Add OpenSSL::Digest.digests to get a list of available digests

ext/openssl/ossl_digest.c

@@ -103,7 +103,8 @@ VALUE ossl_digest_update(VALUE, VALUE);
  *     Digest.new(string [, data]) -> Digest
  *
  * Creates a Digest instance based on _string_, which is either the ln
- * (long name) or sn (short name) of a supported digest algorithm.
+ * (long name) or sn (short name) of a supported digest algorithm. A list of
+ * supported algorithms can be obtained by calling OpenSSL::Digest.digests.
  *
  * If _data_ (a String) is given, it is used as the initial input to the
  * Digest instance, i.e.
@@ -162,6 +163,32 @@ ossl_digest_copy(VALUE self, VALUE other)
     return self;
 }
 
+static void
+add_digest_name_to_ary(const OBJ_NAME *name, void *arg)
+{
+    VALUE ary = (VALUE)arg;
+    rb_ary_push(ary, rb_str_new2(name->name));
+}
+
+/*
+ *  call-seq:
+ *     OpenSSL::Digest.digests -> array[string...]
+ *
+ *  Returns the names of all available digests in an array.
+ */
+static VALUE
+ossl_s_digests(VALUE self)
+{
+    VALUE ary;
+
+    ary = rb_ary_new();
+    OBJ_NAME_do_all_sorted(OBJ_NAME_TYPE_MD_METH,
+                    add_digest_name_to_ary,
+                    (void*)ary);
+
+    return ary;
+}
+
 /*
  *  call-seq:
  *     digest.reset -> self
@@ -245,7 +272,8 @@ ossl_digest_finish(int argc, VALUE *argv, VALUE self)
  *  call-seq:
  *      digest.name -> string
  *
- * Returns the sn of this Digest algorithm.
+ * Returns the short name of this Digest algorithm which may differ slightly
+ * from the original name provided.
  *
  * === Example
  *   digest = OpenSSL::Digest.new('SHA512')
@@ -412,6 +440,7 @@ Init_ossl_digest(void)
 
     rb_define_alloc_func(cDigest, ossl_digest_alloc);
 
+    rb_define_module_function(cDigest, "digests", ossl_s_digests, 0);
     rb_define_method(cDigest, "initialize", ossl_digest_initialize, -1);
     rb_define_method(cDigest, "initialize_copy", ossl_digest_copy, 1);
     rb_define_method(cDigest, "reset", ossl_digest_reset, 0);

test/openssl/test_digest.rb

@@ -88,7 +88,7 @@ def test_sha2
   end
 
   def test_sha512_truncate
-    pend "SHA512_224 is not implemented" unless digest_available?('SHA512-224')
+    pend "SHA512_224 is not implemented" unless digest_available?('sha512-224')
     sha512_224_a = "d5cdb9ccc769a5121d4175f2bfdd13d6310e0d3d361ea75d82108327"
     sha512_256_a = "455e518824bc0601f9fb858ff5c37d417d67c2f8e0df2babe4808858aea830f8"
 
@@ -100,7 +100,7 @@ def test_sha512_truncate
   end
 
   def test_sha3
-    pend "SHA3 is not implemented" unless digest_available?('SHA3-224')
+    pend "SHA3 is not implemented" unless digest_available?('sha3-224')
     s224 = '6b4e03423667dbb73b6e15454f0eb1abd4597f9a1b078e3f5b5a6bc7'
     s256 = 'a7ffc6f8bf1ed76651c14756a061d662f580ff4de43b49fa82d80a4b80f8434a'
     s384 = '0c63a75b845e4f7d01107d852e4c2485c51a50aaaa94fc61995e71bbee983a2ac3713831264adb47fb6bd1e058d5f004'
@@ -126,6 +126,15 @@ def test_openssl_digest
     end
   end
 
+  def test_digests
+    digests = OpenSSL::Digest.digests
+    assert_kind_of Array, digests
+    assert_include digests, "md5"
+    assert_include digests, "sha1"
+    assert_include digests, "sha256"
+    assert_include digests, "sha512"
+  end
+
   private
 
   def check_digest(oid)
@@ -138,11 +147,8 @@ def check_digest(oid)
   end
 
   def digest_available?(name)
-    begin
-      OpenSSL::Digest.new(name)
-    rescue RuntimeError
-      false
-    end
+    @digests ||= OpenSSL::Digest.digests
+    @digests.include?(name)
   end
 end