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-// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://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::{self, Read};
-use std::mem;
-use Rng;
-
-/// An RNG that reads random bytes straight from a `Read`. This will
-/// work best with an infinite reader, but this is not required.
-///
-/// # Panics
-///
-/// It will panic if it there is insufficient data to fulfill a request.
-///
-/// # 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> Rng for ReadRng<R> {
- fn next_u32(&mut self) -> u32 {
- // This is designed for speed: reading a LE integer on a LE
- // platform just involves blitting the bytes into the memory
- // of the u32, similarly for BE on BE; avoiding byteswapping.
- let mut buf = [0; 4];
- fill(&mut self.reader, &mut buf).unwrap();
- unsafe { *(buf.as_ptr() as *const u32) }
- }
- fn next_u64(&mut self) -> u64 {
- // see above for explanation.
- let mut buf = [0; 8];
- fill(&mut self.reader, &mut buf).unwrap();
- unsafe { *(buf.as_ptr() as *const u64) }
- }
- fn fill_bytes(&mut self, v: &mut [u8]) {
- if v.len() == 0 { return }
- fill(&mut self.reader, v).unwrap();
- }
-}
-
-fn fill(r: &mut Read, mut buf: &mut [u8]) -> io::Result<()> {
- while buf.len() > 0 {
- match try!(r.read(buf)) {
- 0 => return Err(io::Error::new(io::ErrorKind::Other,
- "end of file reached")),
- n => buf = &mut mem::replace(&mut buf, &mut [])[n..],
- }
- }
- Ok(())
-}
-
-#[cfg(test)]
-mod test {
- use super::ReadRng;
- use Rng;
-
- #[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);
- }
-}