Initial vendor packages

Signed-off-by: Valentin Popov <valentin@popov.link>

1 files changed, 687 insertions, 0 deletions

diff --git a/vendor/encode_unicode/src/utf16_char.rs b/vendor/encode_unicode/src/utf16_char.rs
new file mode 100644
index 0000000..d8a6cec
--- /dev/null
+++ b/vendor/encode_unicode/src/utf16_char.rs
@@ -0,0 +1,687 @@
+/* Copyright 2016 The encode_unicode Developers
+ *
+ * Licensed under the Apache License, Version 2.0, <LICENSE-APACHE or
+ * http://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.
+ */
+
+use utf16_iterators::Utf16Iterator;
+use traits::{CharExt, U16UtfExt};
+use utf8_char::Utf8Char;
+use errors::{InvalidUtf16Slice, InvalidUtf16Array, InvalidUtf16Tuple};
+use errors::{NonBMPError, EmptyStrError, FromStrError};
+extern crate core;
+use self::core::{hash,fmt};
+use self::core::cmp::Ordering;
+use self::core::borrow::Borrow;
+use self::core::ops::Deref;
+use self::core::str::FromStr;
+#[cfg(feature="std")]
+use self::core::iter::FromIterator;
+#[cfg(feature="std")]
+#[allow(deprecated)]
+use std::ascii::AsciiExt;
+#[cfg(feature="ascii")]
+use self::core::char;
+#[cfg(feature="ascii")]
+extern crate ascii;
+#[cfg(feature="ascii")]
+use self::ascii::{AsciiChar,ToAsciiChar,ToAsciiCharError};
+
+
+// I don't think there is any good default value for char, but char does.
+#[derive(Default)]
+// char doesn't do anything more advanced than u32 for Eq/Ord, so we shouldn't either.
+// When it's a single unit, the second is zero, so Eq works.
+// #[derive(Ord)] however, breaks on surrogate pairs.
+#[derive(PartialEq,Eq)]
+#[derive(Clone,Copy)]
+
+
+/// An unicode codepoint stored as UTF-16.
+///
+/// It can be borrowed as an `u16` slice, and has the same size as `char`.
+pub struct Utf16Char {
+    units: [u16; 2],
+}
+
+
+  /////////////////////
+ //conversion traits//
+/////////////////////
+impl FromStr for Utf16Char {
+    type Err = FromStrError;
+    /// Create an `Utf16Char` from a string slice.
+    /// The string must contain exactly one codepoint.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use encode_unicode::error::FromStrError::*;
+    /// use encode_unicode::Utf16Char;
+    /// use std::str::FromStr;
+    ///
+    /// assert_eq!(Utf16Char::from_str("a"), Ok(Utf16Char::from('a')));
+    /// assert_eq!(Utf16Char::from_str("🂠"), Ok(Utf16Char::from('🂠')));
+    /// assert_eq!(Utf16Char::from_str(""), Err(Empty));
+    /// assert_eq!(Utf16Char::from_str("ab"), Err(MultipleCodepoints));
+    /// assert_eq!(Utf16Char::from_str("é"), Err(MultipleCodepoints));// 'e'+u301 combining mark
+    /// ```
+    fn from_str(s: &str) -> Result<Self, FromStrError> {
+        match Utf16Char::from_str_start(s) {
+            Ok((u16c,bytes)) if bytes == s.len() => Ok(u16c),
+            Ok((_,_)) => Err(FromStrError::MultipleCodepoints),
+            Err(EmptyStrError) => Err(FromStrError::Empty),
+        }
+    }
+}
+impl From<char> for Utf16Char {
+    fn from(c: char) -> Self {
+        let (first, second) = c.to_utf16_tuple();
+        Utf16Char{ units: [first, second.unwrap_or(0)] }
+    }
+}
+impl From<Utf8Char> for Utf16Char {
+    fn from(utf8: Utf8Char) -> Utf16Char {
+        let (b, utf8_len) = utf8.to_array();
+        match utf8_len {
+            1 => Utf16Char{ units: [b[0] as u16, 0] },
+            4 => {// need surrogate
+                let mut first = 0xd800 - (0x01_00_00u32 >> 10) as u16;
+                first += (b[0] as u16 & 0x07) << 8;
+                first += (b[1] as u16 & 0x3f) << 2;
+                first += (b[2] as u16 & 0x30) >> 4;
+                let mut second = 0xdc00;
+                second |= (b[2] as u16 & 0x0f) << 6;
+                second |=  b[3] as u16 & 0x3f;
+                Utf16Char{ units: [first, second] }
+            },
+            _ => { // 2 or 3
+                let mut unit = ((b[0] as u16 & 0x1f) << 6) | (b[1] as u16 & 0x3f);
+                if utf8_len == 3 {
+                    unit = (unit << 6) | (b[2] as u16 & 0x3f);
+                }
+                Utf16Char{ units: [unit, 0] }
+            },
+        }
+    }
+}
+impl From<Utf16Char> for char {
+    fn from(uc: Utf16Char) -> char {
+        char::from_utf16_array_unchecked(uc.to_array())
+    }
+}
+impl IntoIterator for Utf16Char {
+    type Item=u16;
+    type IntoIter=Utf16Iterator;
+    /// Iterate over the units.
