| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
| // "License"); you may not use this file except in compliance |
| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License.. |
| |
| //! A wrapper around any Read to treat it as an RNG. |
| |
| use std::io::{self, Read}; |
| use std::mem; |
| use crate::Rng; |
| |
| /// An RNG that reads random bytes straight from a `Read`. This will |
| /// work best with an infinite reader, but this is not required. |
| /// |
| /// # Panics |
| /// |
| /// It will panic if it there is insufficient data to fulfill a request. |
| /// |
| /// # Example |
| /// |
| /// ```rust |
| /// use sgx_rand::{read, Rng}; |
| /// |
| /// let data = vec![1, 2, 3, 4, 5, 6, 7, 8]; |
| /// let mut rng = read::ReadRng::new(&data[..]); |
| /// println!("{:x}", rng.gen::<u32>()); |
| /// ``` |
| #[derive(Debug)] |
| pub struct ReadRng<R> { |
| reader: R |
| } |
| |
| impl<R: Read> ReadRng<R> { |
| /// Create a new `ReadRng` from a `Read`. |
| pub fn new(r: R) -> ReadRng<R> { |
| ReadRng { |
| reader: r |
| } |
| } |
| } |
| |
| impl<R: Read> Rng for ReadRng<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. |
| let mut buf = [0; 4]; |
| fill(&mut self.reader, &mut buf).unwrap(); |
| unsafe { *(buf.as_ptr() as *const u32) } |
| } |
| fn next_u64(&mut self) -> u64 { |
| // see above for explanation. |
| let mut buf = [0; 8]; |
| fill(&mut self.reader, &mut buf).unwrap(); |
| unsafe { *(buf.as_ptr() as *const u64) } |
| } |
| fn fill_bytes(&mut self, v: &mut [u8]) { |
| if v.len() == 0 { return } |
| fill(&mut self.reader, v).unwrap(); |
| } |
| } |
| |
| fn fill(r: &mut dyn Read, mut buf: &mut [u8]) -> io::Result<()> { |
| while buf.len() > 0 { |
| match (r.read(buf))? { |
| 0 => return Err(io::Error::new( |
| io::ErrorKind::Other, |
| "end of file reached", |
| )), |
| n => buf = &mut mem::replace(&mut buf, &mut [])[n..], |
| } |
| } |
| Ok(()) |
| } |