for i in (0..RAND_SIZE_64 / 8).map(|i| i * 8) {
 342                         a=a+$arr[i  ]; b=b+$arr[i+1];
 343                         c=c+$arr[i+2]; d=d+$arr[i+3];
 344                         e=e+$arr[i+4]; f=f+$arr[i+5];
 345                         g=g+$arr[i+6]; h=h+$arr[i+7];
 346                         mix!();
 347                         self.mem[i  ]=a; self.mem[i+1]=b;
 348                         self.mem[i+2]=c; self.mem[i+3]=d;
 349                         self.mem[i+4]=e; self.mem[i+5]=f;
 350                         self.mem[i+6]=g; self.mem[i+7]=h;
 351                     }
 352                 }}
 353             }
 354
 355             memloop!(self.rsl);
 356             memloop!(self.mem);
 357         } else {
 358             for i in (0..RAND_SIZE_64 / 8).map(|i| i * 8) {
 359                 mix!();
 360                 self.mem[i  ]=a; self.mem[i+1]=b;
 361                 self.mem[i+2]=c; self.mem[i+3]=d;
 362                 self.mem[i+4]=e; self.mem[i+5]=f;
 363                 self.mem[i+6]=g; self.mem[i+7]=h;
 364             }
 365         }
 366
 367         self.isaac64();
 368     }
 369
 370     /// Refills the output buffer (`self.rsl`)
 371     fn isaac64(&mut self) {
 372         self.c = self.c + w(1);
 373         // abbreviations
 374         let mut a = self.a;
 375         let mut b = self.b + self.c;
 376         const MIDPOINT: usize =  RAND_SIZE_64 / 2;
 377         const MP_VEC: [(usize, usize); 2] = [(0,MIDPOINT), (MIDPOINT, 0)];
 378         macro_rules! ind {
 379             ($x:expr) => {
 380                 *self.mem.get_unchecked((($x >> 3usize).0 as usize) & (RAND_SIZE_64 - 1))
 381             }
 382         }
 383
 384         for &(mr_offset, m2_offset) in MP_VEC.iter() {
 385             for base in (0..MIDPOINT / 4).map(|i| i * 4) {
 386
 387                 macro_rules! rngstepp {
 388                     ($j:expr, $shift:expr) => {{
 389                         let base = base + $j;
 390                         let mix = a ^ (a << $shift);
 391                         let mix = if $j == 0 {!mix} else {mix};
 392
 393                         unsafe {
 394                             let x = *self.mem.get_unchecked(base + mr_offset);
 395                             a = mix + *self.mem.get_unchecked(base + m2_offset);
 396                             let y = ind!(x) + a + b;
 397                             *self.mem.get_unchecked_mut(base + mr_offset) = y;
 398
 399                             b = ind!(y >> RAND_SIZE_64_LEN) + x;
 400                             *self.rsl.get_unchecked_mut(base + mr_offset) = b;
 401                         }
 402                     }}
 403                 }
 404
 405                 macro_rules! rngstepn {
 406                     ($j:expr, $shift:expr) => {{
 407                         let base = base + $j;
 408                         let mix = a ^ (a >> $shift);
 409                         let mix = if $j == 0 {!mix} else {mix};
 410
 411                         unsafe {
 412                             let x = *self.mem.get_unchecked(base + mr_offset);
 413                             a = mix + *self.mem.get_unchecked(base + m2_offset);
 414                             let y = ind!(x) + a + b;
 415                             *self.mem.get_unchecked_mut(base + mr_offset) = y;
 416
 417                             b = ind!(y >> RAND_SIZE_64_LEN) + x;
 418                             *self.rsl.get_unchecked_mut(base + mr_offset) = b;
 419                         }
 420                     }}
 421                 }
 422
 423                 rngstepp!(0, 21);
 424                 rngstepn!(1, 5);
 425                 rngstepp!(2, 12);
 426                 rngstepn!(3, 33);
 427             }
 428         }
 429
 430         self.a = a;
 431         self.b = b;
 432         self.cnt = RAND_SIZE_64;
 433     }
 434 }
 435
 436 // Cannot be derived because [u32; 256] does not implement Clone
 437 impl Clone for Isaac64Rng {
 438     fn clone(&self) -> Isaac64Rng {
 439         *self
 440     }
 441 }
 442
 443 impl Rng for Isaac64Rng {
 444     // FIXME #7771: having next_u32 like this should be unnecessary
 445     #[inline]
 446     fn next_u32(&mut self) -> u32 {
 447         self.next_u64() as u32
 448     }
 449
 450     #[inline]
 451     fn next_u64(&mut self) -> u64 {
 452         if self.cnt == 0 {
 453             // make some more numbers
 454             self.isaac64();
 455         }
 456         self.cnt -= 1;
 457
 458         // See corresponding location in IsaacRng.next_u32 for
 459         // explanation.
