// 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.
//
// ignore-lexer-test FIXME #15679

//! Unicode string manipulation (`str` type)
//!
//! # Basic Usage
//!
//! Rust's string type is one of the core primitive types of the language. While
//! represented by the name `str`, the name `str` is not actually a valid type in
//! Rust. Each string must also be decorated with a pointer. `String` is used
//! for an owned string, so there is only one commonly-used `str` type in Rust:
//! `&str`.
//!
//! `&str` is the borrowed string type. This type of string can only be created
//! from other strings, unless it is a static string (see below). As the word
//! "borrowed" implies, this type of string is owned elsewhere, and this string
//! cannot be moved out of.
//!
//! As an example, here's some code that uses a string.
//!
//! ```rust
//! fn main() {
//!     let borrowed_string = "This string is borrowed with the 'static lifetime";
//! }
//! ```
//!
//! From the example above, you can guess that Rust's string literals have the
//! `'static` lifetime. This is akin to C's concept of a static string.
//! More precisely, string literals are immutable views with a 'static lifetime
//! (otherwise known as the lifetime of the entire program), and thus have the
//! type `&'static str`.
//!
//! # Representation
//!
//! Rust's string type, `str`, is a sequence of Unicode scalar values encoded as a
//! stream of UTF-8 bytes. All [strings](../../reference.html#literals) are
//! guaranteed to be validly encoded UTF-8 sequences. Additionally, strings are
//! not null-terminated and can thus contain null bytes.
//!
//! The actual representation of strings have direct mappings to slices: `&str`
//! is the same as `&[u8]`.

#![doc(primitive = "str")]

use self::MaybeOwned::*;
use self::RecompositionState::*;
use self::DecompositionType::*;

use core::borrow::{BorrowFrom, Cow, ToOwned};
use core::clone::Clone;
use core::default::Default;
use core::fmt;
use core::hash;
use core::char::Char;
use core::cmp::{mod, Eq, Equiv, Ord, Ordering, PartialEq, PartialOrd};
use core::iter::{range, AdditiveIterator, Iterator, IteratorExt};
use core::kinds::Sized;
use core::option::Option::{mod, Some, None};
use core::slice::{AsSlice, SliceExt};

use ring_buf::RingBuf;
use string::String;
use unicode;
use vec::Vec;

pub use core::str::{from_utf8, CharEq, Chars, CharOffsets};
pub use core::str::{Bytes, CharSplits};
pub use core::str::{CharSplitsN, AnyLines, MatchIndices, StrSplits};
pub use core::str::{Utf16Encoder, Utf16CodeUnits};
pub use core::str::{eq_slice, is_utf8, is_utf16, Utf16Items};
pub use core::str::{Utf16Item, ScalarValue, LoneSurrogate, utf16_items};
pub use core::str::{truncate_utf16_at_nul, utf8_char_width, CharRange};
pub use core::str::{FromStr, from_str};
pub use core::str::{Str, StrPrelude};
pub use core::str::{from_utf8_unchecked, from_c_str};
pub use unicode::str::{UnicodeStrPrelude, Words, Graphemes, GraphemeIndices};

// FIXME(conventions): ensure bit/char conventions are followed by str's API

/*
Section: Creating a string
*/

/// Methods for vectors of strings.
pub trait StrVector for Sized? {
    /// Concatenates a vector of strings.
    ///
    /// # Examples
    ///
    /// ```rust
    /// let first = "Restaurant at the End of the".to_string();
    /// let second = " Universe".to_string();
    /// let string_vec = vec![first, second];
    /// assert_eq!(string_vec.concat(), "Restaurant at the End of the Universe".to_string());
    /// ```
    fn concat(&self) -> String;

    /// Concatenates a vector of strings, placing a given separator between each.
    ///
    /// # Examples
    ///
    /// ```rust
    /// let first = "Roast".to_string();
    /// let second = "Sirloin Steak".to_string();
    /// let string_vec = vec![first, second];
    /// assert_eq!(string_vec.connect(", "), "Roast, Sirloin Steak".to_string());
    /// ```
    fn connect(&self, sep: &str) -> String;
}

impl<S: Str> StrVector for [S] {
    fn concat(&self) -> String {
        if self.is_empty() {
            return String::new();
        }

        // `len` calculation may overflow but push_str will check boundaries
        let len = self.iter().map(|s| s.as_slice().len()).sum();

        let mut result = String::with_capacity(len);

        for s in self.iter() {
            result.push_str(s.as_slice())
        }

        result
    }

    fn connect(&self, sep: &str) -> String {
        if self.is_empty() {
            return String::new();
        }

        // concat is faster
        if sep.is_empty() {
            return self.concat();
        }

        // this is wrong without the guarantee that `self` is non-empty
        // `len` calculation may overflow but push_str but will check boundaries
        let len = sep.len() * (self.len() - 1)
            + self.iter().map(|s| s.as_slice().len()).sum();
        let mut result = String::with_capacity(len);
        let mut first = true;

        for s in self.iter() {
            if first {
                first = false;
            } else {
                result.push_str(sep);
            }
            result.push_str(s.as_slice());
        }
        result
    }
}

impl<S: Str, T: AsSlice<S>> StrVector for T {
    #[inline]
    fn concat(&self) -> String {
        self.as_slice().concat()
    }

    #[inline]
    fn connect(&self, sep: &str) -> String {
        self.as_slice().connect(sep)
    }
}

/*
Section: Iterators
*/

// Helper functions used for Unicode normalization
fn canonical_sort(comb: &mut [(char, u8)]) {
    let len = comb.len();
    for i in range(0, len) {
        let mut swapped = false;
        for j in range(1, len-i) {
            let class_a = comb[j-1].1;
            let class_b = comb[j].1;
            if class_a != 0 && class_b != 0 && class_a > class_b {
                comb.swap(j-1, j);
                swapped = true;
            }
        }
        if !swapped { break; }
    }
}

#[deriving(Clone)]
enum DecompositionType {
    Canonical,
    Compatible
}

/// External iterator for a string's decomposition's characters.
/// Use with the `std::iter` module.
#[deriving(Clone)]
pub struct Decompositions<'a> {
    kind: DecompositionType,
    iter: Chars<'a>,
    buffer: Vec<(char, u8)>,
    sorted: bool
}

impl<'a> Iterator<char> for Decompositions<'a> {
    #[inline]
    fn next(&mut self) -> Option<char> {
        match self.buffer.head() {
            Some(&(c, 0)) => {
                self.sorted = false;
                self.buffer.remove(0);
                return Some(c);
            }
            Some(&(c, _)) if self.sorted => {
                self.buffer.remove(0);
                return Some(c);
            }
            _ => self.sorted = false
        }

        if !self.sorted {
            for ch in self.iter {
                let buffer = &mut self.buffer;
                let sorted = &mut self.sorted;
                {
                    let callback = |d| {
                        let class =
                            unicode::char::canonical_combining_class(d);
                        if class == 0 && !*sorted {
                            canonical_sort(buffer.as_mut_slice());
                            *sorted = true;
                        }
                        buffer.push((d, class));
                    };
                    match self.kind {
                        Canonical => {
                            unicode::char::decompose_canonical(ch, callback)
                        }
                        Compatible => {
                            unicode::char::decompose_compatible(ch, callback)
                        }
                    }
                }
                if *sorted {
                    break
                }
            }
        }

        if !self.sorted {
            canonical_sort(self.buffer.as_mut_slice());
            self.sorted = true;
        }

        match self.buffer.remove(0) {
            Some((c, 0)) => {
                self.sorted = false;
                Some(c)
            }
            Some((c, _)) => Some(c),
            None => None
        }
    }

    fn size_hint(&self) -> (uint, Option<uint>) {
        let (lower, _) = self.iter.size_hint();
        (lower, None)
    }
}

#[deriving(Clone)]
enum RecompositionState {
    Composing,
    Purging,
    Finished
}

/// External iterator for a string's recomposition's characters.
/// Use with the `std::iter` module.
#[deriving(Clone)]
pub struct Recompositions<'a> {
    iter: Decompositions<'a>,
    state: RecompositionState,
    buffer: RingBuf<char>,
    composee: Option<char>,
    last_ccc: Option<u8>
}

impl<'a> Iterator<char> for Recompositions<'a> {
    #[inline]
    fn next(&mut self) -> Option<char> {
        loop {
            match self.state {
                Composing => {
                    for ch in self.iter {
                        let ch_class = unicode::char::canonical_combining_class(ch);
                        if self.composee.is_none() {
                            if ch_class != 0 {
                                return Some(ch);
                            }
                            self.composee = Some(ch);
                            continue;
                        }
                        let k = self.composee.clone().unwrap();

                        match self.last_ccc {
                            None => {
                                match unicode::char::compose(k, ch) {
                                    Some(r) => {
                                        self.composee = Some(r);
                                        continue;
                                    }
                                    None => {
                                        if ch_class == 0 {
                                            self.composee = Some(ch);
                                            return Some(k);
                                        }
                                        self.buffer.push_back(ch);
                                        self.last_ccc = Some(ch_class);
                                    }
                                }
                            }
                            Some(l_class) => {
                                if l_class >= ch_class {
                                    // `ch` is blocked from `composee`
                                    if ch_class == 0 {
                                        self.composee = Some(ch);
                                        self.last_ccc = None;
                                        self.state = Purging;
                                        return Some(k);
                                    }
                                    self.buffer.push_back(ch);
                                    self.last_ccc = Some(ch_class);
                                    continue;
                                }
                                match unicode::char::compose(k, ch) {
                                    Some(r) => {
                                        self.composee = Some(r);
                                        continue;
                                    }
                                    None => {
                                        self.buffer.push_back(ch);
                                        self.last_ccc = Some(ch_class);
                                    }
                                }
                            }
                        }
                    }
                    self.state = Finished;
                    if self.composee.is_some() {
                        return self.composee.take();
                    }
                }
                Purging => {
                    match self.buffer.pop_front() {
                        None => self.state = Composing,
                        s => return s
                    }
                }
                Finished => {
                    match self.buffer.pop_front() {
                        None => return self.composee.take(),
                        s => return s
                    }
                }
            }
        }
    }
}

/// Replaces all occurrences of one string with another.
///
/// # Arguments
///
/// * s - The string containing substrings to replace
/// * from - The string to replace
/// * to - The replacement string
///
/// # Return value
///
/// The original string with all occurrences of `from` replaced with `to`.
///
/// # Examples
///
/// ```rust
/// use std::str;
/// let string = "orange";
/// let new_string = str::replace(string, "or", "str");
/// assert_eq!(new_string.as_slice(), "strange");
/// ```
pub fn replace(s: &str, from: &str, to: &str) -> String {
    let mut result = String::new();
    let mut last_end = 0;
    for (start, end) in s.match_indices(from) {
        result.push_str(unsafe { s.slice_unchecked(last_end, start) });
        result.push_str(to);
        last_end = end;
    }
    result.push_str(unsafe { s.slice_unchecked(last_end, s.len()) });
    result
}

/*
Section: Misc
*/

// Return the initial codepoint accumulator for the first byte.
// The first byte is special, only want bottom 5 bits for width 2, 4 bits
// for width 3, and 3 bits for width 4
macro_rules! utf8_first_byte {
    ($byte:expr, $width:expr) => (($byte & (0x7F >> $width)) as u32)
}

// return the value of $ch updated with continuation byte $byte
macro_rules! utf8_acc_cont_byte {
    ($ch:expr, $byte:expr) => (($ch << 6) | ($byte & 63u8) as u32)
}

/*
Section: MaybeOwned
*/

/// A string type that can hold either a `String` or a `&str`.
/// This can be useful as an optimization when an allocation is sometimes
/// needed but not always.
#[deprecated = "use std::str::CowString"]
pub enum MaybeOwned<'a> {
    /// A borrowed string.
    Slice(&'a str),
    /// An owned string.
    Owned(String)
}

/// A specialization of `CowString` to be sendable.
pub type SendStr = CowString<'static>;

#[deprecated = "use std::str::CowString"]
impl<'a> MaybeOwned<'a> {
    /// Returns `true` if this `MaybeOwned` wraps an owned string.
    ///
    /// # Examples
    ///
    /// ``` ignore
    /// let string = String::from_str("orange");
    /// let maybe_owned_string = string.into_maybe_owned();
    /// assert_eq!(true, maybe_owned_string.is_owned());
    /// ```
    #[inline]
    pub fn is_owned(&self) -> bool {
        match *self {
            Slice(_) => false,
            Owned(_) => true
        }
    }

    /// Returns `true` if this `MaybeOwned` wraps a borrowed string.
    ///
    /// # Examples
    ///
    /// ``` ignore
    /// let string = "orange";
    /// let maybe_owned_string = string.as_slice().into_maybe_owned();
    /// assert_eq!(true, maybe_owned_string.is_slice());
    /// ```
    #[inline]
    pub fn is_slice(&self) -> bool {
        match *self {
            Slice(_) => true,
            Owned(_) => false
        }
    }

    /// Return the number of bytes in this string.
    #[inline]
    pub fn len(&self) -> uint { self.as_slice().len() }

    /// Returns true if the string contains no bytes
    #[allow(deprecated)]
    #[inline]
    pub fn is_empty(&self) -> bool { self.len() == 0 }
}

#[deprecated = "use std::borrow::IntoCow"]
/// Trait for moving into a `MaybeOwned`.
pub trait IntoMaybeOwned<'a> {
    /// Moves `self` into a `MaybeOwned`.
    fn into_maybe_owned(self) -> MaybeOwned<'a>;
}

#[deprecated = "use std::borrow::IntoCow"]
#[allow(deprecated)]
impl<'a> IntoMaybeOwned<'a> for String {
    /// # Examples
    ///
    /// ``` ignore
    /// let owned_string = String::from_str("orange");
    /// let maybe_owned_string = owned_string.into_maybe_owned();
    /// assert_eq!(true, maybe_owned_string.is_owned());
    /// ```
    #[allow(deprecated)]
    #[inline]
    fn into_maybe_owned(self) -> MaybeOwned<'a> {
        Owned(self)
    }
}

#[deprecated = "use std::borrow::IntoCow"]
#[allow(deprecated)]
impl<'a> IntoMaybeOwned<'a> for &'a str {
    /// # Examples
    ///
    /// ``` ignore
    /// let string = "orange";
    /// let maybe_owned_str = string.as_slice().into_maybe_owned();
    /// assert_eq!(false, maybe_owned_str.is_owned());
    /// ```
    #[allow(deprecated)]
    #[inline]
    fn into_maybe_owned(self) -> MaybeOwned<'a> { Slice(self) }
}

