redox 0.0.3

A library implementing the bittorrent protocol and a few key extensions.
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//! Utilities used throughout the library.

use std::collections::{BTreeMap};

use rand;
use sha1::{Sha1};

pub const SHA1_HASH_LEN: usize = 20;

pub struct Iter<'a, T: 'a + ?Sized> {
    item: &'a T,
    yielded: bool
}

impl<'a, T: 'a + ?Sized> Iter<'a, T> {
    pub fn new(item: &'a T) -> Iter<'a, T> {
        Iter{ item: item, yielded: false }
    }
}

impl<'a, T: 'a + ?Sized> Iterator for Iter<'a, T> {
    type Item = &'a T;
    
    fn next(&mut self) -> Option<&'a T> {
        if !self.yielded {
            self.yielded = true;
            
            Some(self.item)
        } else {
            None
        }
    }
}

/// Trait for working with generic map data structures.
pub trait Dictionary<'a, V> {
    /// Convert the dictionary to an unordered list of key/value pairs.
    fn to_list(&self) -> Vec<(&&'a str, &V)>;

    /// Lookup a value in the dictionary.
    fn lookup(&self, key: &str) -> Option<&V>;
    
    /// Lookup a mutable value in the dictionary.
    fn lookup_mut(&mut self, key: &str) -> Option<&mut V>;

    /// Insert a key/value pair into the dictionary.
    fn insert(&mut self, key: &'a str, value: V) -> Option<V>;
    
    /// Remove a value from the dictionary and return it.
    fn remove(&mut self, key: &str) -> Option<V>;
}

impl<'a, V> Dictionary<'a, V> for BTreeMap<&'a str, V> {
    fn to_list(&self) -> Vec<(&&'a str, &V)> {
        self.iter().collect()
    }

    fn lookup(&self, key: &str) -> Option<&V> {
        self.get(key)
    }
    
    fn lookup_mut(&mut self, key: &str) -> Option<&mut V> {
        self.get_mut(key)
    }

    fn insert(&mut self, key: &'a str, value: V) -> Option<V> {
        self.insert(key, value)
    }
    
    fn remove(&mut self, key: &str) -> Option<V> {
        self.remove(key)
    }
}

/// Applies a sha1 hash to the src and outputs it in dst.
pub fn apply_sha1(src: &[u8], dst: &mut [u8]) {
    let mut sha = Sha1::new();
    
    sha.update(src);
    
    sha.output(dst);
}
/// Applies a Fisher-Yates shuffle on the given list.
pub fn fisher_shuffle<T: Copy>(list: &mut [T]) {
    for i in 0..list.len() {
        let swap_index = (rand::random::<usize>() % (list.len() - i)) + i;
        
        let temp = list[i];
        list[i] = list[swap_index];
        list[swap_index] = temp;
    }
}

#[cfg(test)]
mod tests {

    #[test]
    fn positive_fisher_shuffle() {
        let mut test_slice = [1, 2, 3, 4];
        
        super::fisher_shuffle(&mut test_slice);
        
        assert!(test_slice.contains(&1));
        assert!(test_slice.contains(&2));
        assert!(test_slice.contains(&3));
        assert!(test_slice.contains(&4));
    }
}