Adds a base32 component.

components/base32/base32.h

Index: components/base32/base32.h
diff --git a/components/base32/base32.h b/components/base32/base32.h
new file mode 100644
index 0000000000000000000000000000000000000000..b07637968f4fb46cba6e39c5e6906972115cdc86
--- /dev/null
+++ b/components/base32/base32.h
@@ -0,0 +1,32 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_BASE32_BASE32_H_
+#define COMPONENTS_BASE32_BASE32_H_
+
+#include <string>
+
+#include "base/strings/string_piece.h"
+
+namespace base32 {
+
+enum class Base32EncodePolicy {
+  // Include the trailing padding in the output, when necessary.
+  INCLUDE_PADDING,
+  // Remove the trailing padding from the output.
+  OMIT_PADDING
+};
+
+// Encodes the |input| string in base32, defined in RFC 4648:
+// https://tools.ietf.org/html/rfc4648#section-5
+//
+// The |policy| defines whether padding should be included or omitted from the
+// encoded |*output|. |input| and |*output| must not reference the same storage.
+void Base32Encode(base::StringPiece input,

[sdefresne, 2016/06/01 14:45:10]

It looks like this class is usually passed by const-reference, so maybe do it
here too

void Base32Encode(const base::StringPiece& input, ...);

It also looks strange to have this class return a std::string by pointer. The
compiler should generally be able to do return value optimisation for such a
class, so why not have the simpler interface?

std::string Base32Encode(const base::StringPiece& input, Base32EncodePolicy
policy);

[Rob Percival, 2016/06/01 14:49:52]

RE StringPiece const-ref: base/strings/string_piece.h says to pass it by value
unless circumstances require otherwise
(https://code.google.com/p/chromium/codesearch#chromium/src/base/strings/strin...).

RE returning string: I thought you might say that - I'd actually prefer
returning a string like that. I only did it this way to match the
Base64UrlEncode function signature
(https://code.google.com/p/chromium/codesearch#chromium/src/base/base64url.h&l=30),
but I'm happy to change it.

[sdefresne, 2016/06/01 14:57:30]

Ack. I was looking for that very comment thank you finding it.
I'd prefer to have the function return a std::string if possible even if it make
the signature differ from Base64UrlEncode (I think Base64UrlEncode takes output
by pointer because it support input and output to point to the same storage
which is not the case here).

[Rob Percival, 2016/06/01 15:04:40]

Done.

+                  Base32EncodePolicy policy,
+                  std::string* output);
+
+}  // namespace base32
+
+#endif  // COMPONENTS_BASE32_BASE32_H_