#[allow(deprecated)]
#[deprecated = "use std::borrow::IntoCow"]
impl<'a> IntoMaybeOwned<'a> for MaybeOwned<'a> {
    /// # Examples
    ///
    /// ``` ignore
    /// let str = "orange";
    /// let maybe_owned_str = str.as_slice().into_maybe_owned();
    /// let maybe_maybe_owned_str = maybe_owned_str.into_maybe_owned();
    /// assert_eq!(false, maybe_maybe_owned_str.is_owned());
    /// ```
    #[inline]
    fn into_maybe_owned(self) -> MaybeOwned<'a> { self }
}

#[deprecated = "use std::str::CowString"]
impl<'a> PartialEq for MaybeOwned<'a> {
    #[inline]
    fn eq(&self, other: &MaybeOwned) -> bool {
        self.as_slice() == other.as_slice()
    }
}

#[deprecated = "use std::str::CowString"]
impl<'a> Eq for MaybeOwned<'a> {}

#[deprecated = "use std::str::CowString"]
impl<'a> PartialOrd for MaybeOwned<'a> {
    #[inline]
    fn partial_cmp(&self, other: &MaybeOwned) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

#[deprecated = "use std::str::CowString"]
impl<'a> Ord for MaybeOwned<'a> {
    #[inline]
    fn cmp(&self, other: &MaybeOwned) -> Ordering {
        self.as_slice().cmp(other.as_slice())
    }
}

#[allow(deprecated)]
#[deprecated = "use std::str::CowString"]
impl<'a, S: Str> Equiv<S> for MaybeOwned<'a> {
    #[inline]
    fn equiv(&self, other: &S) -> bool {
        self.as_slice() == other.as_slice()
    }
}

#[deprecated = "use std::str::CowString"]
impl<'a> Str for MaybeOwned<'a> {
    #[allow(deprecated)]
    #[inline]
    fn as_slice<'b>(&'b self) -> &'b str {
        match *self {
            Slice(s) => s,
            Owned(ref s) => s.as_slice()
        }
    }
}

#[deprecated = "use std::str::CowString"]
impl<'a> StrAllocating for MaybeOwned<'a> {
    #[allow(deprecated)]
    #[inline]
    fn into_string(self) -> String {
        match self {
            Slice(s) => String::from_str(s),
            Owned(s) => s
        }
    }
}

#[deprecated = "use std::str::CowString"]
impl<'a> Clone for MaybeOwned<'a> {
    #[allow(deprecated)]
    #[inline]
    fn clone(&self) -> MaybeOwned<'a> {
        match *self {
            Slice(s) => Slice(s),
            Owned(ref s) => Owned(String::from_str(s.as_slice()))
        }
    }
}

#[deprecated = "use std::str::CowString"]
impl<'a> Default for MaybeOwned<'a> {
    #[allow(deprecated)]
    #[inline]
    fn default() -> MaybeOwned<'a> { Slice("") }
}

#[deprecated = "use std::str::CowString"]
impl<'a, H: hash::Writer> hash::Hash<H> for MaybeOwned<'a> {
    #[inline]
    fn hash(&self, hasher: &mut H) {
        self.as_slice().hash(hasher)
    }
}

#[deprecated = "use std::str::CowString"]
impl<'a> fmt::Show for MaybeOwned<'a> {
    #[inline]
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match *self {
            Slice(ref s) => s.fmt(f),
            Owned(ref s) => s.fmt(f)
        }
    }
}

#[unstable = "trait is unstable"]
impl BorrowFrom<String> for str {
    fn borrow_from(owned: &String) -> &str { owned[] }
}

#[unstable = "trait is unstable"]
impl ToOwned<String> for str {
    fn to_owned(&self) -> String { self.into_string() }
}

/// Unsafe string operations.
pub mod raw {
    pub use core::str::raw::{from_utf8, c_str_to_static_slice, slice_bytes};
    pub use core::str::raw::{slice_unchecked};
}

/*
Section: CowString
*/

/// A clone-on-write string
pub type CowString<'a> = Cow<'a, String, str>;

impl<'a> Str for CowString<'a> {
    #[inline]
    fn as_slice<'b>(&'b self) -> &'b str {
        (**self).as_slice()
    }
}

/*
Section: Trait implementations
*/

/// Any string that can be represented as a slice.
pub trait StrAllocating: Str {
    /// Converts `self` into a `String`, not making a copy if possible.
    fn into_string(self) -> String;

    /// Escapes each char in `s` with `char::escape_default`.
    fn escape_default(&self) -> String {
        let me = self.as_slice();
        let mut out = String::with_capacity(me.len());
        for c in me.chars() {
            for c in c.escape_default() {
                out.push(c);
            }
        }
        out
    }

    /// Escapes each char in `s` with `char::escape_unicode`.
    fn escape_unicode(&self) -> String {
        let me = self.as_slice();
        let mut out = String::with_capacity(me.len());
        for c in me.chars() {
            for c in c.escape_unicode() {
                out.push(c);
            }
        }
        out
    }

    /// Replaces all occurrences of one string with another.
    ///
    /// # Arguments
    ///
    /// * `from` - The string to replace
    /// * `to` - The replacement string
    ///
    /// # Return value
    ///
    /// The original string with all occurrences of `from` replaced with `to`.
    ///
    /// # Examples
    ///
    /// ```rust
    /// let s = "Do you know the muffin man,
    /// The muffin man, the muffin man, ...".to_string();
    ///
    /// assert_eq!(s.replace("muffin man", "little lamb"),
    ///            "Do you know the little lamb,
    /// The little lamb, the little lamb, ...".to_string());
    ///
    /// // not found, so no change.
    /// assert_eq!(s.replace("cookie monster", "little lamb"), s);
    /// ```
    fn replace(&self, from: &str, to: &str) -> String {
        replace(self.as_slice(), from, to)
    }

    /// Given a string, makes a new string with repeated copies of it.
    fn repeat(&self, nn: uint) -> String {
        let me = self.as_slice();
        let mut ret = String::with_capacity(nn * me.len());
        for _ in range(0, nn) {
            ret.push_str(me);
        }
        ret
    }

    /// Returns the Levenshtein Distance between two strings.
    fn lev_distance(&self, t: &str) -> uint {
        let me = self.as_slice();
        if me.is_empty() { return t.char_len(); }
        if t.is_empty() { return me.char_len(); }

        let mut dcol = Vec::from_fn(t.len() + 1, |x| x);
        let mut t_last = 0;

        for (i, sc) in me.chars().enumerate() {

            let mut current = i;
            dcol[0] = current + 1;

            for (j, tc) in t.chars().enumerate() {

                let next = dcol[j + 1];

                if sc == tc {
                    dcol[j + 1] = current;
                } else {
                    dcol[j + 1] = cmp::min(current, next);
                    dcol[j + 1] = cmp::min(dcol[j + 1], dcol[j]) + 1;
                }

                current = next;
                t_last = j;
            }
        }

        dcol[t_last + 1]
    }

    /// Returns an iterator over the string in Unicode Normalization Form D
    /// (canonical decomposition).
    #[inline]
    fn nfd_chars<'a>(&'a self) -> Decompositions<'a> {
        Decompositions {
            iter: self.as_slice().chars(),
            buffer: Vec::new(),
            sorted: false,
            kind: Canonical
        }
    }

    /// Returns an iterator over the string in Unicode Normalization Form KD
    /// (compatibility decomposition).
    #[inline]
    fn nfkd_chars<'a>(&'a self) -> Decompositions<'a> {
        Decompositions {
            iter: self.as_slice().chars(),
            buffer: Vec::new(),
            sorted: false,
            kind: Compatible
        }
    }

    /// An Iterator over the string in Unicode Normalization Form C
    /// (canonical decomposition followed by canonical composition).
    #[inline]
    fn nfc_chars<'a>(&'a self) -> Recompositions<'a> {
        Recompositions {
            iter: self.nfd_chars(),
            state: Composing,
            buffer: RingBuf::new(),
            composee: None,
            last_ccc: None
        }
    }

    /// An Iterator over the string in Unicode Normalization Form KC
    /// (compatibility decomposition followed by canonical composition).
    #[inline]
    fn nfkc_chars<'a>(&'a self) -> Recompositions<'a> {
        Recompositions {
            iter: self.nfkd_chars(),
            state: Composing,
            buffer: RingBuf::new(),
            composee: None,
            last_ccc: None
        }
    }
}

impl<'a> StrAllocating for &'a str {
    #[inline]
    fn into_string(self) -> String {
        String::from_str(self)
    }
}

#[cfg(test)]
mod tests {
    use prelude::*;
    use core::default::Default;
    use core::iter::AdditiveIterator;
    use super::{eq_slice, from_utf8, is_utf8, is_utf16, raw};
    use super::truncate_utf16_at_nul;
    use super::MaybeOwned::{Owned, Slice};

    #[test]
    fn test_eq_slice() {
        assert!((eq_slice("foobar".slice(0, 3), "foo")));
        assert!((eq_slice("barfoo".slice(3, 6), "foo")));
        assert!((!eq_slice("foo1", "foo2")));
    }

    #[test]
    fn test_le() {
        assert!("" <= "");
        assert!("" <= "foo");
        assert!("foo" <= "foo");
        assert!("foo" != "bar");
    }

    #[test]
    fn test_len() {
        assert_eq!("".len(), 0u);
        assert_eq!("hello world".len(), 11u);
        assert_eq!("\x63".len(), 1u);
        assert_eq!("\u{a2}".len(), 2u);
        assert_eq!("\u{3c0}".len(), 2u);
        assert_eq!("\u{2620}".len(), 3u);
        assert_eq!("\u{1d11e}".len(), 4u);

        assert_eq!("".char_len(), 0u);
        assert_eq!("hello world".char_len(), 11u);
        assert_eq!("\x63".char_len(), 1u);
        assert_eq!("\u{a2}".char_len(), 1u);
        assert_eq!("\u{3c0}".char_len(), 1u);
        assert_eq!("\u{2620}".char_len(), 1u);
        assert_eq!("\u{1d11e}".char_len(), 1u);
        assert_eq!("ประเทศไทย中华Việt Nam".char_len(), 19u);

        assert_eq!("ｈｅｌｌｏ".width(false), 10u);
        assert_eq!("ｈｅｌｌｏ".width(true), 10u);
        assert_eq!("\0\0\0\0\0".width(false), 0u);
        assert_eq!("\0\0\0\0\0".width(true), 0u);
        assert_eq!("".width(false), 0u);
        assert_eq!("".width(true), 0u);
        assert_eq!("\u{2081}\u{2082}\u{2083}\u{2084}".width(false), 4u);
        assert_eq!("\u{2081}\u{2082}\u{2083}\u{2084}".width(true), 8u);
    }

    #[test]
    fn test_find() {
        assert_eq!("hello".find('l'), Some(2u));
        assert_eq!("hello".find(|&: c:char| c == 'o'), Some(4u));
        assert!("hello".find('x').is_none());
        assert!("hello".find(|&: c:char| c == 'x').is_none());
        assert_eq!("ประเทศไทย中华Việt Nam".find('华'), Some(30u));
        assert_eq!("ประเทศไทย中华Việt Nam".find(|&: c: char| c == '华'), Some(30u));
    }

    #[test]
    fn test_rfind() {
        assert_eq!("hello".rfind('l'), Some(3u));
        assert_eq!("hello".rfind(|&: c:char| c == 'o'), Some(4u));
        assert!("hello".rfind('x').is_none());
        assert!("hello".rfind(|&: c:char| c == 'x').is_none());
        assert_eq!("ประเทศไทย中华Việt Nam".rfind('华'), Some(30u));
        assert_eq!("ประเทศไทย中华Việt Nam".rfind(|&: c: char| c == '华'), Some(30u));
    }

    #[test]
    fn test_collect() {
        let empty = String::from_str("");
        let s: String = empty.chars().collect();
        assert_eq!(empty, s);
        let data = String::from_str("ประเทศไทย中");
        let s: String = data.chars().collect();
        assert_eq!(data, s);
    }

    #[test]
    fn test_into_bytes() {
        let data = String::from_str("asdf");
        let buf = data.into_bytes();
        assert_eq!(b"asdf", buf);
    }

    #[test]
    fn test_find_str() {
        // byte positions
        assert_eq!("".find_str(""), Some(0u));
        assert!("banana".find_str("apple pie").is_none());

        let data = "abcabc";
        assert_eq!(data.slice(0u, 6u).find_str("ab"), Some(0u));
        assert_eq!(data.slice(2u, 6u).find_str("ab"), Some(3u - 2u));
        assert!(data.slice(2u, 4u).find_str("ab").is_none());

        let string = "ประเทศไทย中华Việt Nam";
        let mut data = String::from_str(string);
        data.push_str(string);
        assert!(data.find_str("ไท华").is_none());
        assert_eq!(data.slice(0u, 43u).find_str(""), Some(0u));
        assert_eq!(data.slice(6u, 43u).find_str(""), Some(6u - 6u));

        assert_eq!(data.slice(0u, 43u).find_str("ประ"), Some( 0u));
        assert_eq!(data.slice(0u, 43u).find_str("ทศไ"), Some(12u));
        assert_eq!(data.slice(0u, 43u).find_str("ย中"), Some(24u));
        assert_eq!(data.slice(0u, 43u).find_str("iệt"), Some(34u));
        assert_eq!(data.slice(0u, 43u).find_str("Nam"), Some(40u));

        assert_eq!(data.slice(43u, 86u).find_str("ประ"), Some(43u - 43u));
        assert_eq!(data.slice(43u, 86u).find_str("ทศไ"), Some(55u - 43u));
        assert_eq!(data.slice(43u, 86u).find_str("ย中"), Some(67u - 43u));
        assert_eq!(data.slice(43u, 86u).find_str("iệt"), Some(77u - 43u));
        assert_eq!(data.slice(43u, 86u).find_str("Nam"), Some(83u - 43u));
    }

    #[test]
    fn test_slice_chars() {
        fn t(a: &str, b: &str, start: uint) {
            assert_eq!(a.slice_chars(start, start + b.char_len()), b);
        }
        t("", "", 0);
        t("hello", "llo", 2);
        t("hello", "el", 1);
        t("αβλ", "β", 1);
        t("αβλ", "", 3);
        assert_eq!("ะเทศไท", "ประเทศไทย中华Việt Nam".slice_chars(2, 8));
    }

    struct S {
        x: [String, .. 2]
    }

    impl AsSlice<String> for S {
        fn as_slice<'a> (&'a self) -> &'a [String] {
            &self.x
        }
    }

    fn s(x: &str) -> String { x.into_string() }

    macro_rules! test_concat {
        ($expected: expr, $string: expr) => {
            {
                let s = $string.concat();
                assert_eq!($expected, s);
            }
        }
    }

