Use sodium_init to optimize and ensure thread safety

src/nacl/_lib/sodium_core.h

+/* Copyright 2013 Donald Stufft and individual contributors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+int sodium_init();

src/nacl/c/__init__.py

@@ -39,6 +39,7 @@ from nacl.c.crypto_sign import (
     crypto_sign, crypto_sign_open,
 )
 from nacl.c.randombytes import randombytes
+from nacl.c.sodium_core import sodium_init
 
 
 __all__ = [
@@ -84,4 +85,9 @@ __all__ = [
     "crypto_sign_open",
 
     "randombytes",
+
+    "sodium_init",
 ]
+
+# Initialize Sodium
+sodium_init()

src/nacl/c/sodium_core.py

+# Copyright 2013 Donald Stufft and individual contributors
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+from __future__ import absolute_import, division, print_function
+
+from nacl._lib import lib
+from nacl.exceptions import CryptoError
+
+
+def sodium_init():
+    """
+    Initializes sodium, picking the best implementations available for this
+    machine.
+    """
+    if lib.sodium_init() != 0:
+        raise CryptoError("Could not initialize sodium")