56290a0044
This commit is an implementation of [RFC 503][rfc] which is a stabilization story for the prelude. Most of the RFC was directly applied, removing reexports. Some reexports are kept around, however: * `range` remains until range syntax has landed to reduce churn. * `Path` and `GenericPath` remain until path reform lands. This is done to prevent many imports of `GenericPath` which will soon be removed. * All `io` traits remain until I/O reform lands so imports can be rewritten all at once to `std::io::prelude::*`. This is a breaking change because many prelude reexports have been removed, and the RFC can be consulted for the exact list of removed reexports, as well as to find the locations of where to import them. [rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0503-prelude-stabilization.md [breaking-change] Closes #20068
123 lines
3.5 KiB
Rust
123 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::Result::{Ok, Err};
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use slice::SliceExt;
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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::v1::*;
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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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