Implement conversions between AsciiString and Cow<'a, AsciiStr>

Closes #43

Author: tormol

src/ascii_string.rs

@@ -1,7 +1,7 @@
 #![cfg_attr(rustfmt, rustfmt_skip)]
 
 use std::{fmt, mem};
-use std::borrow::Borrow;
+use std::borrow::{Borrow, Cow};
 use std::error::Error;
 use std::any::Any;
 use std::str::FromStr;
@@ -449,6 +449,24 @@ impl Into<String> for AsciiString {
     }
 }
 
+impl<'a> From<Cow<'a,AsciiStr>> for AsciiString {
+    fn from(cow: Cow<'a,AsciiStr>) -> AsciiString {
+        cow.into_owned()
+    }
+}
+
+impl From<AsciiString> for Cow<'static,AsciiStr> {
+    fn from(string: AsciiString) -> Cow<'static,AsciiStr> {
+        Cow::Owned(string)
+    }
+}
+
+impl<'a> From<&'a AsciiStr> for Cow<'a,AsciiStr> {
+    fn from(s: &'a AsciiStr) -> Cow<'a,AsciiStr> {
+        Cow::Borrowed(s)
+    }
+}
+
 impl AsRef<AsciiStr> for AsciiString {
     #[inline]
     fn as_ref(&self) -> &AsciiStr {
@@ -524,6 +542,14 @@ impl<'a> FromIterator<&'a AsciiStr> for AsciiString {
     }
 }
 
+impl<'a> FromIterator<Cow<'a, AsciiStr>> for AsciiString {
+    fn from_iter<I: IntoIterator<Item = Cow<'a, AsciiStr>>>(iter: I) -> AsciiString {
+        let mut buf = AsciiString::new();
+        buf.extend(iter);
+        buf
+    }
+}
+
 impl Extend<AsciiChar> for AsciiString {
     fn extend<I: IntoIterator<Item = AsciiChar>>(&mut self, iterable: I) {
         let iterator = iterable.into_iter();
@@ -552,6 +578,17 @@ impl<'a> Extend<&'a AsciiStr> for AsciiString {
     }
 }
 
+impl<'a> Extend<Cow<'a, AsciiStr>> for AsciiString {
+    fn extend<I: IntoIterator<Item = Cow<'a,AsciiStr>>>(&mut self, iterable: I) {
+        let iterator = iterable.into_iter();
+        let (lower_bound, _) = iterator.size_hint();
+        self.reserve(lower_bound);
+        for s in iterator {
+            self.push_str(&*s);
+        }
+    }
+}
+
 impl<'a> Add<&'a AsciiStr> for AsciiString {
     type Output = AsciiString;
 

tests.rs

@@ -111,3 +111,31 @@ fn compare_ascii_string_slice() {
     assert_eq!(&b[..2], &c[..]);
     assert_eq!(c[1].as_char(), 'b');
 }
+
+#[test]
+#[cfg(feature = "std")]
+fn extend_from_iterator() {
+    use ::std::borrow::Cow;
+
+    let abc = "abc".as_ascii_str().unwrap();
+    let mut s = abc.chars().cloned().collect::<AsciiString>();
+    assert_eq!(s, abc);
+    s.extend(abc);
+    assert_eq!(s, "abcabc");
+
+    let lines = "one\ntwo\nthree".as_ascii_str().unwrap().lines();
+    s.extend(lines);
+    assert_eq!(s, "abcabconetwothree");
+
+    let cows = "ASCII Ascii ascii".as_ascii_str().unwrap()
+        .split(AsciiChar::Space)
+        .map(|case| {
+            if case.chars().all(|a| a.is_uppercase() ) {
+                Cow::from(case)
+            } else {
+                Cow::from(case.to_ascii_uppercase())
+            }
+        });
+    s.extend(cows);
+    assert_eq!(s, "abcabconetwothreeASCIIASCIIASCII");
+}