From 594b379a77317bee80b3eb8c9197c7935065dbbf Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonygarnockjones@gmail.com>
Date: Mon, 19 Nov 2018 16:55:14 +0000
Subject: [PATCH] Ability to feed JS Decoder

---
 implementations/javascript/src/codec.js | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/implementations/javascript/src/codec.js b/implementations/javascript/src/codec.js
index 61482e0..d2cf154 100644
--- a/implementations/javascript/src/codec.js
+++ b/implementations/javascript/src/codec.js
@@ -18,11 +18,18 @@ class ShortPacket extends DecodeError {}
 class Decoder {
   constructor(packet, options) {
     options = options || {};
-    this.packet = packet._view || packet; // strip off Bytes wrapper, if any
+    this.packet = packet
+      ? (packet._view || packet) // strip off Bytes wrapper, if any
+      : new Uint8Array(0);
     this.index = 0;
     this.shortForms = options.shortForms || {};
   }
 
+  write(data) {
+    this.packet = Bytes.concat([this.packet.slice(this.index), data])._view;
+    this.index = 0;
+  }
+
   nextbyte() {
     if (this.index >= this.packet.length) throw new ShortPacket("Short packet");
     // ^ NOTE: greater-than-or-equal-to, not greater-than.
@@ -174,6 +181,19 @@ class Decoder {
         return this.decodecollection(minor, this.nextvalues(this.wirelength(arg)));
     }
   }
+
+  try_next() {
+    const start = this.index;
+    try {
+      return this.next();
+    } catch (e) {
+      if (e instanceof ShortPacket) {
+        this.index = start;
+        return void 0;
+      }
+      throw e;
+    }
+  }
 }
 
 class Encoder {