Writing partial lengths

src/packet/packet.js

@@ -68,6 +68,18 @@ export default {
     return util.concatUint8Array([new Uint8Array([255]), util.writeNumber(length, 4)]);
   },
 
+  writePartialLength: function(power) {
+    if (power < 0 || power > 30) {
+      throw new Error('Partial Length power must be between 1 and 30');
+    }
+    return new Uint8Array([224 + power]);
+  },
+
+  writeTag: function(tag_type) {
+    /* we're only generating v4 packet headers here */
+    return new Uint8Array([0xC0 | tag_type]);
+  },
+
   /**
    * Writes a packet header version 4 with the given tag_type and length to a
    * string
@@ -78,7 +90,7 @@ export default {
    */
   writeHeader: function(tag_type, length) {
     /* we're only generating v4 packet headers here */
-    return util.concatUint8Array([new Uint8Array([0xC0 | tag_type]), this.writeSimpleLength(length)]);
+    return util.concatUint8Array([this.writeTag(tag_type), this.writeSimpleLength(length)]);
   },
 
   /**

src/packet/packetlist.js

@@ -72,8 +72,31 @@ List.prototype.write = function () {
 
   for (let i = 0; i < this.length; i++) {
     const packetbytes = this[i].write();
-    arr.push(packetParser.writeHeader(this[i].tag, packetbytes.length));
-    arr.push(packetbytes);
+    if (util.isStream(packetbytes)) {
+      let buffer = [];
+      let bufferLength = 0;
+      const minLength = 512;
+      arr.push(packetParser.writeTag(this[i].tag));
+      arr.push(packetbytes.transform((done, value) => {
+        if (!done) {
+          buffer.push(value);
+          bufferLength += value.length;
+          if (bufferLength >= minLength) {
+            const powerOf2 = Math.min(Math.log(bufferLength) / Math.LN2 | 0, 30);
+            const chunkSize = 2 ** powerOf2;
+            const bufferConcat = util.concatUint8Array([packetParser.writePartialLength(powerOf2)].concat(buffer));
+            buffer = [bufferConcat.subarray(1 + chunkSize)];
+            bufferLength = buffer[0].length;
+            return bufferConcat.subarray(0, 1 + chunkSize);
+          }
+        } else {
+          return util.concatUint8Array([packetParser.writeSimpleLength(bufferLength)].concat(buffer));
+        }
+      }));
+    } else {
+      arr.push(packetParser.writeHeader(this[i].tag, packetbytes.length));
+      arr.push(packetbytes);
+    }
   }
 
   return util.concatUint8Array(arr);