instance method unquote

# File activesupport/lib/active_support/json/backends/okjson.rb, line 267
    def unquote(q)
      q = q[1...-1]
      a = q.dup # allocate a big enough string
      rubydoesenc = false
      # In ruby >= 1.9, a[w] is a codepoint, not a byte.
      if a.class.method_defined?(:force_encoding)
        a.force_encoding('UTF-8')
        rubydoesenc = true
      end
      r, w = 0, 0
      while r < q.length
        c = q[r]
        case true
        when c == ?\\
          r += 1
          if r >= q.length
            raise Error, "string literal ends with a \"\\\": \"#{q}\""
          end

          case q[r]
          when ?",?\\,?/,?'
            a[w] = q[r]
            r += 1
            w += 1
          when ?b,?f,?n,?r,?t
            a[w] = Unesc[q[r]]
            r += 1
            w += 1
          when ?u
            r += 1
            uchar = begin
              hexdec4(q[r,4])
            rescue RuntimeError => e
              raise Error, "invalid escape sequence \\u#{q[r,4]}: #{e}"
            end
            r += 4
            if surrogate? uchar
              if q.length >= r+6
                uchar1 = hexdec4(q[r+2,4])
                uchar = subst(uchar, uchar1)
                if uchar != Ucharerr
                  # A valid pair; consume.
                  r += 6
                end
              end
            end
            if rubydoesenc
              a[w] = '' << uchar
              w += 1
            else
              w += ucharenc(a, w, uchar)
            end
          else
            raise Error, "invalid escape char #{q[r]} in \"#{q}\""
          end
        when c == ?", c < Spc
          raise Error, "invalid character in string literal \"#{q}\""
        else
          # Copy anything else byte-for-byte.
          # Valid UTF-8 will remain valid UTF-8.
          # Invalid UTF-8 will remain invalid UTF-8.
          # In ruby >= 1.9, c is a codepoint, not a byte,
          # in which case this is still what we want.
          a[w] = c
          r += 1
          w += 1
        end
      end
      a[0,w]
    end