Change implementation of syntax::util::SmallVector to use data_structures::SmallVec.

1 files changed, 203 insertions, 0 deletions

diff --git a/src/librustc_data_structures/small_vec.rs b/src/librustc_data_structures/small_vec.rs
new file mode 100644
index 00000000000..565a3c443a3
--- /dev/null
+++ b/src/librustc_data_structures/small_vec.rs
@@ -0,0 +1,203 @@
+// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! A vector type intended to be used for collecting from iterators onto the stack.
+//!
+//! Space for up to N elements is provided on the stack.  If more elements are collected, Vec is
+//! used to store the values on the heap. SmallVec is similar to AccumulateVec, but adds
+//! the ability to push elements.
+//!
+//! The N above is determined by Array's implementor, by way of an associatated constant.
+
+use std::ops::{Deref, DerefMut};
+use std::iter::{IntoIterator, FromIterator};
+use std::fmt::{self, Debug};
+use std::mem;
+use std::ptr;
+
+use rustc_serialize::{Encodable, Encoder, Decodable, Decoder};
+
+use accumulate_vec::{IntoIter, AccumulateVec};
+use array_vec::Array;
+
+pub struct SmallVec<A: Array>(AccumulateVec<A>);
+
+impl<A> Clone for SmallVec<A>
+    where A: Array,
+          A::Element: Clone {
+    fn clone(&self) -> Self {
+        SmallVec(self.0.clone())
+    }
+}
+
+impl<A> Debug for SmallVec<A>
+    where A: Array + Debug,
+          A::Element: Debug {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_tuple("SmallVec").field(&self.0).finish()
+    }
+}
+
+impl<A: Array> SmallVec<A> {
+    pub fn new() -> Self {
+        SmallVec(AccumulateVec::new())
+    }
+
+    pub fn with_capacity(cap: usize) -> Self {
+        let mut vec = SmallVec::new();
+        vec.reserve(cap);
+        vec
+    }
+
+    pub fn one(el: A::Element) -> Self {
+        SmallVec(AccumulateVec::one(el))
+    }
+
+    pub fn many<I: IntoIterator<Item=A::Element>>(els: I) -> Self {
+        SmallVec(AccumulateVec::many(els))
+    }
+
+    pub fn expect_one(self, err: &'static str) -> A::Element {
+        assert!(self.len() == 1, err);
+        match self.0 {
+            AccumulateVec::Array(arr) => arr.into_iter().next().unwrap(),
+            AccumulateVec::Heap(vec) => vec.into_iter().next().unwrap(),
+        }
+    }
+
+    /// Will reallocate onto the heap if needed.
+    pub fn push(&mut self, el: A::Element) {
+        self.reserve(1);
+        match self.0 {
+            AccumulateVec::Array(ref mut array) => array.push(el),
+            AccumulateVec::Heap(ref mut vec) => vec.push(el),
+        }
+    }
+
+    pub fn reserve(&mut self, n: usize) {
+        match self.0 {
+            AccumulateVec::Array(_) => {
+                if self.len() + n > A::LEN {
+                    let len = self.len();
+                    let array = mem::replace(&mut self.0,
+                            AccumulateVec::Heap(Vec::with_capacity(len + n)));
+                    if let AccumulateVec::Array(array) = array {
+                        match self.0 {
+                            AccumulateVec::Heap(ref mut vec) => vec.extend(array),
+                            _ => unreachable!()
+                        }
+                    }
+                }
+            }
+            AccumulateVec::Heap(ref mut vec) => vec.reserve(n)
+        }
+    }
+
+    pub unsafe fn set_len(&mut self, len: usize) {
+        match self.0 {
+            AccumulateVec::Array(ref mut arr) => arr.set_len(len),
+            AccumulateVec::Heap(ref mut vec) => vec.set_len(len),
+        }
+    }
+
+    pub fn insert(&mut self, index: usize, element: A::Element) {
+        let len = self.len();
+
+        // Reserve space for shifting elements to the right
+        self.reserve(1);
+
+        assert!(index <= len);
+
+        unsafe {
+            // infallible
+            // The spot to put the new value
+            {
+                let p = self.as_mut_ptr().offset(index as isize);
+                // Shift everything over to make space. (Duplicating the
+                // `index`th element into two consecutive places.)
+                ptr::copy(p, p.offset(1), len - index);
+                // Write it in, overwriting the first copy of the `index`th
+                // element.
+                ptr::write(p, element);
+            }
+            self.set_len(len + 1);
+        }
+    }
+}
+
+impl<A: Array> Deref for SmallVec<A> {
+    type Target = AccumulateVec<A>;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<A: Array> DerefMut for SmallVec<A> {
+    fn deref_mut(&mut self) -> &mut AccumulateVec<A> {
+        &mut self.0
+    }
+}
+
+impl<A: Array> FromIterator<A::Element> for SmallVec<A> {
+    fn from_iter<I>(iter: I) -> Self where I: IntoIterator<Item=A::Element> {
+        SmallVec(iter.into_iter().collect())
+    }
+}
+
+impl<A: Array> Extend<A::Element> for SmallVec<A> {
+    fn extend<I: IntoIterator<Item=A::Element>>(&mut self, iter: I) {
+        let iter = iter.into_iter();
+        self.reserve(iter.size_hint().0);
+        for el in iter {
+            self.push(el);
+        }
+    }
+}
+
+impl<A: Array> IntoIterator for SmallVec<A> {
+    type Item = A::Element;
+    type IntoIter = IntoIter<A>;
+    fn into_iter(self) -> Self::IntoIter {
+        self.0.into_iter()
+    }
+}
+
+impl<A: Array> Default for SmallVec<A> {
+    fn default() -> SmallVec<A> {
+        SmallVec::new()
+    }
+}
+
+impl<A> Encodable for SmallVec<A>
+    where A: Array,
+          A::Element: Encodable {
+    fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
+        s.emit_seq(self.len(), |s| {
+            for (i, e) in self.iter().enumerate() {
+                try!(s.emit_seq_elt(i, |s| e.encode(s)));
+            }
+            Ok(())
+        })
+    }
+}
+
+impl<A> Decodable for SmallVec<A>
+    where A: Array,
+          A::Element: Decodable {
+    fn decode<D: Decoder>(d: &mut D) -> Result<SmallVec<A>, D::Error> {
+        d.read_seq(|d, len| {
+            let mut vec = SmallVec::with_capacity(len);
+            for i in 0..len {
+                vec.push(try!(d.read_seq_elt(i, |d| Decodable::decode(d))));
+            }
+            Ok(vec)
+        })
+    }
+}