BitString type and codecs reimplemented

Targeting high-performance and convenience to use.
Sampling just BitString en/decoding performance -- new implementation is 100x faster. ;-\

1 files changed, 96 insertions, 0 deletions

diff --git a/pyasn1/compat/integer.py b/pyasn1/compat/integer.py
new file mode 100644
index 0000000..ae9c7e1
--- /dev/null
+++ b/pyasn1/compat/integer.py
@@ -0,0 +1,96 @@
+#
+# This file is part of pyasn1 software.
+#
+# Copyright (c) 2005-2017, Ilya Etingof <etingof@gmail.com>
+# License: http://pyasn1.sf.net/license.html
+#
+import sys
+if sys.version_info[0:2] < (3, 2):
+    from binascii import a2b_hex, b2a_hex
+from pyasn1.compat.octets import oct2int, null
+
+if sys.version_info[0:2] < (3, 2):
+    def from_bytes(octets, signed=False):
+        value = long(b2a_hex(str(octets)), 16)
+
+        if signed and oct2int(octets[0]) & 0x80:
+            return value - (1 << len(octets) * 8)
+
+        return value
+
+    def to_bytes(value, signed=False, length=0):
+        if value < 0:
+            if signed:
+                bits = bitLength(value)
+
+                # two's complement form
+                maxValue = 1 << bits
+                valueToEncode = (value + maxValue) % maxValue
+
+            else:
+                raise OverflowError('can\'t convert negative int to unsigned')
+        elif value == 0 and length == 0:
+            return null
+        else:
+            bits = 0
+            valueToEncode = value
+
+        hexValue = hex(valueToEncode)[2:]
+        if hexValue.endswith('L'):
+            hexValue = hexValue[:-1]
+
+        if len(hexValue) & 1:
+            hexValue = '0' + hexValue
+
+        # padding may be needed for two's complement encoding
+        if value != valueToEncode or length:
+            hexLength = len(hexValue) * 4
+
+            padLength = max(length, bits)
+
+            if padLength > hexLength:
+                hexValue = '00' * ((padLength - hexLength - 1) // 8 + 1) + hexValue
+            elif length and hexLength - length > 7:
+                raise OverflowError('int too big to convert')
+
+        firstOctet = int(hexValue[:2], 16)
+
+        if signed:
+            if firstOctet & 0x80:
+                if value >= 0:
+                    hexValue = '00' + hexValue
+            elif value < 0:
+                hexValue = 'ff' + hexValue
+
+        octets_value = a2b_hex(hexValue)
+
+        return octets_value
+
+    def bitLength(number):
+        # bits in unsigned number
+        hexValue = hex(abs(number))
+        bits = len(hexValue) - 2
+        if hexValue.endswith('L'):
+            bits -= 1
+        if bits & 1:
+            bits += 1
+        bits *= 4
+        # TODO: strip lhs zeros
+        return bits
+
+else:
+
+    def from_bytes(octets, signed=False):
+        return int.from_bytes(bytes(octets), 'big', signed=signed)
+
+    def to_bytes(value, signed=False, length=0):
+        length = max(value.bit_length(), length)
+
+        if signed and length % 8 == 0:
+            length += 1
+
+        return value.to_bytes(length // 8 + (length % 8 and 1 or 0), 'big', signed=signed)
+
+    def bitLength(number):
+        return int(number).bit_length()
+