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Diffstat (limited to 'websdk/mercurial/base85.py')
-rw-r--r-- | websdk/mercurial/base85.py | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/websdk/mercurial/base85.py b/websdk/mercurial/base85.py new file mode 100644 index 0000000..930d251 --- /dev/null +++ b/websdk/mercurial/base85.py @@ -0,0 +1,74 @@ +# base85.py: pure python base85 codec +# +# Copyright (C) 2009 Brendan Cully <brendan@kublai.com> +# +# This software may be used and distributed according to the terms of the +# GNU General Public License version 2 or any later version. + +import struct + +_b85chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" \ + "abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~" +_b85chars2 = [(a + b) for a in _b85chars for b in _b85chars] +_b85dec = {} + +def _mkb85dec(): + for i, c in enumerate(_b85chars): + _b85dec[c] = i + +def b85encode(text, pad=False): + """encode text in base85 format""" + l = len(text) + r = l % 4 + if r: + text += '\0' * (4 - r) + longs = len(text) >> 2 + words = struct.unpack('>%dL' % (longs), text) + + out = ''.join(_b85chars[(word // 52200625) % 85] + + _b85chars2[(word // 7225) % 7225] + + _b85chars2[word % 7225] + for word in words) + + if pad: + return out + + # Trim padding + olen = l % 4 + if olen: + olen += 1 + olen += l // 4 * 5 + return out[:olen] + +def b85decode(text): + """decode base85-encoded text""" + if not _b85dec: + _mkb85dec() + + l = len(text) + out = [] + for i in range(0, len(text), 5): + chunk = text[i:i + 5] + acc = 0 + for j, c in enumerate(chunk): + try: + acc = acc * 85 + _b85dec[c] + except KeyError: + raise TypeError('Bad base85 character at byte %d' % (i + j)) + if acc > 4294967295: + raise OverflowError('Base85 overflow in hunk starting at byte %d' % i) + out.append(acc) + + # Pad final chunk if necessary + cl = l % 5 + if cl: + acc *= 85 ** (5 - cl) + if cl > 1: + acc += 0xffffff >> (cl - 2) * 8 + out[-1] = acc + + out = struct.pack('>%dL' % (len(out)), *out) + if cl: + out = out[:-(5 - cl)] + + return out |