Mercurial > hg
view mercurial/pure/base85.py @ 47387:75e1104f23a2
revlog: use dedicated code for reading sidedata
We are about to introduce a new, dedicated, file to store sidedata. Before doing so, we make sidedata reading go through different code as reading data chunk. This will simplify some of the complexity of the next changesets.
The reading is very simple right now and will need some improvement later to
reuse some of the caching strategy we use for the data file.
Differential Revision: https://phab.mercurial-scm.org/D10785
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
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date | Thu, 27 May 2021 04:09:30 +0200 |
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