    #[test]
    fn test_concat_for_different_types() {
        test_concat!("ab", ["a", "b"]);
        test_concat!("ab", [s("a"), s("b")]);
        test_concat!("ab", vec!["a", "b"]);
        test_concat!("ab", vec!["a", "b"].as_slice());
        test_concat!("ab", vec![s("a"), s("b")]);

        let mut v0 = ["a", "b"];
        let mut v1 = [s("a"), s("b")];
        unsafe {
            use std::c_vec::CVec;

            test_concat!("ab", CVec::new(v0.as_mut_ptr(), v0.len()));
            test_concat!("ab", CVec::new(v1.as_mut_ptr(), v1.len()));
        }

        test_concat!("ab", S { x: [s("a"), s("b")] });
    }

    #[test]
    fn test_concat_for_different_lengths() {
        let empty: &[&str] = &[];
        test_concat!("", empty);
        test_concat!("a", ["a"]);
        test_concat!("ab", ["a", "b"]);
        test_concat!("abc", ["", "a", "bc"]);
    }

    macro_rules! test_connect {
        ($expected: expr, $string: expr, $delim: expr) => {
            {
                let s = $string.connect($delim);
                assert_eq!($expected, s);
            }
        }
    }

    #[test]
    fn test_connect_for_different_types() {
        test_connect!("a-b", ["a", "b"], "-");
        let hyphen = "-".into_string();
        test_connect!("a-b", [s("a"), s("b")], hyphen.as_slice());
        test_connect!("a-b", vec!["a", "b"], hyphen.as_slice());
        test_connect!("a-b", vec!["a", "b"].as_slice(), "-");
        test_connect!("a-b", vec![s("a"), s("b")], "-");

        let mut v0 = ["a", "b"];
        let mut v1 = [s("a"), s("b")];
        unsafe {
            use std::c_vec::CVec;

            test_connect!("a-b", CVec::new(v0.as_mut_ptr(), v0.len()), "-");
            test_connect!("a-b", CVec::new(v1.as_mut_ptr(), v1.len()), hyphen.as_slice());
        }

        test_connect!("a-b", S { x: [s("a"), s("b")] }, "-");
    }

    #[test]
    fn test_connect_for_different_lengths() {
        let empty: &[&str] = &[];
        test_connect!("", empty, "-");
        test_connect!("a", ["a"], "-");
        test_connect!("a-b", ["a", "b"], "-");
        test_connect!("-a-bc", ["", "a", "bc"], "-");
    }

    #[test]
    fn test_repeat() {
        assert_eq!("x".repeat(4), String::from_str("xxxx"));
        assert_eq!("hi".repeat(4), String::from_str("hihihihi"));
        assert_eq!("ไท华".repeat(3), String::from_str("ไท华ไท华ไท华"));
        assert_eq!("".repeat(4), String::from_str(""));
        assert_eq!("hi".repeat(0), String::from_str(""));
    }

    #[test]
    fn test_unsafe_slice() {
        assert_eq!("ab", unsafe {raw::slice_bytes("abc", 0, 2)});
        assert_eq!("bc", unsafe {raw::slice_bytes("abc", 1, 3)});
        assert_eq!("", unsafe {raw::slice_bytes("abc", 1, 1)});
        fn a_million_letter_a() -> String {
            let mut i = 0u;
            let mut rs = String::new();
            while i < 100000 {
                rs.push_str("aaaaaaaaaa");
                i += 1;
            }
            rs
        }
        fn half_a_million_letter_a() -> String {
            let mut i = 0u;
            let mut rs = String::new();
            while i < 100000 {
                rs.push_str("aaaaa");
                i += 1;
            }
            rs
        }
        let letters = a_million_letter_a();
        assert!(half_a_million_letter_a() ==
            unsafe {String::from_str(raw::slice_bytes(letters.as_slice(),
                                     0u,
                                     500000))});
    }

    #[test]
    fn test_starts_with() {
        assert!(("".starts_with("")));
        assert!(("abc".starts_with("")));
        assert!(("abc".starts_with("a")));
        assert!((!"a".starts_with("abc")));
        assert!((!"".starts_with("abc")));
        assert!((!"ödd".starts_with("-")));
        assert!(("ödd".starts_with("öd")));
    }

    #[test]
    fn test_ends_with() {
        assert!(("".ends_with("")));
        assert!(("abc".ends_with("")));
        assert!(("abc".ends_with("c")));
        assert!((!"a".ends_with("abc")));
        assert!((!"".ends_with("abc")));
        assert!((!"ddö".ends_with("-")));
        assert!(("ddö".ends_with("dö")));
    }

    #[test]
    fn test_is_empty() {
        assert!("".is_empty());
        assert!(!"a".is_empty());
    }

    #[test]
    fn test_replace() {
        let a = "a";
        assert_eq!("".replace(a, "b"), String::from_str(""));
        assert_eq!("a".replace(a, "b"), String::from_str("b"));
        assert_eq!("ab".replace(a, "b"), String::from_str("bb"));
        let test = "test";
        assert!(" test test ".replace(test, "toast") ==
            String::from_str(" toast toast "));
        assert_eq!(" test test ".replace(test, ""), String::from_str("   "));
    }

    #[test]
    fn test_replace_2a() {
        let data = "ประเทศไทย中华";
        let repl = "دولة الكويت";

        let a = "ประเ";
        let a2 = "دولة الكويتทศไทย中华";
        assert_eq!(data.replace(a, repl), a2);
    }

    #[test]
    fn test_replace_2b() {
        let data = "ประเทศไทย中华";
        let repl = "دولة الكويت";

        let b = "ะเ";
        let b2 = "ปรدولة الكويتทศไทย中华";
        assert_eq!(data.replace(b, repl), b2);
    }

    #[test]
    fn test_replace_2c() {
        let data = "ประเทศไทย中华";
        let repl = "دولة الكويت";

        let c = "中华";
        let c2 = "ประเทศไทยدولة الكويت";
        assert_eq!(data.replace(c, repl), c2);
    }

    #[test]
    fn test_replace_2d() {
        let data = "ประเทศไทย中华";
        let repl = "دولة الكويت";

        let d = "ไท华";
        assert_eq!(data.replace(d, repl), data);
    }

    #[test]
    fn test_slice() {
        assert_eq!("ab", "abc".slice(0, 2));
        assert_eq!("bc", "abc".slice(1, 3));
        assert_eq!("", "abc".slice(1, 1));
        assert_eq!("\u{65e5}", "\u{65e5}\u{672c}".slice(0, 3));

        let data = "ประเทศไทย中华";
        assert_eq!("ป", data.slice(0, 3));
        assert_eq!("ร", data.slice(3, 6));
        assert_eq!("", data.slice(3, 3));
        assert_eq!("华", data.slice(30, 33));

        fn a_million_letter_x() -> String {
            let mut i = 0u;
            let mut rs = String::new();
            while i < 100000 {
                rs.push_str("华华华华华华华华华华");
                i += 1;
            }
            rs
        }
        fn half_a_million_letter_x() -> String {
            let mut i = 0u;
            let mut rs = String::new();
            while i < 100000 {
                rs.push_str("华华华华华");
                i += 1;
            }
            rs
        }
        let letters = a_million_letter_x();
        assert!(half_a_million_letter_x() ==
            String::from_str(letters.slice(0u, 3u * 500000u)));
    }

    #[test]
    fn test_slice_2() {
        let ss = "中华Việt Nam";

        assert_eq!("华", ss.slice(3u, 6u));
        assert_eq!("Việt Nam", ss.slice(6u, 16u));

        assert_eq!("ab", "abc".slice(0u, 2u));
        assert_eq!("bc", "abc".slice(1u, 3u));
        assert_eq!("", "abc".slice(1u, 1u));

        assert_eq!("中", ss.slice(0u, 3u));
        assert_eq!("华V", ss.slice(3u, 7u));
        assert_eq!("", ss.slice(3u, 3u));
        /*0: 中
          3: 华
          6: V
          7: i
          8: ệ
         11: t
         12:
         13: N
         14: a
         15: m */
    }

    #[test]
    #[should_fail]
    fn test_slice_fail() {
        "中华Việt Nam".slice(0u, 2u);
    }

    #[test]
    fn test_slice_from() {
        assert_eq!("abcd".slice_from(0), "abcd");
        assert_eq!("abcd".slice_from(2), "cd");
        assert_eq!("abcd".slice_from(4), "");
    }
    #[test]
    fn test_slice_to() {
        assert_eq!("abcd".slice_to(0), "");
        assert_eq!("abcd".slice_to(2), "ab");
        assert_eq!("abcd".slice_to(4), "abcd");
    }

    #[test]
    fn test_trim_left_chars() {
        let v: &[char] = &[];
        assert_eq!(" *** foo *** ".trim_left_chars(v), " *** foo *** ");
        let chars: &[char] = &['*', ' '];
        assert_eq!(" *** foo *** ".trim_left_chars(chars), "foo *** ");
        assert_eq!(" ***  *** ".trim_left_chars(chars), "");
        assert_eq!("foo *** ".trim_left_chars(chars), "foo *** ");

        assert_eq!("11foo1bar11".trim_left_chars('1'), "foo1bar11");
        let chars: &[char] = &['1', '2'];
        assert_eq!("12foo1bar12".trim_left_chars(chars), "foo1bar12");
        assert_eq!("123foo1bar123".trim_left_chars(|&: c: char| c.is_numeric()), "foo1bar123");
    }

    #[test]
    fn test_trim_right_chars() {
        let v: &[char] = &[];
        assert_eq!(" *** foo *** ".trim_right_chars(v), " *** foo *** ");
        let chars: &[char] = &['*', ' '];
        assert_eq!(" *** foo *** ".trim_right_chars(chars), " *** foo");
        assert_eq!(" ***  *** ".trim_right_chars(chars), "");
        assert_eq!(" *** foo".trim_right_chars(chars), " *** foo");

        assert_eq!("11foo1bar11".trim_right_chars('1'), "11foo1bar");
        let chars: &[char] = &['1', '2'];
        assert_eq!("12foo1bar12".trim_right_chars(chars), "12foo1bar");
        assert_eq!("123foo1bar123".trim_right_chars(|&: c: char| c.is_numeric()), "123foo1bar");
    }

    #[test]
    fn test_trim_chars() {
        let v: &[char] = &[];
        assert_eq!(" *** foo *** ".trim_chars(v), " *** foo *** ");
        let chars: &[char] = &['*', ' '];
        assert_eq!(" *** foo *** ".trim_chars(chars), "foo");
        assert_eq!(" ***  *** ".trim_chars(chars), "");
        assert_eq!("foo".trim_chars(chars), "foo");

        assert_eq!("11foo1bar11".trim_chars('1'), "foo1bar");
        let chars: &[char] = &['1', '2'];
        assert_eq!("12foo1bar12".trim_chars(chars), "foo1bar");
        assert_eq!("123foo1bar123".trim_chars(|&: c: char| c.is_numeric()), "foo1bar");
    }

    #[test]
    fn test_trim_left() {
        assert_eq!("".trim_left(), "");
        assert_eq!("a".trim_left(), "a");
        assert_eq!("    ".trim_left(), "");
        assert_eq!("     blah".trim_left(), "blah");
        assert_eq!("   \u{3000}  wut".trim_left(), "wut");
        assert_eq!("hey ".trim_left(), "hey ");
    }

    #[test]
    fn test_trim_right() {
        assert_eq!("".trim_right(), "");
        assert_eq!("a".trim_right(), "a");
        assert_eq!("    ".trim_right(), "");
        assert_eq!("blah     ".trim_right(), "blah");
        assert_eq!("wut   \u{3000}  ".trim_right(), "wut");
        assert_eq!(" hey".trim_right(), " hey");
    }

    #[test]
    fn test_trim() {
        assert_eq!("".trim(), "");
        assert_eq!("a".trim(), "a");
        assert_eq!("    ".trim(), "");
        assert_eq!("    blah     ".trim(), "blah");
        assert_eq!("\nwut   \u{3000}  ".trim(), "wut");
        assert_eq!(" hey dude ".trim(), "hey dude");
    }

    #[test]
    fn test_is_whitespace() {
        assert!("".is_whitespace());
        assert!(" ".is_whitespace());
        assert!("\u{2009}".is_whitespace()); // Thin space
        assert!("  \n\t   ".is_whitespace());
        assert!(!"   _   ".is_whitespace());
    }

    #[test]
    fn test_slice_shift_char() {
        let data = "ประเทศไทย中";
        assert_eq!(data.slice_shift_char(), Some(('ป', "ระเทศไทย中")));
    }

    #[test]
    fn test_slice_shift_char_2() {
        let empty = "";
        assert_eq!(empty.slice_shift_char(), None);
    }

    #[test]
    fn test_is_utf8() {
        // deny overlong encodings
        assert!(!is_utf8(&[0xc0, 0x80]));
        assert!(!is_utf8(&[0xc0, 0xae]));
        assert!(!is_utf8(&[0xe0, 0x80, 0x80]));
        assert!(!is_utf8(&[0xe0, 0x80, 0xaf]));
        assert!(!is_utf8(&[0xe0, 0x81, 0x81]));
        assert!(!is_utf8(&[0xf0, 0x82, 0x82, 0xac]));
        assert!(!is_utf8(&[0xf4, 0x90, 0x80, 0x80]));

        // deny surrogates
        assert!(!is_utf8(&[0xED, 0xA0, 0x80]));
        assert!(!is_utf8(&[0xED, 0xBF, 0xBF]));

        assert!(is_utf8(&[0xC2, 0x80]));
        assert!(is_utf8(&[0xDF, 0xBF]));
        assert!(is_utf8(&[0xE0, 0xA0, 0x80]));
        assert!(is_utf8(&[0xED, 0x9F, 0xBF]));
        assert!(is_utf8(&[0xEE, 0x80, 0x80]));
        assert!(is_utf8(&[0xEF, 0xBF, 0xBF]));
        assert!(is_utf8(&[0xF0, 0x90, 0x80, 0x80]));
        assert!(is_utf8(&[0xF4, 0x8F, 0xBF, 0xBF]));
    }

    #[test]
    fn test_is_utf16() {
        macro_rules! pos ( ($($e:expr),*) => { { $(assert!(is_utf16($e));)* } });

        // non-surrogates
        pos!(&[0x0000],
             &[0x0001, 0x0002],
             &[0xD7FF],
             &[0xE000]);

        // surrogate pairs (randomly generated with Python 3's
        // .encode('utf-16be'))
        pos!(&[0xdb54, 0xdf16, 0xd880, 0xdee0, 0xdb6a, 0xdd45],
             &[0xd91f, 0xdeb1, 0xdb31, 0xdd84, 0xd8e2, 0xde14],
             &[0xdb9f, 0xdc26, 0xdb6f, 0xde58, 0xd850, 0xdfae]);

