Mercurial > public > mercurial-scm > hg-stable
annotate mercurial/pure/base85.py @ 39883:3e896b51aa5d
storageutil: move metadata parsing and packing from revlog (API)
Parsing and writing of revision text metadata is likely identical
across storage backends. Let's move the code out of revlog so we
don't need to import the revlog module in order to use it.
Differential Revision: https://phab.mercurial-scm.org/D4754
| author | Gregory Szorc <gregory.szorc@gmail.com> |
|---|---|
| date | Mon, 24 Sep 2018 14:31:31 -0700 |
| parents | 80301c90a2dc |
| children | 2372284d9457 |
| rev | line source |
|---|---|
| 7701 | 1 # base85.py: pure python base85 codec |
| 2 # | |
| 3 # Copyright (C) 2009 Brendan Cully <brendan@kublai.com> | |
| 4 # | |
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5 # This software may be used and distributed according to the terms of the |
| 10263 | 6 # GNU General Public License version 2 or any later version. |
| 7701 | 7 |
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8 from __future__ import absolute_import |
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9 |
| 7701 | 10 import struct |
| 11 | |
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12 from .. import pycompat |
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13 |
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14 _b85chars = pycompat.bytestr("0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdef" |
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15 "ghijklmnopqrstuvwxyz!#$%&()*+-;<=>?@^_`{|}~") |
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16 _b85chars2 = [(a + b) for a in _b85chars for b in _b85chars] |
| 7701 | 17 _b85dec = {} |
| 18 | |
| 19 def _mkb85dec(): | |
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20 for i, c in enumerate(_b85chars): |
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21 _b85dec[c] = i |
| 7701 | 22 |
| 23 def b85encode(text, pad=False): | |
| 24 """encode text in base85 format""" | |
| 25 l = len(text) | |
| 26 r = l % 4 | |
| 27 if r: | |
| 28 text += '\0' * (4 - r) | |
| 29 longs = len(text) >> 2 | |
| 30 words = struct.unpack('>%dL' % (longs), text) | |
| 31 | |
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32 out = ''.join(_b85chars[(word // 52200625) % 85] + |
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33 _b85chars2[(word // 7225) % 7225] + |
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34 _b85chars2[word % 7225] |
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35 for word in words) |
| 7701 | 36 |
| 37 if pad: | |
| 38 return out | |
| 39 | |
| 40 # Trim padding | |
| 41 olen = l % 4 | |
| 42 if olen: | |
| 43 olen += 1 | |
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44 olen += l // 4 * 5 |
| 7701 | 45 return out[:olen] |
| 46 | |
| 47 def b85decode(text): | |
| 48 """decode base85-encoded text""" | |
| 49 if not _b85dec: | |
| 50 _mkb85dec() | |
| 51 | |
| 52 l = len(text) | |
| 53 out = [] | |
| 54 for i in range(0, len(text), 5): | |
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55 chunk = text[i:i + 5] |
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56 chunk = pycompat.bytestr(chunk) |
| 7701 | 57 acc = 0 |
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58 for j, c in enumerate(chunk): |
| 7701 | 59 try: |
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60 acc = acc * 85 + _b85dec[c] |
| 7701 | 61 except KeyError: |
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62 raise ValueError('bad base85 character at position %d' |
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63 % (i + j)) |
| 7701 | 64 if acc > 4294967295: |
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65 raise ValueError('Base85 overflow in hunk starting at byte %d' % i) |
| 7701 | 66 out.append(acc) |
| 67 | |
| 68 # Pad final chunk if necessary | |
| 69 cl = l % 5 | |
| 70 if cl: | |
| 71 acc *= 85 ** (5 - cl) | |
| 72 if cl > 1: | |
| 73 acc += 0xffffff >> (cl - 2) * 8 | |
| 74 out[-1] = acc | |
| 75 | |
| 76 out = struct.pack('>%dL' % (len(out)), *out) | |
| 77 if cl: | |
| 78 out = out[:-(5 - cl)] | |
| 79 | |
| 80 return out |