 460         debug_assert!(self.cnt < RAND_SIZE_64);
 461         self.rsl[(self.cnt % RAND_SIZE_64) as usize].0
 462     }
 463 }
 464
 465 impl<'a> SeedableRng<&'a [u64]> for Isaac64Rng {
 466     fn reseed(&mut self, seed: &'a [u64]) {
 467         // make the seed into [seed[0], seed[1], ..., seed[seed.len()
 468         // - 1], 0, 0, ...], to fill rng.rsl.
 469         let seed_iter = seed.iter().map(|&x| x).chain(repeat(0u64));
 470
 471         for (rsl_elem, seed_elem) in self.rsl.iter_mut().zip(seed_iter) {
 472             *rsl_elem = w(seed_elem);
 473         }
 474         self.cnt = 0;
 475         self.a = w(0);
 476         self.b = w(0);
 477         self.c = w(0);
 478
 479         self.init(true);
 480     }
 481
 482     /// Create an ISAAC random number generator with a seed. This can
 483     /// be any length, although the maximum number of elements used is
 484     /// 256 and any more will be silently ignored. A generator
 485     /// constructed with a given seed will generate the same sequence
 486     /// of values as all other generators constructed with that seed.
 487     fn from_seed(seed: &'a [u64]) -> Isaac64Rng {
 488         let mut rng = EMPTY_64;
 489         rng.reseed(seed);
 490         rng
 491     }
 492 }
 493
 494 impl Rand for Isaac64Rng {
 495     fn rand<R: Rng>(other: &mut R) -> Isaac64Rng {
 496         let mut ret = EMPTY_64;
 497         unsafe {
 498             let ptr = ret.rsl.as_mut_ptr() as *mut u8;
 499
 500             let slice = slice::from_raw_parts_mut(ptr, RAND_SIZE_64 * 8);
 501             other.fill_bytes(slice);
 502         }
 503         ret.cnt = 0;
 504         ret.a = w(0);
 505         ret.b = w(0);
 506         ret.c = w(0);
 507
 508         ret.init(true);
 509         return ret;
 510     }
 511 }
 512
 513 impl fmt::Debug for Isaac64Rng {
 514     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 515         write!(f, "Isaac64Rng {{}}")
 516     }
 517 }
 518
 519 #[cfg(test)]
 520 mod test {
 521     use {Rng, SeedableRng};
 522     use super::{IsaacRng, Isaac64Rng};
 523
 524     #[test]
 525     fn test_rng_32_rand_seeded() {
 526         let s = ::test::rng().gen_iter::<u32>().take(256).collect::<Vec<u32>>();
 527         let mut ra: IsaacRng = SeedableRng::from_seed(&s[..]);
 528         let mut rb: IsaacRng = SeedableRng::from_seed(&s[..]);
 529         assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
 530                                 rb.gen_ascii_chars().take(100)));
 531     }
 532     #[test]
 533     fn test_rng_64_rand_seeded() {
 534         let s = ::test::rng().gen_iter::<u64>().take(256).collect::<Vec<u64>>();
 535         let mut ra: Isaac64Rng = SeedableRng::from_seed(&s[..]);
 536         let mut rb: Isaac64Rng = SeedableRng::from_seed(&s[..]);
 537         assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
 538                                 rb.gen_ascii_chars().take(100)));
 539     }
 540
 541     #[test]
 542     fn test_rng_32_seeded() {
 543         let seed: &[_] = &[1, 23, 456, 7890, 12345];
 544         let mut ra: IsaacRng = SeedableRng::from_seed(seed);
 545         let mut rb: IsaacRng = SeedableRng::from_seed(seed);
 546         assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
 547                                 rb.gen_ascii_chars().take(100)));
 548     }
 549     #[test]
 550     fn test_rng_64_seeded() {
 551         let seed: &[_] = &[1, 23, 456, 7890, 12345];
 552         let mut ra: Isaac64Rng = SeedableRng::from_seed(seed);
 553         let mut rb: Isaac64Rng = SeedableRng::from_seed(seed);
 554         assert!(::test::iter_eq(ra.gen_ascii_chars().take(100),
 555                                 rb.gen_ascii_chars().take(100)));
