124 lines
3.5 KiB
Rust
124 lines
3.5 KiB
Rust
// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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//! A wrapper around any Reader to treat it as an RNG.
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use io::Reader;
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use rand::Rng;
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use result::{Ok, Err};
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use slice::SlicePrelude;
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/// An RNG that reads random bytes straight from a `Reader`. This will
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/// work best with an infinite reader, but this is not required.
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///
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/// # Panics
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///
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/// It will panic if it there is insufficient data to fulfill a request.
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///
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/// # Example
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///
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/// ```rust
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/// use std::rand::{reader, Rng};
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/// use std::io::MemReader;
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///
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/// let mut rng = reader::ReaderRng::new(MemReader::new(vec!(1,2,3,4,5,6,7,8)));
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/// println!("{:x}", rng.gen::<uint>());
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/// ```
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pub struct ReaderRng<R> {
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reader: R
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}
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impl<R: Reader> ReaderRng<R> {
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/// Create a new `ReaderRng` from a `Reader`.
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pub fn new(r: R) -> ReaderRng<R> {
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ReaderRng {
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reader: r
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}
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}
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}
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impl<R: Reader> Rng for ReaderRng<R> {
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fn next_u32(&mut self) -> u32 {
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// This is designed for speed: reading a LE integer on a LE
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// platform just involves blitting the bytes into the memory
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// of the u32, similarly for BE on BE; avoiding byteswapping.
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if cfg!(target_endian="little") {
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self.reader.read_le_u32().unwrap()
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} else {
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self.reader.read_be_u32().unwrap()
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}
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}
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fn next_u64(&mut self) -> u64 {
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// see above for explanation.
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if cfg!(target_endian="little") {
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self.reader.read_le_u64().unwrap()
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} else {
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self.reader.read_be_u64().unwrap()
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}
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}
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fn fill_bytes(&mut self, v: &mut [u8]) {
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if v.len() == 0 { return }
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match self.reader.read_at_least(v.len(), v) {
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Ok(_) => {}
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Err(e) => panic!("ReaderRng.fill_bytes error: {}", e)
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}
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}
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}
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#[cfg(test)]
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mod test {
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use prelude::*;
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use super::ReaderRng;
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use io::MemReader;
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use num::Int;
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use rand::Rng;
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#[test]
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fn test_reader_rng_u64() {
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// transmute from the target to avoid endianness concerns.
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let v = vec![0u8, 0, 0, 0, 0, 0, 0, 1,
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0 , 0, 0, 0, 0, 0, 0, 2,
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0, 0, 0, 0, 0, 0, 0, 3];
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let mut rng = ReaderRng::new(MemReader::new(v));
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assert_eq!(rng.next_u64(), 1_u64.to_be());
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assert_eq!(rng.next_u64(), 2_u64.to_be());
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assert_eq!(rng.next_u64(), 3_u64.to_be());
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}
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#[test]
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fn test_reader_rng_u32() {
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let v = vec![0u8, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3];
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let mut rng = ReaderRng::new(MemReader::new(v));
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assert_eq!(rng.next_u32(), 1_u32.to_be());
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assert_eq!(rng.next_u32(), 2_u32.to_be());
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assert_eq!(rng.next_u32(), 3_u32.to_be());
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}
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#[test]
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fn test_reader_rng_fill_bytes() {
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let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
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let mut w = [0u8, .. 8];
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let mut rng = ReaderRng::new(MemReader::new(v.as_slice().to_vec()));
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rng.fill_bytes(&mut w);
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assert!(v == w);
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}
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#[test]
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#[should_fail]
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fn test_reader_rng_insufficient_bytes() {
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let mut rng = ReaderRng::new(MemReader::new(vec!()));
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let mut v = [0u8, .. 3];
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rng.fill_bytes(&mut v);
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}
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}
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