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uCLexer.py
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uCLexer.py
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'''
First Project: Lexer for the uC language.
Subject:
MC921 - Construction of Compilers
Authors:
Victor Ferreira Ferrari - RA 187890
Vinicius Couto Espindola - RA 188115
University of Campinas - UNICAMP - 2020
Last Modified: 27/04/2020.
'''
import ply.lex as lex
from os.path import exists
#### CONFLICTING TYPES ####
# ID & KEYWORDS => Longest Match & Rule Order Using Dictionary
# COMMENT & UNTCOMMENT => Rule Order (comment func comes first)
# STRING & UNTSTRING => Rule Order (string func comes first)
# CCONST & UNTCCHAR => Rule Order (cconst func comes first)
class uCLexer():
'''A Lexer for the uC language.
'''
# Creating a new Lexer.
# error_func: error function to be called with error message and position.
def __init__(self, error_func):
self.error_func = error_func
self.last_token = None
# Build the lexer. Needs to be called after object is created.
def build(self, **kwargs):
self.lexer = lex.lex(object=self, optimize=True, **kwargs)
# Resets line counter.
def reset_line_num(self):
self.lexer.lineno = 1
def input(self, text):
self.lexer.input(text)
def token(self):
self.last_token = self.lexer.token()
return self.last_token
def find_tok_column(self, token):
# Find the column of the token in its line.
last_cr = self.lexer.lexdata.rfind('\n', 0, token.lexpos)
return token.lexpos - last_cr
# Internal auxiliary methods
def _error(self, msg, token):
location = self._make_tok_location(token)
if self.error_func is not None:
self.error_func(msg, location[0], location[1])
self.lexer.skip(1)
def _make_tok_location(self, token):
return (token.lineno, self.find_tok_column(token))
# Test the output
def test(self, data):
self.reset_line_num()
# If filename.
if exists(data):
with open(data, 'r') as content_file :
data = content_file.read()
self.lexer.input(data)
while True:
tok = self.lexer.token()
if not tok:
break
print(tok)
# Reserved keywords
keywords = (
'ASSERT', 'BREAK', 'CHAR', 'ELSE', 'FLOAT', 'FOR', 'IF',
'INT', 'PRINT', 'READ', 'RETURN', 'VOID', 'WHILE',
)
keyword_map = {}
for keyword in keywords:
keyword_map[keyword.lower()] = keyword
#
# All the tokens recognized by the lexer
#
tokens = keywords + (
# Identifiers
'ID', 'ICONST', 'FCONST', 'CCONST', 'STRING',
# Math Operators
'PLUSPLUS', 'MINUSMINUS',
# Logical Operators
'EQ', 'OR', 'AND', 'UNEQ', 'GE', 'LE',
# Assignment Operators
'PLUSEQ', 'MINUSEQ', 'TIMESEQ', 'DIVEQ', 'MODEQ'
)
# A string containing ignored characters (spaces and tabs)
t_ignore = ' \t'
# Regular expression rules for simple tokens
t_EQ = r'=='
t_OR = r'\|\|'
t_AND = r'&&'
t_UNEQ = r'!='
t_GE = r'>='
t_LE = r'<='
t_PLUSPLUS = r'\+\+'
t_MINUSMINUS = r'--'
t_PLUSEQ = r'\+='
t_MINUSEQ = r'-='
t_TIMESEQ = r'\*='
t_DIVEQ = r'/='
t_MODEQ = r'%='
literals = ['+', '-', '/', '*', '%', '=', '&', '!', ',', ';', '(', ')', '{', '}', '[', ']', '<', '>']
# Define a rule so we can track line numbers
def t_newline(self, t):
r'\n+'
t.lexer.lineno += t.value.count("\n")
def t_ID(self, t):
r'[a-zA-Z_][0-9a-zA-Z_]*'
t.type = self.keyword_map.get(t.value, "ID")
return t
def t_FCONST(self, t):
r'\d+\.\d*|\d*\.\d+'
t.value = float(t.value)
return t
def t_ICONST(self, t):
r'\d+'
t.value = int(t.value)
return t
def t_CCONST(self, t):
r'\'([^"\'\\\n]|\\["\'\\]|\\[avfntber0])\''
return t
def t_STRING (self, t) :
r'\".*?\"'
t.value = t.value[1:-1]
return t
def t_LINECOMMENT (self, t) :
r'//.*(\n|$)'
t.lexer.lineno += t.value.count("\n")
pass
def t_COMMENT (self, t) :
r'/\*(.|\n)*?\*/'
t.lexer.lineno += t.value.count("\n")
pass
#### ERROR HANDLING RULES ####
# Unterminated Comment
def t_UNTCOMMENT (self, t) :
r'/\*(.|\n)*?$'
t.lexer.lineno += t.value.count('\n')
msg = "Unterminated comment"
self._error(msg, t)
# Unmatched Quotes (unterminated string)
def t_UNTSTRING (self, t) :
r'\".*?($|\n)'
t.lexer.lineno += t.value.count('\n')
msg = "Unterminated string"
self._error(msg, t)
# Unmatched quotes (unterminated character)
def t_UNTCCHAR (self, t) :
r'\'.*?($|\n|\')'
t.lexer.lineno += t.value.count('\n')
msg = "Invalid char constant"
self._error(msg, t)
# If an unmatched character is found
def t_error(self, t):
msg = f"Illegal character {t.value[0]}"
self._error(msg, t)