sxp.py

xen虚拟机源代码安装包

#!/usr/bin/env python
#============================================================================
# This library is free software; you can redistribute it and/or
# modify it under the terms of version 2.1 of the GNU Lesser General Public
# License as published by the Free Software Foundation.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library; if not, write to the Free Software
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
#============================================================================
# Copyright (C) 2004, 2005 Mike Wray <[e-mail]>
#============================================================================

"""
Input-driven parsing for s-expression (sxp) format.
Create a parser: pin = Parser();
Then call pin.input(buf) with your input.
Call pin.input_eof() when done.
Use pin.read() to see if a value has been parsed, pin.get_val()
to get a parsed value. You can call ready and get_val at any time -
you don't have to wait until after calling input_eof.

"""
from __future__ import generators

import sys
import types
import errno
import string
from StringIO import StringIO

__all__ = [
    "mime_type", 
    "ParseError", 
    "Parser", 
    "atomp", 
    "show", 
    "show_xml", 
    "elementp", 
    "name", 
    "attributes", 
    "attribute", 
    "children", 
    "child", 
    "child_at", 
    "child0", 
    "child1", 
    "child2", 
    "child3", 
    "child4", 
    "child_value",
    "has_id", 
    "with_id", 
    "child_with_id", 
    "elements",
    "merge",
    "to_string",
    "from_string",
    "all_from_string",
    "parse", 
    ]

mime_type = "application/sxp"

escapes = {
    'a': '\a',
    'b': '\b',
    't': '\t',
    'n': '\n',
    'v': '\v',
    'f': '\f',
    'r': '\r',
    '\\': '\\',
    '\'': '\'',
    '\"': '\"'}

k_list_open  = "("
k_list_close = ")"
k_attr_open  = "@"
k_eval       = "!"

escapes_rev = {}
for k in escapes:
    escapes_rev[escapes[k]] = k

class ParseError(StandardError):

    def __init__(self, parser, value):
        self.parser = parser
        self.value = value

    def __str__(self):
        return self.value

class ParserState:

    def __init__(self, fn, parent=None):
        self.parent = parent
        self.buf = ''
        self.val = []
        self.delim = None
        self.fn = fn

    def push(self, fn):
        return ParserState(fn, parent=self)
    
class Parser:

    def __init__(self):
        self.error = sys.stderr
        self.reset()

    def reset(self):
        self.val = []
        self.eof = 0
        self.err = 0
        self.line_no = 0
        self.char_no = 0
        self.state = None

    def push_state(self, fn):
        self.state = self.state.push(fn)

    def pop_state(self):
        val = self.state
        self.state = self.state.parent
        if self.state and self.state.fn == self.state_start:
            # Return to start state - produce the value.
            self.val += self.state.val
            self.state.val = []
        return val

    def in_class(self, c, s):
        return s.find(c) >= 0
        
    def in_space_class(self, c):
        return self.in_class(c, ' \t\n\v\f\r')

    def is_separator(self, c):
        return self.in_class(c, '{}()<>[]!;')

    def in_comment_class(self, c):
        return self.in_class(c, '#')

    def in_string_quote_class(self, c):
        return self.in_class(c, '"\'')

    def in_printable_class(self, c):
        return self.in_class(c, string.printable)

    def set_error_stream(self, error):
        self.error = error

    def has_error(self):
        return self.err > 0

    def at_eof(self):
        return self.eof

    def input_eof(self):
        self.eof = 1
        self.input_char(-1)

    def input(self, buf):
        if not buf or len(buf) == 0:
            self.input_eof()
        else:
            for c in buf:
                self.input_char(c)

    def input_char(self, c):
        if self.at_eof():
            pass
        elif c == '\n':
            self.line_no += 1
            self.char_no = 0
        else:
           self.char_no += 1 

        if self.state is None:
            self.begin_start(None)
        self.state.fn(c)

    def ready(self):
        return len(self.val) > 0

    def get_val(self):
        v = self.val[0]
        self.val = self.val[1:]
        return v

    def get_all(self):
        return self.val

    def begin_start(self, c):
        self.state = ParserState(self.state_start)

    def end_start(self):
        self.val += self.state.val
        self.pop_state()
    
    def state_start(self, c):
        if self.at_eof():
            self.end_start()
        elif self.in_space_class(c):
            pass
        elif self.in_comment_class(c):
            self.begin_comment(c)
        elif c == k_list_open:
            self.begin_list(c)
        elif c == k_list_close:
            raise ParseError(self, "syntax error: "+c)
        elif self.in_string_quote_class(c):
            self.begin_string(c)
        elif self.in_printable_class(c):
            self.begin_atom(c)
        elif c == chr(4):
            # ctrl-D, EOT: end-of-text.
            self.input_eof()
        else:
            raise ParseError(self, "invalid character: code %d" % ord(c))