        // mixtures (also random)
        pos!(&[0xd921, 0xdcc2, 0x002d, 0x004d, 0xdb32, 0xdf65],
             &[0xdb45, 0xdd2d, 0x006a, 0xdacd, 0xddfe, 0x0006],
             &[0x0067, 0xd8ff, 0xddb7, 0x000f, 0xd900, 0xdc80]);

        // negative tests
        macro_rules! neg ( ($($e:expr),*) => { { $(assert!(!is_utf16($e));)* } });

        neg!(
            // surrogate + regular unit
            &[0xdb45, 0x0000],
            // surrogate + lead surrogate
            &[0xd900, 0xd900],
            // unterminated surrogate
            &[0xd8ff],
            // trail surrogate without a lead
            &[0xddb7]);

        // random byte sequences that Python 3's .decode('utf-16be')
        // failed on
        neg!(&[0x5b3d, 0x0141, 0xde9e, 0x8fdc, 0xc6e7],
             &[0xdf5a, 0x82a5, 0x62b9, 0xb447, 0x92f3],
             &[0xda4e, 0x42bc, 0x4462, 0xee98, 0xc2ca],
             &[0xbe00, 0xb04a, 0x6ecb, 0xdd89, 0xe278],
             &[0x0465, 0xab56, 0xdbb6, 0xa893, 0x665e],
             &[0x6b7f, 0x0a19, 0x40f4, 0xa657, 0xdcc5],
             &[0x9b50, 0xda5e, 0x24ec, 0x03ad, 0x6dee],
             &[0x8d17, 0xcaa7, 0xf4ae, 0xdf6e, 0xbed7],
             &[0xdaee, 0x2584, 0x7d30, 0xa626, 0x121a],
             &[0xd956, 0x4b43, 0x7570, 0xccd6, 0x4f4a],
             &[0x9dcf, 0x1b49, 0x4ba5, 0xfce9, 0xdffe],
             &[0x6572, 0xce53, 0xb05a, 0xf6af, 0xdacf],
             &[0x1b90, 0x728c, 0x9906, 0xdb68, 0xf46e],
             &[0x1606, 0xbeca, 0xbe76, 0x860f, 0xdfa5],
             &[0x8b4f, 0xde7a, 0xd220, 0x9fac, 0x2b6f],
             &[0xb8fe, 0xebbe, 0xda32, 0x1a5f, 0x8b8b],
             &[0x934b, 0x8956, 0xc434, 0x1881, 0xddf7],
             &[0x5a95, 0x13fc, 0xf116, 0xd89b, 0x93f9],
             &[0xd640, 0x71f1, 0xdd7d, 0x77eb, 0x1cd8],
             &[0x348b, 0xaef0, 0xdb2c, 0xebf1, 0x1282],
             &[0x50d7, 0xd824, 0x5010, 0xb369, 0x22ea]);
    }

    #[test]
    fn test_as_bytes() {
        // no null
        let v = [
            224, 184, 168, 224, 185, 132, 224, 184, 151, 224, 184, 162, 228,
            184, 173, 229, 141, 142, 86, 105, 225, 187, 135, 116, 32, 78, 97,
            109
        ];
        let b: &[u8] = &[];
        assert_eq!("".as_bytes(), b);
        assert_eq!("abc".as_bytes(), b"abc");
        assert_eq!("ศไทย中华Việt Nam".as_bytes(), v);
    }

    #[test]
    #[should_fail]
    fn test_as_bytes_fail() {
        // Don't double free. (I'm not sure if this exercises the
        // original problem code path anymore.)
        let s = String::from_str("");
        let _bytes = s.as_bytes();
        panic!();
    }

    #[test]
    fn test_as_ptr() {
        let buf = "hello".as_ptr();
        unsafe {
            assert_eq!(*buf.offset(0), b'h');
            assert_eq!(*buf.offset(1), b'e');
            assert_eq!(*buf.offset(2), b'l');
            assert_eq!(*buf.offset(3), b'l');
            assert_eq!(*buf.offset(4), b'o');
        }
    }

    #[test]
    fn test_subslice_offset() {
        let a = "kernelsprite";
        let b = a.slice(7, a.len());
        let c = a.slice(0, a.len() - 6);
        assert_eq!(a.subslice_offset(b), 7);
        assert_eq!(a.subslice_offset(c), 0);

        let string = "a\nb\nc";
        let lines: Vec<&str> = string.lines().collect();
        assert_eq!(string.subslice_offset(lines[0]), 0);
        assert_eq!(string.subslice_offset(lines[1]), 2);
        assert_eq!(string.subslice_offset(lines[2]), 4);
    }

    #[test]
    #[should_fail]
    fn test_subslice_offset_2() {
        let a = "alchemiter";
        let b = "cruxtruder";
        a.subslice_offset(b);
    }

    #[test]
    fn vec_str_conversions() {
        let s1: String = String::from_str("All mimsy were the borogoves");

        let v: Vec<u8> = s1.as_bytes().to_vec();
        let s2: String = String::from_str(from_utf8(v.as_slice()).unwrap());
        let mut i: uint = 0u;
        let n1: uint = s1.len();
        let n2: uint = v.len();
        assert_eq!(n1, n2);
        while i < n1 {
            let a: u8 = s1.as_bytes()[i];
            let b: u8 = s2.as_bytes()[i];
            debug!("{}", a);
            debug!("{}", b);
            assert_eq!(a, b);
            i += 1u;
        }
    }

    #[test]
    fn test_contains() {
        assert!("abcde".contains("bcd"));
        assert!("abcde".contains("abcd"));
        assert!("abcde".contains("bcde"));
        assert!("abcde".contains(""));
        assert!("".contains(""));
        assert!(!"abcde".contains("def"));
        assert!(!"".contains("a"));

        let data = "ประเทศไทย中华Việt Nam";
        assert!(data.contains("ประเ"));
        assert!(data.contains("ะเ"));
        assert!(data.contains("中华"));
        assert!(!data.contains("ไท华"));
    }

    #[test]
    fn test_contains_char() {
        assert!("abc".contains_char('b'));
        assert!("a".contains_char('a'));
        assert!(!"abc".contains_char('d'));
        assert!(!"".contains_char('a'));
    }

    #[test]
    fn test_truncate_utf16_at_nul() {
        let v = [];
        let b: &[u16] = &[];
        assert_eq!(truncate_utf16_at_nul(&v), b);

        let v = [0, 2, 3];
        assert_eq!(truncate_utf16_at_nul(&v), b);

        let v = [1, 0, 3];
        let b: &[u16] = &[1];
        assert_eq!(truncate_utf16_at_nul(&v), b);

        let v = [1, 2, 0];
        let b: &[u16] = &[1, 2];
        assert_eq!(truncate_utf16_at_nul(&v), b);

        let v = [1, 2, 3];
        let b: &[u16] = &[1, 2, 3];
        assert_eq!(truncate_utf16_at_nul(&v), b);
    }

    #[test]
    fn test_char_at() {
        let s = "ศไทย中华Việt Nam";
        let v = vec!['ศ','ไ','ท','ย','中','华','V','i','ệ','t',' ','N','a','m'];
        let mut pos = 0;
        for ch in v.iter() {
            assert!(s.char_at(pos) == *ch);
            pos += String::from_char(1, *ch).len();
        }
    }

    #[test]
    fn test_char_at_reverse() {
        let s = "ศไทย中华Việt Nam";
        let v = vec!['ศ','ไ','ท','ย','中','华','V','i','ệ','t',' ','N','a','m'];
        let mut pos = s.len();
        for ch in v.iter().rev() {
            assert!(s.char_at_reverse(pos) == *ch);
            pos -= String::from_char(1, *ch).len();
        }
    }

    #[test]
    fn test_escape_unicode() {
        assert_eq!("abc".escape_unicode(),
                   String::from_str("\\u{61}\\u{62}\\u{63}"));
        assert_eq!("a c".escape_unicode(),
                   String::from_str("\\u{61}\\u{20}\\u{63}"));
        assert_eq!("\r\n\t".escape_unicode(),
                   String::from_str("\\u{d}\\u{a}\\u{9}"));
        assert_eq!("'\"\\".escape_unicode(),
                   String::from_str("\\u{27}\\u{22}\\u{5c}"));
        assert_eq!("\x00\x01\u{fe}\u{ff}".escape_unicode(),
                   String::from_str("\\u{0}\\u{1}\\u{fe}\\u{ff}"));
        assert_eq!("\u{100}\u{ffff}".escape_unicode(),
                   String::from_str("\\u{100}\\u{ffff}"));
        assert_eq!("\u{10000}\u{10ffff}".escape_unicode(),
                   String::from_str("\\u{10000}\\u{10ffff}"));
        assert_eq!("ab\u{fb00}".escape_unicode(),
                   String::from_str("\\u{61}\\u{62}\\u{fb00}"));
        assert_eq!("\u{1d4ea}\r".escape_unicode(),
                   String::from_str("\\u{1d4ea}\\u{d}"));
    }

    #[test]
    fn test_escape_default() {
        assert_eq!("abc".escape_default(), String::from_str("abc"));
        assert_eq!("a c".escape_default(), String::from_str("a c"));
        assert_eq!("\r\n\t".escape_default(), String::from_str("\\r\\n\\t"));
        assert_eq!("'\"\\".escape_default(), String::from_str("\\'\\\"\\\\"));
        assert_eq!("\u{100}\u{ffff}".escape_default(),
                   String::from_str("\\u{100}\\u{ffff}"));
        assert_eq!("\u{10000}\u{10ffff}".escape_default(),
                   String::from_str("\\u{10000}\\u{10ffff}"));
        assert_eq!("ab\u{fb00}".escape_default(),
                   String::from_str("ab\\u{fb00}"));
        assert_eq!("\u{1d4ea}\r".escape_default(),
                   String::from_str("\\u{1d4ea}\\r"));
    }

    #[test]
    fn test_total_ord() {
        "1234".cmp("123") == Greater;
        "123".cmp("1234") == Less;
        "1234".cmp("1234") == Equal;
        "12345555".cmp("123456") == Less;
        "22".cmp("1234") == Greater;
    }

    #[test]
    fn test_char_range_at() {
        let data = "b¢€𤭢𤭢€¢b";
        assert_eq!('b', data.char_range_at(0).ch);
        assert_eq!('¢', data.char_range_at(1).ch);
        assert_eq!('€', data.char_range_at(3).ch);
        assert_eq!('𤭢', data.char_range_at(6).ch);
        assert_eq!('𤭢', data.char_range_at(10).ch);
        assert_eq!('€', data.char_range_at(14).ch);
        assert_eq!('¢', data.char_range_at(17).ch);
        assert_eq!('b', data.char_range_at(19).ch);
    }

    #[test]
    fn test_char_range_at_reverse_underflow() {
        assert_eq!("abc".char_range_at_reverse(0).next, 0);
    }

    #[test]
    fn test_iterator() {
        let s = "ศไทย中华Việt Nam";
        let v = ['ศ','ไ','ท','ย','中','华','V','i','ệ','t',' ','N','a','m'];

        let mut pos = 0;
        let mut it = s.chars();

        for c in it {
            assert_eq!(c, v[pos]);
            pos += 1;
        }
        assert_eq!(pos, v.len());
    }

    #[test]
    fn test_rev_iterator() {
        let s = "ศไทย中华Việt Nam";
        let v = ['m', 'a', 'N', ' ', 't', 'ệ','i','V','华','中','ย','ท','ไ','ศ'];

        let mut pos = 0;
        let mut it = s.chars().rev();

        for c in it {
            assert_eq!(c, v[pos]);
            pos += 1;
        }
        assert_eq!(pos, v.len());
    }

    #[test]
    fn test_chars_decoding() {
        let mut bytes = [0u8, ..4];
        for c in range(0u32, 0x110000).filter_map(|c| ::core::char::from_u32(c)) {
            let len = c.encode_utf8(&mut bytes).unwrap_or(0);
            let s = ::core::str::from_utf8(bytes[..len]).unwrap();
            if Some(c) != s.chars().next() {
                panic!("character {:x}={} does not decode correctly", c as u32, c);
            }
        }
    }

    #[test]
    fn test_chars_rev_decoding() {
        let mut bytes = [0u8, ..4];
        for c in range(0u32, 0x110000).filter_map(|c| ::core::char::from_u32(c)) {
            let len = c.encode_utf8(&mut bytes).unwrap_or(0);
            let s = ::core::str::from_utf8(bytes[..len]).unwrap();
            if Some(c) != s.chars().rev().next() {
                panic!("character {:x}={} does not decode correctly", c as u32, c);
            }
        }
    }

    #[test]
    fn test_iterator_clone() {
        let s = "ศไทย中华Việt Nam";
        let mut it = s.chars();
        it.next();
        assert!(it.zip(it.clone()).all(|(x,y)| x == y));
    }

    #[test]
    fn test_bytesator() {
        let s = "ศไทย中华Việt Nam";
        let v = [
            224, 184, 168, 224, 185, 132, 224, 184, 151, 224, 184, 162, 228,
            184, 173, 229, 141, 142, 86, 105, 225, 187, 135, 116, 32, 78, 97,
            109
        ];
        let mut pos = 0;

        for b in s.bytes() {
            assert_eq!(b, v[pos]);
            pos += 1;
        }
    }

    #[test]
    fn test_bytes_revator() {
        let s = "ศไทย中华Việt Nam";
        let v = [
            224, 184, 168, 224, 185, 132, 224, 184, 151, 224, 184, 162, 228,
            184, 173, 229, 141, 142, 86, 105, 225, 187, 135, 116, 32, 78, 97,
            109
        ];
        let mut pos = v.len();

        for b in s.bytes().rev() {
            pos -= 1;
            assert_eq!(b, v[pos]);
        }
    }

    #[test]
    fn test_char_indicesator() {
        let s = "ศไทย中华Việt Nam";
        let p = [0, 3, 6, 9, 12, 15, 18, 19, 20, 23, 24, 25, 26, 27];
        let v = ['ศ','ไ','ท','ย','中','华','V','i','ệ','t',' ','N','a','m'];

        let mut pos = 0;
        let mut it = s.char_indices();

        for c in it {
            assert_eq!(c, (p[pos], v[pos]));
            pos += 1;
        }
        assert_eq!(pos, v.len());
        assert_eq!(pos, p.len());
    }

    #[test]
    fn test_char_indices_revator() {
        let s = "ศไทย中华Việt Nam";
        let p = [27, 26, 25, 24, 23, 20, 19, 18, 15, 12, 9, 6, 3, 0];
        let v = ['m', 'a', 'N', ' ', 't', 'ệ','i','V','华','中','ย','ท','ไ','ศ'];

        let mut pos = 0;
        let mut it = s.char_indices().rev();

        for c in it {
            assert_eq!(c, (p[pos], v[pos]));
            pos += 1;
        }
        assert_eq!(pos, v.len());
        assert_eq!(pos, p.len());
    }

