pkey: allow specifying conversion form in EC::Point#to_bntopic/pkey-ec-conversion-form

Currently, when we want to convert a point data into an octet string
with non-default conversion form, we have to set the desirable form to
the associated EC::Group beforehand. This is inconvenient and
counterintuitive because the conversion form is not actually related to
the EC group.

  point = ...
  point.group.point_conversion_form = :compressed
  point.to_bn

So, allow specifying the form as an optional parameter, like this:

  point = ...
  point.to_bn(:compressed)

1 files changed, 3 insertions, 0 deletions

diff --git a/History.md b/History.md
index e7434521..cea01b2c 100644
--- a/History.md
+++ b/History.md
@@ -70,6 +70,9 @@ Notable changes
     linked with the EC key. Modifications to the EC::Group have no effect on the
     key. [[GH ruby/openssl#71]](https://github.com/ruby/openssl/pull/71)
 
+  - OpenSSL::PKey::EC::Point#to_bn allows specifying the point conversion form
+    by the optional argument.
+
 * OpenSSL::SSL
 
   - OpenSSL::SSL::SSLSocket#tmp_key is added. A client can call it after the