125 lines
3.6 KiB
Rust
125 lines
3.6 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 option::{Some, None};
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use rt::io::Reader;
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use rt::io::ReaderByteConversions;
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use rand::Rng;
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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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/// It will fail 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::rt::io::mem;
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///
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/// fn main() {
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/// let mut rng = reader::ReaderRng::new(mem::MemReader::new(~[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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/// ```
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pub struct ReaderRng<R> {
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priv 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_()
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} else {
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self.reader.read_be_u32_()
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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_()
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} else {
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self.reader.read_be_u64_()
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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(v) {
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Some(n) if n == v.len() => return,
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Some(n) => fail!("ReaderRng.fill_bytes could not fill buffer: \
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read {} out of {} bytes.", n, v.len()),
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None => fail!("ReaderRng.fill_bytes reached eof.")
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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 super::*;
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use rt::io::mem::MemReader;
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use cast;
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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 = ~[1u64, 2u64, 3u64];
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let bytes: ~[u8] = unsafe {cast::transmute(v)};
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let mut rng = ReaderRng::new(MemReader::new(bytes));
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assert_eq!(rng.next_u64(), 1);
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assert_eq!(rng.next_u64(), 2);
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assert_eq!(rng.next_u64(), 3);
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}
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#[test]
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fn test_reader_rng_u32() {
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// transmute from the target to avoid endianness concerns.
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let v = ~[1u32, 2u32, 3u32];
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let bytes: ~[u8] = unsafe {cast::transmute(v)};
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let mut rng = ReaderRng::new(MemReader::new(bytes));
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assert_eq!(rng.next_u32(), 1);
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assert_eq!(rng.next_u32(), 2);
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assert_eq!(rng.next_u32(), 3);
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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.to_owned()));
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rng.fill_bytes(w);
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assert_eq!(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(~[]));
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let mut v = [0u8, .. 3];
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rng.fill_bytes(v);
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}
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}
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