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@cvogt
Created October 17, 2016 20:33
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package tut
import java.io.{ OutputStream, FilterOutputStream }
// FilterOutputStream that removes ANSI escapes. This should be fairly efficient, I guess, since
// it's all case switches on constants. Can inline more if needed but it seems fine. For the
// record, the format is ESC '[' digits (';' digits)* terminal
case class AnsiFilterStream(os: OutputStream) extends FilterOutputStream(os) {
case class State(apply: Int => State)
val S: State = State {
case 27 => I0
case _ => F
}
val F: State = State(_ => F)
val T: State = State(_ => T)
val I0: State = State {
case '[' => I1
case _ => F
}
val I1: State = State {
case '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
=> I2
case _ => F
}
val I2: State = State {
case '0' | '1' | '2' | '3' | '4' | '5' | '6' | '7' | '8' | '9'
=> I2
case ';' => I1
case '@' | 'A' | 'B' | 'C' | 'D' | 'E' | 'F' | 'G' | 'H' | 'I' | 'J' | 'K' | 'L' | 'M' | 'N' |
'O' | 'P' | 'Q' | 'R' | 'S' | 'T' | 'U' | 'V' | 'W' | 'X' | 'Y' | 'Z' | '[' | '\\'| ']' |
'^' | '_' | '`' | 'a' | 'b' | 'c' | 'd' | 'e' | 'f' | 'g' | 'h' | 'i' | 'j' | 'k' | 'l' |
'm' | 'n' | 'o' | 'p' | 'q' | 'r' | 's' | 't' | 'u' | 'v' | 'w' | 'x' | 'y' | 'z' | '{' |
'|' | '}' | '~'
=> T // end of ANSI escape
case _ => F
}
// Strategy is, accumulate values as long as we're in a non-terminal state, then either discard
// them if we reach T (which means we accumulated an ANSI escape sequence) or print them out if
// we reach F.
private var stack: List[Int] = Nil
private var state: State = S // Start
override def write(n: Int): Unit =
state.apply(n) match {
case F =>
stack.foldRight(())((c, _) => super.write(c))
super.write(n)
stack = Nil
state = S
case T =>
stack = Nil
state = S
case s =>
stack = n :: stack
state = s
}
}
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