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use std::io;
use crate::{Random, Rng};
#[derive(Clone, Debug)]
pub struct ReadRng<R>(pub R);
impl<R> ReadRng<R> {
pub fn new(reader: R) -> Random<ReadRng<R>> {
Random(ReadRng(reader))
}
}
impl<R: io::Read> Rng for ReadRng<R> {
#[inline]
fn next_u32(&mut self) -> u32 {
let mut buf = [0u8; 4];
if let Err(err) = self.0.read_exact(&mut buf) {
read_failed(err);
}
u32::from_le_bytes(buf)
}
#[inline]
fn next_u64(&mut self) -> u64 {
let mut buf = [0u8; 8];
if let Err(err) = self.0.read_exact(&mut buf) {
read_failed(err);
}
u64::from_le_bytes(buf)
}
#[inline]
fn fill_u32(&mut self, buffer: &mut [u32]) {
if let Err(err) = self.0.read_exact(dataview::bytes_mut(buffer)) {
read_failed(err);
}
}
#[inline]
fn fill_u64(&mut self, buffer: &mut [u64]) {
if let Err(err) = self.0.read_exact(dataview::bytes_mut(buffer)) {
read_failed(err);
}
}
#[inline]
fn fill_bytes(&mut self, buffer: &mut [u8]) {
if let Err(err) = self.0.read_exact(buffer) {
read_failed(err);
}
}
#[inline]
fn jump(&mut self) {}
}
#[inline(never)]
#[cold]
fn read_failed(err: io::Error) -> ! {
panic!("random bytes from Read implementation failed: {:?}", err)
}
#[test]
fn test_next_u64() {
let v = [
0, 0, 0, 0, 0, 0, 0, 1,
0, 4, 0, 0, 3, 0, 0, 2,
5, 0, 0, 0, 0, 0, 0, 0u8];
let mut rng = ReadRng::new(&v[..]);
assert_eq!(rng.next_u64(), 1 << 56);
assert_eq!(rng.next_u64(), (2 << 56) + (3 << 32) + (4 << 8));
assert_eq!(rng.next_u64(), 5);
}
#[test]
fn test_next_u32() {
let v = [0u8, 0, 0, 1, 0, 0, 2, 0, 3, 0, 0, 0];
let mut rng = ReadRng::new(&v[..]);
assert_eq!(rng.next_u32(), 1 << 24);
assert_eq!(rng.next_u32(), 2 << 16);
assert_eq!(rng.next_u32(), 3);
}
#[test]
fn test_fill_bytes() {
let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
let mut w = [0u8; 8];
let mut rng = ReadRng::new(&v[..]);
rng.fill_bytes(&mut w);
assert!(v == w);
}
#[test]
#[should_panic(expected = "random bytes from Read implementation failed")]
fn test_insufficient_bytes() {
let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
let mut w = [0u8; 9];
let mut rng = ReadRng::new(&v[..]);
rng.fill_bytes(&mut w);
}