1 files changed, 55 insertions, 0 deletions
diff --git a/js/flatbuffers.ts b/js/flatbuffers.ts
new file mode 100644
index 000000000..1ceb87951
--- /dev/null
+++ b/js/flatbuffers.ts
@@ -0,0 +1,55 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+
+import { flatbuffers } from "flatbuffers";
+import * as util from "./util";
+
+// Re-export some types.
+export type Offset = flatbuffers.Offset;
+export class ByteBuffer extends flatbuffers.ByteBuffer {}
+export interface Builder extends flatbuffers.Builder {
+  inUse: boolean;
+}
+
+const globalBuilder = new flatbuffers.Builder() as Builder;
+globalBuilder.inUse = false;
+
+// This is a wrapper around the real Builder .
+// The purpose is to reuse a single ArrayBuffer for every message.
+// We can do this because the "control" messages sent to the privileged
+// side are guarenteed to be used during the call to libdeno.send().
+export function createBuilder(): Builder {
+  // tslint:disable-next-line:no-any
+  const gb = globalBuilder as any;
+  util.assert(!gb.inUse);
+
+  let bb = globalBuilder.dataBuffer();
+  // Only create a new backing ArrayBuffer if the previous one had grown very
+  // large in capacity. This should only happen rarely.
+  if (bb.capacity() > 1024) {
+    util.log(`realloc flatbuffer ArrayBuffer because it was ${bb.capacity()}`);
+    bb = ByteBuffer.allocate(1024);
+  }
+  gb.bb = bb;
+  // Remaining space in the ByteBuffer.
+  gb.space = globalBuilder.dataBuffer().capacity();
+  // Minimum alignment encountered so far.
+  gb.minalign = 1;
+  // The vtable for the current table.
+  gb.vtable = null;
+  // The amount of fields we're actually using.
+  gb.vtable_in_use = 0;
+  // Whether we are currently serializing a table.
+  gb.isNested = false;
+  // Starting offset of the current struct/table.
+  gb.object_start = 0;
+  // List of offsets of all vtables.
+  gb.vtables = [];
+  // For the current vector being built.
+  gb.vector_num_elems = 0;
+  // False omits default values from the serialized data
+  gb.force_defaults = false;
+
+  gb.inUse = true;
+
+  return gb as Builder;
+}