Mercurial > hg
view mercurial/pure/base85.py @ 39814:d059cb669632
wireprotov2: allow multiple fields to follow revision maps
The *data wire protocol commands emit a series of CBOR values.
Because revision/delta data may be large, their data is emitted
outside the map as a top-level bytestring value.
Before this commit, we'd emit a single optional bytestring
value after the revision descriptor map. This got the job done.
But it was limiting in that we could only send a single field.
And, it required the consumer to know that the presence of a
key in the map implied the existence of a following bytestring
value.
This commit changes the encoding strategy so top-level bytestring
values in the stream are explicitly denoted in a "fieldsfollowing"
key. This key contains an array defining what fields that follow
and the expected size of each field.
By defining things this way, we can easily send N bytestring
values without any ambiguity about their order. In addition,
clients only need to know how to parse ``fieldsfollowing`` to
know if extra values are present.
Because this breaks backwards compatibility, we've bumped the version
number of the wire protocol version 2 API endpoint.
Differential Revision: https://phab.mercurial-scm.org/D4620
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Thu, 20 Sep 2018 12:57:23 -0700 |
parents | 80301c90a2dc |
children | 2372284d9457 |
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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("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef" "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 += '\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] 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('>%dL' % (len(out)), *out) if cl: out = out[:-(5 - cl)] return out