rand/rngs/adapter/
read.rs

1// Copyright 2018 Developers of the Rand project.
2// Copyright 2013 The Rust Project Developers.
3//
4// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
5// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
6// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
7// option. This file may not be copied, modified, or distributed
8// except according to those terms.
9
10//! A wrapper around any Read to treat it as an RNG.
11
12#![allow(deprecated)]
13
14use std::fmt;
15use std::io::Read;
16
17use rand_core::{impls, Error, RngCore};
18
19
20/// An RNG that reads random bytes straight from any type supporting
21/// [`std::io::Read`], for example files.
22///
23/// This will work best with an infinite reader, but that is not required.
24///
25/// This can be used with `/dev/urandom` on Unix but it is recommended to use
26/// [`OsRng`] instead.
27///
28/// # Panics
29///
30/// `ReadRng` uses [`std::io::Read::read_exact`], which retries on interrupts.
31/// All other errors from the underlying reader, including when it does not
32/// have enough data, will only be reported through [`try_fill_bytes`].
33/// The other [`RngCore`] methods will panic in case of an error.
34///
35/// [`OsRng`]: crate::rngs::OsRng
36/// [`try_fill_bytes`]: RngCore::try_fill_bytes
37#[derive(Debug)]
38#[deprecated(since="0.8.4", note="removal due to lack of usage")]
39pub struct ReadRng<R> {
40    reader: R,
41}
42
43impl<R: Read> ReadRng<R> {
44    /// Create a new `ReadRng` from a `Read`.
45    pub fn new(r: R) -> ReadRng<R> {
46        ReadRng { reader: r }
47    }
48}
49
50impl<R: Read> RngCore for ReadRng<R> {
51    fn next_u32(&mut self) -> u32 {
52        impls::next_u32_via_fill(self)
53    }
54
55    fn next_u64(&mut self) -> u64 {
56        impls::next_u64_via_fill(self)
57    }
58
59    fn fill_bytes(&mut self, dest: &mut [u8]) {
60        self.try_fill_bytes(dest).unwrap_or_else(|err| {
61            panic!(
62                "reading random bytes from Read implementation failed; error: {}",
63                err
64            )
65        });
66    }
67
68    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> {
69        if dest.is_empty() {
70            return Ok(());
71        }
72        // Use `std::io::read_exact`, which retries on `ErrorKind::Interrupted`.
73        self.reader
74            .read_exact(dest)
75            .map_err(|e| Error::new(ReadError(e)))
76    }
77}
78
79/// `ReadRng` error type
80#[derive(Debug)]
81#[deprecated(since="0.8.4")]
82pub struct ReadError(std::io::Error);
83
84impl fmt::Display for ReadError {
85    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
86        write!(f, "ReadError: {}", self.0)
87    }
88}
89
90impl std::error::Error for ReadError {
91    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
92        Some(&self.0)
93    }
94}
95
96
97#[cfg(test)]
98mod test {
99    use std::println;
100
101    use super::ReadRng;
102    use crate::RngCore;
103
104    #[test]
105    fn test_reader_rng_u64() {
106        // transmute from the target to avoid endianness concerns.
107        #[rustfmt::skip]
108        let v = [0u8, 0, 0, 0, 0, 0, 0, 1,
109                 0,   4, 0, 0, 3, 0, 0, 2,
110                 5,   0, 0, 0, 0, 0, 0, 0];
111        let mut rng = ReadRng::new(&v[..]);
112
113        assert_eq!(rng.next_u64(), 1 << 56);
114        assert_eq!(rng.next_u64(), (2 << 56) + (3 << 32) + (4 << 8));
115        assert_eq!(rng.next_u64(), 5);
116    }
117
118    #[test]
119    fn test_reader_rng_u32() {
120        let v = [0u8, 0, 0, 1, 0, 0, 2, 0, 3, 0, 0, 0];
121        let mut rng = ReadRng::new(&v[..]);
122
123        assert_eq!(rng.next_u32(), 1 << 24);
124        assert_eq!(rng.next_u32(), 2 << 16);
125        assert_eq!(rng.next_u32(), 3);
126    }
127
128    #[test]
129    fn test_reader_rng_fill_bytes() {
130        let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
131        let mut w = [0u8; 8];
132
133        let mut rng = ReadRng::new(&v[..]);
134        rng.fill_bytes(&mut w);
135
136        assert!(v == w);
137    }
138
139    #[test]
140    fn test_reader_rng_insufficient_bytes() {
141        let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
142        let mut w = [0u8; 9];
143
144        let mut rng = ReadRng::new(&v[..]);
145
146        let result = rng.try_fill_bytes(&mut w);
147        assert!(result.is_err());
148        println!("Error: {}", result.unwrap_err());
149    }
150}
rand/rngs/adapter/read.rs

rand/rngs/adapter/
read.rs
