vendor/rand-0.3.16/src/rand_impls.rs

   1 // Copyright 2013-2014 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 implementations of `Rand` for the built-in types.
  12
  13 use std::char;
  14 use std::mem;
  15
  16 use {Rand,Rng};
  17
  18 impl Rand for isize {
  19     #[inline]
  20     fn rand<R: Rng>(rng: &mut R) -> isize {
  21         if mem::size_of::<isize>() == 4 {
  22             rng.gen::<i32>() as isize
  23         } else {
  24             rng.gen::<i64>() as isize
  25         }
  26     }
  27 }
  28
  29 impl Rand for i8 {
  30     #[inline]
  31     fn rand<R: Rng>(rng: &mut R) -> i8 {
  32         rng.next_u32() as i8
  33     }
  34 }
  35
  36 impl Rand for i16 {
  37     #[inline]
  38     fn rand<R: Rng>(rng: &mut R) -> i16 {
  39         rng.next_u32() as i16
  40     }
  41 }
  42
  43 impl Rand for i32 {
  44     #[inline]
  45     fn rand<R: Rng>(rng: &mut R) -> i32 {
  46         rng.next_u32() as i32
  47     }
  48 }
  49
  50 impl Rand for i64 {
  51     #[inline]
  52     fn rand<R: Rng>(rng: &mut R) -> i64 {
  53         rng.next_u64() as i64
  54     }
  55 }
  56
  57 #[cfg(feature = "i128_support")]
  58 impl Rand for i128 {
  59     #[inline]
  60     fn rand<R: Rng>(rng: &mut R) -> i128 {
  61         rng.gen::<u128>() as i128
  62     }
  63 }
  64
  65 impl Rand for usize {
  66     #[inline]
  67     fn rand<R: Rng>(rng: &mut R) -> usize {
  68         if mem::size_of::<usize>() == 4 {
  69             rng.gen::<u32>() as usize
  70         } else {
  71             rng.gen::<u64>() as usize
  72         }
  73     }
  74 }
  75
  76 impl Rand for u8 {
  77     #[inline]
  78     fn rand<R: Rng>(rng: &mut R) -> u8 {
  79         rng.next_u32() as u8
  80     }
  81 }
  82
  83 impl Rand for u16 {
  84     #[inline]
  85     fn rand<R: Rng>(rng: &mut R) -> u16 {
  86         rng.next_u32() as u16
  87     }
  88 }
  89
  90 impl Rand for u32 {
  91     #[inline]
  92     fn rand<R: Rng>(rng: &mut R) -> u32 {
  93         rng.next_u32()
  94     }
  95 }
  96
  97 impl Rand for u64 {
  98     #[inline]
  99     fn rand<R: Rng>(rng: &mut R) -> u64 {
 100         rng.next_u64()
 101     }
 102 }
 103
 104 #[cfg(feature = "i128_support")]
 105 impl Rand for u128 {
 106     #[inline]
 107     fn rand<R: Rng>(rng: &mut R) -> u128 {
 108         ((rng.next_u64() as u128) << 64) | (rng.next_u64() as u128)
 109     }
 110 }
 111
 112
 113 macro_rules! float_impls {
 114     ($mod_name:ident, $ty:ty, $mantissa_bits:expr, $method_name:ident) => {
 115         mod $mod_name {
 116             use {Rand, Rng, Open01, Closed01};
 117
 118             const SCALE: $ty = (1u64 << $mantissa_bits) as $ty;
 119
 120             impl Rand for $ty {
 121                 /// Generate a floating point number in the half-open
 122                 /// interval `[0,1)`.
 123                 ///
 124                 /// See `Closed01` for the closed interval `[0,1]`,
 125                 /// and `Open01` for the open interval `(0,1)`.
 126                 #[inline]
 127                 fn rand<R: Rng>(rng: &mut R) -> $ty {
 128                     rng.$method_name()
 129                 }
 130             }
 131             impl Rand for Open01<$ty> {
 132                 #[inline]
 133                 fn rand<R: Rng>(rng: &mut R) -> Open01<$ty> {
 134                     // add a small amount (specifically 2 bits below
 135                     // the precision of f64/f32 at 1.0), so that small
 136                     // numbers are larger than 0, but large numbers
 137                     // aren't pushed to/above 1.
 138                     Open01(rng.$method_name() + 0.25 / SCALE)
 139                 }
 140             }
 141             impl Rand for Closed01<$ty> {
 142                 #[inline]
 143                 fn rand<R: Rng>(rng: &mut R) -> Closed01<$ty> {
 144                     // rescale so that 1.0 - epsilon becomes 1.0
 145                     // precisely.
 146                     Closed01(rng.$method_name() * SCALE / (SCALE - 1.0))
 147                 }
 148             }
 149         }
 150     }
 151 }
 152 float_impls! { f64_rand_impls, f64, 53, next_f64 }
 153 float_impls! { f32_rand_impls, f32, 24, next_f32 }
 154
 155 impl Rand for char {
 156     #[inline]
 157     fn rand<R: Rng>(rng: &mut R) -> char {
 158         // a char is 21 bits
 159         const CHAR_MASK: u32 = 0x001f_ffff;
 160         loop {
 161             // Rejection sampling. About 0.2% of numbers with at most
 162             // 21-bits are invalid codepoints (surrogates), so this
 163             // will succeed first go almost every time.