    #[test]
    fn test_splitn_char_iterator() {
        let data = "\nMäry häd ä little lämb\nLittle lämb\n";

        let split: Vec<&str> = data.splitn(3, ' ').collect();
        assert_eq!(split, vec!["\nMäry", "häd", "ä", "little lämb\nLittle lämb\n"]);

        let split: Vec<&str> = data.splitn(3, |&: c: char| c == ' ').collect();
        assert_eq!(split, vec!["\nMäry", "häd", "ä", "little lämb\nLittle lämb\n"]);

        // Unicode
        let split: Vec<&str> = data.splitn(3, 'ä').collect();
        assert_eq!(split, vec!["\nM", "ry h", "d ", " little lämb\nLittle lämb\n"]);

        let split: Vec<&str> = data.splitn(3, |&: c: char| c == 'ä').collect();
        assert_eq!(split, vec!["\nM", "ry h", "d ", " little lämb\nLittle lämb\n"]);
    }

    #[test]
    fn test_split_char_iterator_no_trailing() {
        let data = "\nMäry häd ä little lämb\nLittle lämb\n";

        let split: Vec<&str> = data.split('\n').collect();
        assert_eq!(split, vec!["", "Märy häd ä little lämb", "Little lämb", ""]);

        let split: Vec<&str> = data.split_terminator('\n').collect();
        assert_eq!(split, vec!["", "Märy häd ä little lämb", "Little lämb"]);
    }

    #[test]
    fn test_words() {
        let data = "\n \tMäry   häd\tä  little lämb\nLittle lämb\n";
        let words: Vec<&str> = data.words().collect();
        assert_eq!(words, vec!["Märy", "häd", "ä", "little", "lämb", "Little", "lämb"])
    }

    #[test]
    fn test_lev_distance() {
        use core::char::{ from_u32, MAX };
        // Test bytelength agnosticity
        for c in range(0u32, MAX as u32)
                 .filter_map(|i| from_u32(i))
                 .map(|i| String::from_char(1, i)) {
            assert_eq!(c[].lev_distance(c[]), 0);
        }

        let a = "\nMäry häd ä little lämb\n\nLittle lämb\n";
        let b = "\nMary häd ä little lämb\n\nLittle lämb\n";
        let c = "Mary häd ä little lämb\n\nLittle lämb\n";
        assert_eq!(a.lev_distance(b), 1);
        assert_eq!(b.lev_distance(a), 1);
        assert_eq!(a.lev_distance(c), 2);
        assert_eq!(c.lev_distance(a), 2);
        assert_eq!(b.lev_distance(c), 1);
        assert_eq!(c.lev_distance(b), 1);
    }

    #[test]
    fn test_nfd_chars() {
        macro_rules! t {
            ($input: expr, $expected: expr) => {
                assert_eq!($input.nfd_chars().collect::<String>(), $expected);
            }
        }
        t!("abc", "abc");
        t!("\u{1e0b}\u{1c4}", "d\u{307}\u{1c4}");
        t!("\u{2026}", "\u{2026}");
        t!("\u{2126}", "\u{3a9}");
        t!("\u{1e0b}\u{323}", "d\u{323}\u{307}");
        t!("\u{1e0d}\u{307}", "d\u{323}\u{307}");
        t!("a\u{301}", "a\u{301}");
        t!("\u{301}a", "\u{301}a");
        t!("\u{d4db}", "\u{1111}\u{1171}\u{11b6}");
        t!("\u{ac1c}", "\u{1100}\u{1162}");
    }

    #[test]
    fn test_nfkd_chars() {
        macro_rules! t {
            ($input: expr, $expected: expr) => {
                assert_eq!($input.nfkd_chars().collect::<String>(), $expected);
            }
        }
        t!("abc", "abc");
        t!("\u{1e0b}\u{1c4}", "d\u{307}DZ\u{30c}");
        t!("\u{2026}", "...");
        t!("\u{2126}", "\u{3a9}");
        t!("\u{1e0b}\u{323}", "d\u{323}\u{307}");
        t!("\u{1e0d}\u{307}", "d\u{323}\u{307}");
        t!("a\u{301}", "a\u{301}");
        t!("\u{301}a", "\u{301}a");
        t!("\u{d4db}", "\u{1111}\u{1171}\u{11b6}");
        t!("\u{ac1c}", "\u{1100}\u{1162}");
    }

    #[test]
    fn test_nfc_chars() {
        macro_rules! t {
            ($input: expr, $expected: expr) => {
                assert_eq!($input.nfc_chars().collect::<String>(), $expected);
            }
        }
        t!("abc", "abc");
        t!("\u{1e0b}\u{1c4}", "\u{1e0b}\u{1c4}");
        t!("\u{2026}", "\u{2026}");
        t!("\u{2126}", "\u{3a9}");
        t!("\u{1e0b}\u{323}", "\u{1e0d}\u{307}");
        t!("\u{1e0d}\u{307}", "\u{1e0d}\u{307}");
        t!("a\u{301}", "\u{e1}");
        t!("\u{301}a", "\u{301}a");
        t!("\u{d4db}", "\u{d4db}");
        t!("\u{ac1c}", "\u{ac1c}");
        t!("a\u{300}\u{305}\u{315}\u{5ae}b", "\u{e0}\u{5ae}\u{305}\u{315}b");
    }

    #[test]
    fn test_nfkc_chars() {
        macro_rules! t {
            ($input: expr, $expected: expr) => {
                assert_eq!($input.nfkc_chars().collect::<String>(), $expected);
            }
        }
        t!("abc", "abc");
        t!("\u{1e0b}\u{1c4}", "\u{1e0b}D\u{17d}");
        t!("\u{2026}", "...");
        t!("\u{2126}", "\u{3a9}");
        t!("\u{1e0b}\u{323}", "\u{1e0d}\u{307}");
        t!("\u{1e0d}\u{307}", "\u{1e0d}\u{307}");
        t!("a\u{301}", "\u{e1}");
        t!("\u{301}a", "\u{301}a");
        t!("\u{d4db}", "\u{d4db}");
        t!("\u{ac1c}", "\u{ac1c}");
        t!("a\u{300}\u{305}\u{315}\u{5ae}b", "\u{e0}\u{5ae}\u{305}\u{315}b");
    }

    #[test]
    fn test_lines() {
        let data = "\nMäry häd ä little lämb\n\nLittle lämb\n";
        let lines: Vec<&str> = data.lines().collect();
        assert_eq!(lines, vec!["", "Märy häd ä little lämb", "", "Little lämb"]);

        let data = "\nMäry häd ä little lämb\n\nLittle lämb"; // no trailing \n
        let lines: Vec<&str> = data.lines().collect();
        assert_eq!(lines, vec!["", "Märy häd ä little lämb", "", "Little lämb"]);
    }

