From 4284c8b5675def76af8b140e1073bf69840c9283 Mon Sep 17 00:00:00 2001
From: Louis Chatriot <louis.chatriot@gmail.com>
Date: Fri, 12 Jul 2013 16:59:55 +0200
Subject: [PATCH] Browser-specific customUtils module

---
 .gitignore                                    |  2 +
 .../browser-specific/customUtils.js           | 78 +++++++++++++++++++
 2 files changed, 80 insertions(+)
 create mode 100644 browser-version/browser-specific/customUtils.js

diff --git a/.gitignore b/.gitignore
index f6d5264..8b3ab2f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,3 +14,5 @@ results
 npm-debug.log
 workspace
 node_modules
+
+browser-version/src
diff --git a/browser-version/browser-specific/customUtils.js b/browser-version/browser-specific/customUtils.js
new file mode 100644
index 0000000..e1dfeeb
--- /dev/null
+++ b/browser-version/browser-specific/customUtils.js
@@ -0,0 +1,78 @@
+/**
+ * Specific customUtils for the browser, where we don't have access to the Crypto and Buffer modules
+ */
+
+/**
+ * Taken from the crypto-browserify module
+ * https://github.com/dominictarr/crypto-browserify
+ * NOTE: Math.random() does not guarantee "cryptographic quality" but we actually don't need it
+ */
+function randomBytes (size) {
+  var bytes = new Array(size);
+  var r;
+
+  for (var i = 0, r; i < size; i++) {
+    if ((i & 0x03) == 0) r = Math.random() * 0x100000000;
+    bytes[i] = r >>> ((i & 0x03) << 3) & 0xff;
+  }
+
+  return bytes;
+}
+
+
+/**
+ * Taken from the base64-js module
+ * https://github.com/beatgammit/base64-js/
+ */
+function byteArrayToBase64 (uint8) {
+  var lookup = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'
+    , extraBytes = uint8.length % 3   // if we have 1 byte left, pad 2 bytes
+    , output = ""
+    , temp, length, i;
+
+  function tripletToBase64 (num) {
+    return lookup[num >> 18 & 0x3F] + lookup[num >> 12 & 0x3F] + lookup[num >> 6 & 0x3F] + lookup[num & 0x3F];
+  };
+
+  // go through the array every three bytes, we'll deal with trailing stuff later
+  for (i = 0, length = uint8.length - extraBytes; i < length; i += 3) {
+    temp = (uint8[i] << 16) + (uint8[i + 1] << 8) + (uint8[i + 2]);
+    output += tripletToBase64(temp);
+  }
+
+  // pad the end with zeros, but make sure to not forget the extra bytes
+  switch (extraBytes) {
+    case 1:
+      temp = uint8[uint8.length - 1];
+      output += lookup[temp >> 2];
+      output += lookup[(temp << 4) & 0x3F];
+      output += '==';
+      break;
+    case 2:
+      temp = (uint8[uint8.length - 2] << 8) + (uint8[uint8.length - 1]);
+      output += lookup[temp >> 10];
+      output += lookup[(temp >> 4) & 0x3F];
+      output += lookup[(temp << 2) & 0x3F];
+      output += '=';
+      break;
+  }
+
+  return output;
+}
+
+
+/**
+ * Return a random alphanumerical string of length len
+ * There is a very small probability (less than 1/1,000,000) for the length to be less than len
+ * (il the base64 conversion yields too many pluses and slashes) but
+ * that's not an issue here
+ * The probability of a collision is extremely small (need 3*10^12 documents to have one chance in a million of a collision)
+ * See http://en.wikipedia.org/wiki/Birthday_problem
+ */
+function uid (len) {
+  return byteArrayToBase64(randomBytes(Math.ceil(Math.max(8, len * 2)))).replace(/[+\/]/g, '').slice(0, len);
+}
+
+
+
+module.exports.uid = uid;