Port base62 to Python 3.

src/allmydata/test/test_base62.py

@@ -25,7 +25,7 @@ from hypothesis import (
 from allmydata.util import base62, mathutil
 
 def insecurerandstr(n):
-    return b''.join(map(byteschr, map(random.randrange, [0]*n, [256]*n)))
+    return bytes(list(map(random.randrange, [0]*n, [256]*n)))
 
 class T(unittest.TestCase):
     def _test_num_octets_that_encode_to_this_many_chars(self, chars, octets):
@@ -77,7 +77,7 @@ class T(unittest.TestCase):
             bs = insecurerandstr(numos)
             # zero-out unused least-sig bits
             if lib%8:
-                b=ord(bs[-1])
+                b = ord(bs[-1:])
                 b = b >> (8 - (lib%8))
                 b = b << (8 - (lib%8))
                 bs = bs[:-1] + byteschr(b)

src/allmydata/util/_python3.py

@@ -16,6 +16,7 @@ if PY2:
 # Keep these sorted alphabetically, to reduce merge conflicts:
 PORTED_MODULES = [
     "allmydata.util.assertutil",
+    "allmydata.util.base62",
     "allmydata.util.deferredutil",
     "allmydata.util.humanreadable",
     "allmydata.util.mathutil",
@@ -25,6 +26,7 @@ PORTED_MODULES = [
 ]
 
 PORTED_TEST_MODULES = [
+    "allmydata.test.test_base62",
     "allmydata.test.test_deferredutil",
     "allmydata.test.test_humanreadable",
     "allmydata.test.test_python3",

src/allmydata/util/base62.py

@@ -1,16 +1,24 @@
-# from the Python Standard Library
-import string
+from __future__ import absolute_import
+from __future__ import division
+from __future__ import print_function
+from __future__ import unicode_literals
+
+from future.utils import PY2
+if PY2:
+    from builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, int, list, object, range, str, max, min  # noqa: F401
+
+from past.builtins import chr as byteschr
 
 from allmydata.util.mathutil import log_ceil, log_floor
 
-chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+chars = b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
 
-BASE62CHAR = '[' + chars + ']'
+BASE62CHAR = b'[' + chars + b']'
 
-vals = ''.join([chr(i) for i in range(62)])
-c2vtranstable = string.maketrans(chars, vals)
-v2ctranstable = string.maketrans(vals, chars)
-identitytranstable = string.maketrans(chars, chars)
+vals = b''.join([byteschr(i) for i in range(62)])
+c2vtranstable = bytes.maketrans(chars, vals)
+v2ctranstable = bytes.maketrans(vals, chars)
+identitytranstable = bytes.maketrans(chars, chars)
 
 def b2a(os):
     """
@@ -47,7 +55,9 @@ def b2a_l(os, lengthinbits):
 
     @return the contents of os in base-62 encoded form
     """
-    os = [ord(o) for o in reversed(os)] # treat os as big-endian -- and we want to process the least-significant o first
+    # We call bytes() again for Python 2, to ensure literals are using future's
+    # Python 3-compatible variant.
+    os = [o for o in reversed(bytes(os))] # treat os as big-endian -- and we want to process the least-significant o first
 
     value = 0
     numvalues = 1 # the number of possible values that value could be
@@ -62,7 +72,7 @@ def b2a_l(os, lengthinbits):
         value //= 62
         numvalues //= 62
 
-    return string.translate(''.join([chr(c) for c in reversed(chars)]), v2ctranstable) # make it big-endian
+    return bytes.translate(bytes([c for c in reversed(chars)]), v2ctranstable) # make it big-endian
 
 def num_octets_that_encode_to_this_many_chars(numcs):
     return log_floor(62**numcs, 256)
@@ -91,7 +101,9 @@ def a2b_l(cs, lengthinbits):
 
     @return the data encoded in cs
     """
-    cs = [ord(c) for c in reversed(string.translate(cs, c2vtranstable))] # treat cs as big-endian -- and we want to process the least-significant c first
+    # We call bytes() again for Python 2, to ensure literals are using future's
+    # Python 3-compatible variant.
+    cs = [c for c in reversed(bytes(bytes.translate(cs, c2vtranstable)))] # treat cs as big-endian -- and we want to process the least-significant c first
 
     value = 0
     numvalues = 1 # the number of possible values that value could be
@@ -101,10 +113,10 @@ def a2b_l(cs, lengthinbits):
         numvalues *= 62
 
     numvalues = 2**lengthinbits
-    bytes = []
+    result_bytes = []
     while numvalues > 1:
-        bytes.append(value % 256)
+        result_bytes.append(value % 256)
         value //= 256
         numvalues //= 256
 
-    return ''.join([chr(b) for b in reversed(bytes)]) # make it big-endian
+    return bytes([b for b in reversed(result_bytes)]) # make it big-endian