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}
151