Added pycrc library (MIT License) for CRC calculations to the repository.
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Christian Sltrop
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c35e26f025
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418
pycrc/crc_parser.py
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418
pycrc/crc_parser.py
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# -*- coding: Latin-1 -*-
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# pycrc -- parametrisable CRC calculation utility and C source code generator
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#
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# Copyright (c) 2006-2012 Thomas Pircher <tehpeh@gmx.net>
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#
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# Permission is hereby granted, free of charge, to any person obtaining a copy
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# of this software and associated documentation files (the "Software"), to
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# deal in the Software without restriction, including without limitation the
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# rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
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# sell copies of the Software, and to permit persons to whom the Software is
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# furnished to do so, subject to the following conditions:
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#
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# The above copyright notice and this permission notice shall be included in
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# all copies or substantial portions of the Software.
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#
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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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# IN THE SOFTWARE.
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"""
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Macro Language parser for pycrc.
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use as follows:
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import sys
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from crc_opt import Options
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from crc_parser import MacroParser
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opt = Options()
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opt.parse(sys.argv[1:])
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mp = MacroParser(opt)
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if mp.parse("Test 1 2 3"):
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print(mp.out_str)
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"""
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from crc_symtable import SymbolTable
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from crc_lexer import Lexer
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import re
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import sys
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# Class ParseError
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###############################################################################
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class ParseError(Exception):
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"""
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The exception class for the parser.
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"""
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# Class constructor
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###############################################################################
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def __init__(self, reason):
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self.reason = reason
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# function __str__
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###############################################################################
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def __str__(self):
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return self.reason
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# Class MacroParser
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###############################################################################
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class MacroParser(object):
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"""
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The macro language parser and code generator class.
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"""
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re_is_int = re.compile("^[-+]?[0-9]+$")
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#re_is_hex = re.compile("^(0[xX])?[0-9a-fA-F]+$")
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re_is_hex = re.compile("^0[xX][0-9a-fA-F]+$")
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opt = None
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sym = None
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lex = Lexer()
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# Class constructor
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###############################################################################
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def __init__(self, opt):
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self.opt = opt
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self.sym = SymbolTable(opt)
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self.out_str = None
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# function parse
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#
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# The used grammar is:
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# term: LITERAL
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# | IDENTIFIER
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# | '(' or_exp ')'
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# ;
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#
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# comp_exp: term OP_COMPARISON term
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# ;
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#
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# and_exp: term
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# | and_exp OP_AND comp_exp
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# ;
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#
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# or_exp: and_exp
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# | or_exp OP_OR and_exp
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# ;
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#
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# else_block: /* empty */
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# | ELSE '{:' data ':}'
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# ;
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#
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# elif_blocks: /* empty */
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# | elif_blocks ELIF '(' or_exp ')' '{:' data ':}'
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# ;
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#
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# if_block: IF '(' or_exp ')' '{:' data ':}' elif_blocks else_block
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# ;
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#
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# data: /* empty */
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# | data GIBBERISH
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# | data IDENTIFIER
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# | data '{:' data ':}'
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# | data if_block
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# ;
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###############################################################################
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def parse(self, in_str):
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"""
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Parse a macro string.
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"""
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self.lex.set_str(in_str)
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self.out_str = ""
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self._parse_data(do_print = True)
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tok = self.lex.peek()
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if tok != self.lex.tok_EOF:
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raise ParseError("%s: error: misaligned closing block '%s'" % (sys.argv[0], self.lex.text))
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# function _parse_data
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###############################################################################
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def _parse_data(self, do_print):
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"""
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Private top-level parsing function.
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"""
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tok = self.lex.peek()
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while tok != self.lex.tok_EOF:
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if tok == self.lex.tok_gibberish:
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self._parse_gibberish(do_print)
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elif tok == self.lex.tok_block_open:
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self._parse_data_block(do_print)
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elif tok == self.lex.tok_identifier and self.lex.text == "if":
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self._parse_if_block(do_print)
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elif tok == self.lex.tok_identifier:
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self._parse_identifier(do_print)
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elif tok == self.lex.tok_block_close:
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return
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else:
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raise ParseError("%s: error: wrong token '%s'" % (sys.argv[0], self.lex.text))
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tok = self.lex.peek()
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# function _parse_gibberish
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###############################################################################
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def _parse_gibberish(self, do_print):
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"""
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Parse gibberish.
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Actually, just print the characters in 'text' if do_print is True.
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"""
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if do_print:
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self.out_str = self.out_str + self.lex.text
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self.lex.advance()
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# function _parse_identifier
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###############################################################################
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def _parse_identifier(self, do_print):
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"""
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Parse an identifier.
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"""
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try:
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sym_value = self.sym.getTerminal(self.lex.text)
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except LookupError:
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raise ParseError("%s: error: unknown terminal '%s'" % (sys.argv[0], self.lex.text))
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self.lex.advance()
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if do_print:
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self.lex.prepend(sym_value)
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# function _parse_if_block
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###############################################################################
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def _parse_if_block(self, do_print):
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"""
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Parse an if block.
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"""
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# parse the expression following the 'if' and the associated block.
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exp_res = self._parse_conditional_block(do_print)
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do_print = do_print and not exp_res
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# try $elif
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tok = self.lex.peek()
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while tok == self.lex.tok_identifier and self.lex.text == "elif":
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exp_res = self._parse_conditional_block(do_print)
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do_print = do_print and not exp_res
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tok = self.lex.peek()
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# try $else
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if tok == self.lex.tok_identifier and self.lex.text == "else":
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# get rid of the tok_identifier, 'else' and following spaces
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self.lex.advance()
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self.lex.delete_spaces()
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# expect a data block
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self._parse_data_block(do_print)
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# function _parse_conditional_block
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###############################################################################
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def _parse_conditional_block(self, do_print):
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"""
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Parse a conditional block (such as $if or $elif).
