Mercurial > hg
view mercurial/parser.py @ 20997:d7df4b7378ae
bundle2: produce a bundle2 reply
We do not know yet what kind of data future features and extensions will need to
exchange. To handle that, bundle2 allows to send arbitrary content to the
server. As a consequence, we need to be able to reply arbitrary content to the
client. And, we can use bundle2 to transmit those arbitrary data.
When a client will push a bundle2 to the server, the server will reply with a
bundle2 itself.
This changeset installs the first stone of this logic and test it.
author | Pierre-Yves David <pierre-yves.david@fb.com> |
---|---|
date | Fri, 04 Apr 2014 14:24:11 -0700 |
parents | 7c4778bc29f0 |
children | d647f97f88dd |
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# parser.py - simple top-down operator precedence parser for mercurial # # Copyright 2010 Matt Mackall <mpm@selenic.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. # see http://effbot.org/zone/simple-top-down-parsing.htm and # http://eli.thegreenplace.net/2010/01/02/top-down-operator-precedence-parsing/ # for background # takes a tokenizer and elements # tokenizer is an iterator that returns type, value pairs # elements is a mapping of types to binding strength, prefix and infix actions # an action is a tree node name, a tree label, and an optional match # __call__(program) parses program into a labeled tree import error from i18n import _ class parser(object): def __init__(self, tokenizer, elements, methods=None): self._tokenizer = tokenizer self._elements = elements self._methods = methods self.current = None def _advance(self): 'advance the tokenizer' t = self.current try: self.current = self._iter.next() except StopIteration: pass return t def _match(self, m, pos): 'make sure the tokenizer matches an end condition' if self.current[0] != m: raise error.ParseError(_("unexpected token: %s") % self.current[0], self.current[2]) self._advance() def _parse(self, bind=0): token, value, pos = self._advance() # handle prefix rules on current token prefix = self._elements[token][1] if not prefix: raise error.ParseError(_("not a prefix: %s") % token, pos) if len(prefix) == 1: expr = (prefix[0], value) else: if len(prefix) > 2 and prefix[2] == self.current[0]: self._match(prefix[2], pos) expr = (prefix[0], None) else: expr = (prefix[0], self._parse(prefix[1])) if len(prefix) > 2: self._match(prefix[2], pos) # gather tokens until we meet a lower binding strength while bind < self._elements[self.current[0]][0]: token, value, pos = self._advance() e = self._elements[token] # check for suffix - next token isn't a valid prefix if len(e) == 4 and not self._elements[self.current[0]][1]: suffix = e[3] expr = (suffix[0], expr) else: # handle infix rules if len(e) < 3 or not e[2]: raise error.ParseError(_("not an infix: %s") % token, pos) infix = e[2] if len(infix) == 3 and infix[2] == self.current[0]: self._match(infix[2], pos) expr = (infix[0], expr, (None)) else: expr = (infix[0], expr, self._parse(infix[1])) if len(infix) == 3: self._match(infix[2], pos) return expr def parse(self, message, lookup=None): 'generate a parse tree from a message' if lookup: self._iter = self._tokenizer(message, lookup) else: self._iter = self._tokenizer(message) self._advance() res = self._parse() token, value, pos = self.current return res, pos def eval(self, tree): 'recursively evaluate a parse tree using node methods' if not isinstance(tree, tuple): return tree return self._methods[tree[0]](*[self.eval(t) for t in tree[1:]]) def __call__(self, message): 'parse a message into a parse tree and evaluate if methods given' t = self.parse(message) if self._methods: return self.eval(t) return t