    #[test]
    fn test_graphemes() {
        use core::iter::order;
        // official Unicode test data
        // from http://www.unicode.org/Public/UCD/latest/ucd/auxiliary/GraphemeBreakTest.txt
        let test_same: [(_, &[_]), .. 325] = [
            ("\u{20}\u{20}", &["\u{20}", "\u{20}"]),
            ("\u{20}\u{308}\u{20}", &["\u{20}\u{308}", "\u{20}"]),
            ("\u{20}\u{D}", &["\u{20}", "\u{D}"]),
            ("\u{20}\u{308}\u{D}", &["\u{20}\u{308}", "\u{D}"]),
            ("\u{20}\u{A}", &["\u{20}", "\u{A}"]),
            ("\u{20}\u{308}\u{A}", &["\u{20}\u{308}", "\u{A}"]),
            ("\u{20}\u{1}", &["\u{20}", "\u{1}"]),
            ("\u{20}\u{308}\u{1}", &["\u{20}\u{308}", "\u{1}"]),
            ("\u{20}\u{300}", &["\u{20}\u{300}"]),
            ("\u{20}\u{308}\u{300}", &["\u{20}\u{308}\u{300}"]),
            ("\u{20}\u{1100}", &["\u{20}", "\u{1100}"]),
            ("\u{20}\u{308}\u{1100}", &["\u{20}\u{308}", "\u{1100}"]),
            ("\u{20}\u{1160}", &["\u{20}", "\u{1160}"]),
            ("\u{20}\u{308}\u{1160}", &["\u{20}\u{308}", "\u{1160}"]),
            ("\u{20}\u{11A8}", &["\u{20}", "\u{11A8}"]),
            ("\u{20}\u{308}\u{11A8}", &["\u{20}\u{308}", "\u{11A8}"]),
            ("\u{20}\u{AC00}", &["\u{20}", "\u{AC00}"]),
            ("\u{20}\u{308}\u{AC00}", &["\u{20}\u{308}", "\u{AC00}"]),
            ("\u{20}\u{AC01}", &["\u{20}", "\u{AC01}"]),
            ("\u{20}\u{308}\u{AC01}", &["\u{20}\u{308}", "\u{AC01}"]),
            ("\u{20}\u{1F1E6}", &["\u{20}", "\u{1F1E6}"]),
            ("\u{20}\u{308}\u{1F1E6}", &["\u{20}\u{308}", "\u{1F1E6}"]),
            ("\u{20}\u{378}", &["\u{20}", "\u{378}"]),
            ("\u{20}\u{308}\u{378}", &["\u{20}\u{308}", "\u{378}"]),
            ("\u{D}\u{20}", &["\u{D}", "\u{20}"]),
            ("\u{D}\u{308}\u{20}", &["\u{D}", "\u{308}", "\u{20}"]),
            ("\u{D}\u{D}", &["\u{D}", "\u{D}"]),
            ("\u{D}\u{308}\u{D}", &["\u{D}", "\u{308}", "\u{D}"]),
            ("\u{D}\u{A}", &["\u{D}\u{A}"]),
            ("\u{D}\u{308}\u{A}", &["\u{D}", "\u{308}", "\u{A}"]),
            ("\u{D}\u{1}", &["\u{D}", "\u{1}"]),
            ("\u{D}\u{308}\u{1}", &["\u{D}", "\u{308}", "\u{1}"]),
            ("\u{D}\u{300}", &["\u{D}", "\u{300}"]),
            ("\u{D}\u{308}\u{300}", &["\u{D}", "\u{308}\u{300}"]),
            ("\u{D}\u{903}", &["\u{D}", "\u{903}"]),
            ("\u{D}\u{1100}", &["\u{D}", "\u{1100}"]),
            ("\u{D}\u{308}\u{1100}", &["\u{D}", "\u{308}", "\u{1100}"]),
            ("\u{D}\u{1160}", &["\u{D}", "\u{1160}"]),
            ("\u{D}\u{308}\u{1160}", &["\u{D}", "\u{308}", "\u{1160}"]),
            ("\u{D}\u{11A8}", &["\u{D}", "\u{11A8}"]),
            ("\u{D}\u{308}\u{11A8}", &["\u{D}", "\u{308}", "\u{11A8}"]),
            ("\u{D}\u{AC00}", &["\u{D}", "\u{AC00}"]),
            ("\u{D}\u{308}\u{AC00}", &["\u{D}", "\u{308}", "\u{AC00}"]),
            ("\u{D}\u{AC01}", &["\u{D}", "\u{AC01}"]),
            ("\u{D}\u{308}\u{AC01}", &["\u{D}", "\u{308}", "\u{AC01}"]),
            ("\u{D}\u{1F1E6}", &["\u{D}", "\u{1F1E6}"]),
            ("\u{D}\u{308}\u{1F1E6}", &["\u{D}", "\u{308}", "\u{1F1E6}"]),
            ("\u{D}\u{378}", &["\u{D}", "\u{378}"]),
            ("\u{D}\u{308}\u{378}", &["\u{D}", "\u{308}", "\u{378}"]),
            ("\u{A}\u{20}", &["\u{A}", "\u{20}"]),
            ("\u{A}\u{308}\u{20}", &["\u{A}", "\u{308}", "\u{20}"]),
            ("\u{A}\u{D}", &["\u{A}", "\u{D}"]),
            ("\u{A}\u{308}\u{D}", &["\u{A}", "\u{308}", "\u{D}"]),
            ("\u{A}\u{A}", &["\u{A}", "\u{A}"]),
            ("\u{A}\u{308}\u{A}", &["\u{A}", "\u{308}", "\u{A}"]),
            ("\u{A}\u{1}", &["\u{A}", "\u{1}"]),
            ("\u{A}\u{308}\u{1}", &["\u{A}", "\u{308}", "\u{1}"]),
            ("\u{A}\u{300}", &["\u{A}", "\u{300}"]),
            ("\u{A}\u{308}\u{300}", &["\u{A}", "\u{308}\u{300}"]),
            ("\u{A}\u{903}", &["\u{A}", "\u{903}"]),
            ("\u{A}\u{1100}", &["\u{A}", "\u{1100}"]),
            ("\u{A}\u{308}\u{1100}", &["\u{A}", "\u{308}", "\u{1100}"]),
            ("\u{A}\u{1160}", &["\u{A}", "\u{1160}"]),
            ("\u{A}\u{308}\u{1160}", &["\u{A}", "\u{308}", "\u{1160}"]),
            ("\u{A}\u{11A8}", &["\u{A}", "\u{11A8}"]),
            ("\u{A}\u{308}\u{11A8}", &["\u{A}", "\u{308}", "\u{11A8}"]),
            ("\u{A}\u{AC00}", &["\u{A}", "\u{AC00}"]),
            ("\u{A}\u{308}\u{AC00}", &["\u{A}", "\u{308}", "\u{AC00}"]),
            ("\u{A}\u{AC01}", &["\u{A}", "\u{AC01}"]),
            ("\u{A}\u{308}\u{AC01}", &["\u{A}", "\u{308}", "\u{AC01}"]),
            ("\u{A}\u{1F1E6}", &["\u{A}", "\u{1F1E6}"]),
            ("\u{A}\u{308}\u{1F1E6}", &["\u{A}", "\u{308}", "\u{1F1E6}"]),
            ("\u{A}\u{378}", &["\u{A}", "\u{378}"]),
            ("\u{A}\u{308}\u{378}", &["\u{A}", "\u{308}", "\u{378}"]),
            ("\u{1}\u{20}", &["\u{1}", "\u{20}"]),
            ("\u{1}\u{308}\u{20}", &["\u{1}", "\u{308}", "\u{20}"]),
            ("\u{1}\u{D}", &["\u{1}", "\u{D}"]),
            ("\u{1}\u{308}\u{D}", &["\u{1}", "\u{308}", "\u{D}"]),
            ("\u{1}\u{A}", &["\u{1}", "\u{A}"]),
            ("\u{1}\u{308}\u{A}", &["\u{1}", "\u{308}", "\u{A}"]),
            ("\u{1}\u{1}", &["\u{1}", "\u{1}"]),
            ("\u{1}\u{308}\u{1}", &["\u{1}", "\u{308}", "\u{1}"]),
            ("\u{1}\u{300}", &["\u{1}", "\u{300}"]),
            ("\u{1}\u{308}\u{300}", &["\u{1}", "\u{308}\u{300}"]),
            ("\u{1}\u{903}", &["\u{1}", "\u{903}"]),
            ("\u{1}\u{1100}", &["\u{1}", "\u{1100}"]),
            ("\u{1}\u{308}\u{1100}", &["\u{1}", "\u{308}", "\u{1100}"]),
            ("\u{1}\u{1160}", &["\u{1}", "\u{1160}"]),
            ("\u{1}\u{308}\u{1160}", &["\u{1}", "\u{308}", "\u{1160}"]),
            ("\u{1}\u{11A8}", &["\u{1}", "\u{11A8}"]),
            ("\u{1}\u{308}\u{11A8}", &["\u{1}", "\u{308}", "\u{11A8}"]),
            ("\u{1}\u{AC00}", &["\u{1}", "\u{AC00}"]),
            ("\u{1}\u{308}\u{AC00}", &["\u{1}", "\u{308}", "\u{AC00}"]),
            ("\u{1}\u{AC01}", &["\u{1}", "\u{AC01}"]),
            ("\u{1}\u{308}\u{AC01}", &["\u{1}", "\u{308}", "\u{AC01}"]),
            ("\u{1}\u{1F1E6}", &["\u{1}", "\u{1F1E6}"]),
            ("\u{1}\u{308}\u{1F1E6}", &["\u{1}", "\u{308}", "\u{1F1E6}"]),
            ("\u{1}\u{378}", &["\u{1}", "\u{378}"]),
            ("\u{1}\u{308}\u{378}", &["\u{1}", "\u{308}", "\u{378}"]),
            ("\u{300}\u{20}", &["\u{300}", "\u{20}"]),
            ("\u{300}\u{308}\u{20}", &["\u{300}\u{308}", "\u{20}"]),
            ("\u{300}\u{D}", &["\u{300}", "\u{D}"]),
            ("\u{300}\u{308}\u{D}", &["\u{300}\u{308}", "\u{D}"]),
            ("\u{300}\u{A}", &["\u{300}", "\u{A}"]),
            ("\u{300}\u{308}\u{A}", &["\u{300}\u{308}", "\u{A}"]),
            ("\u{300}\u{1}", &["\u{300}", "\u{1}"]),
            ("\u{300}\u{308}\u{1}", &["\u{300}\u{308}", "\u{1}"]),
            ("\u{300}\u{300}", &["\u{300}\u{300}"]),
            ("\u{300}\u{308}\u{300}", &["\u{300}\u{308}\u{300}"]),
            ("\u{300}\u{1100}", &["\u{300}", "\u{1100}"]),
            ("\u{300}\u{308}\u{1100}", &["\u{300}\u{308}", "\u{1100}"]),
            ("\u{300}\u{1160}", &["\u{300}", "\u{1160}"]),
            ("\u{300}\u{308}\u{1160}", &["\u{300}\u{308}", "\u{1160}"]),
            ("\u{300}\u{11A8}", &["\u{300}", "\u{11A8}"]),
            ("\u{300}\u{308}\u{11A8}", &["\u{300}\u{308}", "\u{11A8}"]),
            ("\u{300}\u{AC00}", &["\u{300}", "\u{AC00}"]),
            ("\u{300}\u{308}\u{AC00}", &["\u{300}\u{308}", "\u{AC00}"]),
            ("\u{300}\u{AC01}", &["\u{300}", "\u{AC01}"]),
            ("\u{300}\u{308}\u{AC01}", &["\u{300}\u{308}", "\u{AC01}"]),
            ("\u{300}\u{1F1E6}", &["\u{300}", "\u{1F1E6}"]),
            ("\u{300}\u{308}\u{1F1E6}", &["\u{300}\u{308}", "\u{1F1E6}"]),
            ("\u{300}\u{378}", &["\u{300}", "\u{378}"]),
            ("\u{300}\u{308}\u{378}", &["\u{300}\u{308}", "\u{378}"]),
            ("\u{903}\u{20}", &["\u{903}", "\u{20}"]),
            ("\u{903}\u{308}\u{20}", &["\u{903}\u{308}", "\u{20}"]),
            ("\u{903}\u{D}", &["\u{903}", "\u{D}"]),
            ("\u{903}\u{308}\u{D}", &["\u{903}\u{308}", "\u{D}"]),
            ("\u{903}\u{A}", &["\u{903}", "\u{A}"]),
            ("\u{903}\u{308}\u{A}", &["\u{903}\u{308}", "\u{A}"]),
            ("\u{903}\u{1}", &["\u{903}", "\u{1}"]),
            ("\u{903}\u{308}\u{1}", &["\u{903}\u{308}", "\u{1}"]),
            ("\u{903}\u{300}", &["\u{903}\u{300}"]),
            ("\u{903}\u{308}\u{300}", &["\u{903}\u{308}\u{300}"]),
            ("\u{903}\u{1100}", &["\u{903}", "\u{1100}"]),
            ("\u{903}\u{308}\u{1100}", &["\u{903}\u{308}", "\u{1100}"]),
            ("\u{903}\u{1160}", &["\u{903}", "\u{1160}"]),
            ("\u{903}\u{308}\u{1160}", &["\u{903}\u{308}", "\u{1160}"]),
            ("\u{903}\u{11A8}", &["\u{903}", "\u{11A8}"]),
            ("\u{903}\u{308}\u{11A8}", &["\u{903}\u{308}", "\u{11A8}"]),
            ("\u{903}\u{AC00}", &["\u{903}", "\u{AC00}"]),
            ("\u{903}\u{308}\u{AC00}", &["\u{903}\u{308}", "\u{AC00}"]),
            ("\u{903}\u{AC01}", &["\u{903}", "\u{AC01}"]),
            ("\u{903}\u{308}\u{AC01}", &["\u{903}\u{308}", "\u{AC01}"]),
            ("\u{903}\u{1F1E6}", &["\u{903}", "\u{1F1E6}"]),
            ("\u{903}\u{308}\u{1F1E6}", &["\u{903}\u{308}", "\u{1F1E6}"]),
            ("\u{903}\u{378}", &["\u{903}", "\u{378}"]),
            ("\u{903}\u{308}\u{378}", &["\u{903}\u{308}", "\u{378}"]),
            ("\u{1100}\u{20}", &["\u{1100}", "\u{20}"]),
            ("\u{1100}\u{308}\u{20}", &["\u{1100}\u{308}", "\u{20}"]),
            ("\u{1100}\u{D}", &["\u{1100}", "\u{D}"]),
            ("\u{1100}\u{308}\u{D}", &["\u{1100}\u{308}", "\u{D}"]),
            ("\u{1100}\u{A}", &["\u{1100}", "\u{A}"]),
            ("\u{1100}\u{308}\u{A}", &["\u{1100}\u{308}", "\u{A}"]),
            ("\u{1100}\u{1}", &["\u{1100}", "\u{1}"]),
            ("\u{1100}\u{308}\u{1}", &["\u{1100}\u{308}", "\u{1}"]),
            ("\u{1100}\u{300}", &["\u{1100}\u{300}"]),
            ("\u{1100}\u{308}\u{300}", &["\u{1100}\u{308}\u{300}"]),
            ("\u{1100}\u{1100}", &["\u{1100}\u{1100}"]),
            ("\u{1100}\u{308}\u{1100}", &["\u{1100}\u{308}", "\u{1100}"]),
            ("\u{1100}\u{1160}", &["\u{1100}\u{1160}"]),
            ("\u{1100}\u{308}\u{1160}", &["\u{1100}\u{308}", "\u{1160}"]),
            ("\u{1100}\u{11A8}", &["\u{1100}", "\u{11A8}"]),
            ("\u{1100}\u{308}\u{11A8}", &["\u{1100}\u{308}", "\u{11A8}"]),
            ("\u{1100}\u{AC00}", &["\u{1100}\u{AC00}"]),
            ("\u{1100}\u{308}\u{AC00}", &["\u{1100}\u{308}", "\u{AC00}"]),
            ("\u{1100}\u{AC01}", &["\u{1100}\u{AC01}"]),
            ("\u{1100}\u{308}\u{AC01}", &["\u{1100}\u{308}", "\u{AC01}"]),
            ("\u{1100}\u{1F1E6}", &["\u{1100}", "\u{1F1E6}"]),
            ("\u{1100}\u{308}\u{1F1E6}", &["\u{1100}\u{308}", "\u{1F1E6}"]),
            ("\u{1100}\u{378}", &["\u{1100}", "\u{378}"]),
            ("\u{1100}\u{308}\u{378}", &["\u{1100}\u{308}", "\u{378}"]),
            ("\u{1160}\u{20}", &["\u{1160}", "\u{20}"]),
            ("\u{1160}\u{308}\u{20}", &["\u{1160}\u{308}", "\u{20}"]),
            ("\u{1160}\u{D}", &["\u{1160}", "\u{D}"]),
            ("\u{1160}\u{308}\u{D}", &["\u{1160}\u{308}", "\u{D}"]),
            ("\u{1160}\u{A}", &["\u{1160}", "\u{A}"]),
            ("\u{1160}\u{308}\u{A}", &["\u{1160}\u{308}", "\u{A}"]),
            ("\u{1160}\u{1}", &["\u{1160}", "\u{1}"]),
            ("\u{1160}\u{308}\u{1}", &["\u{1160}\u{308}", "\u{1}"]),
            ("\u{1160}\u{300}", &["\u{1160}\u{300}"]),
            ("\u{1160}\u{308}\u{300}", &["\u{1160}\u{308}\u{300}"]),
            ("\u{1160}\u{1100}", &["\u{1160}", "\u{1100}"]),
            ("\u{1160}\u{308}\u{1100}", &["\u{1160}\u{308}", "\u{1100}"]),
            ("\u{1160}\u{1160}", &["\u{1160}\u{1160}"]),
            ("\u{1160}\u{308}\u{1160}", &["\u{1160}\u{308}", "\u{1160}"]),
            ("\u{1160}\u{11A8}", &["\u{1160}\u{11A8}"]),
            ("\u{1160}\u{308}\u{11A8}", &["\u{1160}\u{308}", "\u{11A8}"]),
            ("\u{1160}\u{AC00}", &["\u{1160}", "\u{AC00}"]),
            ("\u{1160}\u{308}\u{AC00}", &["\u{1160}\u{308}", "\u{AC00}"]),
            ("\u{1160}\u{AC01}", &["\u{1160}", "\u{AC01}"]),
            ("\u{1160}\u{308}\u{AC01}", &["\u{1160}\u{308}", "\u{AC01}"]),
            ("\u{1160}\u{1F1E6}", &["\u{1160}", "\u{1F1E6}"]),
            ("\u{1160}\u{308}\u{1F1E6}", &["\u{1160}\u{308}", "\u{1F1E6}"]),
            ("\u{1160}\u{378}", &["\u{1160}", "\u{378}"]),
            ("\u{1160}\u{308}\u{378}", &["\u{1160}\u{308}", "\u{378}"]),
            ("\u{11A8}\u{20}", &["\u{11A8}", "\u{20}"]),
            ("\u{11A8}\u{308}\u{20}", &["\u{11A8}\u{308}", "\u{20}"]),
            ("\u{11A8}\u{D}", &["\u{11A8}", "\u{D}"]),
            ("\u{11A8}\u{308}\u{D}", &["\u{11A8}\u{308}", "\u{D}"]),
            ("\u{11A8}\u{A}", &["\u{11A8}", "\u{A}"]),
            ("\u{11A8}\u{308}\u{A}", &["\u{11A8}\u{308}", "\u{A}"]),
            ("\u{11A8}\u{1}", &["\u{11A8}", "\u{1}"]),
            ("\u{11A8}\u{308}\u{1}", &["\u{11A8}\u{308}", "\u{1}"]),
            ("\u{11A8}\u{300}", &["\u{11A8}\u{300}"]),
            ("\u{11A8}\u{308}\u{300}", &["\u{11A8}\u{308}\u{300}"]),
            ("\u{11A8}\u{1100}", &["\u{11A8}", "\u{1100}"]),
            ("\u{11A8}\u{308}\u{1100}", &["\u{11A8}\u{308}", "\u{1100}"]),
            ("\u{11A8}\u{1160}", &["\u{11A8}", "\u{1160}"]),
            ("\u{11A8}\u{308}\u{1160}", &["\u{11A8}\u{308}", "\u{1160}"]),
            ("\u{11A8}\u{11A8}", &["\u{11A8}\u{11A8}"]),
            ("\u{11A8}\u{308}\u{11A8}", &["\u{11A8}\u{308}", "\u{11A8}"]),
            ("\u{11A8}\u{AC00}", &["\u{11A8}", "\u{AC00}"]),
            ("\u{11A8}\u{308}\u{AC00}", &["\u{11A8}\u{308}", "\u{AC00}"]),
            ("\u{11A8}\u{AC01}", &["\u{11A8}", "\u{AC01}"]),
            ("\u{11A8}\u{308}\u{AC01}", &["\u{11A8}\u{308}", "\u{AC01}"]),
            ("\u{11A8}\u{1F1E6}", &["\u{11A8}", "\u{1F1E6}"]),
            ("\u{11A8}\u{308}\u{1F1E6}", &["\u{11A8}\u{308}", "\u{1F1E6}"]),
            ("\u{11A8}\u{378}", &["\u{11A8}", "\u{378}"]),
            ("\u{11A8}\u{308}\u{378}", &["\u{11A8}\u{308}", "\u{378}"]),
            ("\u{AC00}\u{20}", &["\u{AC00}", "\u{20}"]),
            ("\u{AC00}\u{308}\u{20}", &["\u{AC00}\u{308}", "\u{20}"]),
            ("\u{AC00}\u{D}", &["\u{AC00}", "\u{D}"]),
            ("\u{AC00}\u{308}\u{D}", &["\u{AC00}\u{308}", "\u{D}"]),
            ("\u{AC00}\u{A}", &["\u{AC00}", "\u{A}"]),
            ("\u{AC00}\u{308}\u{A}", &["\u{AC00}\u{308}", "\u{A}"]),
            ("\u{AC00}\u{1}", &["\u{AC00}", "\u{1}"]),
            ("\u{AC00}\u{308}\u{1}", &["\u{AC00}\u{308}", "\u{1}"]),
            ("\u{AC00}\u{300}", &["\u{AC00}\u{300}"]),
            ("\u{AC00}\u{308}\u{300}", &["\u{AC00}\u{308}\u{300}"]),
            ("\u{AC00}\u{1100}", &["\u{AC00}", "\u{1100}"]),
            ("\u{AC00}\u{308}\u{1100}", &["\u{AC00}\u{308}", "\u{1100}"]),
            ("\u{AC00}\u{1160}", &["\u{AC00}\u{1160}"]),
            ("\u{AC00}\u{308}\u{1160}", &["\u{AC00}\u{308}", "\u{1160}"]),
            ("\u{AC00}\u{11A8}", &["\u{AC00}\u{11A8}"]),
            ("\u{AC00}\u{308}\u{11A8}", &["\u{AC00}\u{308}", "\u{11A8}"]),
            ("\u{AC00}\u{AC00}", &["\u{AC00}", "\u{AC00}"]),
            ("\u{AC00}\u{308}\u{AC00}", &["\u{AC00}\u{308}", "\u{AC00}"]),
            ("\u{AC00}\u{AC01}", &["\u{AC00}", "\u{AC01}"]),
            ("\u{AC00}\u{308}\u{AC01}", &["\u{AC00}\u{308}", "\u{AC01}"]),
            ("\u{AC00}\u{1F1E6}", &["\u{AC00}", "\u{1F1E6}"]),
            ("\u{AC00}\u{308}\u{1F1E6}", &["\u{AC00}\u{308}", "\u{1F1E6}"]),
            ("\u{AC00}\u{378}", &["\u{AC00}", "\u{378}"]),
            ("\u{AC00}\u{308}\u{378}", &["\u{AC00}\u{308}", "\u{378}"]),
            ("\u{AC01}\u{20}", &["\u{AC01}", "\u{20}"]),
            ("\u{AC01}\u{308}\u{20}", &["\u{AC01}\u{308}", "\u{20}"]),
            ("\u{AC01}\u{D}", &["\u{AC01}", "\u{D}"]),
            ("\u{AC01}\u{308}\u{D}", &["\u{AC01}\u{308}", "\u{D}"]),
            ("\u{AC01}\u{A}", &["\u{AC01}", "\u{A}"]),
            ("\u{AC01}\u{308}\u{A}", &["\u{AC01}\u{308}", "\u{A}"]),
            ("\u{AC01}\u{1}", &["\u{AC01}", "\u{1}"]),
            ("\u{AC01}\u{308}\u{1}", &["\u{AC01}\u{308}", "\u{1}"]),
            ("\u{AC01}\u{300}", &["\u{AC01}\u{300}"]),
            ("\u{AC01}\u{308}\u{300}", &["\u{AC01}\u{308}\u{300}"]),
            ("\u{AC01}\u{1100}", &["\u{AC01}", "\u{1100}"]),
            ("\u{AC01}\u{308}\u{1100}", &["\u{AC01}\u{308}", "\u{1100}"]),
            ("\u{AC01}\u{1160}", &["\u{AC01}", "\u{1160}"]),
            ("\u{AC01}\u{308}\u{1160}", &["\u{AC01}\u{308}", "\u{1160}"]),
            ("\u{AC01}\u{11A8}", &["\u{AC01}\u{11A8}"]),
            ("\u{AC01}\u{308}\u{11A8}", &["\u{AC01}\u{308}", "\u{11A8}"]),
            ("\u{AC01}\u{AC00}", &["\u{AC01}", "\u{AC00}"]),
            ("\u{AC01}\u{308}\u{AC00}", &["\u{AC01}\u{308}", "\u{AC00}"]),
            ("\u{AC01}\u{AC01}", &["\u{AC01}", "\u{AC01}"]),
            ("\u{AC01}\u{308}\u{AC01}", &["\u{AC01}\u{308}", "\u{AC01}"]),
            ("\u{AC01}\u{1F1E6}", &["\u{AC01}", "\u{1F1E6}"]),
            ("\u{AC01}\u{308}\u{1F1E6}", &["\u{AC01}\u{308}", "\u{1F1E6}"]),
            ("\u{AC01}\u{378}", &["\u{AC01}", "\u{378}"]),
            ("\u{AC01}\u{308}\u{378}", &["\u{AC01}\u{308}", "\u{378}"]),
            ("\u{1F1E6}\u{20}", &["\u{1F1E6}", "\u{20}"]),
            ("\u{1F1E6}\u{308}\u{20}", &["\u{1F1E6}\u{308}", "\u{20}"]),
            ("\u{1F1E6}\u{D}", &["\u{1F1E6}", "\u{D}"]),
            ("\u{1F1E6}\u{308}\u{D}", &["\u{1F1E6}\u{308}", "\u{D}"]),
            ("\u{1F1E6}\u{A}", &["\u{1F1E6}", "\u{A}"]),
            ("\u{1F1E6}\u{308}\u{A}", &["\u{1F1E6}\u{308}", "\u{A}"]),
            ("\u{1F1E6}\u{1}", &["\u{1F1E6}", "\u{1}"]),
            ("\u{1F1E6}\u{308}\u{1}", &["\u{1F1E6}\u{308}", "\u{1}"]),
            ("\u{1F1E6}\u{300}", &["\u{1F1E6}\u{300}"]),
            ("\u{1F1E6}\u{308}\u{300}", &["\u{1F1E6}\u{308}\u{300}"]),
            ("\u{1F1E6}\u{1100}", &["\u{1F1E6}", "\u{1100}"]),
            ("\u{1F1E6}\u{308}\u{1100}", &["\u{1F1E6}\u{308}", "\u{1100}"]),
            ("\u{1F1E6}\u{1160}", &["\u{1F1E6}", "\u{1160}"]),
            ("\u{1F1E6}\u{308}\u{1160}", &["\u{1F1E6}\u{308}", "\u{1160}"]),
            ("\u{1F1E6}\u{11A8}", &["\u{1F1E6}", "\u{11A8}"]),
            ("\u{1F1E6}\u{308}\u{11A8}", &["\u{1F1E6}\u{308}", "\u{11A8}"]),
            ("\u{1F1E6}\u{AC00}", &["\u{1F1E6}", "\u{AC00}"]),
            ("\u{1F1E6}\u{308}\u{AC00}", &["\u{1F1E6}\u{308}", "\u{AC00}"]),
            ("\u{1F1E6}\u{AC01}", &["\u{1F1E6}", "\u{AC01}"]),
            ("\u{1F1E6}\u{308}\u{AC01}", &["\u{1F1E6}\u{308}", "\u{AC01}"]),
            ("\u{1F1E6}\u{1F1E6}", &["\u{1F1E6}\u{1F1E6}"]),
            ("\u{1F1E6}\u{308}\u{1F1E6}", &["\u{1F1E6}\u{308}", "\u{1F1E6}"]),
            ("\u{1F1E6}\u{378}", &["\u{1F1E6}", "\u{378}"]),
            ("\u{1F1E6}\u{308}\u{378}", &["\u{1F1E6}\u{308}", "\u{378}"]),
            ("\u{378}\u{20}", &["\u{378}", "\u{20}"]),
            ("\u{378}\u{308}\u{20}", &["\u{378}\u{308}", "\u{20}"]),
            ("\u{378}\u{D}", &["\u{378}", "\u{D}"]),
            ("\u{378}\u{308}\u{D}", &["\u{378}\u{308}", "\u{D}"]),
            ("\u{378}\u{A}", &["\u{378}", "\u{A}"]),
            ("\u{378}\u{308}\u{A}", &["\u{378}\u{308}", "\u{A}"]),
            ("\u{378}\u{1}", &["\u{378}", "\u{1}"]),
            ("\u{378}\u{308}\u{1}", &["\u{378}\u{308}", "\u{1}"]),
            ("\u{378}\u{300}", &["\u{378}\u{300}"]),
            ("\u{378}\u{308}\u{300}", &["\u{378}\u{308}\u{300}"]),
            ("\u{378}\u{1100}", &["\u{378}", "\u{1100}"]),
            ("\u{378}\u{308}\u{1100}", &["\u{378}\u{308}", "\u{1100}"]),
            ("\u{378}\u{1160}", &["\u{378}", "\u{1160}"]),
            ("\u{378}\u{308}\u{1160}", &["\u{378}\u{308}", "\u{1160}"]),
            ("\u{378}\u{11A8}", &["\u{378}", "\u{11A8}"]),
            ("\u{378}\u{308}\u{11A8}", &["\u{378}\u{308}", "\u{11A8}"]),
            ("\u{378}\u{AC00}", &["\u{378}", "\u{AC00}"]),
            ("\u{378}\u{308}\u{AC00}", &["\u{378}\u{308}", "\u{AC00}"]),
            ("\u{378}\u{AC01}", &["\u{378}", "\u{AC01}"]),
            ("\u{378}\u{308}\u{AC01}", &["\u{378}\u{308}", "\u{AC01}"]),
            ("\u{378}\u{1F1E6}", &["\u{378}", "\u{1F1E6}"]),
            ("\u{378}\u{308}\u{1F1E6}", &["\u{378}\u{308}", "\u{1F1E6}"]),
            ("\u{378}\u{378}", &["\u{378}", "\u{378}"]),
            ("\u{378}\u{308}\u{378}", &["\u{378}\u{308}", "\u{378}"]),
            ("\u{61}\u{1F1E6}\u{62}", &["\u{61}", "\u{1F1E6}", "\u{62}"]),
            ("\u{1F1F7}\u{1F1FA}", &["\u{1F1F7}\u{1F1FA}"]),
            ("\u{1F1F7}\u{1F1FA}\u{1F1F8}", &["\u{1F1F7}\u{1F1FA}\u{1F1F8}"]),
            ("\u{1F1F7}\u{1F1FA}\u{1F1F8}\u{1F1EA}",
            &["\u{1F1F7}\u{1F1FA}\u{1F1F8}\u{1F1EA}"]),
            ("\u{1F1F7}\u{1F1FA}\u{200B}\u{1F1F8}\u{1F1EA}",
             &["\u{1F1F7}\u{1F1FA}", "\u{200B}", "\u{1F1F8}\u{1F1EA}"]),
            ("\u{1F1E6}\u{1F1E7}\u{1F1E8}", &["\u{1F1E6}\u{1F1E7}\u{1F1E8}"]),
            ("\u{1F1E6}\u{200D}\u{1F1E7}\u{1F1E8}", &["\u{1F1E6}\u{200D}",
             "\u{1F1E7}\u{1F1E8}"]),
            ("\u{1F1E6}\u{1F1E7}\u{200D}\u{1F1E8}",
             &["\u{1F1E6}\u{1F1E7}\u{200D}", "\u{1F1E8}"]),
            ("\u{20}\u{200D}\u{646}", &["\u{20}\u{200D}", "\u{646}"]),
            ("\u{646}\u{200D}\u{20}", &["\u{646}\u{200D}", "\u{20}"]),
        ];