+    fn into_iter(self) -> Utf16Iterator {
+        Utf16Iterator::from(self)
+    }
+}
+
+#[cfg(feature="std")]
+impl Extend<Utf16Char> for Vec<u16> {
+    fn extend<I:IntoIterator<Item=Utf16Char>>(&mut self,  iter: I) {
+        let iter = iter.into_iter();
+        self.reserve(iter.size_hint().0);
+        for u16c in iter {
+            self.push(u16c.units[0]);
+            if u16c.units[1] != 0 {
+                self.push(u16c.units[1]);
+            }
+        }
+    }
+}
+#[cfg(feature="std")]
+impl<'a> Extend<&'a Utf16Char> for Vec<u16> {
+    fn extend<I:IntoIterator<Item=&'a Utf16Char>>(&mut self,  iter: I) {
+        self.extend(iter.into_iter().cloned())
+    }
+}
+#[cfg(feature="std")]
+impl FromIterator<Utf16Char> for Vec<u16> {
+    fn from_iter<I:IntoIterator<Item=Utf16Char>>(iter: I) -> Self {
+        let mut vec = Vec::new();
+        vec.extend(iter);
+        return vec;
+    }
+}
+#[cfg(feature="std")]
+impl<'a> FromIterator<&'a Utf16Char> for Vec<u16> {
+    fn from_iter<I:IntoIterator<Item=&'a Utf16Char>>(iter: I) -> Self {
+        Self::from_iter(iter.into_iter().cloned())
+    }
+}
+
+#[cfg(feature="std")]
+impl Extend<Utf16Char> for String {
+    fn extend<I:IntoIterator<Item=Utf16Char>>(&mut self,  iter: I) {
+        self.extend(iter.into_iter().map(|u16c| Utf8Char::from(u16c) ));
+    }
+}
+#[cfg(feature="std")]
+impl<'a> Extend<&'a Utf16Char> for String {
+    fn extend<I:IntoIterator<Item=&'a Utf16Char>>(&mut self,  iter: I) {
+        self.extend(iter.into_iter().cloned());
+    }
+}
+#[cfg(feature="std")]
+impl FromIterator<Utf16Char> for String {
+    fn from_iter<I:IntoIterator<Item=Utf16Char>>(iter: I) -> Self {
+        let mut s = String::new();
+        s.extend(iter);
+        return s;
+    }
+}
+#[cfg(feature="std")]
+impl<'a> FromIterator<&'a Utf16Char> for String {
+    fn from_iter<I:IntoIterator<Item=&'a Utf16Char>>(iter: I) -> Self {
+        Self::from_iter(iter.into_iter().cloned())
+    }
+}
+
+
+  /////////////////
+ //getter traits//
+/////////////////
+impl AsRef<[u16]> for Utf16Char {
+    #[inline]
+    fn as_ref(&self) -> &[u16] {
+        &self.units[..self.len()]
+    }
+}
+impl Borrow<[u16]> for Utf16Char {
+    #[inline]
+    fn borrow(&self) -> &[u16] {
+        self.as_ref()
+    }
+}
+impl Deref for Utf16Char {
+    type Target = [u16];
+    #[inline]
+    fn deref(&self) -> &[u16] {
+        self.as_ref()
+    }
+}
+
+
+  ////////////////
+ //ascii traits//
+////////////////
+#[cfg(feature="std")]
+#[allow(deprecated)]
+impl AsciiExt for Utf16Char {
+    type Owned = Self;
+    fn is_ascii(&self) -> bool {
+        self.units[0] < 128
+    }
+    fn eq_ignore_ascii_case(&self,  other: &Self) -> bool {
+        self.to_ascii_lowercase() == other.to_ascii_lowercase()
+    }
+    fn to_ascii_uppercase(&self) -> Self {
+        let n = self.units[0].wrapping_sub(b'a' as u16);
+        if n < 26 {Utf16Char{ units: [n+b'A' as u16, 0] }}
+        else      {*self}
+    }
+    fn to_ascii_lowercase(&self) -> Self {
+        let n = self.units[0].wrapping_sub(b'A' as u16);
+        if n < 26 {Utf16Char{ units: [n+b'a' as u16, 0] }}
+        else      {*self}
+    }
+    fn make_ascii_uppercase(&mut self) {
+        *self = self.to_ascii_uppercase()
+    }
+    fn make_ascii_lowercase(&mut self) {
+        *self = self.to_ascii_lowercase();
+    }
+}
+
+#[cfg(feature="ascii")]
+/// Requires the feature "ascii".
