1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! A wrapper around any Reader to treat it as an RNG.
15 use result::{Ok, Err};
16 use slice::SlicePrelude;
18 /// An RNG that reads random bytes straight from a `Reader`. This will
19 /// work best with an infinite reader, but this is not required.
23 /// It will panic if it there is insufficient data to fulfill a request.
28 /// use std::rand::{reader, Rng};
29 /// use std::io::MemReader;
31 /// let mut rng = reader::ReaderRng::new(MemReader::new(vec!(1,2,3,4,5,6,7,8)));
32 /// println!("{:x}", rng.gen::<uint>());
34 pub struct ReaderRng<R> {
38 impl<R: Reader> ReaderRng<R> {
39 /// Create a new `ReaderRng` from a `Reader`.
40 pub fn new(r: R) -> ReaderRng<R> {
47 impl<R: Reader> Rng for ReaderRng<R> {
48 fn next_u32(&mut self) -> u32 {
49 // This is designed for speed: reading a LE integer on a LE
50 // platform just involves blitting the bytes into the memory
51 // of the u32, similarly for BE on BE; avoiding byteswapping.
52 if cfg!(target_endian="little") {
53 self.reader.read_le_u32().unwrap()
55 self.reader.read_be_u32().unwrap()
58 fn next_u64(&mut self) -> u64 {
59 // see above for explanation.
60 if cfg!(target_endian="little") {
61 self.reader.read_le_u64().unwrap()
63 self.reader.read_be_u64().unwrap()
66 fn fill_bytes(&mut self, v: &mut [u8]) {
67 if v.len() == 0 { return }
68 match self.reader.read_at_least(v.len(), v) {
70 Err(e) => panic!("ReaderRng.fill_bytes error: {}", e)
85 fn test_reader_rng_u64() {
86 // transmute from the target to avoid endianness concerns.
87 let v = vec![0u8, 0, 0, 0, 0, 0, 0, 1,
88 0 , 0, 0, 0, 0, 0, 0, 2,
89 0, 0, 0, 0, 0, 0, 0, 3];
90 let mut rng = ReaderRng::new(MemReader::new(v));
92 assert_eq!(rng.next_u64(), 1_u64.to_be());
93 assert_eq!(rng.next_u64(), 2_u64.to_be());
94 assert_eq!(rng.next_u64(), 3_u64.to_be());
97 fn test_reader_rng_u32() {
98 let v = vec![0u8, 0, 0, 1, 0, 0, 0, 2, 0, 0, 0, 3];
99 let mut rng = ReaderRng::new(MemReader::new(v));
101 assert_eq!(rng.next_u32(), 1_u32.to_be());
102 assert_eq!(rng.next_u32(), 2_u32.to_be());
103 assert_eq!(rng.next_u32(), 3_u32.to_be());
106 fn test_reader_rng_fill_bytes() {
107 let v = [1u8, 2, 3, 4, 5, 6, 7, 8];
108 let mut w = [0u8, .. 8];
110 let mut rng = ReaderRng::new(MemReader::new(v.as_slice().to_vec()));
111 rng.fill_bytes(&mut w);
118 fn test_reader_rng_insufficient_bytes() {
119 let mut rng = ReaderRng::new(MemReader::new(vec!()));
120 let mut v = [0u8, .. 3];
121 rng.fill_bytes(&mut v);