        let test_diff: [(_, &[_], &[_]), .. 23] = [
            ("\u{20}\u{903}", &["\u{20}\u{903}"], &["\u{20}", "\u{903}"]), ("\u{20}\u{308}\u{903}",
            &["\u{20}\u{308}\u{903}"], &["\u{20}\u{308}", "\u{903}"]), ("\u{D}\u{308}\u{903}",
            &["\u{D}", "\u{308}\u{903}"], &["\u{D}", "\u{308}", "\u{903}"]), ("\u{A}\u{308}\u{903}",
            &["\u{A}", "\u{308}\u{903}"], &["\u{A}", "\u{308}", "\u{903}"]), ("\u{1}\u{308}\u{903}",
            &["\u{1}", "\u{308}\u{903}"], &["\u{1}", "\u{308}", "\u{903}"]), ("\u{300}\u{903}",
            &["\u{300}\u{903}"], &["\u{300}", "\u{903}"]), ("\u{300}\u{308}\u{903}",
            &["\u{300}\u{308}\u{903}"], &["\u{300}\u{308}", "\u{903}"]), ("\u{903}\u{903}",
            &["\u{903}\u{903}"], &["\u{903}", "\u{903}"]), ("\u{903}\u{308}\u{903}",
            &["\u{903}\u{308}\u{903}"], &["\u{903}\u{308}", "\u{903}"]), ("\u{1100}\u{903}",
            &["\u{1100}\u{903}"], &["\u{1100}", "\u{903}"]), ("\u{1100}\u{308}\u{903}",
            &["\u{1100}\u{308}\u{903}"], &["\u{1100}\u{308}", "\u{903}"]), ("\u{1160}\u{903}",
            &["\u{1160}\u{903}"], &["\u{1160}", "\u{903}"]), ("\u{1160}\u{308}\u{903}",
            &["\u{1160}\u{308}\u{903}"], &["\u{1160}\u{308}", "\u{903}"]), ("\u{11A8}\u{903}",
            &["\u{11A8}\u{903}"], &["\u{11A8}", "\u{903}"]), ("\u{11A8}\u{308}\u{903}",
            &["\u{11A8}\u{308}\u{903}"], &["\u{11A8}\u{308}", "\u{903}"]), ("\u{AC00}\u{903}",
            &["\u{AC00}\u{903}"], &["\u{AC00}", "\u{903}"]), ("\u{AC00}\u{308}\u{903}",
            &["\u{AC00}\u{308}\u{903}"], &["\u{AC00}\u{308}", "\u{903}"]), ("\u{AC01}\u{903}",
            &["\u{AC01}\u{903}"], &["\u{AC01}", "\u{903}"]), ("\u{AC01}\u{308}\u{903}",
            &["\u{AC01}\u{308}\u{903}"], &["\u{AC01}\u{308}", "\u{903}"]), ("\u{1F1E6}\u{903}",
            &["\u{1F1E6}\u{903}"], &["\u{1F1E6}", "\u{903}"]), ("\u{1F1E6}\u{308}\u{903}",
            &["\u{1F1E6}\u{308}\u{903}"], &["\u{1F1E6}\u{308}", "\u{903}"]), ("\u{378}\u{903}",
            &["\u{378}\u{903}"], &["\u{378}", "\u{903}"]), ("\u{378}\u{308}\u{903}",
            &["\u{378}\u{308}\u{903}"], &["\u{378}\u{308}", "\u{903}"]),
        ];

        for &(s, g) in test_same.iter() {
            // test forward iterator
            assert!(order::equals(s.graphemes(true), g.iter().map(|&x| x)));
            assert!(order::equals(s.graphemes(false), g.iter().map(|&x| x)));

            // test reverse iterator
            assert!(order::equals(s.graphemes(true).rev(), g.iter().rev().map(|&x| x)));
            assert!(order::equals(s.graphemes(false).rev(), g.iter().rev().map(|&x| x)));
        }

        for &(s, gt, gf) in test_diff.iter() {
            // test forward iterator
            assert!(order::equals(s.graphemes(true), gt.iter().map(|&x| x)));
            assert!(order::equals(s.graphemes(false), gf.iter().map(|&x| x)));

            // test reverse iterator
            assert!(order::equals(s.graphemes(true).rev(), gt.iter().rev().map(|&x| x)));
            assert!(order::equals(s.graphemes(false).rev(), gf.iter().rev().map(|&x| x)));
        }