+impl From<AsciiChar> for Utf16Char {
+    #[inline]
+    fn from(ac: AsciiChar) -> Self {
+        Utf16Char{ units: [ac.as_byte() as u16, 0] }
+    }
+}
+#[cfg(feature="ascii")]
+/// Requires the feature "ascii".
+impl ToAsciiChar for Utf16Char {
+    #[inline]
+    fn to_ascii_char(self) -> Result<AsciiChar, ToAsciiCharError> {
+        // ToAsciiCHar is not implemented for u16 in ascii 0.9.0
+        if self.is_ascii() {self.units[0] as u8} else {255}.to_ascii_char()
+    }
+    #[inline]
+    unsafe fn to_ascii_char_unchecked(self) -> AsciiChar {
+        (self.units[0] as u8).to_ascii_char_unchecked()
+    }
+}
+
+
+  /////////////////////////////////////////////////////////
+ //Genaral traits that cannot be derived to emulate char//
+/////////////////////////////////////////////////////////
+impl hash::Hash for Utf16Char {
+    fn hash<H : hash::Hasher>(&self,  state: &mut H) {
+        self.to_char().hash(state);
+    }
+}
+impl fmt::Debug for Utf16Char {
+    fn fmt(&self,  fmtr: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Debug::fmt(&self.to_char(), fmtr)
+    }
+}
+impl fmt::Display for Utf16Char {
+    fn fmt(&self,  fmtr: &mut fmt::Formatter) -> fmt::Result {
+        fmt::Display::fmt(&Utf8Char::from(*self), fmtr)
+    }
+}
+// Cannot derive these impls because two-unit characters must always compare
+// greater than one-unit ones.
+impl PartialOrd for Utf16Char {
+    #[inline]
+    fn partial_cmp(&self,  rhs: &Self) -> Option<Ordering> {
+        Some(self.cmp(rhs))
+    }
+}
+impl Ord for Utf16Char {
+    #[inline]
+    fn cmp(&self,  rhs: &Self) -> Ordering {
+        // Shift the first unit by 0xd if surrogate, and 0 otherwise.
+        // This ensures surrogates are always greater than 0xffff, and
+        // that the second unit only affect the result when the first are equal.
+        // Multiplying by a constant factor isn't enough because that factor
+        // would have to be greater than 1023 and smaller than 5.5.
+        // This transformation is less complicated than combine_surrogates().
