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Checksum.scala
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Checksum.scala
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/*
* Copyright (c) 2013 Functional Streams for Scala
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
// Adapted from scodec-protocols, licensed under 3-clause BSD
package fs2.protocols.ip
import scodec.bits.BitVector
object Checksum {
/** Computes the 16-bit one's complement checksum of the specified bit vector.
* @see [[https://tools.ietf.org/html/rfc1071]]
*/
def checksum(bits: BitVector): BitVector = {
var sum = bits.bytes.grouped(2).foldLeft(0) { (acc, b) =>
acc + b.toInt(signed = false)
}
while ((sum >> 16) != 0)
sum = (0xffff & sum) + (sum >> 16)
~BitVector.fromInt(sum).drop(16)
}
}