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FibInputStream.scala
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FibInputStream.scala
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package services
import java.io.InputStream
/**
* [[InputStream]] for (potentially unbounded) Fibonacci numbers. Starts with a [[memoizer]] to get its initial
* values, then once those are exhausted a [[FibGenerator]] is used for subsequent values up to the [[n]]th value.
*
* @param n the last Fibonacci number to stream
* @param memoizer the memoizer used before generating
*/
protected class FibInputStream(val n: Int, val memoizer: FibMemoizer) extends InputStream {
if (n < 0) throw new IndexOutOfBoundsException
val generator = new FibGenerator(memoizer)
var s_pos = 1 // stream position, 1 = initial '[', 2 = numbers, 3 = final newline, 4 = eos
var i = 0 // current number we are streaming
var token = 1 // 1 = number, 2 = ',', 3 = ']'
var bytes: Array[Byte] = Array() // the bytes in the token when it is a number
var pos = 0 // position within bytes
override def read(): Int = s_pos match {
case 1 =>
s_pos = 2
'['
case 2 =>
token match {
case 1 =>
if (pos == 0)
bytes = (if (i < memoizer.upTo) memoizer.fib(i) else generator.next).toString.getBytes
if (pos < bytes.length - 1) {
pos += 1
bytes(pos - 1)
} else {
token = 2
pos = 0
bytes(bytes.length - 1)
}
case 2 =>
token = 3
if (i == n) {
s_pos = 3
']'
} else
','
case 3 =>
token = 1
i += 1
' '
}
case 3 =>
s_pos = 4
'\n'
case 4 =>
-1
}
}