+        let lhs = (self.units[0] as u32, self.units[1] as u32);
+        let rhs = (rhs.units[0] as u32, rhs.units[1] as u32);
+        let lhs = (lhs.0 << (lhs.1 >> 12)) + lhs.1;
+        let rhs = (rhs.0 << (rhs.1 >> 12)) + rhs.1;
+        lhs.cmp(&rhs)
+    }
+}
+
+
+  ////////////////////////////////
+ //Comparisons with other types//
+////////////////////////////////
+impl PartialEq<char> for Utf16Char {
+    fn eq(&self,  u32c: &char) -> bool {
+        *self == Utf16Char::from(*u32c)
+    }
+}
+impl PartialEq<Utf16Char> for char {
+    fn eq(&self,  u16c: &Utf16Char) -> bool {
+        Utf16Char::from(*self) == *u16c
+    }
+}
+impl PartialOrd<char> for Utf16Char {
+    fn partial_cmp(&self,  u32c: &char) -> Option<Ordering> {
+        self.partial_cmp(&Utf16Char::from(*u32c))
+    }
+}
+impl PartialOrd<Utf16Char> for char {
+    fn partial_cmp(&self,  u16c: &Utf16Char) -> Option<Ordering> {
+        Utf16Char::from(*self).partial_cmp(u16c)
+    }
+}
+
+impl PartialEq<Utf8Char> for Utf16Char {
+    fn eq(&self,  u8c: &Utf8Char) -> bool {
+        *self == Utf16Char::from(*u8c)
+    }
+}
+impl PartialOrd<Utf8Char> for Utf16Char {
+    fn partial_cmp(&self,  u8c: &Utf8Char) -> Option<Ordering> {
+        self.partial_cmp(&Utf16Char::from(*u8c))
+    }
+}
+// The other direction is implemented in utf8_char.rs
+
+/// Only considers the unit equal if the codepoint of the `Utf16Char` is not
+/// made up of a surrogate pair.
+///
+/// There is no impl in the opposite direction, as this should only be used to
+/// compare `Utf16Char`s against constants.
+///
+/// # Examples
+///
+/// ```
+/// # use encode_unicode::Utf16Char;
+/// assert!(Utf16Char::from('6') == b'6' as u16);
+/// assert!(Utf16Char::from('\u{FFFF}') == 0xffff_u16);
+/// assert!(Utf16Char::from_tuple((0xd876, Some(0xdef9))).unwrap() != 0xd876_u16);
+/// ```
+impl PartialEq<u16> for Utf16Char {
+    fn eq(&self,  unit: &u16) -> bool {
+        self.units[0] == *unit  &&  self.units[1] == 0
+    }
+}
+/// Only considers the byte equal if the codepoint of the `Utf16Char` is <= U+FF.
+///
+/// # Examples
+///
+/// ```
+/// # use encode_unicode::Utf16Char;
+/// assert!(Utf16Char::from('6') == b'6');
+/// assert!(Utf16Char::from('\u{00FF}') == b'\xff');
+/// assert!(Utf16Char::from('\u{0100}') != b'\0');
+/// ```
+impl PartialEq<u8> for Utf16Char {
+    fn eq(&self,  byte: &u8) -> bool {
+        self.units[0] == *byte as u16
+    }
+}
+#[cfg(feature = "ascii")]
+/// `Utf16Char`s that are not ASCII never compare equal.
+impl PartialEq<AsciiChar> for Utf16Char {
+    #[inline]
+    fn eq(&self,  ascii: &AsciiChar) -> bool {
+        self.units[0] == *ascii as u16
+    }
+}
+#[cfg(feature = "ascii")]
+/// `Utf16Char`s that are not ASCII never compare equal.
+impl PartialEq<Utf16Char> for AsciiChar {
+    #[inline]
+    fn eq(&self,  u16c: &Utf16Char) -> bool {
+        *self as u16 == u16c.units[0]
+    }
+}
+#[cfg(feature = "ascii")]
+/// `Utf16Char`s that are not ASCII always compare greater.
+impl PartialOrd<AsciiChar> for Utf16Char {
+    #[inline]
+    fn partial_cmp(&self,  ascii: &AsciiChar) -> Option<Ordering> {
+        self.units[0].partial_cmp(&(*ascii as u16))
+    }
+}
+#[cfg(feature = "ascii")]
+/// `Utf16Char`s that are not ASCII always compare greater.
+impl PartialOrd<Utf16Char> for AsciiChar {
+    #[inline]
+    fn partial_cmp(&self,  u16c: &Utf16Char) -> Option<Ordering> {
+        (*self as u16).partial_cmp(&u16c.units[0])
+    }
+}
+
+
+  ///////////////////////////////////////////////////////
+ //pub impls that should be together for nicer rustdoc//
+///////////////////////////////////////////////////////
+impl Utf16Char {
+    /// Create an `Utf16Char` from the first codepoint in a string slice,
+    /// converting from UTF-8 to UTF-16.
+    ///
+    /// The returned `usize` is the number of UTF-8 bytes used from the str,
+    /// and not the number of UTF-16 units.
