rust/src/libcollections/ringbuf.rs
2014-07-23 13:20:17 -07:00

860 lines
24 KiB
Rust

// Copyright 2012-2014 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 double-ended queue implemented as a circular buffer
//!
//! RingBuf implements the trait Deque. It should be imported with `use
//! collections::Deque`.
use core::prelude::*;
use core::cmp;
use core::default::Default;
use core::fmt;
use core::iter::RandomAccessIterator;
use {Deque, Collection, Mutable, MutableSeq};
use vec::Vec;
static INITIAL_CAPACITY: uint = 8u; // 2^3
static MINIMUM_CAPACITY: uint = 2u;
/// RingBuf is a circular buffer that implements Deque.
#[deriving(Clone)]
pub struct RingBuf<T> {
nelts: uint,
lo: uint,
elts: Vec<Option<T>>
}
impl<T> Collection for RingBuf<T> {
/// Return the number of elements in the RingBuf
fn len(&self) -> uint { self.nelts }
}
impl<T> Mutable for RingBuf<T> {
/// Clear the RingBuf, removing all values.
fn clear(&mut self) {
for x in self.elts.mut_iter() { *x = None }
self.nelts = 0;
self.lo = 0;
}
}
impl<T> Deque<T> for RingBuf<T> {
/// Return a reference to the first element in the RingBuf
fn front<'a>(&'a self) -> Option<&'a T> {
if self.nelts > 0 { Some(self.get(0)) } else { None }
}
/// Return a mutable reference to the first element in the RingBuf
fn front_mut<'a>(&'a mut self) -> Option<&'a mut T> {
if self.nelts > 0 { Some(self.get_mut(0)) } else { None }
}
/// Return a reference to the last element in the RingBuf
fn back<'a>(&'a self) -> Option<&'a T> {
if self.nelts > 0 { Some(self.get(self.nelts - 1)) } else { None }
}
/// Return a mutable reference to the last element in the RingBuf
fn back_mut<'a>(&'a mut self) -> Option<&'a mut T> {
let nelts = self.nelts;
if nelts > 0 { Some(self.get_mut(nelts - 1)) } else { None }
}
/// Remove and return the first element in the RingBuf, or None if it is empty
fn pop_front(&mut self) -> Option<T> {
let result = self.elts.get_mut(self.lo).take();
if result.is_some() {
self.lo = (self.lo + 1u) % self.elts.len();
self.nelts -= 1u;
}
result
}
/// Prepend an element to the RingBuf
fn push_front(&mut self, t: T) {
if self.nelts == self.elts.len() {
grow(self.nelts, &mut self.lo, &mut self.elts);
}
if self.lo == 0u {
self.lo = self.elts.len() - 1u;
} else { self.lo -= 1u; }
*self.elts.get_mut(self.lo) = Some(t);
self.nelts += 1u;
}
}
impl<T> MutableSeq<T> for RingBuf<T> {
fn push(&mut self, t: T) {
if self.nelts == self.elts.len() {
grow(self.nelts, &mut self.lo, &mut self.elts);
}
let hi = self.raw_index(self.nelts);
*self.elts.get_mut(hi) = Some(t);
self.nelts += 1u;
}
fn pop(&mut self) -> Option<T> {
if self.nelts > 0 {
self.nelts -= 1;
let hi = self.raw_index(self.nelts);
self.elts.get_mut(hi).take()
} else {
None
}
}
}
impl<T> Default for RingBuf<T> {
#[inline]
fn default() -> RingBuf<T> { RingBuf::new() }
}
impl<T> RingBuf<T> {
/// Create an empty RingBuf
pub fn new() -> RingBuf<T> {
RingBuf::with_capacity(INITIAL_CAPACITY)
}
/// Create an empty RingBuf with space for at least `n` elements.
pub fn with_capacity(n: uint) -> RingBuf<T> {
RingBuf{nelts: 0, lo: 0,
elts: Vec::from_fn(cmp::max(MINIMUM_CAPACITY, n), |_| None)}
}
/// Retrieve an element in the RingBuf by index
///
/// Fails if there is no element with the given index
pub fn get<'a>(&'a self, i: uint) -> &'a T {
let idx = self.raw_index(i);
match *self.elts.get(idx) {
None => fail!(),
Some(ref v) => v
}
}
/// Retrieve an element in the RingBuf by index
///
/// Fails if there is no element with the given index
pub fn get_mut<'a>(&'a mut self, i: uint) -> &'a mut T {
let idx = self.raw_index(i);
match *self.elts.get_mut(idx) {
None => fail!(),
Some(ref mut v) => v
}
}
/// Swap elements at indices `i` and `j`
///
/// `i` and `j` may be equal.
