Vendor things

third-party/vendor/peeking_take_while/README.md

@@ -0,0 +1,58 @@
+# `peeking_take_while`
+
+[![Build Status](https://travis-ci.org/fitzgen/peeking_take_while.png?branch=master)](https://travis-ci.org/fitzgen/peeking_take_while)
+
+Provides the `peeking_take_while` iterator adaptor method.
+
+The `peeking_take_while` method is very similar to `take_while`, but behaves
+differently when used with a borrowed iterator (perhaps returned by
+`Iterator::by_ref`).
+
+`peeking_take_while` peeks at the next item in the iterator and runs the
+predicate on that peeked item. This avoids consuming the first item yielded by
+the underlying iterator for which the predicate returns `false`. On the other
+hand, `take_while` will consume that first item for which the predicate returns
+`false`, and it will be lost.
+
+```rust
+extern crate peeking_take_while;
+
+// Bring the `peeking_take_while` method for peekable iterators into
+// scope.
+use peeking_take_while::PeekableExt;
+
+// Let's say we have two collections we want to iterate through: `xs` and
+// `ys`. We want to perform one operation on all the leading contiguous
+// elements that match some predicate, and a different thing with the rest of
+// the elements. With the `xs`, we will use the normal `take_while`. With the
+// `ys`, we will use `peeking_take_while`.
+
+let xs: Vec<u8> = (0..100).collect();
+let ys = xs.clone();
+
+let mut iter_xs = xs.into_iter();
+let mut iter_ys = ys.into_iter().peekable();
+
+{
+    // Let's do one thing with all the items that are less than 10.
+
+    let xs_less_than_ten = iter_xs.by_ref().take_while(|x| *x < 10);
+    for x in xs_less_than_ten {
+        do_things_with(x);
+    }
+
+    let ys_less_than_ten = iter_ys.by_ref().peeking_take_while(|y| *y < 10);
+    for y in ys_less_than_ten {
+        do_things_with(y);
+    }
+}
+
+// And now we will do some other thing with the items that are greater than
+// or equal to 10.
+
+// ...except, when using plain old `take_while` we lost 10!
+assert_eq!(iter_xs.next(), Some(11));
+
+// However, when using `peeking_take_while` we did not! Great!
+assert_eq!(iter_ys.next(), Some(10));
+```