Struct rug::rand::ThreadRandState

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pub struct ThreadRandState<'a> { /* private fields */ }

Expand description

The state of a random number generator that is suitable for a single thread only.

This is similar to RandState but can only be used in a single thread.

§Examples

use rug::rand::ThreadRandState;
let mut gen = create_generator();
let mut rand = ThreadRandState::new_custom(&mut gen);
let u = rand.bits(32);
println!("32 random bits: {:032b}", u);

Implementations§

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impl ThreadRandState<'_>

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pub fn new_custom(custom: &mut dyn ThreadRandGen) -> ThreadRandState<'_>

Creates a new custom random generator.

This is similar to RandState::new_custom. The difference is that this method takes a ThreadRandGen that does not have to implement Send or Sync.

§Examples

use rug::rand::{ThreadRandGen, ThreadRandState};
use rug::Integer;
// dummy pointer field to ensure Seed is not Send and not Sync
struct Seed { _unused_ptr: *const () }
impl ThreadRandGen for Seed {
    fn gen(&mut self) -> u32 {
        // not really random
        0x8CEF_7310
    }
}
let mut seed = Seed { _unused_ptr: &() };
let mut rand = ThreadRandState::new_custom(&mut seed);
let mut i = Integer::from(15);
i.random_below_mut(&mut rand);
println!("0 ≤ {} < 15", i);
assert!(i < 15);

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pub fn new_custom_boxed( custom: Box<dyn ThreadRandGen> ) -> ThreadRandState<'static>

Creates a new custom random generator.

This is similar to RandState::new_custom_boxed. The difference is that this method takes a ThreadRandGen that does not have to implement Send or Sync.

§Examples

use rug::rand::{ThreadRandGen, ThreadRandState};
use rug::Integer;
// dummy pointer field to ensure Seed is not Send and not Sync
struct Seed { _unused_ptr: *const () }
impl ThreadRandGen for Seed {
    fn gen(&mut self) -> u32 {
        // not really random
        0x8CEF_7310
    }
}
let seed = Box::new(Seed { _unused_ptr: &() });
let mut rand = ThreadRandState::new_custom_boxed(seed);
let mut i = Integer::from(15);
i.random_below_mut(&mut rand);
println!("0 ≤ {} < 15", i);
assert!(i < 15);

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pub unsafe fn from_raw(raw: randstate_t) -> ThreadRandState<'static>

Creates a random generator from an initialized GMP random generator.

This is similar to RandState::from_raw, but the object does not need to be thread safe. You can use this method if the object is thread safe, but in that case RandState::from_raw is probably better as it allows the returned object to be shared and transferred across threads.

§Safety

The value must be initialized as a valid randstate_t.
The randstate_t type can be considered as a kind of pointer, so there can be multiple copies of it. Since this function takes over ownership, no other copies of the passed value should exist.

§Examples

use core::mem::MaybeUninit;
use gmp_mpfr_sys::gmp;
use rug::rand::ThreadRandState;
let mut rand = unsafe {
    let mut raw = MaybeUninit::uninit();
    gmp::randinit_default(raw.as_mut_ptr());
    let raw = raw.assume_init();
    // raw is initialized and unique
    ThreadRandState::from_raw(raw)
};
let u = rand.bits(32);
println!("32 random bits: {:032b}", u);
// since rand is a ThreadRandState now, deallocation is automatic

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pub fn into_raw(self) -> randstate_t

Converts a random generator into a GMP random generator.

The returned object should be freed to avoid memory leaks.

This is similar to RandState::into_raw, but the returned object is not thread safe. Notably, it should not be used in RandState::from_raw.

§Panics

This method panics if the ThreadRandState object was created using new_custom, as the borrow into the custom generator would be terminated once self is consumed. This would lead to undefined behavior if the returned object is used. This method does work with objects created using new_custom_boxed.