        // test the indices iterators
        let s = "a̐éö̲\r\n";
        let gr_inds = s.grapheme_indices(true).collect::<Vec<(uint, &str)>>();
        let b: &[_] = &[(0u, "a̐"), (3, "é"), (6, "ö̲"), (11, "\r\n")];
        assert_eq!(gr_inds, b);
        let gr_inds = s.grapheme_indices(true).rev().collect::<Vec<(uint, &str)>>();
        let b: &[_] = &[(11, "\r\n"), (6, "ö̲"), (3, "é"), (0u, "a̐")];
        assert_eq!(gr_inds, b);
        let mut gr_inds_iter = s.grapheme_indices(true);
        {
            let gr_inds = gr_inds_iter.by_ref();
            let e1 = gr_inds.size_hint();
            assert_eq!(e1, (1, Some(13)));
            let c = gr_inds.count();
            assert_eq!(c, 4);
        }
        let e2 = gr_inds_iter.size_hint();
        assert_eq!(e2, (0, Some(0)));

        // make sure the reverse iterator does the right thing with "\n" at beginning of string
        let s = "\n\r\n\r";
        let gr = s.graphemes(true).rev().collect::<Vec<&str>>();
        let b: &[_] = &["\r", "\r\n", "\n"];
        assert_eq!(gr, b);
    }

    #[test]
    fn test_split_strator() {
        fn t(s: &str, sep: &str, u: &[&str]) {
            let v: Vec<&str> = s.split_str(sep).collect();
            assert_eq!(v, u);
        }
        t("--1233345--", "12345", &["--1233345--"]);
        t("abc::hello::there", "::", &["abc", "hello", "there"]);
        t("::hello::there", "::", &["", "hello", "there"]);
        t("hello::there::", "::", &["hello", "there", ""]);
        t("::hello::there::", "::", &["", "hello", "there", ""]);
        t("ประเทศไทย中华Việt Nam", "中华", &["ประเทศไทย", "Việt Nam"]);
        t("zzXXXzzYYYzz", "zz", &["", "XXX", "YYY", ""]);
        t("zzXXXzYYYz", "XXX", &["zz", "zYYYz"]);
        t(".XXX.YYY.", ".", &["", "XXX", "YYY", ""]);
        t("", ".", &[""]);
        t("zz", "zz", &["",""]);
        t("ok", "z", &["ok"]);
        t("zzz", "zz", &["","z"]);
        t("zzzzz", "zz", &["","","z"]);
    }

    #[test]
    fn test_str_default() {
        use core::default::Default;
        fn t<S: Default + Str>() {
            let s: S = Default::default();
            assert_eq!(s.as_slice(), "");
        }

        t::<&str>();
        t::<String>();
    }

    #[test]
    fn test_str_container() {
        fn sum_len(v: &[&str]) -> uint {
            v.iter().map(|x| x.len()).sum()
        }

        let s = String::from_str("01234");
        assert_eq!(5, sum_len(&["012", "", "34"]));
        assert_eq!(5, sum_len(&[String::from_str("01").as_slice(),
                                String::from_str("2").as_slice(),
                                String::from_str("34").as_slice(),
                                String::from_str("").as_slice()]));
        assert_eq!(5, sum_len(&[s.as_slice()]));
    }

    #[test]
    fn test_str_from_utf8() {
        let xs = b"hello";
        assert_eq!(from_utf8(xs), Some("hello"));

        let xs = "ศไทย中华Việt Nam".as_bytes();
        assert_eq!(from_utf8(xs), Some("ศไทย中华Việt Nam"));

        let xs = b"hello\xFF";
        assert_eq!(from_utf8(xs), None);
    }

    #[test]
    fn test_maybe_owned_traits() {
        let s = Slice("abcde");
        assert_eq!(s.len(), 5);
        assert_eq!(s.as_slice(), "abcde");
        assert_eq!(String::from_str(s.as_slice()).as_slice(), "abcde");
        assert_eq!(format!("{}", s).as_slice(), "abcde");
        assert!(s.lt(&Owned(String::from_str("bcdef"))));
        assert_eq!(Slice(""), Default::default());

        let o = Owned(String::from_str("abcde"));
        assert_eq!(o.len(), 5);
        assert_eq!(o.as_slice(), "abcde");
        assert_eq!(String::from_str(o.as_slice()).as_slice(), "abcde");
        assert_eq!(format!("{}", o).as_slice(), "abcde");
        assert!(o.lt(&Slice("bcdef")));
        assert_eq!(Owned(String::from_str("")), Default::default());

        assert!(s.cmp(&o) == Equal);
        assert!(s.equiv(&o));

        assert!(o.cmp(&s) == Equal);
        assert!(o.equiv(&s));
    }

    #[test]
    fn test_maybe_owned_methods() {
        let s = Slice("abcde");
        assert!(s.is_slice());
        assert!(!s.is_owned());

        let o = Owned(String::from_str("abcde"));
        assert!(!o.is_slice());
        assert!(o.is_owned());
    }

    #[test]
    fn test_maybe_owned_clone() {
        assert_eq!(Owned(String::from_str("abcde")), Slice("abcde").clone());
        assert_eq!(Owned(String::from_str("abcde")), Owned(String::from_str("abcde")).clone());
        assert_eq!(Slice("abcde"), Slice("abcde").clone());
        assert_eq!(Slice("abcde"), Owned(String::from_str("abcde")).clone());
    }

    #[test]
    fn test_maybe_owned_into_string() {
        assert_eq!(Slice("abcde").into_string(), String::from_str("abcde"));
        assert_eq!(Owned(String::from_str("abcde")).into_string(),
                   String::from_str("abcde"));
    }

    #[test]
    fn test_into_maybe_owned() {
        assert_eq!("abcde".into_maybe_owned(), Slice("abcde"));
        assert_eq!((String::from_str("abcde")).into_maybe_owned(), Slice("abcde"));
        assert_eq!("abcde".into_maybe_owned(), Owned(String::from_str("abcde")));
        assert_eq!((String::from_str("abcde")).into_maybe_owned(),
                   Owned(String::from_str("abcde")));
    }
}

#[cfg(test)]
mod bench {
    use prelude::*;
    use test::Bencher;
    use test::black_box;
    use super::*;

    #[bench]
    fn char_iterator(b: &mut Bencher) {
        let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";

        b.iter(|| s.chars().count());
    }

    #[bench]
    fn char_iterator_for(b: &mut Bencher) {
        let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";

        b.iter(|| {
            for ch in s.chars() { black_box(ch) }
        });
    }

    #[bench]
    fn char_iterator_ascii(b: &mut Bencher) {
        let s = "Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb
        Mary had a little lamb, Little lamb";

        b.iter(|| s.chars().count());
    }

    #[bench]
    fn char_iterator_rev(b: &mut Bencher) {
        let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";

        b.iter(|| s.chars().rev().count());
    }

    #[bench]
    fn char_iterator_rev_for(b: &mut Bencher) {
        let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";

        b.iter(|| {
            for ch in s.chars().rev() { black_box(ch) }
        });
    }

    #[bench]
    fn char_indicesator(b: &mut Bencher) {
        let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";
        let len = s.char_len();

        b.iter(|| assert_eq!(s.char_indices().count(), len));
    }

    #[bench]
    fn char_indicesator_rev(b: &mut Bencher) {
        let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";
        let len = s.char_len();

        b.iter(|| assert_eq!(s.char_indices().rev().count(), len));
    }

    #[bench]
    fn split_unicode_ascii(b: &mut Bencher) {
        let s = "ประเทศไทย中华Việt Namประเทศไทย中华Việt Nam";

        b.iter(|| assert_eq!(s.split('V').count(), 3));
    }

    #[bench]
    fn split_unicode_not_ascii(b: &mut Bencher) {
        struct NotAscii(char);
        impl CharEq for NotAscii {
            fn matches(&mut self, c: char) -> bool {
                let NotAscii(cc) = *self;
                cc == c
            }
            fn only_ascii(&self) -> bool { false }
        }
        let s = "ประเทศไทย中华Việt Namประเทศไทย中华Việt Nam";

        b.iter(|| assert_eq!(s.split(NotAscii('V')).count(), 3));
    }


    #[bench]
    fn split_ascii(b: &mut Bencher) {
        let s = "Mary had a little lamb, Little lamb, little-lamb.";
        let len = s.split(' ').count();

        b.iter(|| assert_eq!(s.split(' ').count(), len));
    }

    #[bench]
    fn split_not_ascii(b: &mut Bencher) {
        struct NotAscii(char);
        impl CharEq for NotAscii {
            #[inline]
            fn matches(&mut self, c: char) -> bool {
                let NotAscii(cc) = *self;
                cc == c
            }
            fn only_ascii(&self) -> bool { false }
        }
        let s = "Mary had a little lamb, Little lamb, little-lamb.";
        let len = s.split(' ').count();

        b.iter(|| assert_eq!(s.split(NotAscii(' ')).count(), len));
    }

    #[bench]
    fn split_extern_fn(b: &mut Bencher) {
        let s = "Mary had a little lamb, Little lamb, little-lamb.";
        let len = s.split(' ').count();
        fn pred(c: char) -> bool { c == ' ' }

        b.iter(|| assert_eq!(s.split(pred).count(), len));
    }

    #[bench]
    fn split_closure(b: &mut Bencher) {
        let s = "Mary had a little lamb, Little lamb, little-lamb.";
        let len = s.split(' ').count();

        b.iter(|| assert_eq!(s.split(|&: c: char| c == ' ').count(), len));
    }

    #[bench]
    fn split_slice(b: &mut Bencher) {
        let s = "Mary had a little lamb, Little lamb, little-lamb.";
        let len = s.split(' ').count();

        let c: &[char] = &[' '];
        b.iter(|| assert_eq!(s.split(c).count(), len));
    }

    #[bench]
    fn is_utf8_100_ascii(b: &mut Bencher) {

        let s = b"Hello there, the quick brown fox jumped over the lazy dog! \
                  Lorem ipsum dolor sit amet, consectetur. ";

        assert_eq!(100, s.len());
        b.iter(|| {
            is_utf8(s)
        });
    }

    #[bench]
    fn is_utf8_100_multibyte(b: &mut Bencher) {
        let s = "𐌀𐌖𐌋𐌄𐌑𐌉ปรدولة الكويتทศไทย中华𐍅𐌿𐌻𐍆𐌹𐌻𐌰".as_bytes();
        assert_eq!(100, s.len());
        b.iter(|| {
            is_utf8(s)
        });
    }

    #[bench]
    fn bench_connect(b: &mut Bencher) {
        let s = "ศไทย中华Việt Nam; Mary had a little lamb, Little lamb";
        let sep = "→";
        let v = [s, s, s, s, s, s, s, s, s, s];
        b.iter(|| {
            assert_eq!(v.connect(sep).len(), s.len() * 10 + sep.len() * 9);
        })
    }

    #[bench]
    fn bench_contains_short_short(b: &mut Bencher) {
        let haystack = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.";
        let needle = "sit";

        b.iter(|| {
            assert!(haystack.contains(needle));
        })
    }

    #[bench]
    fn bench_contains_short_long(b: &mut Bencher) {
        let haystack = "\
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Suspendisse quis lorem sit amet dolor \
ultricies condimentum. Praesent iaculis purus elit, ac malesuada quam malesuada in. Duis sed orci \
eros. Suspendisse sit amet magna mollis, mollis nunc luctus, imperdiet mi. Integer fringilla non \
sem ut lacinia. Fusce varius tortor a risus porttitor hendrerit. Morbi mauris dui, ultricies nec \
tempus vel, gravida nec quam.

In est dui, tincidunt sed tempus interdum, adipiscing laoreet ante. Etiam tempor, tellus quis \
sagittis interdum, nulla purus mattis sem, quis auctor erat odio ac tellus. In nec nunc sit amet \
diam volutpat molestie at sed ipsum. Vestibulum laoreet consequat vulputate. Integer accumsan \
lorem ac dignissim placerat. Suspendisse convallis faucibus lorem. Aliquam erat volutpat. In vel \
eleifend felis. Sed suscipit nulla lorem, sed mollis est sollicitudin et. Nam fermentum egestas \
interdum. Curabitur ut nisi justo.

Sed sollicitudin ipsum tellus, ut condimentum leo eleifend nec. Cras ut velit ante. Phasellus nec \
mollis odio. Mauris molestie erat in arcu mattis, at aliquet dolor vehicula. Quisque malesuada \
lectus sit amet nisi pretium, a condimentum ipsum porta. Morbi at dapibus diam. Praesent egestas \
est sed risus elementum, eu rutrum metus ultrices. Etiam fermentum consectetur magna, id rutrum \
felis accumsan a. Aliquam ut pellentesque libero. Sed mi nulla, lobortis eu tortor id, suscipit \
ultricies neque. Morbi iaculis sit amet risus at iaculis. Praesent eget ligula quis turpis \
feugiat suscipit vel non arcu. Interdum et malesuada fames ac ante ipsum primis in faucibus. \
Aliquam sit amet placerat lorem.

Cras a lacus vel ante posuere elementum. Nunc est leo, bibendum ut facilisis vel, bibendum at \
mauris. Nullam adipiscing diam vel odio ornare, luctus adipiscing mi luctus. Nulla facilisi. \
Mauris adipiscing bibendum neque, quis adipiscing lectus tempus et. Sed feugiat erat et nisl \
lobortis pharetra. Donec vitae erat enim. Nullam sit amet felis et quam lacinia tincidunt. Aliquam \
suscipit dapibus urna. Sed volutpat urna in magna pulvinar volutpat. Phasellus nec tellus ac diam \
cursus accumsan.

Nam lectus enim, dapibus non nisi tempor, consectetur convallis massa. Maecenas eleifend dictum \
feugiat. Etiam quis mauris vel risus luctus mattis a a nunc. Nullam orci quam, imperdiet id \
vehicula in, porttitor ut nibh. Duis sagittis adipiscing nisl vitae congue. Donec mollis risus eu \
leo suscipit, varius porttitor nulla porta. Pellentesque ut sem nec nisi euismod vehicula. Nulla \
malesuada sollicitudin quam eu fermentum.";
        let needle = "english";

        b.iter(|| {
            assert!(!haystack.contains(needle));
        })
    }

    #[bench]
    fn bench_contains_bad_naive(b: &mut Bencher) {
        let haystack = "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa";
        let needle = "aaaaaaaab";

        b.iter(|| {
            assert!(!haystack.contains(needle));
        })
    }

    #[bench]
    fn bench_contains_equal(b: &mut Bencher) {
        let haystack = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.";
        let needle = "Lorem ipsum dolor sit amet, consectetur adipiscing elit.";

        b.iter(|| {
            assert!(haystack.contains(needle));
        })
    }
}