| // Copyright 2018 Developers of the Rand project. |
| // Copyright 2013 The Rust Project Developers. |
| // |
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or |
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license |
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your |
| // option. This file may not be copied, modified, or distributed |
| // except according to those terms. |
| |
| //! A wrapper around any Read to treat it as an RNG. |
| |
| use std::io::Read; |
| use std::fmt; |
| |
| use rand_core::{RngCore, Error, impls}; |
| |
| |
| /// An RNG that reads random bytes straight from any type supporting |
| /// [`std::io::Read`], for example files. |
| /// |
| /// This will work best with an infinite reader, but that is not required. |
| /// |
| /// This can be used with `/dev/urandom` on Unix but it is recommended to use |
| /// [`OsRng`] instead. |
| /// |
| /// # Panics |
| /// |
| /// `ReadRng` uses [`std::io::Read::read_exact`], which retries on interrupts. |
| /// All other errors from the underlying reader, including when it does not |
| /// have enough data, will only be reported through [`try_fill_bytes`]. |
| /// The other [`RngCore`] methods will panic in case of an error. |
| /// |
| /// # Example |
| /// |
| /// ``` |
| /// use rand::Rng; |
| /// use rand::rngs::adapter::ReadRng; |
| /// |
| /// let data = vec![1, 2, 3, 4, 5, 6, 7, 8]; |
| /// let mut rng = ReadRng::new(&data[..]); |
| /// println!("{:x}", rng.gen::<u32>()); |
| /// ``` |
| /// |
| /// [`OsRng`]: crate::rngs::OsRng |
| /// [`try_fill_bytes`]: RngCore::try_fill_bytes |
| #[derive(Debug)] |
| pub struct ReadRng<R> { |
| reader: R |
| } |
| |
| impl<R: Read> ReadRng<R> { |
| /// Create a new `ReadRng` from a `Read`. |
| pub fn new(r: R) -> ReadRng<R> { |
| ReadRng { |
| reader: r |
| } |
| } |
| } |
| |
| impl<R: Read> RngCore for ReadRng<R> { |
| fn next_u32(&mut self) -> u32 { |
| impls::next_u32_via_fill(self) |
| } |
| |
| fn next_u64(&mut self) -> u64 { |
| impls::next_u64_via_fill(self) |
| } |
| |
| fn fill_bytes(&mut self, dest: &mut [u8]) { |
| self.try_fill_bytes(dest).unwrap_or_else(|err| |
| panic!("reading random bytes from Read implementation failed; error: {}", err)); |
| } |
| |
| fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error> { |
| if dest.is_empty() { return Ok(()); } |
| // Use `std::io::read_exact`, which retries on `ErrorKind::Interrupted`. |
| self.reader.read_exact(dest).map_err(|e| Error::new(ReadError(e))) |
| } |
| } |
| |
| /// `ReadRng` error type |
| #[derive(Debug)] |
| pub struct ReadError(std::io::Error); |
| |
| impl fmt::Display for ReadError { |
| fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { |
| write!(f, "ReadError: {}", self.0) |
| } |
| } |
| |
| impl std::error::Error for ReadError { |
| fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { |
| Some(&self.0) |
| } |
| } |
| |
| |
| #[cfg(test)] |
| mod test { |
| use super::ReadRng; |
| use crate::RngCore; |
| |
| #[test] |
| fn test_reader_rng_u64() { |
| // transmute from the target to avoid endianness concerns. |
| let v = vec![0u8, 0, 0, 0, 0, 0, 0, 1, |
| 0 , 0, 0, 0, 0, 0, 0, 2, |
| 0, 0, 0, 0, 0, 0, 0, 3]; |
| let mut rng = ReadRng::new(&v[..]); |
| |
| assert_eq!(rng.next_u64(), 1_u64.to_be()); |
| assert_eq!(rng.next_u64(), 2_u64.to_be()); |
| assert_eq!(rng.next_u64(), 3_u64.to_be()); |
| } |
| |
| #[test] |
| fn test_reader_rng_u32() { |
| let v = vec![0u8, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3]; |
| let mut rng = ReadRng::new(&v[..]); |
| |
| assert_eq!(rng.next_u32(), 1_u32.to_be()); |
| assert_eq!(rng.next_u32(), 2_u32.to_be()); |
| assert_eq!(rng.next_u32(), 3_u32.to_be()); |
| } |
| |
| #[test] |
| fn test_reader_rng_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] |
| fn test_reader_rng_insufficient_bytes() { |
| let v = [1u8, 2, 3, 4, 5, 6, 7, 8]; |
| let mut w = [0u8; 9]; |
| |
| let mut rng = ReadRng::new(&v[..]); |
| |
| let result = rng.try_fill_bytes(&mut w); |
| assert!(result.is_err()); |
| println!("Error: {}", result.unwrap_err()); |
| } |
| } |