    def begin_comment(self, c):
        self.push_state(self.state_comment)
        self.state.buf += c

    def end_comment(self):
        self.pop_state()
    
    def state_comment(self, c):
        if c == '\n' or self.at_eof():
            self.end_comment()
        else:
            self.state.buf += c

    def begin_string(self, c):
        self.push_state(self.state_string)
        self.state.delim = c

    def end_string(self):
        val = self.state.buf
        self.state.parent.val.append(val)
        self.pop_state()
        
    def state_string(self, c):
        if self.at_eof():
            raise ParseError(self, "unexpected EOF")
        elif c == self.state.delim:
            self.end_string()
        elif c == '\\':
            self.push_state(self.state_escape)
        else:
            self.state.buf += c

    def state_escape(self, c):
        if self.at_eof():
            raise ParseError(self, "unexpected EOF")
        d = escapes.get(c)
        if d:
            self.state.parent.buf += d
            self.pop_state()
        elif c == 'x':
            self.state.fn = self.state_hex
            self.state.val = 0
        elif c in string.octdigits:
            self.state.fn = self.state_octal
            self.state.val = 0
            self.input_char(c)
        else:
            # ignore escape if it doesn't match anything we know
            self.state.parent.buf += '\\'
            self.pop_state()

    def state_octal(self, c):
        def octaldigit(c):
            self.state.val *= 8
            self.state.val += ord(c) - ord('0')
            self.state.buf += c
            if self.state.val < 0 or self.state.val > 0xff:
                raise ParseError(self, "invalid octal escape: out of range " + self.state.buf)
            if len(self.state.buf) == 3:
               octaldone()
               
        def octaldone():
            d = chr(self.state.val)
            self.state.parent.buf += d
            self.pop_state()
            
        if self.at_eof():
            raise ParseError(self, "unexpected EOF")
        elif '0' <= c <= '7':
            octaldigit(c)
        elif len(self.state.buf):
            octaldone()
            self.input_char(c)

    def state_hex(self, c):
        def hexdone():
            d = chr(self.state.val)
            self.state.parent.buf += d
            self.pop_state()
            
        def hexdigit(c, d):
            self.state.val *= 16
            self.state.val += ord(c) - ord(d)
            self.state.buf += c
            if self.state.val < 0 or self.state.val > 0xff:
                raise ParseError(self, "invalid hex escape: out of range " + self.state.buf)
            if len(self.state.buf) == 2:
                hexdone()
            
        if self.at_eof():
            raise ParseError(self, "unexpected EOF")
        elif '0' <= c <= '9':
            hexdigit(c, '0')
        elif 'A' <= c <= 'F':
            hexdigit(c, 'A')
        elif 'a' <= c <= 'f':
            hexdigit(c, 'a')
        elif len(buf):
            hexdone()
            self.input_char(c)

    def begin_atom(self, c):
        self.push_state(self.state_atom)
        self.state.buf = c

    def end_atom(self):
        val = self.state.buf
        self.state.parent.val.append(val)
        self.pop_state()
    
    def state_atom(self, c):
        if self.at_eof():
            self.end_atom()
        elif (self.is_separator(c) or
              self.in_space_class(c) or
              self.in_comment_class(c)):
            self.end_atom()
            self.input_char(c)
        else:
            self.state.buf += c

    def begin_list(self, c):
        self.push_state(self.state_list)

    def end_list(self):
        val = self.state.val
        self.state.parent.val.append(val)
        self.pop_state()

    def state_list(self, c):
        if self.at_eof():
            raise ParseError(self, "unexpected EOF")
        elif c == k_list_close:
            self.end_list()
        else:
            self.state_start(c)

def atomp(sxpr):
    """Check if an sxpr is an atom.
    """
    if sxpr.isalnum() or sxpr == '@':
        return 1
    for c in sxpr:
        if c in string.whitespace: return 0
        if c in '"\'\\(){}[]<>$#&%^': return 0
        if c in string.ascii_letters: continue
        if c in string.digits: continue
        if c in '.-_:/~': continue
        return 0
    return 1
    
def show(sxpr, out=sys.stdout):
    """Print an sxpr in bracketed (lisp-style) syntax.
    """
    if isinstance(sxpr, (types.ListType, types.TupleType)):