Added ByteEnum interface to ActionScript, and ByteEnumUtil.

Use this if you want your enums to persist to a byte reliably.
Coming soonesque: narya streaming support for ByteEnum.


git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@5859 542714f4-19e9-0310-aa3c-eee0fc999fb1

src/as/com/threerings/util/ByteEnum.as

@@ -0,0 +1,16 @@
+//
+// $Id$
+
+package com.threerings.util {
+
+/**
+ * An enum value that can be persisted as a byte.
+ */
+public interface ByteEnum
+{
+    /**
+     * Return the byte form of this enum.
+     */
+    function toByte () :int;
+}
+}

src/as/com/threerings/util/ByteEnumUtil.as

@@ -0,0 +1,26 @@
+//
+// $Id$
+
+package com.threerings.util {
+
+/**
+ * ByteEnum utility methods.
+ */
+public class ByteEnumUtil
+{
+    /**
+     * Returns the enum value with the specified code in the supplied enum class.
+     * Throws ArgumentError if the enum lacks a value that maps to the supplied code.
+     */
+    public static function fromByte (clazz :Class, code :int) :Enum
+    {
+        // we could do something fancier than this O(n) impl, in the future...
+        for each (var e :Enum in Enum.values(clazz)) {
+            if (ByteEnum(e).toByte() == code) {
+                return e;
+            }
+        }
+        throw new ArgumentError(clazz + " has no value with code " + code);
+    }
+}
+}