§Examples

use gmp_mpfr_sys::gmp;
use rug::rand::ThreadRandState;
let gen = Box::new(create_generator());
let rand = ThreadRandState::new_custom_boxed(gen);
let mut raw = rand.into_raw();
unsafe {
    let u = gmp::urandomb_ui(&mut raw, 32) as u32;
    println!("32 random bits: {:032b}", u);
    // free object to prevent memory leak
    gmp::randclear(&mut raw);
}

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pub fn as_raw(&self) -> *const randstate_t

Returns a pointer to the inner GMP random generator.

The returned pointer will be valid for as long as self is valid.

This is similar to RandState::as_raw.

§Examples

use rug::rand::ThreadRandState;
let mut gen = create_generator();
let mut rand = ThreadRandState::new_custom(&mut gen);
let raw_ptr = rand.as_raw();
// There is not much you can do with an immutable randstate_t pointer.
println!("pointer: {:p}", raw_ptr);
let u = rand.bits(32);
println!("32 random bits: {:032b}", u);

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pub fn as_raw_mut(&mut self) -> *mut randstate_t

Returns an unsafe mutable pointer to the inner GMP random generator.

The returned pointer will be valid for as long as self is valid.

This is similar to RandState::as_raw_mut.

§Examples

use gmp_mpfr_sys::gmp;
use rug::rand::ThreadRandState;
let mut gen = create_generator();
let mut rand = ThreadRandState::new_custom(&mut gen);
let raw_ptr = rand.as_raw_mut();
unsafe {
    let u1 = gmp::urandomb_ui(raw_ptr, 32) as u32;
    println!("32 random bits: {:032b}", u1);
}
let u2 = rand.bits(32);
println!("another 32 random bits: {:032b}", u2);

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pub fn into_custom_boxed(self) -> Result<Box<dyn ThreadRandGen>, Self>

Converts a random generator into Box<dyn ThreadRandGen> if possible.

If the conversion is not possible, Err(self) is returned.

This conversion is always possible when the random generator was created with new_custom_boxed. It is also possible if the generator was cloned, directly or indirectly, from another generator that was created with new_custom or new_custom_boxed.

This is similar to RandState::into_custom_boxed.

§Examples

use rug::rand::{ThreadRandGen, ThreadRandState};
struct Seed;
impl ThreadRandGen for Seed {
    fn gen(&mut self) -> u32 {
        // not really random
        0x8CEF_7310
    }
}
let seed = Box::new(Seed);
let rand = ThreadRandState::new_custom_boxed(seed);
let mut back_to_seed = rand.into_custom_boxed().unwrap();
assert_eq!(back_to_seed.gen(), 0x8CEF_7310);

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pub fn seed(&mut self, seed: &Integer)

Seeds the random generator.

This is similar to RandState::seed.

§Examples

use rug::rand::ThreadRandState;
use rug::Integer;
let mut gen = create_generator_with_seed();
let seed = Integer::from(123456);
let mut rand = ThreadRandState::new_custom(&mut gen);
rand.seed(&seed);
let u1a = rand.bits(32);
let u1b = rand.bits(32);
// reseed with the same seed
rand.seed(&seed);
let u2a = rand.bits(32);
let u2b = rand.bits(32);
assert_eq!(u1a, u2a);
assert_eq!(u1b, u2b);

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pub fn bits(&mut self, bits: u32) -> u32

Generates a random number with the specified number of bits.

This is similar to RandState::bits.

§Panics

Panics if bits is greater than 32.

§Examples

use rug::rand::ThreadRandState;
let mut gen = create_generator();
let mut rand = ThreadRandState::new_custom(&mut gen);
let u = rand.bits(16);
assert!(u < (1 << 16));
println!("16 random bits: {:016b}", u);

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pub fn below(&mut self, bound: u32) -> u32

Generates a random number below the given boundary value.

This is similar to RandState::below.

§Panics

Panics if the boundary value is zero.

§Examples

use rug::rand::ThreadRandState;
let mut gen = create_generator();
let mut rand = ThreadRandState::new_custom(&mut gen);
let u = rand.below(10000);
assert!(u < 10000);
println!("0 ≤ {} < 10000", u);