June 2018 Update

Task/Bitcoin-address-validation/Scala/bitcoin-address-validation.scala

@@ -0,0 +1,67 @@
+import java.security.MessageDigest
+import java.util.Arrays.copyOfRange
+
+import scala.annotation.tailrec
+import scala.math.BigInt
+
+object BitcoinAddressValidator extends App {
+
+  private def bitcoinTestHarness(address: String, expected: Boolean): Unit =
+    assert(validateBitcoinAddress(address) == expected, s"Expected $expected for $address%s, but got ${!expected}.")
+
+  private def validateBitcoinAddress(addr: String): Boolean = {
+    def sha256(data: Array[Byte]) = {
+      val md: MessageDigest = MessageDigest.getInstance("SHA-256")
+      md.update(data)
+      md.digest
+    }
+
+    def decodeBase58To25Bytes(input: String): Option[Array[Byte]] = {
+      def ALPHABET = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz"
+
+      @tailrec
+      def loop(s: String, accu: BigInt): BigInt = {
+        if (s.isEmpty) accu
+        else {
+          val p = ALPHABET.indexOf(s.head)
+          if (p >= 0) loop(s.tail, accu * 58 + p)
+          else -1
+        }
+      }
+
+      val num = loop(input, 0)
+      if (num >= 0) {
+        val (result, numBytes) = (new Array[Byte](25), num.toByteArray)
+        System.arraycopy(numBytes, 0, result, result.length - numBytes.length, numBytes.length)
+        Some(result)
+      }
+      else None
+    }
+
+    if (27 to 34 contains addr.length) {
+      val decoded = decodeBase58To25Bytes(addr)
+      if (decoded.isEmpty) false
+      else {
+        val hash1 = sha256(copyOfRange(decoded.get, 0, 21))
+        copyOfRange(sha256(hash1), 0, 4)
+          .sameElements(copyOfRange(decoded.get, 21, 25))
+      }
+    } else false
+  } // validateBitcoinAddress
+
+  bitcoinTestHarness("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i", true)
+  bitcoinTestHarness("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j", false)
+  bitcoinTestHarness("1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nK9", true)
+  bitcoinTestHarness("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62X", false)
+  bitcoinTestHarness("1ANNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i", false)
+  bitcoinTestHarness("1A Na15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i", false)
+  bitcoinTestHarness("BZbvjr", false)
+  bitcoinTestHarness("i55j", false)
+  bitcoinTestHarness("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62!", false)
+  bitcoinTestHarness("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz", false)
+  bitcoinTestHarness("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz", false)
+  bitcoinTestHarness("1Q1pE5vPGEEMqRcVRMbtBK842Y6Pzo6nJ9", false)
+  bitcoinTestHarness("1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62I", false)
+  println(s"Successfully completed without errors. [total ${scala.compat.Platform.currentTime - executionStart}ms]")
+
+}