///
/// Fails if there is no element with the given index
pub fn swap(&mut self, i: uint, j: uint) {
assert!(i < self.len());
assert!(j < self.len());
let ri = self.raw_index(i);
let rj = self.raw_index(j);
self.elts.as_mut_slice().swap(ri, rj);
}
/// Return index in underlying vec for a given logical element index
fn raw_index(&self, idx: uint) -> uint {
raw_index(self.lo, self.elts.len(), idx)
}
/// Reserve capacity for exactly `n` elements in the given RingBuf,
/// doing nothing if `self`'s capacity is already equal to or greater
/// than the requested capacity
///
/// # Arguments
///
/// * n - The number of elements to reserve space for
pub fn reserve_exact(&mut self, n: uint) {
self.elts.reserve_exact(n);
}
/// Reserve capacity for at least `n` elements in the given RingBuf,
/// over-allocating in case the caller needs to reserve additional
/// space.
///
/// Do nothing if `self`'s capacity is already equal to or greater
/// than the requested capacity.
///
/// # Arguments
///
/// * n - The number of elements to reserve space for
pub fn reserve(&mut self, n: uint) {
self.elts.reserve(n);
}
/// Front-to-back iterator.
pub fn iter<'a>(&'a self) -> Items<'a, T> {
Items{index: 0, rindex: self.nelts, lo: self.lo, elts: self.elts.as_slice()}
}
/// Front-to-back iterator which returns mutable values.
pub fn mut_iter<'a>(&'a mut self) -> MutItems<'a, T> {
let start_index = raw_index(self.lo, self.elts.len(), 0);
let end_index = raw_index(self.lo, self.elts.len(), self.nelts);
// Divide up the array
if end_index <= start_index {
// Items to iterate goes from:
// start_index to self.elts.len()
// and then
// 0 to end_index
let (temp, remaining1) = self.elts.mut_split_at(start_index);
let (remaining2, _) = temp.mut_split_at(end_index);
MutItems { remaining1: remaining1,
remaining2: remaining2,
nelts: self.nelts }
} else {
// Items to iterate goes from start_index to end_index:
let (empty, elts) = self.elts.mut_split_at(0);
let remaining1 = elts.mut_slice(start_index, end_index);
MutItems { remaining1: remaining1,
remaining2: empty,
nelts: self.nelts }
}
}
}
/// RingBuf iterator
pub struct Items<'a, T> {
lo: uint,
index: uint,
rindex: uint,
elts: &'a [Option<T>],
}
impl<'a, T> Iterator<&'a T> for Items<'a, T> {
#[inline]
fn next(&mut self) -> Option<&'a T> {
if self.index == self.rindex {
return None;
}
let raw_index = raw_index(self.lo, self.elts.len(), self.index);
self.index += 1;
Some(self.elts[raw_index].get_ref())
}
#[inline]
fn size_hint(&self) -> (uint, Option<uint>) {
let len = self.rindex - self.index;
(len, Some(len))
}
}
impl<'a, T> DoubleEndedIterator<&'a T> for Items<'a, T> {
#[inline]
fn next_back(&mut self) -> Option<&'a T> {
if self.index == self.rindex {
return None;
}
self.rindex -= 1;
let raw_index = raw_index(self.lo, self.elts.len(), self.rindex);
Some(self.elts[raw_index].get_ref())
}
}
impl<'a, T> ExactSize<&'a T> for Items<'a, T> {}
impl<'a, T> RandomAccessIterator<&'a T> for Items<'a, T> {
#[inline]
fn indexable(&self) -> uint { self.rindex - self.index }
#[inline]
