vendored parslet, deemed stable enough and better without dependency

lib/parslet/source.rb

@@ -0,0 +1,87 @@
+
+require 'stringio'
+require 'strscan'
+
+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)
+      original_pos = @str.pos
+      slice_str = @str.scan(@re_cache[n])
+      slice = Parslet::Slice.new(
+        slice_str,
+        original_pos,
+        @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: Encodings...
+    def pos
+      @str.pos
+    end
+    def pos=(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.pos)
+    end
+  end
+end