| // 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 Reader to treat it as an RNG. |
| |
| use std::old_io::Reader; |
| use Rng; |
| |
| /// An RNG that reads random bytes straight from a `Reader`. 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::{reader, Rng}; |
| /// use std::old_io::MemReader; |
| /// |
| /// let mut rng = reader::ReaderRng::new(MemReader::new(vec!(1,2,3,4,5,6,7,8))); |
| /// println!("{:x}", rng.gen::<u32>()); |
| /// ``` |
| pub struct ReaderRng<R> { |
| reader: R |
| } |
| |
| impl<R: Reader> ReaderRng<R> { |
| /// Create a new `ReaderRng` from a `Reader`. |
| pub fn new(r: R) -> ReaderRng<R> { |
| ReaderRng { |
| reader: r |
| } |
| } |
| } |
| |
| impl<R: Reader> Rng for ReaderRng<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. |
| if cfg!(target_endian="little") { |
| self.reader.read_le_u32().unwrap() |
| } else { |
| self.reader.read_be_u32().unwrap() |
| } |
| } |
| fn next_u64(&mut self) -> u64 { |
| // see above for explanation. |
| if cfg!(target_endian="little") { |
| self.reader.read_le_u64().unwrap() |
| } else { |
| self.reader.read_be_u64().unwrap() |
| } |
| } |
| fn fill_bytes(&mut self, v: &mut [u8]) { |
| if v.len() == 0 { return } |
| match self.reader.read_at_least(v.len(), v) { |
| Ok(_) => {} |
| Err(e) => panic!("ReaderRng.fill_bytes error: {:?}", e) |
| } |
| } |
| } |
| |
| #[cfg(test)] |
| mod test { |
| use super::ReaderRng; |
| use std::old_io::MemReader; |
| use std::num::Int; |
| 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 = ReaderRng::new(MemReader::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 = ReaderRng::new(MemReader::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 = ReaderRng::new(MemReader::new(v.to_vec())); |
| rng.fill_bytes(&mut w); |
| |
| assert!(v == w); |
| } |
| |
| #[test] |
| #[should_fail] |
| fn test_reader_rng_insufficient_bytes() { |
| let mut rng = ReaderRng::new(MemReader::new(vec!())); |
| let mut v = [0u8; 3]; |
| rng.fill_bytes(&mut v); |
| } |
| } |