 164             match char::from_u32(rng.next_u32() & CHAR_MASK) {
 165                 Some(c) => return c,
 166                 None => {}
 167             }
 168         }
 169     }
 170 }
 171
 172 impl Rand for bool {
 173     #[inline]
 174     fn rand<R: Rng>(rng: &mut R) -> bool {
 175         rng.gen::<u8>() & 1 == 1
 176     }
 177 }
 178
 179 macro_rules! tuple_impl {
 180     // use variables to indicate the arity of the tuple
 181     ($($tyvar:ident),* ) => {
 182         // the trailing commas are for the 1 tuple
 183         impl<
 184             $( $tyvar : Rand ),*
 185             > Rand for ( $( $tyvar ),* , ) {
 186
 187             #[inline]
 188             fn rand<R: Rng>(_rng: &mut R) -> ( $( $tyvar ),* , ) {
 189                 (
 190                     // use the $tyvar's to get the appropriate number of
 191                     // repeats (they're not actually needed)
 192                     $(
 193                         _rng.gen::<$tyvar>()
 194                     ),*
 195                     ,
 196                 )
 197             }
 198         }
 199     }
 200 }
 201
 202 impl Rand for () {
 203     #[inline]
 204     fn rand<R: Rng>(_: &mut R) -> () { () }
 205 }
 206 tuple_impl!{A}
 207 tuple_impl!{A, B}
 208 tuple_impl!{A, B, C}
 209 tuple_impl!{A, B, C, D}
 210 tuple_impl!{A, B, C, D, E}
 211 tuple_impl!{A, B, C, D, E, F}
 212 tuple_impl!{A, B, C, D, E, F, G}
 213 tuple_impl!{A, B, C, D, E, F, G, H}
 214 tuple_impl!{A, B, C, D, E, F, G, H, I}
 215 tuple_impl!{A, B, C, D, E, F, G, H, I, J}
 216 tuple_impl!{A, B, C, D, E, F, G, H, I, J, K}
 217 tuple_impl!{A, B, C, D, E, F, G, H, I, J, K, L}
 218
 219 macro_rules! array_impl {
 220     {$n:expr, $t:ident, $($ts:ident,)*} => {
 221         array_impl!{($n - 1), $($ts,)*}
 222
 223         impl<T> Rand for [T; $n] where T: Rand {
 224             #[inline]
 225             fn rand<R: Rng>(_rng: &mut R) -> [T; $n] {
 226                 [_rng.gen::<$t>(), $(_rng.gen::<$ts>()),*]
 227             }
 228         }
 229     };
 230     {$n:expr,} => {
 231         impl<T> Rand for [T; $n] {
 232             fn rand<R: Rng>(_rng: &mut R) -> [T; $n] { [] }
 233         }
 234     };
 235 }
 236
 237 array_impl!{32, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T, T,}
 238
 239 impl<T:Rand> Rand for Option<T> {
 240     #[inline]
 241     fn rand<R: Rng>(rng: &mut R) -> Option<T> {
 242         if rng.gen() {
 243             Some(rng.gen())
 244         } else {
 245             None
 246         }
 247     }
 248 }
 249
 250 #[cfg(test)]
 251 mod tests {
 252     use {Rng, thread_rng, Open01, Closed01};
 253
 254     struct ConstantRng(u64);
 255     impl Rng for ConstantRng {
 256         fn next_u32(&mut self) -> u32 {
 257             let ConstantRng(v) = *self;
 258             v as u32
 259         }
 260         fn next_u64(&mut self) -> u64 {
 261             let ConstantRng(v) = *self;
 262             v
 263         }
 264     }
 265
 266     #[test]
 267     fn floating_point_edge_cases() {
 268         // the test for exact equality is correct here.
 269         assert!(ConstantRng(0xffff_ffff).gen::<f32>() != 1.0);
 270         assert!(ConstantRng(0xffff_ffff_ffff_ffff).gen::<f64>() != 1.0);
 271     }
 272
 273     #[test]
 274     fn rand_open() {
 275         // this is unlikely to catch an incorrect implementation that
 276         // generates exactly 0 or 1, but it keeps it sane.
 277         let mut rng = thread_rng();
 278         for _ in 0..1_000 {
 279             // strict inequalities
 280             let Open01(f) = rng.gen::<Open01<f64>>();
 281             assert!(0.0 < f && f < 1.0);
 282
 283             let Open01(f) = rng.gen::<Open01<f32>>();
 284             assert!(0.0 < f && f < 1.0);
 285         }
 286     }
 287
 288     #[test]
 289     fn rand_closed() {
 290         let mut rng = thread_rng();
 291         for _ in 0..1_000 {
 292             // strict inequalities
 293             let Closed01(f) = rng.gen::<Closed01<f64>>();
 294             assert!(0.0 <= f && f <= 1.0);
 295
 296             let Closed01(f) = rng.gen::<Closed01<f32>>();
 297             assert!(0.0 <= f && f <= 1.0);
 298         }
 299     }
 300 }