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require 'stringio'
require 'strscan'
require 'parslet/position'
require 'parslet/source/line_cache'
module Parslet
# Wraps the input string for parslet.
#
class Source
def initialize(str)
raise(
ArgumentError,
"Must construct Source with a string like object."
) unless str.respond_to?(:to_str)
@str = StringScanner.new(str)
# maps 1 => /./m, 2 => /../m, etc...
@re_cache = Hash.new { |h,k|
h[k] = /(.|$){#{k}}/m }
@line_cache = LineCache.new
@line_cache.scan_for_line_endings(0, str)
end
# Checks if the given pattern matches at the current input position.
#
# @param pattern [Regexp] pattern to check for
# @return [Boolean] true if the pattern matches at #pos
#
def matches?(pattern)
@str.match?(pattern)
end
alias match matches?
# Consumes n characters from the input, returning them as a slice of the
# input.
#
def consume(n)
position = self.pos
slice_str = @str.scan(@re_cache[n])
slice = Parslet::Slice.new(
position,
slice_str,
@line_cache)
return slice
end
# Returns how many chars remain in the input.
#
def chars_left
@str.rest_size
end
# Returns how many chars there are between current position and the
# string given. If the string given doesn't occur in the source, then
# the remaining chars (#chars_left) are returned.
#
# @return [Fixnum] count of chars until str or #chars_left
#
def chars_until str
slice_str = @str.check_until(Regexp.new(Regexp.escape(str)))
return chars_left unless slice_str
return slice_str.size - str.size
end
# Position of the parse as a character offset into the original string.
#
# @note Please be aware of encodings at this point.
#
def pos
Position.new(@str.string, @str.pos)
end
def bytepos
@str.pos
end
# @note Please be aware of encodings at this point.
#
def bytepos=(n)
@str.pos = n
rescue RangeError
end
# Returns a <line, column> tuple for the given position. If no position is
# given, line/column information is returned for the current position
# given by #pos.
#
def line_and_column(position=nil)
@line_cache.line_and_column(position || self.bytepos)
end
end
end
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