fn idx(&mut self, j: uint) -> Option<&'a T> {
if j >= self.indexable() {
None
} else {
let raw_index = raw_index(self.lo, self.elts.len(), self.index + j);
Some(self.elts[raw_index].get_ref())
}
}
}
/// RingBuf mutable iterator
pub struct MutItems<'a, T> {
remaining1: &'a mut [Option<T>],
remaining2: &'a mut [Option<T>],
nelts: uint,
}
impl<'a, T> Iterator<&'a mut T> for MutItems<'a, T> {
#[inline]
fn next(&mut self) -> Option<&'a mut T> {
if self.nelts == 0 {
return None;
}
let r = if self.remaining1.len() > 0 {
&mut self.remaining1
} else {
assert!(self.remaining2.len() > 0);
&mut self.remaining2
};
self.nelts -= 1;
Some(r.mut_shift_ref().unwrap().get_mut_ref())
}
#[inline]
fn size_hint(&self) -> (uint, Option<uint>) {
(self.nelts, Some(self.nelts))
}
}
impl<'a, T> DoubleEndedIterator<&'a mut T> for MutItems<'a, T> {
#[inline]
fn next_back(&mut self) -> Option<&'a mut T> {
if self.nelts == 0 {
return None;
}
let r = if self.remaining2.len() > 0 {
&mut self.remaining2
} else {
assert!(self.remaining1.len() > 0);
&mut self.remaining1
};
self.nelts -= 1;
Some(r.mut_pop_ref().unwrap().get_mut_ref())
}
}
impl<'a, T> ExactSize<&'a mut T> for MutItems<'a, T> {}
/// Grow is only called on full elts, so nelts is also len(elts), unlike
/// elsewhere.
fn grow<T>(nelts: uint, loptr: &mut uint, elts: &mut Vec<Option<T>>) {
assert_eq!(nelts, elts.len());
let lo = *loptr;
let newlen = nelts * 2;
elts.reserve(newlen);
/* fill with None */
for _ in range(elts.len(), elts.capacity()) {
elts.push(None);
}
/*
Move the shortest half into the newly reserved area.
lo ---->|
nelts ----------->|
[o o o|o o o o o]
A [. . .|o o o o o o o o|. . . . .]
B [o o o|. . . . . . . .|o o o o o]
*/
assert!(newlen - nelts/2 >= nelts);
if lo <= (nelts - lo) { // A
for i in range(0u, lo) {
elts.as_mut_slice().swap(i, nelts + i);
}
} else { // B
for i in range(lo, nelts) {
elts.as_mut_slice().swap(i, newlen - nelts + i);
}
*loptr += newlen - nelts;
}
}
/// Return index in underlying vec for a given logical element index
fn raw_index(lo: uint, len: uint, index: uint) -> uint {
if lo >= len - index {
lo + index - len
} else {
lo + index
}
}
impl<A: PartialEq> PartialEq for RingBuf<A> {
fn eq(&self, other: &RingBuf<A>) -> bool {
self.nelts == other.nelts &&
self.iter().zip(other.iter()).all(|(a, b)| a.eq(b))
}
fn ne(&self, other: &RingBuf<A>) -> bool {
!self.eq(other)
}
}
impl<A> FromIterator<A> for RingBuf<A> {
fn from_iter<T: Iterator<A>>(iterator: T) -> RingBuf<A> {
let (lower, _) = iterator.size_hint();
let mut deq = RingBuf::with_capacity(lower);
deq.extend(iterator);
deq
}
}
impl<A> Extendable<A> for RingBuf<A> {
fn extend<T: Iterator<A>>(&mut self, mut iterator: T) {
for elt in iterator {
self.push_back(elt);
}
}
}
impl<T: fmt::Show> fmt::Show for RingBuf<T> {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
try!(write!(f, "["));
for (i, e) in self.iter().enumerate() {
if i != 0 { try!(write!(f, ", ")); }
try!(write!(f, "{}", *e));
}
write!(f, "]")
}
}
#[cfg(test)]
mod tests {
use std::fmt::Show;
use std::prelude::*;
