Add default Sodium::Pwhash algorithm.

src/sodium/lib_sodium.cr

@@ -36,6 +36,7 @@ module Sodium
     fun crypto_pwhash_saltbytes : LibC::SizeT
     fun crypto_pwhash_bytes_min : LibC::SizeT
     fun crypto_pwhash_bytes_max : LibC::SizeT
+    fun crypto_pwhash_alg_default : LibC::Int
     fun crypto_generichash_blake2b_statebytes : LibC::SizeT
     fun crypto_generichash_blake2b_bytes : LibC::SizeT
     fun crypto_generichash_blake2b_bytes_min : LibC::SizeT

src/sodium/pwhash.cr

@@ -29,6 +29,11 @@ module Sodium
     enum Mode
       Argon2i13  = 1
       Argon2id13 = 2
+
+      # The current libsodium default algorithm that may change between versions.
+      def default
+        Mode.new LibSodium.crypto_pwhash_alg_default
+      end
     end
 
     property opslimit = OPSLIMIT_INTERACTIVE

src/sodium/secure_buffer.cr

@@ -82,10 +82,12 @@ module Sodium
       self
     end
 
+    # Timing safe memory compare.
     def ==(other : self)
       Sodium.memcmp self.to_slice, other.to_slice
     end
 
+    # Timing safe memory compare.
     def ==(other : Bytes)
       Sodium.memcmp self.to_slice, other
     end