+    ///
+    /// Returns an error if the `str` is empty.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use encode_unicode::Utf16Char;
+    ///
+    /// assert_eq!(Utf16Char::from_str_start("a"), Ok((Utf16Char::from('a'),1)));
+    /// assert_eq!(Utf16Char::from_str_start("ab"), Ok((Utf16Char::from('a'),1)));
+    /// assert_eq!(Utf16Char::from_str_start("🂠 "), Ok((Utf16Char::from('🂠'),4)));
+    /// assert_eq!(Utf16Char::from_str_start("é"), Ok((Utf16Char::from('e'),1)));// 'e'+u301 combining mark
+    /// assert!(Utf16Char::from_str_start("").is_err());
+    /// ```
+    pub fn from_str_start(s: &str) -> Result<(Self,usize), EmptyStrError> {
+        if s.is_empty() {
+            return Err(EmptyStrError);
+        }
+        let b = s.as_bytes();
+        // Read the last byte first to reduce the number of unnecesary length checks.
+        match b[0] {
+            0...127 => {// 1 byte => 1 unit
+                let unit = b[0] as u16;// 0b0000_0000_0xxx_xxxx
+                Ok((Utf16Char{ units: [unit, 0] }, 1))
+            },
+            0b1000_0000...0b1101_1111 => {// 2 bytes => 1 unit
+                let unit = (((b[1] & 0x3f) as u16) << 0) // 0b0000_0000_00xx_xxxx
+                         | (((b[0] & 0x1f) as u16) << 6);// 0b0000_0xxx_xx00_0000
+                Ok((Utf16Char{ units: [unit, 0] }, 2))
+            },
+            0b1110_0000...0b1110_1111 => {// 3 bytes => 1 unit
+                let unit = (((b[2] & 0x3f) as u16) <<  0) // 0b0000_0000_00xx_xxxx
+                         | (((b[1] & 0x3f) as u16) <<  6) // 0b0000_xxxx_xx00_0000
+                         | (((b[0] & 0x0f) as u16) << 12);// 0bxxxx_0000_0000_0000
+                Ok((Utf16Char{ units: [unit, 0] }, 3))
+            },
+            _ => {// 4 bytes => 2 units
+                let second = 0xdc00                        // 0b1101_1100_0000_0000
+                           | (((b[3] & 0x3f) as u16) << 0) // 0b0000_0000_00xx_xxxx
+                           | (((b[2] & 0x0f) as u16) << 6);// 0b0000_00xx_xx00_0000
+                let first = 0xd800-(0x01_00_00u32>>10) as u16// 0b1101_0111_1100_0000
+                          + (((b[2] & 0x30) as u16) >> 4)    // 0b0000_0000_0000_00xx
+                          + (((b[1] & 0x3f) as u16) << 2)    // 0b0000_0000_xxxx_xx00
+                          + (((b[0] & 0x07) as u16) << 8);   // 0b0000_0xxx_0000_0000
+                Ok((Utf16Char{ units: [first, second] }, 4))
+            }
+        }
+    }
+    /// Validate and store the first UTF-16 codepoint in the slice.
+    /// Also return how many units were needed.
+    pub fn from_slice_start(src: &[u16]) -> Result<(Self,usize), InvalidUtf16Slice> {
+        char::from_utf16_slice_start(src).map(|(_,len)| {
+            let second = if len==2 {src[1]} else {0};
+            (Utf16Char{ units: [src[0], second] }, len)
+        })
+    }
+    /// Store the first UTF-16 codepoint of the slice.
+    ///
+    /// # Safety
+    ///
+    /// The slice must be non-empty and start with a valid UTF-16 codepoint.  
+    /// The length of the slice is never checked.