use std::gc::{GC, Gc};
use test::Bencher;
use test;
use {Deque, Mutable, MutableSeq};
use super::RingBuf;
use vec::Vec;
#[test]
fn test_simple() {
let mut d = RingBuf::new();
assert_eq!(d.len(), 0u);
d.push_front(17i);
d.push_front(42i);
d.push_back(137);
assert_eq!(d.len(), 3u);
d.push_back(137);
assert_eq!(d.len(), 4u);
debug!("{:?}", d.front());
assert_eq!(*d.front().unwrap(), 42);
debug!("{:?}", d.back());
assert_eq!(*d.back().unwrap(), 137);
let mut i = d.pop_front();
debug!("{:?}", i);
assert_eq!(i, Some(42));
i = d.pop_back();
debug!("{:?}", i);
assert_eq!(i, Some(137));
i = d.pop_back();
debug!("{:?}", i);
assert_eq!(i, Some(137));
i = d.pop_back();
debug!("{:?}", i);
assert_eq!(i, Some(17));
assert_eq!(d.len(), 0u);
d.push_back(3);
assert_eq!(d.len(), 1u);
d.push_front(2);
assert_eq!(d.len(), 2u);
d.push_back(4);
assert_eq!(d.len(), 3u);
d.push_front(1);
assert_eq!(d.len(), 4u);
debug!("{:?}", d.get(0));
debug!("{:?}", d.get(1));
debug!("{:?}", d.get(2));
debug!("{:?}", d.get(3));
assert_eq!(*d.get(0), 1);
assert_eq!(*d.get(1), 2);
assert_eq!(*d.get(2), 3);
assert_eq!(*d.get(3), 4);
}
#[test]
fn test_boxes() {
let a: Gc<int> = box(GC) 5;
let b: Gc<int> = box(GC) 72;
let c: Gc<int> = box(GC) 64;
let d: Gc<int> = box(GC) 175;
let mut deq = RingBuf::new();
assert_eq!(deq.len(), 0);
deq.push_front(a);
deq.push_front(b);
deq.push_back(c);
assert_eq!(deq.len(), 3);
deq.push_back(d);
assert_eq!(deq.len(), 4);
assert_eq!(deq.front(), Some(&b));
assert_eq!(deq.back(), Some(&d));
assert_eq!(deq.pop_front(), Some(b));
assert_eq!(deq.pop_back(), Some(d));
assert_eq!(deq.pop_back(), Some(c));
assert_eq!(deq.pop_back(), Some(a));
assert_eq!(deq.len(), 0);
deq.push_back(c);
assert_eq!(deq.len(), 1);
deq.push_front(b);
assert_eq!(deq.len(), 2);
deq.push_back(d);
assert_eq!(deq.len(), 3);
deq.push_front(a);
assert_eq!(deq.len(), 4);
assert_eq!(*deq.get(0), a);
assert_eq!(*deq.get(1), b);
assert_eq!(*deq.get(2), c);
assert_eq!(*deq.get(3), d);
}
#[cfg(test)]
fn test_parameterized<T:Clone + PartialEq + Show>(a: T, b: T, c: T, d: T) {
let mut deq = RingBuf::new();
assert_eq!(deq.len(), 0);
deq.push_front(a.clone());
deq.push_front(b.clone());
deq.push_back(c.clone());
assert_eq!(deq.len(), 3);
deq.push_back(d.clone());
assert_eq!(deq.len(), 4);
assert_eq!((*deq.front().unwrap()).clone(), b.clone());
assert_eq!((*deq.back().unwrap()).clone(), d.clone());
assert_eq!(deq.pop_front().unwrap(), b.clone());
assert_eq!(deq.pop_back().unwrap(), d.clone());
assert_eq!(deq.pop_back().unwrap(), c.clone());
assert_eq!(deq.pop_back().unwrap(), a.clone());
assert_eq!(deq.len(), 0);
deq.push_back(c.clone());
assert_eq!(deq.len(), 1);
deq.push_front(b.clone());
assert_eq!(deq.len(), 2);
deq.push_back(d.clone());
assert_eq!(deq.len(), 3);
deq.push_front(a.clone());
assert_eq!(deq.len(), 4);
assert_eq!((*deq.get(0)).clone(), a.clone());
assert_eq!((*deq.get(1)).clone(), b.clone());
assert_eq!((*deq.get(2)).clone(), c.clone());
assert_eq!((*deq.get(3)).clone(), d.clone());
}
#[test]
fn test_push_front_grow() {
let mut deq = RingBuf::new();
