From 3cdb9039b359ef7e19e2093062909e140320994c Mon Sep 17 00:00:00 2001
From: Andrei Mihu <andrei.mihu@gmx.com>
Date: Sat, 24 Oct 2015 21:18:59 +0100
Subject: [PATCH] Default to strong PRNG for UUID4, allow weak if explicitly
 requested. Closes #9.

---
 .travis.yml  |  5 +++--
 CHANGELOG.md |  4 ++++
 README.md    | 12 +++++++++---
 lib/uuid.ex  | 32 +++++++++++++++++++++++++++++++-
 mix.exs      |  2 +-
 mix.lock     |  4 ++--
 6 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 192f655..442cd96 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,6 @@
 language: elixir
 elixir:
-- 1.0.4
+- 1.0.5
 otp_release:
-- 17.1
+- 18.0
+sudo: false
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 110c22c..f8b473a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@ None.
 
 ---
 
+### v1.1.0, 24 Oct 2015, Elixir `~> 1.0`
+
+* [Enhancement] `uuid4` now accepts an additional first argument `:strong` (default) or `:weak`, indicating whether to use strong PRNG or not.
+
 ### v1.0.1, 30 May 2015, Elixir `~> 1.0`
 
 * [Internal] Use `:os.timestamp/1` instead of `:erlang.now/1`.
diff --git a/README.md b/README.md
index 0bcb75b..cf60cf3 100644
--- a/README.md
+++ b/README.md
@@ -5,12 +5,12 @@ UUID generator and utilities for [Elixir](http://elixir-lang.org/). See [RFC 412
 
 ### Installation
 
-The latest version is `1.0.1` and requires Elixir `~> 1.0`. New releases may change this minimum compatible version depending on breaking language changes. The [changelog](https://github.com/zyro/elixir-uuid/blob/master/CHANGELOG.md) lists every available release and its corresponding language version requirement.
+The latest version is `1.1.0` and requires Elixir `~> 1.0`. New releases may change this minimum compatible version depending on breaking language changes. The [changelog](https://github.com/zyro/elixir-uuid/blob/master/CHANGELOG.md) lists every available release and its corresponding language version requirement.
 
 Releases are published through [hex.pm](https://hex.pm/packages/uuid). Add as a dependency in your `mix.exs` file:
 ```elixir
 defp deps do
-  [ { :uuid, "~> 1.0" } ]
+  [ { :uuid, "~> 1.1" } ]
 end
 ```
 
@@ -37,11 +37,14 @@ iex> UUID.uuid3("5976423a-ee35-11e3-8569-14109ff1a304", "my.domain.com")
 
 ### UUID v4
 
-Generated based on pseudo-random bytes.
+Generated based on pseudo-random bytes. Accepts optional `:strong` (default) or `:weak` parameter.
 
 ```elixir
 iex> UUID.uuid4()
 "fcfe5f21-8a08-4c9a-9f97-29d2fd6a27b9"
+
+iex> UUID.uuid4(:weak)
+"cd63a9c4-0b4e-477a-8229-3f3aa971a37b"
 ```
 
 ### UUID v5
@@ -81,6 +84,9 @@ iex> UUID.uuid5(:dns, "my.domain.com", :default)
 ```elixir
 iex> UUID.uuid4(:hex)
 "19be859d0c1f4a7f95ddced995037350"
+
+iex> UUID.uuid4(:weak, :hex)
+"ebeff765ddc843e486c287fb668d5d37"
 ```
 
 `:urn` is a standard UUID representation prefixed with the UUID URN:
diff --git a/lib/uuid.ex b/lib/uuid.ex
index 86a5cc0..5b04e77 100644
--- a/lib/uuid.ex
+++ b/lib/uuid.ex
@@ -261,29 +261,59 @@ defmodule UUID do
   Generate a new UUID v4. This version uses pseudo-random bytes generated by
   the `crypto` module.
 
+  Accepts optional `:strong` (default) or `:weak` parameter.
+
   ## Examples
 
   ```elixir
+  # Equivalent to: UUID.uuid4(:strong, :default)
   iex> UUID.uuid4()
   "fb49a0ec-d60c-4d20-9264-3b4cfe272106"
 
+  # Equivalent to: UUID.uuid4(:strong, :default)
+  iex> UUID.uuid4(:strong)
+  "fb49a0ec-d60c-4d20-9264-3b4cfe272106"
+
+  # Equivalent to: UUID.uuid4(:weak, :default)
+  iex> UUID.uuid4(:weak)
+  "cd63a9c4-0b4e-477a-8229-3f3aa971a37b"
+
+  # Equivalent to: UUID.uuid4(:strong, :default)
   iex> UUID.uuid4(:default)
   "fb49a0ec-d60c-4d20-9264-3b4cfe272106"
 
+  # Equivalent to: UUID.uuid4(:strong, :hex)
   iex> UUID.uuid4(:hex)
   "fb49a0ecd60c4d2092643b4cfe272106"
 
+  # Equivalent to: UUID.uuid4(:strong, :urn)
   iex> UUID.uuid4(:urn)
   "urn:uuid:fb49a0ec-d60c-4d20-9264-3b4cfe272106"
 
+  iex> UUID.uuid4(:weak, :urn)
+  "urn:uuid:cd63a9c4-0b4e-477a-8229-3f3aa971a37b"
   ```
 
   """
-  def uuid4(format \\ :default) do
+  def uuid4(), do: uuid4(:strong, :default)
+
+  def uuid4(:strong), do: uuid4(:strong, :default)
+  def uuid4(:weak),   do: uuid4(:weak, :default)
+  def uuid4(format),  do: uuid4(:strong, format)
+
+  def uuid4(:strong, format) do
+    <<u0::48, _::4, u1::12, _::2, u2::62>> = :crypto.strong_rand_bytes(16)
+    <<u0::48, @uuid_v4::4, u1::12, @variant10::2, u2::62>>
+      |> uuid_to_string format
+  end
+  def uuid4(:weak, format) do
     <<u0::48, _::4, u1::12, _::2, u2::62>> = :crypto.rand_bytes(16)
     <<u0::48, @uuid_v4::4, u1::12, @variant10::2, u2::62>>
       |> uuid_to_string format
   end
+  def uuid4(_, _) do
+    raise ArgumentError, message: "Invalid argument; Expected :strong|:weak"
+  end
 
   @doc """
   Generate a new UUID v5. This version uses an SHA1 hash of fixed value (chosen
diff --git a/mix.exs b/mix.exs
index d6fa4b5..b708426 100644
--- a/mix.exs
+++ b/mix.exs
@@ -4,7 +4,7 @@ defmodule UUID.Mixfile do
   def project do
     [app: :uuid,
      name: "UUID",
-     version: "1.0.1",
+     version: "1.1.0",
      source_url: "https://github.com/zyro/elixir-uuid",
      homepage_url: "http://hexdocs.pm/uuid",
      elixir: "~> 1.0",
diff --git a/mix.lock b/mix.lock
index ccc3845..ae6730f 100644
--- a/mix.lock
+++ b/mix.lock
@@ -1,3 +1,3 @@
 %{"benchfella": {:hex, :benchfella, "0.2.1"},
-  "earmark": {:hex, :earmark, "0.1.17"},
-  "ex_doc": {:hex, :ex_doc, "0.8.4"}}
+  "earmark": {:hex, :earmark, "0.1.18"},
+  "ex_doc": {:hex, :ex_doc, "0.10.0"}}