Mercurial > hg
view mercurial/parser.py @ 27895:2d6a89e79b48
scmutil: support background file closing
Closing files that have been appended to is relatively slow on
Windows/NTFS. This makes several Mercurial operations slower on
Windows.
The workaround to this issue is conceptually simple: use multiple
threads for I/O. Unfortunately, Python doesn't scale well to multiple
threads because of the GIL. And, refactoring our code to use threads
everywhere would be a huge undertaking. So, we decide to tackle this
problem by starting small: establishing a thread pool for closing
files.
This patch establishes a mechanism for closing file handles on separate
threads. The coordinator object is basically a queue of file handles to
operate on and a thread pool consuming from the queue.
When files are opened through the VFS layer, the caller can specify
that delay closing is allowed.
A proxy class for file handles has been added. We must use a proxy
because it isn't possible to modify __class__ on built-in types. This
adds some overhead. But as future patches will show, this overhead
is cancelled out by the benefit of closing file handles on background
threads.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Thu, 14 Jan 2016 13:34:59 -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))