125 lines
3.6 KiB
Rust
125 lines
3.6 KiB
Rust
// 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 container::Container;
|
|
use option::{Some, None};
|
|
use io::Reader;
|
|
|
|
use rand::Rng;
|
|
|
|
/// An RNG that reads random bytes straight from a `Reader`. This will
|
|
/// work best with an infinite reader, but this is not required.
|
|
///
|
|
/// It will fail if it there is insufficient data to fulfill a request.
|
|
///
|
|
/// # Example
|
|
///
|
|
/// ```rust
|
|
/// use std::rand::{reader, Rng};
|
|
/// use std::io::mem;
|
|
///
|
|
/// let mut rng = reader::ReaderRng::new(mem::MemReader::new(~[1,2,3,4,5,6,7,8]));
|
|
/// println!("{:x}", rng.gen::<uint>());
|
|
/// ```
|
|
pub struct ReaderRng<R> {
|
|
priv 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()
|
|
} else {
|
|
self.reader.read_be_u32()
|
|
}
|
|
}
|
|
fn next_u64(&mut self) -> u64 {
|
|
// see above for explanation.
|
|
if cfg!(target_endian="little") {
|
|
self.reader.read_le_u64()
|
|
} else {
|
|
self.reader.read_be_u64()
|
|
}
|
|
}
|
|
fn fill_bytes(&mut self, v: &mut [u8]) {
|
|
if v.len() == 0 { return }
|
|
match self.reader.read(v) {
|
|
Some(n) if n == v.len() => return,
|
|
Some(n) => fail!("ReaderRng.fill_bytes could not fill buffer: \
|
|
read {} out of {} bytes.", n, v.len()),
|
|
None => fail!("ReaderRng.fill_bytes reached eof.")
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(test)]
|
|
mod test {
|
|
use super::*;
|
|
use io::mem::MemReader;
|
|
use cast;
|
|
use rand::*;
|
|
use prelude::*;
|
|
|
|
#[test]
|
|
fn test_reader_rng_u64() {
|
|
// transmute from the target to avoid endianness concerns.
|
|
let v = ~[1u64, 2u64, 3u64];
|
|
let bytes: ~[u8] = unsafe {cast::transmute(v)};
|
|
let mut rng = ReaderRng::new(MemReader::new(bytes));
|
|
|
|
assert_eq!(rng.next_u64(), 1);
|
|
assert_eq!(rng.next_u64(), 2);
|
|
assert_eq!(rng.next_u64(), 3);
|
|
}
|
|
#[test]
|
|
fn test_reader_rng_u32() {
|
|
// transmute from the target to avoid endianness concerns.
|
|
let v = ~[1u32, 2u32, 3u32];
|
|
let bytes: ~[u8] = unsafe {cast::transmute(v)};
|
|
let mut rng = ReaderRng::new(MemReader::new(bytes));
|
|
|
|
assert_eq!(rng.next_u32(), 1);
|
|
assert_eq!(rng.next_u32(), 2);
|
|
assert_eq!(rng.next_u32(), 3);
|
|
}
|
|
#[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_owned()));
|
|
rng.fill_bytes(w);
|
|
|
|
assert_eq!(v, w);
|
|
}
|
|
|
|
#[test]
|
|
#[should_fail]
|
|
fn test_reader_rng_insufficient_bytes() {
|
|
let mut rng = ReaderRng::new(MemReader::new(~[]));
|
|
let mut v = [0u8, .. 3];
|
|
rng.fill_bytes(v);
|
|
}
|
|
}
|