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Return the truth value of the expression.
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"""
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# get rid of the tok_identifier, 'if' or 'elif'
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self.lex.advance()
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self.lex.set_state(self.lex.state_expr)
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# expect an open parenthesis
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tok = self.lex.peek()
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if tok != self.lex.tok_par_open:
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raise ParseError("%s: error: open parenthesis expected: '%s'" % (sys.argv[0], self.lex.text))
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self.lex.advance()
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# parse the boolean expression
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exp_res = self._parse_exp_or()
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# expect a closed parenthesis
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tok = self.lex.peek()
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if tok != self.lex.tok_par_close:
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raise ParseError("%s: error: closed parenthesis expected: '%s'" % (sys.argv[0], self.lex.text))
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self.lex.advance()
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# get rid of eventual spaces, and switch back to gibberish.
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self.lex.delete_spaces()
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self.lex.set_state(self.lex.state_gibberish)
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# expect a data block
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self._parse_data_block(do_print and exp_res)
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# get rid of eventual spaces
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# but only if followed by $if, $else or $elif
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self.lex.delete_spaces(skip_unconditional = False)
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return exp_res
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# function _parse_data_block
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###############################################################################
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def _parse_data_block(self, do_print):
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"""
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Parse a data block.
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"""
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# expect an open block
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tok = self.lex.peek()
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if tok != self.lex.tok_block_open:
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raise ParseError("%s: error: open block expected: '%s'" % (sys.argv[0], self.lex.text))
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self.lex.advance(skip_nl = True)
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# more data follows...
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self._parse_data(do_print)
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# expect a closed block
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tok = self.lex.peek()
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if tok != self.lex.tok_block_close:
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raise ParseError("%s: error: closed block expected: '%s'" % (sys.argv[0], self.lex.text))
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self.lex.advance(skip_nl = True)
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# function _parse_exp_or
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###############################################################################
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def _parse_exp_or(self):
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"""
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Parse a boolean 'or' expression.
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"""
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ret = False
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while True:
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ret = self._parse_exp_and() or ret
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# is the expression terminated?
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tok = self.lex.peek()
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if tok == self.lex.tok_par_close:
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return ret
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# expect an 'or' token.
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elif tok == self.lex.tok_or:
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self.lex.advance()
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# everything else is the end of the expression.
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# Let the caling function worry about error reporting.
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else:
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return ret
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return False
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# function _parse_exp_and
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###############################################################################
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def _parse_exp_and(self):
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"""
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Parse a boolean 'and' expression.
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"""
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ret = True
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while True:
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ret = self._parse_exp_comparison() and ret
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# is the expression terminated?
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tok = self.lex.peek()
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if tok == self.lex.tok_par_close:
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return ret
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# expect an 'and' token.
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elif tok == self.lex.tok_and:
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self.lex.advance()
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# everything else is a parse error.
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else:
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return ret
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return False
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# function _parse_exp_comparison
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###############################################################################
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def _parse_exp_comparison(self):
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"""
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Parse a boolean comparison.
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"""
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# left hand side of the comparison
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lhs = self._parse_exp_term()
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# expect a comparison
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tok = self.lex.peek()
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if tok != self.lex.tok_op:
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raise ParseError("%s: error: operator expected: '%s'" % (sys.argv[0], self.lex.text))
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operator = self.lex.text
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self.lex.advance()
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# right hand side of the comparison
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rhs = self._parse_exp_term()
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# if both operands ar numbers, convert them
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num_l = self._get_num(lhs)
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num_r = self._get_num(rhs)
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if num_l != None and num_r != None:
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lhs = num_l
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rhs = num_r
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# now calculate the result of the comparison, whatever that means
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if operator == "<=":
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ret = lhs <= rhs
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elif operator == "<":
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ret = lhs < rhs
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elif operator == "==":
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ret = lhs == rhs
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elif operator == "!=":
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ret = lhs != rhs
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elif operator == ">=":
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ret = lhs >= rhs
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elif operator == ">":
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ret = lhs > rhs
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else:
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raise ParseError("%s: error: unknow operator: '%s'" % (sys.argv[0], self.lex.text))
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return ret
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# function _parse_exp_term
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###############################################################################
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def _parse_exp_term(self):
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"""
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Parse a terminal.
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"""
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tok = self.lex.peek()
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# identifier
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if tok == self.lex.tok_identifier:
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try:
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ret = self.sym.getTerminal(self.lex.text)
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except LookupError:
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raise ParseError("%s: error: unknown terminal '%s'" % (sys.argv[0], self.lex.text))
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if ret == None:
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ret = "Undefined"
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# string
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elif tok == self.lex.tok_str:
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ret = self.lex.text
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# number
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elif tok == self.lex.tok_num:
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ret = self.lex.text
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# parenthesised expression
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elif tok == self.lex.tok_par_open:
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self.lex.advance()
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ret = self._parse_exp_or()
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tok = self.lex.peek()
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if tok != self.lex.tok_par_close:
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raise ParseError("%s: error: closed parenthesis expected: '%s'" % (sys.argv[0], self.lex.text))
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self.lex.advance()
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return ret
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# function _get_num
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###############################################################################
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def _get_num(self, in_str):
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"""
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Check if in_str is a number and return the numeric value.
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"""
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ret = None
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if in_str != None:
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m = self.re_is_int.match(in_str)
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if m != None:
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ret = int(in_str)
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m = self.re_is_hex.match(in_str)
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if m != None:
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ret = int(in_str, 16)
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return ret
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