Add SecureRandom.base58

3 files changed, 45 insertions, 0 deletions

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 2756f7e0e2..a7306c2cae 100644
--- a/activesupport/CHANGELOG.md
+++ b/activesupport/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Add `SecureRandom.base58` for generation of random base58 strings.
+
+    *Matthew Draper + Guillermo Iguaran*
+
 *   Add `#prev_day` and `#next_day` counterparts to `#yesterday` and
     `#tomorrow` for `Date`, `Time`, and `DateTime`.
 
diff --git a/activesupport/lib/active_support/core_ext/securerandom.rb b/activesupport/lib/active_support/core_ext/securerandom.rb
new file mode 100644
index 0000000000..394cc76b98
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/securerandom.rb
@@ -0,0 +1,21 @@
+module SecureRandom
+  BASE58_ALPHABET = ('0'..'9').to_a  + ('A'..'Z').to_a + ('a'..'z').to_a - ['0', 'O', 'I', 'l']
+  # SecureRandom.base58 generates a random base58 string.
+  #
+  # The argument _n_ specifies the length, of the random string to be generated.
+  #
+  # If _n_ is not specified or is nil, 16 is assumed. It may be larger in the future.
+  #
+  # The result may contain alphanumeric characters except 0, O, I and l
+  #
+  #   p SecureRandom.base58 #=> "4kUgL2pdQMSCQtjE"
+  #   p SecureRandom.base58(24) #=> "77TMHrHJFvFDwodq8w7Ev2m7"
+  #
+  def self.base58(n = 16)
+    SecureRandom.random_bytes(n).unpack("C*").map do |byte|
+      idx = byte % 64
+      idx = SecureRandom.random_number(58) if idx >= 58
+      BASE58_ALPHABET[idx]
+    end.join
+  end
+end
diff --git a/activesupport/test/core_ext/securerandom.rb b/activesupport/test/core_ext/securerandom.rb
new file mode 100644
index 0000000000..dfacb7fe9f
--- /dev/null
+++ b/activesupport/test/core_ext/securerandom.rb
@@ -0,0 +1,20 @@
+require 'abstract_unit'
+require 'active_support/core_ext/securerandom'
+
+class SecureRandomTest < ActiveSupport::TestCase
+  def test_base58
+    s1 = SecureRandom.base58
+    s2 = SecureRandom.base58
+
+    assert_not_equal s1, s2
+    assert_equal 16, s1.length
+  end
+
+  def test_base58_with_length
+    s1 = SecureRandom.base58(24)
+    s2 = SecureRandom.base58(24)
+
+    assert_not_equal s1, s2
+    assert_equal 24, s1.length
+  end
+end