diff --git a/DIRECTORY.md b/DIRECTORY.md index fa9c26535c9b..31f46916e2b3 100644 --- a/DIRECTORY.md +++ b/DIRECTORY.md @@ -100,6 +100,7 @@ * [IntegerToEnglish](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/IntegerToEnglish.java) * [IntegerToRoman](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/IntegerToRoman.java) * [IPConverter](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/IPConverter.java) + * [IPv6Converter](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/IPv6Converter.java) * [MorseCodeConverter](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/MorseCodeConverter.java) * [OctalToBinary](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/OctalToBinary.java) * [OctalToDecimal](https://github.com/TheAlgorithms/Java/blob/master/src/main/java/com/thealgorithms/conversions/OctalToDecimal.java) @@ -784,6 +785,7 @@ * [IntegerToEnglishTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/IntegerToEnglishTest.java) * [IntegerToRomanTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/IntegerToRomanTest.java) * [IPConverterTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/IPConverterTest.java) + * [IPv6ConverterTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/IPv6ConverterTest.java) * [MorseCodeConverterTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/MorseCodeConverterTest.java) * [OctalToBinaryTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/OctalToBinaryTest.java) * [OctalToDecimalTest](https://github.com/TheAlgorithms/Java/blob/master/src/test/java/com/thealgorithms/conversions/OctalToDecimalTest.java) diff --git a/src/main/java/com/thealgorithms/conversions/IPv6Converter.java b/src/main/java/com/thealgorithms/conversions/IPv6Converter.java new file mode 100644 index 000000000000..d42ffd027514 --- /dev/null +++ b/src/main/java/com/thealgorithms/conversions/IPv6Converter.java @@ -0,0 +1,98 @@ +package com.thealgorithms.conversions; + +import java.net.InetAddress; +import java.net.UnknownHostException; +import java.util.Arrays; + +/** + * A utility class for converting between IPv6 and IPv4 addresses. + * + * - Converts IPv4 to IPv6-mapped IPv6 address. + * - Extracts IPv4 address from IPv6-mapped IPv6. + * - Handles exceptions for invalid inputs. + * + * @author Hardvan + */ +public final class IPv6Converter { + private IPv6Converter() { + } + + /** + * Converts an IPv4 address (e.g., "192.0.2.128") to an IPv6-mapped IPv6 address. + * Example: IPv4 "192.0.2.128" -> IPv6 "::ffff:192.0.2.128" + * + * @param ipv4Address The IPv4 address in string format. + * @return The corresponding IPv6-mapped IPv6 address. + * @throws UnknownHostException If the IPv4 address is invalid. + * @throws IllegalArgumentException If the IPv6 address is not a mapped IPv4 address. + */ + public static String ipv4ToIpv6(String ipv4Address) throws UnknownHostException { + if (ipv4Address == null || ipv4Address.isEmpty()) { + throw new UnknownHostException("IPv4 address is empty."); + } + + InetAddress ipv4 = InetAddress.getByName(ipv4Address); + byte[] ipv4Bytes = ipv4.getAddress(); + + // Create IPv6-mapped IPv6 address (starts with ::ffff:) + byte[] ipv6Bytes = new byte[16]; + ipv6Bytes[10] = (byte) 0xff; + ipv6Bytes[11] = (byte) 0xff; + System.arraycopy(ipv4Bytes, 0, ipv6Bytes, 12, 4); + + // Manually format to "::ffff:x.x.x.x" format + StringBuilder ipv6String = new StringBuilder("::ffff:"); + for (int i = 12; i < 16; i++) { + ipv6String.append(ipv6Bytes[i] & 0xFF); + if (i < 15) { + ipv6String.append('.'); + } + } + return ipv6String.toString(); + } + + /** + * Extracts the IPv4 address from an IPv6-mapped