use kerl package if installed

README.rst

@@ -37,12 +37,12 @@ To install the latest version::
 
 Optional C Extension
 ====================
-PyOTA has an optional C extension that improves the performance of its
+PyOTA has optional C extensions that improve the performance of its
 cryptography features significantly (speedups of **60x** are common!).
 
-To install this extension, use the following command::
+To install these extensions, use the following command::
 
-   pip install pyota[ccurl]
+   pip install pyota[speedups]
 
 
 Installing from Source

iota/crypto/kerl/__init__.py

@@ -2,4 +2,11 @@
 from __future__ import absolute_import, division, print_function, \
   unicode_literals
 
-from .pykerl import *
+
+try:
+  from kerl import Kerl, trits_to_bytes, bytes_to_trits, trits_to_trytes, \
+    trytes_to_trits
+except ImportError:
+  from .pykerl import Kerl
+  from .conv import trits_to_bytes, bytes_to_trits, trits_to_trytes, \
+    trytes_to_trits

iota/crypto/kerl/conv.py

@@ -55,12 +55,12 @@ def trits_to_trytes(trits):
 
     return ''.join(trytes)
 
-def convertToTrits(bytes_k):
+def bytes_to_trits(bytes_k):
     bigInt = convertBytesToBigInt(bytes_k)
     trits = convertBigintToBase(bigInt, 3, TRIT_HASH_LENGTH)
     return trits
 
-def convertToBytes(trits):
+def trits_to_bytes(trits):
     bigInt = convertBaseToBigint(trits, 3)
     bytes_k = convertBigintToBytes(bigInt)
     return bytes_k

iota/crypto/kerl/pykerl.py

@@ -64,7 +64,7 @@ def absorb(self, trits, offset=0, length=None):
       if stop - offset == TRIT_HASH_LENGTH:
         trits[stop - 1] = 0
 
-      signed_nums = conv.convertToBytes(trits[offset:stop])
+      signed_nums = conv.trits_to_bytes(trits[offset:stop])
 
       # Convert signed bytes into their equivalent unsigned representation
       # In order to use Python's built-in bytes type
@@ -122,7 +122,7 @@ def squeeze(self, trits, offset=0, length=None):
 
       signed_hash = [conv.convert_sign(b) for b in unsigned_hash]
 
-      trits_from_hash = conv.convertToTrits(signed_hash)
+      trits_from_hash = conv.bytes_to_trits(signed_hash)
       trits_from_hash[TRIT_HASH_LENGTH - 1] = 0
 
       stop = min(TRIT_HASH_LENGTH, length-offset)

setup.py

@@ -76,6 +76,8 @@
 
   extras_require = {
     'ccurl': ['pyota-ccurl'],
+    'kerl': ['kerl'],
+    'speedups': ['pyota-ccurl', 'kerl'],
     'docs-builder': ['sphinx', 'sphinx_rtd_theme'],
     'test-runner': ['detox'] + tests_require,
   },

test/crypto/kerl/pykerl_test.py

@@ -10,7 +10,7 @@
 from sha3 import keccak_384
 
 from iota.crypto.kerl import Kerl
-from iota.crypto.kerl.conv import convertToBytes, convertToTrits, \
+from iota.crypto.kerl import trits_to_bytes, bytes_to_trits, \
   trits_to_trytes, trytes_to_trits
 
 
@@ -105,16 +105,16 @@ def test_input_greater_243(self):
     def test_all_bytes(self):
         for i in range(-128, 128):
             in_bytes = [i] * 48
-            trits = convertToTrits(in_bytes)
-            out_bytes = convertToBytes(trits)
+            trits = bytes_to_trits(in_bytes)
+            out_bytes = trits_to_bytes(trits)
 
             self.assertEqual(in_bytes, out_bytes)
 
     def test_random_trits(self):
         in_trits = [randrange(-1,2) for _ in range(243)]
         in_trits[242] = 0
-        in_bytes = convertToBytes(in_trits)
-        out_trits = convertToTrits(in_bytes)
+        in_bytes = trits_to_bytes(in_trits)
+        out_trits = bytes_to_trits(in_bytes)
 
         self.assertEqual(in_trits, out_trits)