Add a codec that enables conversion to and from a base N representation

Adds a codec that enables easy conversion from an array of bytes to any
numeric base in [2, 256) and back again, using a supplied custom alphabet.

Implemented by treating the input byte sequence to encode verbatim as a
big-endian `BigInteger` and iteratively doing a `divmod` operation until
the quotient is zero, emitting the modulus mapped onto the alphabet for
each iteration.

Decoding reverses this process, ending up with the same `BigInteger` as
in the initial encoding step.

1 files changed, 21 insertions, 0 deletions

diff --git a/security-utils/src/main/java/com/yahoo/security/Base62.java b/security-utils/src/main/java/com/yahoo/security/Base62.java
new file mode 100644
index 00000000000..86c60a1bb1d
--- /dev/null
+++ b/security-utils/src/main/java/com/yahoo/security/Base62.java
@@ -0,0 +1,21 @@
+// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.security;
+
+/**
+ * Base62 encoding which has the nice property that it does not feature any
+ * potential word/line-breaking characters, which means encoded strings can
+ * usually be selected in one go on web pages or in the terminal.
+ *
+ * @see <a href="https://en.wikipedia.org/wiki/Base62">Base62 on Wiki</a>
+ *
+ * @author vekterli
+ */
+public class Base62 {
+
+    private static final BaseNCodec INSTANCE = BaseNCodec.of("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz");
+
+    public static BaseNCodec codec() {
+        return INSTANCE;
+    }
+
+}