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|
require "strscan"
require "lrama/lexer/location"
require "lrama/lexer/token"
module Lrama
class Lexer
attr_reader :head_line, :head_column
attr_accessor :status
attr_accessor :end_symbol
SYMBOLS = ['%{', '%}', '%%', '{', '}', '\[', '\]', '\(', '\)', '\,', ':', '\|', ';']
PERCENT_TOKENS = %w(
%union
%token
%type
%left
%right
%nonassoc
%expect
%define
%require
%printer
%lex-param
%parse-param
%initial-action
%precedence
%prec
%error-token
%empty
%code
)
def initialize(text)
@scanner = StringScanner.new(text)
@head_column = @head = @scanner.pos
@head_line = @line = 1
@status = :initial
@end_symbol = nil
end
def next_token
case @status
when :initial
lex_token
when :c_declaration
lex_c_code
end
end
def line
@line
end
def column
@scanner.pos - @head
end
def location
Location.new(
first_line: @head_line, first_column: @head_column,
last_line: @line, last_column: column
)
end
def lex_token
while !@scanner.eos? do
case
when @scanner.scan(/\n/)
newline
when @scanner.scan(/\s+/)
# noop
when @scanner.scan(/\/\*/)
lex_comment
when @scanner.scan(/\/\/.*(?<newline>\n)?/)
newline if @scanner[:newline]
else
break
end
end
@head_line = line
@head_column = column
case
when @scanner.eos?
return
when @scanner.scan(/#{SYMBOLS.join('|')}/)
return [@scanner.matched, @scanner.matched]
when @scanner.scan(/#{PERCENT_TOKENS.join('|')}/)
return [@scanner.matched, @scanner.matched]
when @scanner.scan(/[\?\+\*]/)
return [@scanner.matched, @scanner.matched]
when @scanner.scan(/<\w+>/)
return [:TAG, Lrama::Lexer::Token::Tag.new(s_value: @scanner.matched, location: location)]
when @scanner.scan(/'.'/)
return [:CHARACTER, Lrama::Lexer::Token::Char.new(s_value: @scanner.matched, location: location)]
when @scanner.scan(/'\\\\'|'\\b'|'\\t'|'\\f'|'\\r'|'\\n'|'\\v'|'\\13'/)
return [:CHARACTER, Lrama::Lexer::Token::Char.new(s_value: @scanner.matched, location: location)]
when @scanner.scan(/".*?"/)
return [:STRING, %Q(#{@scanner.matched})]
when @scanner.scan(/\d+/)
return [:INTEGER, Integer(@scanner.matched)]
when @scanner.scan(/([a-zA-Z_.][-a-zA-Z0-9_.]*)/)
token = Lrama::Lexer::Token::Ident.new(s_value: @scanner.matched, location: location)
type =
if @scanner.check(/\s*(\[\s*[a-zA-Z_.][-a-zA-Z0-9_.]*\s*\])?\s*:/)
:IDENT_COLON
else
:IDENTIFIER
end
return [type, token]
else
raise ParseError, "Unexpected token: #{@scanner.peek(10).chomp}."
end
end
def lex_c_code
nested = 0
code = ''
while !@scanner.eos? do
case
when @scanner.scan(/{/)
code += @scanner.matched
nested += 1
when @scanner.scan(/}/)
if nested == 0 && @end_symbol == '}'
@scanner.unscan
return [:C_DECLARATION, Lrama::Lexer::Token::UserCode.new(s_value: code, location: location)]
else
code += @scanner.matched
nested -= 1
end
when @scanner.check(/#{@end_symbol}/)
return [:C_DECLARATION, Lrama::Lexer::Token::UserCode.new(s_value: code, location: location)]
when @scanner.scan(/\n/)
code += @scanner.matched
newline
when @scanner.scan(/".*?"/)
code += %Q(#{@scanner.matched})
@line += @scanner.matched.count("\n")
when @scanner.scan(/'.*?'/)
code += %Q(#{@scanner.matched})
else
if @scanner.scan(/[^\"'\{\}\n#{@end_symbol}]+/)
code += @scanner.matched
else
code += @scanner.getch
end
end
end
raise ParseError, "Unexpected code: #{code}."
end
private
def lex_comment
while !@scanner.eos? do
case
when @scanner.scan(/\n/)
@line += 1
@head = @scanner.pos + 1
when @scanner.scan(/\*\//)
return
else
@scanner.getch
end
end
end
def newline
@line += 1
@head = @scanner.pos + 1
end
end
end
|
