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//! Utilities used by the Bittorrent Infrastructure Project.

extern crate crypto;
extern crate num;
extern crate rand;
extern crate chrono;

/// Bittorrent specific types.
pub mod bt;

/// Arrays of buffers as a contiguous buffer.
pub mod contiguous;

/// Converting between data.
pub mod convert;

/// Networking primitives and helpers.
pub mod net;

/// Generic sender utilities.
pub mod send;

/// Hash primitives and helpers.
pub mod sha;

/// Testing fixtures for dependant crates.
/// TODO: Some non test functions in other crates use this, mark that as cfg test
/// when we migrate away from these functions in non test functions.
pub mod test;

/// Generating transaction ids.
pub mod trans;

/// Common error types.
pub mod error;

//----------------------------------------------------------------------------//
use std::mem;

/// Applies a Fisher-Yates shuffle on the given list.
pub fn fisher_shuffle<T: Default>(list: &mut [T]) {
    for i in 0..list.len() {
        let swap_index = (rand::random::<usize>() % (list.len() - i)) + i;

        // Can't push the src_val directly into the swap_index in case i and swap_index
        // are the same value (we will end up setting our index to the default value).
        let src_val = mem::replace(&mut list[i], T::default());
        let dst_val = mem::replace(&mut list[swap_index], T::default());

        list[i] = dst_val;
        list[swap_index] = src_val;
    }
}

#[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));
    }
}