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# frozen_string_literal: true
# A very thin wrapper around the scanner that breaks quantified literal runs,
# collects emitted tokens into an array, calculates their nesting depth, and
# normalizes tokens for the parser, and checks if they are implemented by the
# given syntax flavor.
class Regexp::Lexer
OPENING_TOKENS = %i[
capture passive lookahead nlookahead lookbehind nlookbehind
atomic options options_switch named absence open
].freeze
CLOSING_TOKENS = %i[close].freeze
CONDITION_TOKENS = %i[condition condition_close].freeze
def self.lex(input, syntax = nil, options: nil, collect_tokens: true, &block)
new.lex(input, syntax, options: options, collect_tokens: collect_tokens, &block)
end
def lex(input, syntax = nil, options: nil, collect_tokens: true, &block)
syntax = syntax ? Regexp::Syntax.for(syntax) : Regexp::Syntax::CURRENT
self.block = block
self.collect_tokens = collect_tokens
self.tokens = []
self.prev_token = nil
self.preprev_token = nil
self.nesting = 0
self.set_nesting = 0
self.conditional_nesting = 0
self.shift = 0
Regexp::Scanner.scan(input, options: options, collect_tokens: false) do |type, token, text, ts, te|
type, token = *syntax.normalize(type, token)
syntax.check! type, token
ascend(type, token)
if (last = prev_token) &&
type == :quantifier &&
(
(last.type == :literal && (parts = break_literal(last))) ||
(last.token == :codepoint_list && (parts = break_codepoint_list(last)))
)
emit(parts[0])
last = parts[1]
end
current = Regexp::Token.new(type, token, text, ts + shift, te + shift,
nesting, set_nesting, conditional_nesting)
if type == :conditional && CONDITION_TOKENS.include?(token)
current = merge_condition(current, last)
elsif last
last.next = current
current.previous = last
emit(last)
end
self.preprev_token = last
self.prev_token = current
descend(type, token)
end
emit(prev_token) if prev_token
collect_tokens ? tokens : nil
end
def emit(token)
if block
# TODO: in v3.0.0, remove `collect_tokens:` kwarg and only collect w/o block
res = block.call(token)
tokens << res if collect_tokens
else
tokens << token
end
end
class << self
alias :scan :lex
end
private
attr_accessor :block,
:collect_tokens, :tokens, :prev_token, :preprev_token,
:nesting, :set_nesting, :conditional_nesting, :shift
def ascend(type, token)
return unless CLOSING_TOKENS.include?(token)
case type
when :group, :assertion
self.nesting = nesting - 1
when :set
self.set_nesting = set_nesting - 1
when :conditional
self.conditional_nesting = conditional_nesting - 1
else
raise "unhandled nesting type #{type}"
end
end
def descend(type, token)
return unless OPENING_TOKENS.include?(token)
case type
when :group, :assertion
self.nesting = nesting + 1
when :set
self.set_nesting = set_nesting + 1
when :conditional
self.conditional_nesting = conditional_nesting + 1
else
raise "unhandled nesting type #{type}"
end
end
# called by scan to break a literal run that is longer than one character
# into two separate tokens when it is followed by a quantifier
def break_literal(token)
lead, last, _ = token.text.partition(/.\z/mu)
return if lead.empty?
token_1 = Regexp::Token.new(:literal, :literal, lead,
token.ts, (token.te - last.length),
nesting, set_nesting, conditional_nesting)
token_2 = Regexp::Token.new(:literal, :literal, last,
(token.ts + lead.length), token.te,
nesting, set_nesting, conditional_nesting)
token_1.previous = preprev_token
token_1.next = token_2
token_2.previous = token_1 # .next will be set by #lex
[token_1, token_2]
end
# if a codepoint list is followed by a quantifier, that quantifier applies
# to the last codepoint, e.g. /\u{61 62 63}{3}/ =~ 'abccc'
# c.f. #break_literal.
def break_codepoint_list(token)
lead, _, tail = token.text.rpartition(' ')
return if lead.empty?
token_1 = Regexp::Token.new(:escape, :codepoint_list, lead + '}',
token.ts, (token.te - tail.length),
nesting, set_nesting, conditional_nesting)
token_2 = Regexp::Token.new(:escape, :codepoint_list, '\u{' + tail,
(token.ts + lead.length + 1), (token.te + 3),
nesting, set_nesting, conditional_nesting)
self.shift = shift + 3 # one space less, but extra \, u, {, and }
token_1.previous = preprev_token
token_1.next = token_2
token_2.previous = token_1 # .next will be set by #lex
[token_1, token_2]
end
def merge_condition(current, last)
token = Regexp::Token.new(:conditional, :condition, last.text + current.text,
last.ts, current.te, nesting, set_nesting, conditional_nesting)
token.previous = preprev_token # .next will be set by #lex
token
end
end # module Regexp::Lexer
|
