6fa4bbeed4
This functionality is not super-core and so doesn't need to be included in std. It's possible that std may need rand (it does a little bit now, for io::test) in which case the functionality required could be moved to a secret hidden module and reexposed by librand. Unfortunately, using #[deprecated] here is hard: there's too much to mock to make it feasible, since we have to ensure that programs still typecheck to reach the linting phase.
120 lines
3.5 KiB
Rust
120 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 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 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(~[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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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().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(v) {
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Ok(n) if n == v.len() => return,
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Ok(n) => fail!("ReaderRng.fill_bytes could not fill buffer: \
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read {} out of {} bytes.", n, v.len()),
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Err(e) => fail!("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 super::ReaderRng;
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use std::io::MemReader;
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use std::cast;
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use 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 = ~[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!(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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