Mercurial > hg
view mercurial/pure/base85.py @ 46924:ca0049946e9a
split: avoid strip if split is a no-op (identical to original)
Differential Revision: https://phab.mercurial-scm.org/D10389
author | Kyle Lippincott <spectral@google.com> |
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date | Mon, 12 Apr 2021 19:25:34 -0700 |
parents | 4cd911040ba5 |
children | 6000f5b25c9b |
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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 version 2 or any later version. from __future__ import absolute_import import struct from .. import pycompat _b85chars = pycompat.bytestr( b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef" b"ghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~" ) _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 += b'\0' * (4 - r) longs = len(text) >> 2 words = struct.unpack(b'>%dL' % longs, text) out = b''.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] chunk = pycompat.bytestr(chunk) acc = 0 for j, c in enumerate(chunk): try: acc = acc * 85 + _b85dec[c] except KeyError: raise ValueError( 'bad base85 character at position %d' % (i + j) ) if acc > 4294967295: raise ValueError('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(b'>%dL' % (len(out)), *out) if cl: out = out[: -(5 - cl)] return out