Mercurial > public > mercurial-scm > hg
annotate mercurial/parser.py @ 11635:4da35e02b67c
log: do not redefine cachefunc in walkchangerevs
The same variable is defined a few blocks earlier. The first phases in
walkchangerevs should in fact fill that cache, and allow faster lookups
in the last phase. Redefining and overriding this cached function, (knowing
that it will be called with the same arguments) defeats the caching purpose.
| author | Nicolas Dumazet <nicdumz.commits@gmail.com> |
|---|---|
| date | Tue, 20 Jul 2010 14:42:05 +0900 |
| parents | 05af334bac05 |
| children | 895f54a79c6e |
| rev | line source |
|---|---|
| 11274 | 1 # parser.py - simple top-down operator precedence parser for mercurial |
| 2 # | |
| 3 # Copyright 2010 Matt Mackall <mpm@selenic.com> | |
| 4 # | |
| 5 # This software may be used and distributed according to the terms of the | |
| 6 # GNU General Public License version 2 or any later version. | |
| 7 | |
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8 # see http://effbot.org/zone/simple-top-down-parsing.htm and |
| 11274 | 9 # http://eli.thegreenplace.net/2010/01/02/top-down-operator-precedence-parsing/ |
| 10 # for background | |
| 11 | |
| 12 # takes a tokenizer and elements | |
| 13 # tokenizer is an iterator that returns type, value pairs | |
| 14 # elements is a mapping of types to binding strength, prefix and infix actions | |
| 15 # an action is a tree node name, a tree label, and an optional match | |
| 16 # __call__(program) parses program into a labelled tree | |
| 17 | |
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18 import error |
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19 |
| 11274 | 20 class parser(object): |
| 21 def __init__(self, tokenizer, elements, methods=None): | |
| 22 self._tokenizer = tokenizer | |
| 23 self._elements = elements | |
| 24 self._methods = methods | |
| 25 def _advance(self): | |
| 26 'advance the tokenizer' | |
| 27 t = self.current | |
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28 try: |
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29 self.current = self._iter.next() |
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30 except StopIteration: |
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31 pass |
| 11274 | 32 return t |
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33 def _match(self, m, pos): |
| 11274 | 34 'make sure the tokenizer matches an end condition' |
| 35 if self.current[0] != m: | |
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36 raise error.ParseError("unexpected token: %s" % self.current[0], |
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37 self.current[2]) |
| 11274 | 38 self._advance() |
| 39 def _parse(self, bind=0): | |
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40 token, value, pos = self._advance() |
| 11274 | 41 # handle prefix rules on current token |
| 42 prefix = self._elements[token][1] | |
| 43 if not prefix: | |
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44 raise error.ParseError("not a prefix: %s" % token, pos) |
| 11274 | 45 if len(prefix) == 1: |
| 46 expr = (prefix[0], value) | |
| 47 else: | |
| 48 if len(prefix) > 2 and prefix[2] == self.current[0]: | |
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49 self._match(prefix[2], pos) |
| 11274 | 50 expr = (prefix[0], None) |
| 51 else: | |
| 52 expr = (prefix[0], self._parse(prefix[1])) | |
| 53 if len(prefix) > 2: | |
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54 self._match(prefix[2], pos) |
| 11274 | 55 # gather tokens until we meet a lower binding strength |
| 56 while bind < self._elements[self.current[0]][0]: | |
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57 token, value, pos = self._advance() |
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58 e = self._elements[token] |
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59 # check for suffix - next token isn't a valid prefix |
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60 if len(e) == 4 and not self._elements[self.current[0]][1]: |
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61 suffix = e[3] |
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62 expr = (suffix[0], expr) |
| 11274 | 63 else: |
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64 # handle infix rules |
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65 if len(e) < 3 or not e[2]: |
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66 raise error.ParseError("not an infix: %s" % token, pos) |
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67 infix = e[2] |
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68 if len(infix) == 3 and infix[2] == self.current[0]: |
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69 self._match(infix[2], pos) |
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70 expr = (infix[0], expr, (None)) |
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71 else: |
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72 expr = (infix[0], expr, self._parse(infix[1])) |
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73 if len(infix) == 3: |
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74 self._match(infix[2], pos) |
| 11274 | 75 return expr |
| 76 def parse(self, message): | |
| 77 'generate a parse tree from a message' | |
| 78 self._iter = self._tokenizer(message) | |
| 79 self.current = self._iter.next() | |
| 80 return self._parse() | |
| 81 def eval(self, tree): | |
| 82 'recursively evaluate a parse tree using node methods' | |
| 83 if not isinstance(tree, tuple): | |
| 84 return tree | |
| 85 return self._methods[tree[0]](*[self.eval(t) for t in tree[1:]]) | |
| 86 def __call__(self, message): | |
| 87 'parse a message into a parse tree and evaluate if methods given' | |
| 88 t = self.parse(message) | |
| 89 if self._methods: | |
| 90 return self.eval(t) | |
| 91 return t |