Add SmallVector to libsyntax

Author: sfackler

src/libsyntax/lib.rs

@@ -31,6 +31,7 @@ pub mod util {
     pub mod interner;
     #[cfg(test)]
     pub mod parser_testing;
+    pub mod small_vector;
 }
 
 pub mod syntax {

src/libsyntax/util/small_vector.rs

@@ -0,0 +1,213 @@
+// Copyright 2013 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.
+use std::vec::MoveIterator;
+use std::util;
+
+/// A vector type optimized for cases where the size is almost always 0 or 1
+pub enum SmallVector<T> {
+    priv Zero,
+    priv One(T),
+    priv Many(~[T]),
+}
+
+impl<T> Container for SmallVector<T> {
+    fn len(&self) -> uint {
+        match *self {
+            Zero => 0,
+            One(*) => 1,
+            Many(ref vals) => vals.len()
+        }
+    }
+}
+
+impl<T> FromIterator<T> for SmallVector<T> {
+    fn from_iterator<I: Iterator<T>>(iter: &mut I) -> SmallVector<T> {
+        let mut v = Zero;
+        for val in *iter {
+            v.push(val);
+        }
+        v
+    }
+}
+
+impl<T> SmallVector<T> {
+    pub fn zero() -> SmallVector<T> {
+        Zero
+    }
+
+    pub fn one(v: T) -> SmallVector<T> {
+        One(v)
+    }
+
+    pub fn many(vs: ~[T]) -> SmallVector<T> {
+        Many(vs)
+    }
+
+    pub fn push(&mut self, v: T) {
+        match *self {
+            Zero => *self = One(v),
+            One(*) => {
+                let mut tmp = Many(~[]);
+                util::swap(self, &mut tmp);
+                match *self {
+                    Many(ref mut vs) => {
+                        match tmp {
+                            One(v1) => {
+                                vs.push(v1);
+                                vs.push(v);
+                            }
+                            _ => unreachable!()
+                        }
+                    }
+                    _ => unreachable!()
+                }
+            }
+            Many(ref mut vs) => vs.push(v)
+        }
+    }
+
+    pub fn get<'a>(&'a self, idx: uint) -> &'a T {
+        match *self {
+            One(ref v) if idx == 0 => v,
+            Many(ref vs) => &vs[idx],
+            _ => fail!("Out of bounds access")
+        }
+    }
+
+    pub fn iter<'a>(&'a self) -> SmallVectorIterator<'a, T> {
+        SmallVectorIterator {
+            vec: self,
+            idx: 0
+        }
+    }
+
+    pub fn move_iter(self) -> SmallVectorMoveIterator<T> {
+        match self {
+            Zero => ZeroIterator,
+            One(v) => OneIterator(v),
+            Many(vs) => ManyIterator(vs.move_iter())
+        }
+    }
+}
+
+pub struct SmallVectorIterator<'vec, T> {
+    priv vec: &'vec SmallVector<T>,
+    priv idx: uint
+}
+
+impl<'vec, T> Iterator<&'vec T> for SmallVectorIterator<'vec, T> {
+    fn next(&mut self) -> Option<&'vec T> {
+        if self.idx == self.vec.len() {
+            return None;
+        }
+
+        self.idx += 1;
+        Some(self.vec.get(self.idx - 1))
+    }
+
+    fn size_hint(&self) -> (uint, Option<uint>) {
+        let rem = self.vec.len() - self.idx;
+        (rem, Some(rem))
+    }
+}
+
+pub enum SmallVectorMoveIterator<T> {
+    priv ZeroIterator,
+    priv OneIterator(T),
+    priv ManyIterator(MoveIterator<T>),
+}
+
+impl<T> Iterator<T> for SmallVectorMoveIterator<T> {
+    fn next(&mut self) -> Option<T> {
+        match *self {
+            ZeroIterator => None,
+            OneIterator(*) => {
+                let mut replacement = ZeroIterator;
+                util::swap(self, &mut replacement);
+                match replacement {
+                    OneIterator(v) => Some(v),
+                    _ => unreachable!()
+                }
+            }
+            ManyIterator(ref mut inner) => inner.next()
+        }
+    }
+
+    fn size_hint(&self) -> (uint, Option<uint>) {
+        match *self {
+            ZeroIterator => (0, Some(0)),
+            OneIterator(*) => (1, Some(1)),
+            ManyIterator(ref inner) => inner.size_hint()
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_len() {
+        let v: SmallVector<int> = SmallVector::zero();
+        assert_eq!(0, v.len());
+
+        assert_eq!(1, SmallVector::one(1).len());
+        assert_eq!(5, SmallVector::many(~[1, 2, 3, 4, 5]).len());
+    }
+
+    #[test]
+    fn test_push_get() {
+        let mut v = SmallVector::zero();
+        v.push(1);
+        assert_eq!(1, v.len());
+        assert_eq!(&1, v.get(0));
+        v.push(2);
+        assert_eq!(2, v.len());
+        assert_eq!(&2, v.get(1));
+        v.push(3);
+        assert_eq!(3, v.len());
+        assert_eq!(&3, v.get(2));
+    }
+
+    #[test]
+    fn test_from_iterator() {
+        let v: SmallVector<int> = (~[1, 2, 3]).move_iter().collect();
+        assert_eq!(3, v.len());
+        assert_eq!(&1, v.get(0));
+        assert_eq!(&2, v.get(1));
+        assert_eq!(&3, v.get(2));
+    }
+
+    #[test]
+    fn test_iter() {
+        let v = SmallVector::zero();
+        let v: ~[&int] = v.iter().collect();
+        assert_eq!(~[], v);
+
+        let v = SmallVector::one(1);
+        assert_eq!(~[&1], v.iter().collect());
+
+        let v = SmallVector::many(~[1, 2, 3]);
+        assert_eq!(~[&1, &2, &3], v.iter().collect());
+    }
+
+    #[test]
+    fn test_move_iter() {
+        let v = SmallVector::zero();
+        let v: ~[int] = v.move_iter().collect();
+        assert_eq!(~[], v);
+
+        let v = SmallVector::one(1);
+        assert_eq!(~[1], v.move_iter().collect());
+
+        let v = SmallVector::many(~[1, 2, 3]);
+        assert_eq!(~[1, 2, 3], v.move_iter().collect());
+    }
+}