CBOR support for 64-bit integer arrays

src/util/cborTypedArrayTags.js

@@ -1,22 +1,71 @@
 'use strict';
 
+var warnedPrecision = false;
+function warnPrecision() {
+  if (!warnedPrecision) {
+    warnedPrecision = true;
+    console.warn('64-bit integer array values may lose precision. No further warnings.');
+  }
+}
+
+function decodeUint64LE(data) {
+  warnPrecision();
+
+  var uint32View = new Uint32Array(data);
+  var len = data.byteLength / 8;
+  var arr = new Array(len);
+  for (var i = 0; i < len; i++) {
+    var si = i * 2;
+    var lo = uint32View[si];
+    var hi = uint32View[si+1];
+    arr[i] = lo + Math.pow(2, 32) * hi;
+  }
+
+  return arr;
+}
+
+function decodeInt64LE(data) {
+  warnPrecision();
+
+  var uint32View = new Uint32Array(data);
+  var int32View = new Int32Array(data);
+  var len = data.byteLength / 8;
+  var arr = new Array(len);
+  for (var i = 0; i < len; i++) {
+    var si = i * 2;
+    var lo = uint32View[si];
+    var hi = int32View[si+1];
+    arr[i] = lo + Math.pow(2, 32) * hi;
+  }
+
+  return arr;
+}
+
 // Support a subset of draft CBOR typed array tags:
 //  <https://tools.ietf.org/html/draft-ietf-cbor-array-tags-00>
-// Only support little-endian tags with native JavaScript types for now.
-var taggedArrayTypes = {
+// Only support little-endian tags for now.
+var nativeArrayTypes = {
   64: Uint8Array,
   69: Uint16Array,
   70: Uint32Array,
-  77: Int8Array,
-  78: Int16Array,
-  79: Int32Array,
+  72: Int8Array,
+  77: Int16Array,
+  78: Int32Array,
   85: Float32Array,
   86: Float64Array
 };
 
+var conversionArrayTypes = {
+  71: decodeUint64LE,
+  79: decodeInt64LE
+};
+
 function typedArrayTagger(data, tag) {
-  if (tag in taggedArrayTypes) {
-    return new taggedArrayTypes[tag](data);
+  if (tag in nativeArrayTypes) {
+    return new nativeArrayTypes[tag](data);
+  }
+  if (tag in conversionArrayTypes) {
+    return conversionArrayTypes[tag](data);
   }
   return data;
 }