IPv6 address. + * Example: IPv6 "::ffff:192.0.2.128" -> IPv4 "192.0.2.128" + * + * @param ipv6Address The IPv6 address in string format. + * @return The extracted IPv4 address. + * @throws UnknownHostException If the IPv6 address is invalid or not a mapped IPv4 address. + */ + public static String ipv6ToIpv4(String ipv6Address) throws UnknownHostException { + InetAddress ipv6 = InetAddress.getByName(ipv6Address); + byte[] ipv6Bytes = ipv6.getAddress(); + + // Check if the address is an IPv6-mapped IPv4 address + if (isValidIpv6MappedIpv4(ipv6Bytes)) { + byte[] ipv4Bytes = Arrays.copyOfRange(ipv6Bytes, 12, 16); + InetAddress ipv4 = InetAddress.getByAddress(ipv4Bytes); + return ipv4.getHostAddress(); + } else { + throw new IllegalArgumentException("Not a valid IPv6-mapped IPv4 address."); + } + } + + /** + * Helper function to check if the given byte array represents + * an IPv6-mapped IPv4 address (prefix 0:0:0:0:0:ffff). + * + * @param ipv6Bytes Byte array representation of the IPv6 address. + * @return True if the address is IPv6-mapped IPv4, otherwise false. + */ + private static boolean isValidIpv6MappedIpv4(byte[] ipv6Bytes) { + // IPv6-mapped IPv4 addresses are 16 bytes long, with the first 10 bytes set to 0, + // followed by 0xff, 0xff, and the last 4 bytes representing the IPv4 address. + if (ipv6Bytes.length != 16) { + return false; + } + + for (int i = 0; i < 10; i++) { + if (ipv6Bytes[i] != 0) { + return false; + } + } + + return ipv6Bytes[10] == (byte) 0xff && ipv6Bytes[11] == (byte) 0xff; + } +} diff --git a/src/test/java/com/thealgorithms/conversions/IPv6ConverterTest.java b/src/test/java/com/thealgorithms/conversions/IPv6ConverterTest.java new file mode 100644 index 000000000000..443f865ae0dc --- /dev/null +++ b/src/test/java/com/thealgorithms/conversions/IPv6ConverterTest.java @@ -0,0 +1,64 @@ +package com.thealgorithms.conversions; + +import static org.junit.jupiter.api.Assertions.assertEquals; +import static org.junit.jupiter.api.Assertions.assertThrows; + +import java.net.UnknownHostException; +import org.junit.jupiter.api.Test; + +public class IPv6ConverterTest { + + private static final String VALID_IPV4 = "192." + + "0." + + "2." + + "128"; + private static final String EXPECTED_IPV6_MAPPED = ":" + + ":ff" + + "ff" + + ":19" + + "2." + + "0." + + "2.128"; + private static final String INVALID_IPV6_MAPPED = "2001:" + + "db8" + + ":" + + ":1"; + private static final String INVALID_IPV4 = "999." + + "999." + + "999." + + "999"; + private static final String INVALID_IPV6_FORMAT = "invalid:ipv6" + + "::address"; + private static final String EMPTY_STRING = ""; + + @Test + public void testIpv4ToIpv6ValidInput() throws UnknownHostException { + String actualIpv6 = IPv6Converter.ipv4ToIpv6(VALID_IPV4); + assertEquals(EXPECTED_IPV6_MAPPED, actualIpv6); + } + + @Test + public void testIpv6ToIpv4InvalidIPv6MappedAddress() { + assertThrows(IllegalArgumentException.class, () -> IPv6Converter.ipv6ToIpv4(INVALID_IPV6_MAPPED)); + } + + @Test + public void testIpv4ToIpv6InvalidIPv4Address() { + assertThrows(UnknownHostException.class, () -> IPv6Converter.ipv4ToIpv6(INVALID_IPV4)); + } + + @Test + public void testIpv6ToIpv4InvalidFormat() { + assertThrows(UnknownHostException.class, () -> IPv6Converter.ipv6ToIpv4(INVALID_IPV6_FORMAT)); + } + + @Test + public void testIpv4ToIpv6EmptyString() { + assertThrows(UnknownHostException.class, () -> IPv6Converter.ipv4ToIpv6(EMPTY_STRING)); + } + + @Test + public void testIpv6ToIpv4EmptyString() { + assertThrows(IllegalArgumentException.class, () -> IPv6Converter.ipv6ToIpv4(EMPTY_STRING)); + } +}