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// See README.md for license details.
package chisel.lib

import scala.collection.immutable.Map
import scala.collection.mutable.ListBuffer

package object ecc {
  def pow2(x: Int): Int = {
    if (x == 0) {
      1
    } else {
      1 << x
    }
    //scala.math.ceil(scala.math.pow(2, x)).toInt
  }

  def calcCodeBits(dataBits: Int): Int = {
    var m = 1
    var c = 0
    while (c < dataBits) {
      m += 1
      c = pow2(m) - m - 1
    }
    m
  }

  def calcBitMapping(dataBits: Int, reversed: Boolean): Map[Int, Int] = {
    val outWidth = dataBits + calcCodeBits(dataBits)
    var power: Int = 0
    var mapping1 = new ListBuffer[Int]()
    var mapping2 = new ListBuffer[Int]()

    for (i <- 1 until outWidth + 1) {
      if (pow2(power) == i)
        power += 1
      else {
        mapping1 += (i - 1)
        mapping2 += (i - power - 1)
      }
    }

    if (reversed)(mapping2.zip(mapping1)).toMap
    else
      (mapping1.zip(mapping2)).toMap
  }

  def buildSeq(bitNum: Int, outWidth: Int): List[Int] = {
    var bitIndex = new ListBuffer[Int]()
    var cur = 0
    var skip = pow2(bitNum) - 1
    var check = 0

    if (skip == 0)
      check = pow2(bitNum)
    else
      check = 0

    while (cur < outWidth) {
      if (check > 0) {
        if (cur != pow2(bitNum) - 1)
          bitIndex += cur
        check -= 1
        if (check == 0)
          skip = pow2(bitNum)
      } else {
        skip -= 1
        if (skip == 0)
          check = pow2(bitNum)
      }
      cur += 1
    }

    bitIndex.toList
  }
}