Fix some edge cases and simplifly code

src/main/kotlin/CdirAddress.kt

@@ -0,0 +1,123 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import java.net.InetAddress
+import java.net.UnknownHostException
+import kotlin.math.floor
+import kotlin.math.ln
+import kotlin.math.pow
+
+
+inline class CdirAddress(val cdir: String) {
+  override fun toString(): String {
+    return "$cdir (${this.startAddress()?.hostAddress}...${this.endAddress()?.hostAddress})"
+  }
+}
+
+internal fun CdirAddress.addressCount(): Long {
+  return inet2long(endAddress()) - inet2long(startAddress()) + 1
+}
+
+private fun CdirAddress.inetAddress(): InetAddress {
+  return InetAddress.getByName(cdir.substringBefore("/"))
+}
+
+internal fun CdirAddress.prefix(): Int {
+  return cdir.substringAfter("/").toInt()
+}
+
+internal fun CdirAddress.startAddress(): InetAddress? {
+  return long2inet(inet2long(this.inetAddress()) and prefix2mask(this.prefix()))
+}
+
+internal fun CdirAddress.endAddress(): InetAddress? {
+  return long2inet((inet2long(this.inetAddress()) and prefix2mask(this.prefix())) + (1L shl(32 - this.prefix())) - 1)
+}
+
+internal fun CdirAddress.merge(other: CdirAddress): List<CdirAddress> {
+  val end = this.endAddress()!!.toLong().coerceAtLeast(other.endAddress()!!.toLong()).toInetAddress()!!
+  return toCdirAddresses(this.startAddress()!!, end)
+}
+
+internal fun InetAddress.plus(value: Int): InetAddress? {
+  return long2inet(inet2long(this) + value)
+}
+
+internal fun InetAddress.minus(value: Int): InetAddress? {
+  return long2inet(inet2long(this) - value)
+}
+
+private fun prefix2mask(bits: Int): Long {
+  return -0x100000000L shr bits and 0xFFFFFFFFL
+}
+
+internal fun InetAddress.toLong(): Long {
+  return inet2long(this)
+}
+
+internal fun Long.toInetAddress(): InetAddress? {
+  return long2inet(this)
+}
+
+private fun inet2long(addr: InetAddress?): Long {
+  var result: Long = 0
+  if (addr != null) {
+    for (b in addr.address) {
+      result = (result shl 8) or (b.toLong() and 0xFF)
+    }
+  }
+  return result
+}
+
+
+fun toCdirAddresses(start: InetAddress, end: InetAddress): List<CdirAddress> {
+  val listResult: MutableList<CdirAddress> = ArrayList()
+//  echo("toCdirAddress(" + start.hostAddress + "," + end.hostAddress + ")")
+
+  var from = inet2long(start)
+  val to = inet2long(end)
+
+  while (to >= from) {
+    var prefix: Byte = 32
+    while (prefix > 0) {
+      val mask = prefix2mask(prefix - 1)
+      if (from and mask != from) break
+      prefix--
+    }
+    val max = (32 - floor(ln((to - from + 1).toDouble()) / ln(2.0))).toByte()
+    if (prefix < max) prefix = max
+    listResult.add(CdirAddress("${long2inet(from)?.hostAddress}/$prefix"))
+    from += 2.0.pow((32 - prefix).toDouble()).toLong()
+  }
+
+  return listResult
+}
+
+@Suppress("NAME_SHADOWING")
+private fun long2inet(addr: Long): InetAddress? {
+  var addr = addr
+  return try {
+    val b = ByteArray(4)
+    for (i in b.indices.reversed()) {
+      b[i] = (addr and 0xFF).toByte()
+      addr = addr shr 8
+    }
+    InetAddress.getByAddress(b)
+  } catch (ignore: UnknownHostException) {
+    null
+  }
+}