for i in range(0u, 66) {
deq.push_front(i);
}
assert_eq!(deq.len(), 66);
for i in range(0u, 66) {
assert_eq!(*deq.get(i), 65 - i);
}
let mut deq = RingBuf::new();
for i in range(0u, 66) {
deq.push_back(i);
}
for i in range(0u, 66) {
assert_eq!(*deq.get(i), i);
}
}
#[bench]
fn bench_new(b: &mut test::Bencher) {
b.iter(|| {
let _: RingBuf<u64> = RingBuf::new();
})
}
#[bench]
fn bench_push_back(b: &mut test::Bencher) {
let mut deq = RingBuf::new();
b.iter(|| {
deq.push_back(0i);
})
}
#[bench]
fn bench_push_front(b: &mut test::Bencher) {
let mut deq = RingBuf::new();
b.iter(|| {
deq.push_front(0i);
})
}
#[bench]
fn bench_grow(b: &mut test::Bencher) {
let mut deq = RingBuf::new();
b.iter(|| {
for _ in range(0i, 65) {
deq.push_front(1i);
}
})
}
#[deriving(Clone, PartialEq, Show)]
enum Taggy {
One(int),
Two(int, int),
Three(int, int, int),
}
#[deriving(Clone, PartialEq, Show)]
enum Taggypar<T> {
Onepar(int),
Twopar(int, int),
Threepar(int, int, int),
}
#[deriving(Clone, PartialEq, Show)]
struct RecCy {
x: int,
y: int,
t: Taggy
}
#[test]
fn test_param_int() {
test_parameterized::<int>(5, 72, 64, 175);
}
#[test]
fn test_param_at_int() {
test_parameterized::<Gc<int>>(box(GC) 5, box(GC) 72,
box(GC) 64, box(GC) 175);
}
#[test]
fn test_param_taggy() {
test_parameterized::<Taggy>(One(1), Two(1, 2), Three(1, 2, 3), Two(17, 42));
}
#[test]
fn test_param_taggypar() {
test_parameterized::<Taggypar<int>>(Onepar::<int>(1),
Twopar::<int>(1, 2),
Threepar::<int>(1, 2, 3),
Twopar::<int>(17, 42));
}
#[test]
fn test_param_reccy() {
let reccy1 = RecCy { x: 1, y: 2, t: One(1) };
let reccy2 = RecCy { x: 345, y: 2, t: Two(1, 2) };
let reccy3 = RecCy { x: 1, y: 777, t: Three(1, 2, 3) };
let reccy4 = RecCy { x: 19, y: 252, t: Two(17, 42) };
test_parameterized::<RecCy>(reccy1, reccy2, reccy3, reccy4);
}
#[test]
fn test_with_capacity() {
let mut d = RingBuf::with_capacity(0);
d.push_back(1i);
assert_eq!(d.len(), 1);
let mut d = RingBuf::with_capacity(50);
d.push_back(1i);
assert_eq!(d.len(), 1);
}
#[test]
fn test_reserve_exact() {
let mut d = RingBuf::new();
d.push_back(0u64);
d.reserve_exact(50);
assert_eq!(d.elts.capacity(), 50);
let mut d = RingBuf::new();
d.push_back(0u32);
d.reserve_exact(50);
assert_eq!(d.elts.capacity(), 50);
}
#[test]
fn test_reserve() {
let mut d = RingBuf::new();
d.push_back(0u64);
d.reserve(50);
assert_eq!(d.elts.capacity(), 64);
let mut d = RingBuf::new();
d.push_back(0u32);
d.reserve(50);
assert_eq!(d.elts.capacity(), 64);
}
#[test]
fn test_swap() {
let mut d: RingBuf<int> = range(0i, 5).collect();
d.pop_front();
d.swap(0, 3);
assert_eq!(d.iter().map(|&x|x).collect::<Vec<int>>(), vec!(4, 2, 3, 1));
}
#[test]
fn test_iter() {
let mut d = RingBuf::new();
assert_eq!(d.iter().next(), None);
assert_eq!(d.iter().size_hint(), (0, Some(0)));
for i in range(0i, 5) {
d.push_back(i);
}
assert_eq!(d.iter().collect::<Vec<&int>>().as_slice(), &[&0,&1,&2,&3,&4]);
for i in range(6i, 9) {
d.push_front(i);
}
assert_eq!(d.iter().collect::<Vec<&int>>().as_slice(), &[&8,&7,&6,&0,&1,&2,&3,&4]);
