Mercurial > hg
view mercurial/pure/base85.py @ 7983:7b813bdbd5d0
Change double spaces to single spaces in help texts.
author | Martin Geisler <mg@daimi.au.dk> |
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date | Sat, 04 Apr 2009 21:09:43 +0200 |
parents | 3ac7114c2555 |
children | 46293a0c7e9f |
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# 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, incorporated herein by reference. import struct _b85chars = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ" \ "abcdefghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~" _b85chars2 = [(a + b) for a in _b85chars for b in _b85chars] _b85dec = {} def _mkb85dec(): for i in range(len(_b85chars)): _b85dec[_b85chars[i]] = 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 in range(len(chunk)): try: acc = acc * 85 + _b85dec[chunk[j]] 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