diff --git a/src/protocol.js b/src/protocol.js
index f3b9632..2b154ec 100644
--- a/src/protocol.js
+++ b/src/protocol.js
@@ -591,14 +591,22 @@ function readRestBuffer(buffer, offset, typeArgs, rootNode) {
     };
 }
 
+function evalCount(count,fields)
+{
+    if(fields[count["field"]] in count["map"])
+        return count["map"][fields[count["field"]]];
+    return count["default"];
+}
+
 function readArray(buffer, offset, typeArgs, rootNode) {
     var results = {
         value: [],
         size: 0
     }
     var count;
-    if (typeof typeArgs.count === "function")
-      count = typeArgs.count(rootNode);
+    if (typeof typeArgs.count === "object") {
+        count = evalCount(typeArgs.count,rootNode);
+    }
     else
       count = getField(typeArgs.count, rootNode);
     for (var i = 0; i < count; i++) {
diff --git a/src/protocol_def.js b/src/protocol_def.js
index 528d6db..3ff565f 100644
--- a/src/protocol_def.js
+++ b/src/protocol_def.js
@@ -358,14 +358,9 @@ module.exports= {
                 { name: "offsetZ", type: "float" },
                 { name: "particleData", type: "float" },
                 { name: "particles", type: "int" },
-                { name: "data", type: "array", typeArgs: { count: function(fields) {
-                    if (fields.particleId === 36)
-                        return 2;
-                    else if (fields.particleId === 37 || fields.particleId === 38)
-                        return 1;
-                    else
-                        return 0;
-                }, type: "varint" } }
+                { name: "data", type: "array",
+                    typeArgs: { count: {"field":"particleId","map":{"36":2,"37":1,"38":1},"default":0},
+                        type: "varint" } }
             ]},
             game_state_change:  {id: 0x2b, fields: [
                 { name: "reason", type: "ubyte" },