rustc: Add a "smallintmap" implementation

Author: pcwalton

src/lib/smallintmap.rs

@@ -0,0 +1,40 @@
+/// A simple map based on a vector for small integer keys. Space requirements
+/// are O(highest integer key).
+
+import option::none;
+import option::some;
+
+type smallintmap[T] = rec(mutable vec[mutable option::t[T]] v);
+
+fn mk[T]() -> smallintmap[T] {
+    let vec[mutable option::t[T]] v = [mutable];
+    ret rec(mutable v=v);
+}
+
+fn insert[T](&smallintmap[T] m, uint key, &T val) {
+    vec::grow_set[option::t[T]](m.v, key, none[T], some[T](val));
+}
+
+fn find[T](&smallintmap[T] m, uint key) -> option::t[T] {
+    if (key < vec::len[option::t[T]](m.v)) { ret m.v.(key); }
+    ret none[T];
+}
+
+fn get[T](&smallintmap[T] m, uint key) -> T {
+    alt (find[T](m, key)) {
+        case (none[T]) {
+            log_err "smallintmap::get(): key not present";
+            fail;
+        }
+        case (some[T](?v)) { ret v; }
+    }
+}
+
+fn contains_key[T](&smallintmap[T] m, uint key) -> bool {
+    ret !option::is_none(find[T](m, key));
+}
+
+fn truncate[T](&smallintmap[T] m, uint len) {
+    m.v = vec::slice_mut[option::t[T]](m.v, 0u, len);
+}
+

src/lib/std.rc

@@ -76,6 +76,7 @@ mod box;
 mod getopts;
 mod term;
 mod time;
+mod smallintmap;
 
 // Local Variables:
 // mode: rust;

src/lib/vec.rs

@@ -163,6 +163,19 @@ fn slice[T](array[T] v, uint start, uint end) -> vec[T] {
     ret result;
 }
 
+// FIXME: Should go away eventually.
+fn slice_mut[T](array[T] v, uint start, uint end) -> vec[mutable T] {
+    assert (start <= end);
+    assert (end <= len[T](v));
+    auto result = alloc_mut[T](end - start);
+    let uint i = start;
+    while (i < end) {
+        result += [mutable v.(i)];
+        i += 1u;
+    }
+    ret result;
+}
+
 fn shift[T](&mutable array[T] v) -> T {
     auto ln = len[T](v);
     assert (ln > 0u);