+    pub unsafe fn from_slice_start_unchecked(src: &[u16]) -> (Self,usize) {
+        let first = *src.get_unchecked(0);
+        if first.is_utf16_leading_surrogate() {
+            (Utf16Char{ units: [first, *src.get_unchecked(1)] }, 2)
+        } else {
+            (Utf16Char{ units: [first, 0] }, 1)
+        }
+    }
+    /// Validate and store an UTF-16 array as returned from `char.to_utf16_array()`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use encode_unicode::Utf16Char;
+    /// use encode_unicode::error::InvalidUtf16Array;
+    ///
+    /// assert_eq!(Utf16Char::from_array(['x' as u16, 'y' as u16]), Ok(Utf16Char::from('x')));
+    /// assert_eq!(Utf16Char::from_array(['睷' as u16, 0]), Ok(Utf16Char::from('睷')));
+    /// assert_eq!(Utf16Char::from_array([0xda6f, 0xdcde]), Ok(Utf16Char::from('\u{abcde}')));
+    /// assert_eq!(Utf16Char::from_array([0xf111, 0xdbad]), Ok(Utf16Char::from('\u{f111}')));
+    /// assert_eq!(Utf16Char::from_array([0xdaaf, 0xdaaf]), Err(InvalidUtf16Array::SecondIsNotTrailingSurrogate));
+    /// assert_eq!(Utf16Char::from_array([0xdcac, 0x9000]), Err(InvalidUtf16Array::FirstIsTrailingSurrogate));
+    /// ```
+    pub fn from_array(units: [u16; 2]) -> Result<Self,InvalidUtf16Array> {
+        if (units[0] & 0xf8_00) != 0xd8_00 {
+            Ok(Utf16Char { units: [units[0], 0] })
+        } else if units[0] < 0xdc_00  &&  (units[1] & 0xfc_00) == 0xdc_00 {
+            Ok(Utf16Char { units: units })
+        } else if units[0] < 0xdc_00 {
+            Err(InvalidUtf16Array::SecondIsNotTrailingSurrogate)
+        } else {
+            Err(InvalidUtf16Array::FirstIsTrailingSurrogate)
+        }
+    }
+    /// Create an `Utf16Char` from an array as returned from `char.to_utf16_array()`.
+    ///
+    /// # Safety
+    ///
+    /// The units must form a valid codepoint, and the second unit must be 0
+    /// when a surrogate pair is not required.
+    /// Violating this can easily lead to undefined behavior, although unlike
+    /// `char` bad `Utf16Char`s simply existing is not immediately UB.
+    pub unsafe fn from_array_unchecked(units: [u16; 2]) -> Self {
+        Utf16Char { units: units }
+    }
+    /// Validate and store a UTF-16 pair as returned from `char.to_utf16_tuple()`.
+    pub fn from_tuple(utf16: (u16,Option<u16>)) -> Result<Self,InvalidUtf16Tuple> {
+        unsafe {char::from_utf16_tuple(utf16).map(|_|
+            Self::from_tuple_unchecked(utf16)
+        )}
+    }
+    /// Create an `Utf16Char` from a tuple as returned from `char.to_utf16_tuple()`.
+    ///
+    /// # Safety
+    ///
+    /// The units must form a valid codepoint with the second being 0 when a
+    /// surrogate pair is not required.
+    /// Violating this can easily lead to undefined behavior.
+    pub unsafe fn from_tuple_unchecked(utf16: (u16,Option<u16>)) -> Self {
+        Utf16Char { units: [utf16.0, utf16.1.unwrap_or(0)] }
+    }
+    /// Create an `Utf16Char` from a single unit.
+    ///
+    /// Codepoints < '\u{1_0000}' (which fit in a `u16`) are part of the basic
+    /// multilingual plane unless they are reserved for surrogate pairs.
+    ///
+    /// # Errors
+    ///
+    /// Returns `NonBMPError` if the unit is in the range `0xd800..0xe000`
+    /// (which means that it's part of a surrogat pair)
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use encode_unicode::Utf16Char;
+    /// assert_eq!(Utf16Char::from_bmp(0x40).unwrap(), '@');
+    /// assert_eq!(Utf16Char::from_bmp('ø' as u16).unwrap(), 'ø');
+    /// assert!(Utf16Char::from_bmp(0xdddd).is_err());
+    /// ```
+    pub fn from_bmp(bmp_codepoint: u16) -> Result<Self,NonBMPError> {
+        if bmp_codepoint & 0xf800 != 0xd800 {
+            Ok(Utf16Char{ units: [bmp_codepoint, 0] })
+        } else {
+            Err(NonBMPError)
+        }
+    }
+    /// Create an `Utf16Char` from a single unit without checking that it's a
+    /// valid codepoint on its own.
+    ///
+    /// # Safety
+    ///
+    /// The unit must be less than 0xd800 or greater than 0xdfff.
+    /// In other words, not part of a surrogate pair.  
