stdlib: Implement arenas

Author: pcwalton

src/libstd/arena.rs

@@ -0,0 +1,38 @@
+// Dynamic arenas.
+
+export arena, arena_with_size;
+
+import list;
+
+type chunk = {data: [u8], mut fill: uint};
+type arena = {mut chunks: list::list<@chunk>};
+
+fn chunk(size: uint) -> @chunk {
+    @{ data: vec::from_elem(size, 0u8), mut fill: 0u }
+}
+
+fn arena_with_size(initial_size: uint) -> arena {
+    ret {mut chunks: list::cons(chunk(initial_size), @list::nil)};
+}
+
+fn arena() -> arena {
+    arena_with_size(32u)
+}
+
+impl arena for arena {
+    unsafe fn alloc<T>(n_bytes: uint) -> &self.T {
+        let mut head = list::head(self.chunks);
+        if head.fill + n_bytes > vec::len(head.data) {
+            // Allocate a new chunk.
+            let new_min_chunk_size = uint::max(n_bytes, vec::len(head.data));
+            head = chunk(uint::next_power_of_two(new_min_chunk_size));
+            self.chunks = list::cons(head, @self.chunks);
+        }
+
+        let start = vec::unsafe::to_ptr(head.data);
+        let p = ptr::offset(start, head.fill);
+        head.fill += n_bytes;
+        ret unsafe::reinterpret_cast(p);
+    }
+}
+

src/libstd/std.rc

@@ -11,7 +11,7 @@
 export net, uv;
 export c_vec, four, tri, util;
 export bitv, deque, fun_treemap, list, map, smallintmap, sort, treemap, ufind;
-export rope;
+export rope, arena;
 export ebml, dbg, getopts, json, rand, sha1, term, time, prettyprint;
 export test, tempfile, serialization;
 
@@ -56,6 +56,7 @@ mod tempfile;
 mod term;
 mod time;
 mod prettyprint;
+mod arena;
 
 #[cfg(unicode)]
 mod unicode;

src/rustc/metadata/encoder.rs

@@ -672,9 +672,9 @@ fn encode_info_for_items(ecx: @encode_ctxt, ebml_w: ebml::writer,
                                       *pt, none, tps, ctor.node.dec)
                   }
                   _ {}
+                }
+              }
             }
-           }
-          }
         },
         visit_native_item: {|ni, cx, v|
             visit::visit_native_item(ni, cx, v);