Convert pack sketch to a test.

Closes #319.

release.md

@@ -1,5 +1,6 @@
 ### Issue by Issue
 
+ * Convert pack sketch to a test. #319.
  * Convert signage sketch to a test. #318.
  * Convert unpack sketch to a test. #317.
  * Use `signage` for signed whole integers. #316.

t/serialize/pack.t.js

@@ -0,0 +1,24 @@
+require('proof')(3, function (equal) {
+    require('../..') // satisfy coverage
+
+    function pack (bits, offset, size) {
+        var mask = 0xffffffff, shift
+        mask = mask >>> 32 - bits
+        mask = mask >>> bits - size
+        shift = bits - offset - size
+        mask = mask << shift >>> 0
+        if (shift) {
+            return '(value << ' + shift + ' & 0x' + mask.toString(16) + ') >>> 0'
+        } else {
+            return '(value & 0x' + mask.toString(16) + ') >>> 0'
+        }
+    }
+
+    var f = new Function('value', 'return ' + pack(16, 5, 7))
+    equal(f(0x7f).toString(2), '11111110000', 'short')
+    var f = new Function('value', 'return ' + pack(32, 0, 2))
+    equal(f(0x3).toString(2), '11000000000000000000000000000000', 'short')
+    console.log(pack(16, 13, 3))
+    var f = new Function('value', 'return ' + pack(16, 13, 3))
+    equal(f(0xff).toString(2), '111', 'no left shift')
+})