+    /// Violating this can easily lead to undefined behavior.
+    #[inline]
+    pub unsafe fn from_bmp_unchecked(bmp_codepoint: u16) -> Self {
+        Utf16Char{ units: [bmp_codepoint, 0] }
+    }
+    /// Checks that the codepoint is in the basic multilingual plane.
+    ///
+    /// # Examples
+    /// ```
+    /// # use encode_unicode::Utf16Char;
+    /// assert_eq!(Utf16Char::from('e').is_bmp(), true);
+    /// assert_eq!(Utf16Char::from('€').is_bmp(), true);
+    /// assert_eq!(Utf16Char::from('𝔼').is_bmp(), false);
+    /// ```
+    #[inline]
+    pub fn is_bmp(&self) -> bool {
+        self.units[1] == 0
+    }
+
+    /// The number of units this character is made up of.
+    ///
+    /// Is either 1 or 2 and identical to `.as_char().len_utf16()`
+    /// or `.as_ref().len()`.
+    #[inline]
+    pub fn len(self) -> usize {
+        1 + (self.units[1] as usize >> 15)
+    }
+    // There is no `.is_emty()` because it would always return false.
+
+    /// Checks that the codepoint is an ASCII character.
+    #[inline]
+    pub fn is_ascii(&self) -> bool {
+        self.units[0] <= 127
+    }
+    /// Checks that two characters are an ASCII case-insensitive match.
+    ///
+    /// Is equivalent to `a.to_ascii_lowercase() == b.to_ascii_lowercase()`.
+    #[cfg(feature="std")]
+    pub fn eq_ignore_ascii_case(&self,  other: &Self) -> bool {
+        self.to_ascii_lowercase() == other.to_ascii_lowercase()
+    }
+    /// Converts the character to its ASCII upper case equivalent.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    #[cfg(feature="std")]
+    pub fn to_ascii_uppercase(&self) -> Self {
+        let n = self.units[0].wrapping_sub(b'a' as u16);
+        if n < 26 {Utf16Char{ units: [n+b'A' as u16, 0] }}
+        else      {*self}
+    }
+    /// Converts the character to its ASCII lower case equivalent.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    #[cfg(feature="std")]
+    pub fn to_ascii_lowercase(&self) -> Self {
+        let n = self.units[0].wrapping_sub(b'A' as u16);
+        if n < 26 {Utf16Char{ units: [n+b'a' as u16, 0] }}
+        else      {*self}
+    }
+    /// Converts the character to its ASCII upper case equivalent in-place.
+    ///
+    /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z',
+    /// but non-ASCII letters are unchanged.
+    #[cfg(feature="std")]
+    pub fn make_ascii_uppercase(&mut self) {
+        *self = self.to_ascii_uppercase()
+    }
+    /// Converts the character to its ASCII lower case equivalent in-place.
+    ///
+    /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z',
+    /// but non-ASCII letters are unchanged.
+    #[cfg(feature="std")]
+    pub fn make_ascii_lowercase(&mut self) {
+        *self = self.to_ascii_lowercase();
+    }
+
+    /// Convert from UTF-16 to UTF-32
+    pub fn to_char(self) -> char {
+        self.into()
+    }
+    /// Write the internal representation to a slice,
+    /// and then returns the number of `u16`s written.
+    ///
+    /// # Panics
+    /// Will panic the buffer is too small;
+    /// You can get the required length from `.len()`,
+    /// but a buffer of length two is always large enough.
+    pub fn to_slice(self,  dst: &mut[u16]) -> usize {
+        // Write the last unit first to avoid repeated length checks.
+        let extra = self.units[1] as usize >> 15;
+        match dst.get_mut(extra) {
+            Some(first) => *first = self.units[extra],
+            None => panic!("The provided buffer is too small.")
+        }
+        if extra != 0 {dst[0] = self.units[0];}
+        extra+1
+    }
+    /// Get the character represented as an array of two units.
+    ///
+    /// The second `u16` is zero for codepoints that fit in one unit.
+    #[inline]
+    pub fn to_array(self) -> [u16;2] {
+        self.units
+    }
+    /// The second `u16` is used for surrogate pairs.
+    #[inline]
+    pub fn to_tuple(self) -> (u16,Option<u16>) {
+        (self.units[0],  if self.units[1]==0 {None} else {Some(self.units[1])})
+    }
+}