Mercurial > hg
view mercurial/parser.py @ 27430:e240e914d226 stable
revlog: seek to end of file before writing (issue4943)
Revlogs were recently refactored to open file handles in "a+" and use a
persistent file handle for reading and writing. This drastically
reduced the number of file handles being opened.
Unfortunately, it appears that some versions of Solaris lose the file
offset when performing a write after the handle has been seeked.
The simplest workaround is to seek to EOF on files opened in a+ mode
before writing to them, which is what this patch does.
Ideally, this code would exist in the vfs layer. However, this would
require creating a proxy class for file objects in order to provide a
custom implementation of write(). This would add overhead. Since
revlogs are the only files we open in a+ mode, the one-off workaround
in revlog.py should be sufficient.
This patch appears to have little to no impact on performance on my
Linux machine.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Thu, 17 Dec 2015 17:16:02 -0800 |
parents | 87c9c562c37a |
children | 639e0f1e8ffa |
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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, pos) tuples # elements is a mapping of types to binding strength, primary, prefix, infix # and suffix actions # an action is a tree node name, a tree label, and an optional match # __call__(program) parses program into a labeled tree from __future__ import absolute_import from .i18n import _ from . import error class parser(object): def __init__(self, elements, methods=None): self._elements = elements self._methods = methods self.current = None def _advance(self): 'advance the tokenizer' t = self.current self.current = next(self._iter, None) return t def _hasnewterm(self): 'True if next token may start new term' return any(self._elements[self.current[0]][1:3]) def _match(self, m): '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 _parseoperand(self, bind, m=None): 'gather right-hand-side operand until an end condition or binding met' if m and self.current[0] == m: expr = None else: expr = self._parse(bind) if m: self._match(m) return expr def _parse(self, bind=0): token, value, pos = self._advance() # handle prefix rules on current token, take as primary if unambiguous primary, prefix = self._elements[token][1:3] if primary and not (prefix and self._hasnewterm()): expr = (primary, value) elif prefix: expr = (prefix[0], self._parseoperand(*prefix[1:])) else: raise error.ParseError(_("not a prefix: %s") % token, pos) # gather tokens until we meet a lower binding strength while bind < self._elements[self.current[0]][0]: token, value, pos = self._advance() # handle infix rules, take as suffix if unambiguous infix, suffix = self._elements[token][3:] if suffix and not (infix and self._hasnewterm()): expr = (suffix[0], expr) elif infix: expr = (infix[0], expr, self._parseoperand(*infix[1:])) else: raise error.ParseError(_("not an infix: %s") % token, pos) return expr def parse(self, tokeniter): 'generate a parse tree from tokens' self._iter = tokeniter 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, tokeniter): 'parse tokens into a parse tree and evaluate if methods given' t = self.parse(tokeniter) if self._methods: return self.eval(t) return t def buildargsdict(trees, funcname, keys, keyvaluenode, keynode): """Build dict from list containing positional and keyword arguments Invalid keywords or too many positional arguments are rejected, but missing arguments are just omitted. """ if len(trees) > len(keys): raise error.ParseError(_("%(func)s takes at most %(nargs)d arguments") % {'func': funcname, 'nargs': len(keys)}) args = {} # consume positional arguments for k, x in zip(keys, trees): if x[0] == keyvaluenode: break args[k] = x # remainder should be keyword arguments for x in trees[len(args):]: if x[0] != keyvaluenode or x[1][0] != keynode: raise error.ParseError(_("%(func)s got an invalid argument") % {'func': funcname}) k = x[1][1] if k not in keys: raise error.ParseError(_("%(func)s got an unexpected keyword " "argument '%(key)s'") % {'func': funcname, 'key': k}) if k in args: raise error.ParseError(_("%(func)s got multiple values for keyword " "argument '%(key)s'") % {'func': funcname, 'key': k}) args[k] = x[2] return args def unescapestr(s): try: return s.decode("string_escape") except ValueError as e: # mangle Python's exception into our format raise error.ParseError(str(e).lower()) def _prettyformat(tree, leafnodes, level, lines): if not isinstance(tree, tuple) or tree[0] in leafnodes: lines.append((level, str(tree))) else: lines.append((level, '(%s' % tree[0])) for s in tree[1:]: _prettyformat(s, leafnodes, level + 1, lines) lines[-1:] = [(lines[-1][0], lines[-1][1] + ')')] def prettyformat(tree, leafnodes): lines = [] _prettyformat(tree, leafnodes, 0, lines) output = '\n'.join((' ' * l + s) for l, s in lines) return output def simplifyinfixops(tree, targetnodes): """Flatten chained infix operations to reduce usage of Python stack >>> def f(tree): ... print prettyformat(simplifyinfixops(tree, ('or',)), ('symbol',)) >>> f(('or', ... ('or', ... ('symbol', '1'), ... ('symbol', '2')), ... ('symbol', '3'))) (or ('symbol', '1') ('symbol', '2') ('symbol', '3')) >>> f(('func', ... ('symbol', 'p1'), ... ('or', ... ('or', ... ('func', ... ('symbol', 'sort'), ... ('list', ... ('or', ... ('or', ... ('symbol', '1'), ... ('symbol', '2')), ... ('symbol', '3')), ... ('negate', ... ('symbol', 'rev')))), ... ('and', ... ('symbol', '4'), ... ('group', ... ('or', ... ('or', ... ('symbol', '5'), ... ('symbol', '6')), ... ('symbol', '7'))))), ... ('symbol', '8')))) (func ('symbol', 'p1') (or (func ('symbol', 'sort') (list (or ('symbol', '1') ('symbol', '2') ('symbol', '3')) (negate ('symbol', 'rev')))) (and ('symbol', '4') (group (or ('symbol', '5') ('symbol', '6') ('symbol', '7')))) ('symbol', '8'))) """ if not isinstance(tree, tuple): return tree op = tree[0] if op not in targetnodes: return (op,) + tuple(simplifyinfixops(x, targetnodes) for x in tree[1:]) # walk down left nodes taking each right node. no recursion to left nodes # because infix operators are left-associative, i.e. left tree is deep. # e.g. '1 + 2 + 3' -> (+ (+ 1 2) 3) -> (+ 1 2 3) simplified = [] x = tree while x[0] == op: l, r = x[1:] simplified.append(simplifyinfixops(r, targetnodes)) x = l simplified.append(simplifyinfixops(x, targetnodes)) simplified.append(op) return tuple(reversed(simplified))