| // Copyright 2013 The Rust Project Developers. See the COPYRIGHT |
| // file at the top-level directory of this distribution and at |
| // https://rust-lang.org/COPYRIGHT. |
| // |
| // 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 rand_core::{RngCore, Error, ErrorKind, impls}; |
| |
| |
| /// An RNG that reads random bytes straight from a `Read`. This will |
| /// work best with an infinite reader, but that is not required. |
| /// |
| /// # Panics |
| /// |
| /// `ReadRng` uses `std::io::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 error. |
| /// |
| /// # Example |
| /// |
| /// ```rust |
| /// use rand::{read, Rng}; |
| /// |
| /// let data = vec![1, 2, 3, 4, 5, 6, 7, 8]; |
| /// let mut rng = read::ReadRng::new(&data[..]); |
| /// println!("{:x}", rng.gen::<u32>()); |
| /// ``` |
| #[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.len() == 0 { return Ok(()); } |
| // Use `std::io::read_exact`, which retries on `ErrorKind::Interrupted`. |
| self.reader.read_exact(dest).map_err(|err| { |
| match err.kind() { |
| ::std::io::ErrorKind::UnexpectedEof => Error::with_cause( |
| ErrorKind::Unavailable, |
| "not enough bytes available, reached end of source", err), |
| _ => Error::with_cause(ErrorKind::Unavailable, |
| "error reading from Read source", err) |
| } |
| }) |
| } |
| } |
| |
| #[cfg(test)] |
| mod test { |
| use super::ReadRng; |
| use 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] |
| #[should_panic] |
| fn test_reader_rng_insufficient_bytes() { |
| let mut rng = ReadRng::new(&[][..]); |
| let mut v = [0u8; 3]; |
| rng.fill_bytes(&mut v); |
| } |
| } |