let mut it = d.iter();
let mut len = d.len();
loop {
match it.next() {
None => break,
_ => { len -= 1; assert_eq!(it.size_hint(), (len, Some(len))) }
}
}
}
#[test]
fn test_rev_iter() {
let mut d = RingBuf::new();
assert_eq!(d.iter().rev().next(), None);
for i in range(0i, 5) {
d.push_back(i);
}
assert_eq!(d.iter().rev().collect::<Vec<&int>>().as_slice(), &[&4,&3,&2,&1,&0]);
for i in range(6i, 9) {
d.push_front(i);
}
assert_eq!(d.iter().rev().collect::<Vec<&int>>().as_slice(), &[&4,&3,&2,&1,&0,&6,&7,&8]);
}
#[test]
fn test_mut_rev_iter_wrap() {
let mut d = RingBuf::with_capacity(3);
assert!(d.mut_iter().rev().next().is_none());
d.push_back(1i);
d.push_back(2);
d.push_back(3);
assert_eq!(d.pop_front(), Some(1));
d.push_back(4);
assert_eq!(d.mut_iter().rev().map(|x| *x).collect::<Vec<int>>(),
vec!(4, 3, 2));
}
#[test]
fn test_mut_iter() {
let mut d = RingBuf::new();
assert!(d.mut_iter().next().is_none());
for i in range(0u, 3) {
d.push_front(i);
}
for (i, elt) in d.mut_iter().enumerate() {
assert_eq!(*elt, 2 - i);
*elt = i;
}
{
let mut it = d.mut_iter();
assert_eq!(*it.next().unwrap(), 0);
assert_eq!(*it.next().unwrap(), 1);
assert_eq!(*it.next().unwrap(), 2);
assert!(it.next().is_none());
}
}
#[test]
fn test_mut_rev_iter() {
let mut d = RingBuf::new();
assert!(d.mut_iter().rev().next().is_none());
for i in range(0u, 3) {
d.push_front(i);
}
for (i, elt) in d.mut_iter().rev().enumerate() {
assert_eq!(*elt, i);
*elt = i;
}
{
let mut it = d.mut_iter().rev();
assert_eq!(*it.next().unwrap(), 0);
assert_eq!(*it.next().unwrap(), 1);
assert_eq!(*it.next().unwrap(), 2);
assert!(it.next().is_none());
}
}
#[test]
fn test_from_iter() {
use std::iter;
let v = vec!(1i,2,3,4,5,6,7);
let deq: RingBuf<int> = v.iter().map(|&x| x).collect();
let u: Vec<int> = deq.iter().map(|&x| x).collect();
assert_eq!(u, v);
let mut seq = iter::count(0u, 2).take(256);
let deq: RingBuf<uint> = seq.collect();
for (i, &x) in deq.iter().enumerate() {
assert_eq!(2*i, x);
}
assert_eq!(deq.len(), 256);
}
#[test]
fn test_clone() {
let mut d = RingBuf::new();
d.push_front(17i);
d.push_front(42);
d.push_back(137);
d.push_back(137);
assert_eq!(d.len(), 4u);
let mut e = d.clone();
assert_eq!(e.len(), 4u);
while !d.is_empty() {
assert_eq!(d.pop_back(), e.pop_back());
}
assert_eq!(d.len(), 0u);
assert_eq!(e.len(), 0u);
}
#[test]
fn test_eq() {
let mut d = RingBuf::new();
assert!(d == RingBuf::with_capacity(0));
d.push_front(137i);
d.push_front(17);
d.push_front(42);
d.push_back(137);
let mut e = RingBuf::with_capacity(0);
e.push_back(42);
e.push_back(17);
e.push_back(137);
e.push_back(137);
assert!(&e == &d);
e.pop_back();
e.push_back(0);
assert!(e != d);
e.clear();
assert!(e == RingBuf::new());
}
#[test]
fn test_show() {
let ringbuf: RingBuf<int> = range(0i, 10).collect();
assert!(format!("{}", ringbuf).as_slice() == "[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]");
let ringbuf: RingBuf<&str> = vec!["just", "one", "test", "more"].iter()
.map(|&s| s)
.collect();
assert!(format!("{}", ringbuf).as_slice() == "[just, one, test, more]");
}
}