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annotate mercurial/utils/storageutil.py @ 39883:3e896b51aa5d

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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 f8eb71f9e3bd
children d269ddbf54f0
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39882
f8eb71f9e3bd storageutil: new module for storage primitives (API)
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1 # storageutil.py - Storage functionality agnostic of backend implementation.
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2 #
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3 # Copyright 2018 Gregory Szorc <gregory.szorc@gmail.com>
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4 #
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5 # This software may be used and distributed according to the terms of the
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6 # GNU General Public License version 2 or any later version.
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7
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8 from __future__ import absolute_import
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9
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10 import hashlib
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11 import re
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12
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13 from ..node import (
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14 nullid,
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15 )
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16
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17 _nullhash = hashlib.sha1(nullid)
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18
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19 def hashrevisionsha1(text, p1, p2):
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20 """Compute the SHA-1 for revision data and its parents.
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21
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22 This hash combines both the current file contents and its history
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23 in a manner that makes it easy to distinguish nodes with the same
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24 content in the revision graph.
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25 """
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26 # As of now, if one of the parent node is null, p2 is null
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27 if p2 == nullid:
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28 # deep copy of a hash is faster than creating one
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29 s = _nullhash.copy()
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30 s.update(p1)
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31 else:
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32 # none of the parent nodes are nullid
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33 if p1 < p2:
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34 a = p1
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35 b = p2
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36 else:
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37 a = p2
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38 b = p1
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39 s = hashlib.sha1(a)
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40 s.update(b)
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41 s.update(text)
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42 return s.digest()
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43
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44 METADATA_RE = re.compile(b'\x01\n')
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45
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46 def parsemeta(text):
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47 """Parse metadata header from revision data.
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48
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49 Returns a 2-tuple of (metadata, offset), where both can be None if there
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50 is no metadata.
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51 """
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52 # text can be buffer, so we can't use .startswith or .index
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53 if text[:2] != b'\x01\n':
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54 return None, None
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55 s = METADATA_RE.search(text, 2).start()
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56 mtext = text[2:s]
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57 meta = {}
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58 for l in mtext.splitlines():
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59 k, v = l.split(b': ', 1)
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60 meta[k] = v
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61 return meta, s + 2
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62
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63 def packmeta(meta, text):
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64 """Add metadata to fulltext to produce revision text."""
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65 keys = sorted(meta)
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66 metatext = b''.join(b'%s: %s\n' % (k, meta[k]) for k in keys)
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67 return b'\x01\n%s\x01\n%s' % (metatext, text)