 556     }
 557
 558     #[test]
 559     fn test_rng_32_reseed() {
 560         let s = ::test::rng().gen_iter::<u32>().take(256).collect::<Vec<u32>>();
 561         let mut r: IsaacRng = SeedableRng::from_seed(&s[..]);
 562         let string1: String = r.gen_ascii_chars().take(100).collect();
 563
 564         r.reseed(&s[..]);
 565
 566         let string2: String = r.gen_ascii_chars().take(100).collect();
 567         assert_eq!(string1, string2);
 568     }
 569     #[test]
 570     fn test_rng_64_reseed() {
 571         let s = ::test::rng().gen_iter::<u64>().take(256).collect::<Vec<u64>>();
 572         let mut r: Isaac64Rng = SeedableRng::from_seed(&s[..]);
 573         let string1: String = r.gen_ascii_chars().take(100).collect();
 574
 575         r.reseed(&s[..]);
 576
 577         let string2: String = r.gen_ascii_chars().take(100).collect();
 578         assert_eq!(string1, string2);
 579     }
 580
 581     #[test]
 582     fn test_rng_32_true_values() {
 583         let seed: &[_] = &[1, 23, 456, 7890, 12345];
 584         let mut ra: IsaacRng = SeedableRng::from_seed(seed);
 585         // Regression test that isaac is actually using the above vector
 586         let v = (0..10).map(|_| ra.next_u32()).collect::<Vec<_>>();
 587         assert_eq!(v,
 588                    vec!(2558573138, 873787463, 263499565, 2103644246, 3595684709,
 589                         4203127393, 264982119, 2765226902, 2737944514, 3900253796));
 590
 591         let seed: &[_] = &[12345, 67890, 54321, 9876];
 592         let mut rb: IsaacRng = SeedableRng::from_seed(seed);
 593         // skip forward to the 10000th number
 594         for _ in 0..10000 { rb.next_u32(); }
 595
 596         let v = (0..10).map(|_| rb.next_u32()).collect::<Vec<_>>();
 597         assert_eq!(v,
 598                    vec!(3676831399, 3183332890, 2834741178, 3854698763, 2717568474,
 599                         1576568959, 3507990155, 179069555, 141456972, 2478885421));
 600     }
 601     #[test]
 602     fn test_rng_64_true_values() {
 603         let seed: &[_] = &[1, 23, 456, 7890, 12345];
 604         let mut ra: Isaac64Rng = SeedableRng::from_seed(seed);
 605         // Regression test that isaac is actually using the above vector
 606         let v = (0..10).map(|_| ra.next_u64()).collect::<Vec<_>>();
 607         assert_eq!(v,
 608                    vec!(547121783600835980, 14377643087320773276, 17351601304698403469,
 609                         1238879483818134882, 11952566807690396487, 13970131091560099343,
 610                         4469761996653280935, 15552757044682284409, 6860251611068737823,
 611                         13722198873481261842));
 612
 613         let seed: &[_] = &[12345, 67890, 54321, 9876];
 614         let mut rb: Isaac64Rng = SeedableRng::from_seed(seed);
 615         // skip forward to the 10000th number
 616         for _ in 0..10000 { rb.next_u64(); }
 617
 618         let v = (0..10).map(|_| rb.next_u64()).collect::<Vec<_>>();
 619         assert_eq!(v,
 620                    vec!(18143823860592706164, 8491801882678285927, 2699425367717515619,
 621                         17196852593171130876, 2606123525235546165, 15790932315217671084,
 622                         596345674630742204, 9947027391921273664, 11788097613744130851,
 623                         10391409374914919106));
 624     }
 625
 626     #[test]
 627     fn test_rng_clone() {
 628         let seed: &[_] = &[1, 23, 456, 7890, 12345];
 629         let mut rng: Isaac64Rng = SeedableRng::from_seed(seed);
 630         let mut clone = rng.clone();
 631         for _ in 0..16 {
 632             assert_eq!(rng.next_u64(), clone.next_u64());
 633         }
 634     }
 635 }