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/*
* Copyright 2012 The Netty Project
*
* The Netty Project 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.
*/
package org.jboss.netty.util;
import org.jboss.netty.logging.InternalLogger;
import org.jboss.netty.logging.InternalLoggerFactory;
import java.net.Inet4Address;
import java.net.Inet6Address;
import java.net.InetAddress;
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.StringTokenizer;
/**
* A class that holds a number of network-related constants.
*
* This class borrowed some of its methods from a modified fork of the
* Inet6Util class which was part of Apache Harmony.
*/
public final class NetUtil {
/**
* This defines how many words (represented as ints) are needed to represent an IPv6 address
*/
private static final int IPV6_WORD_COUNT = 8;
/**
* The maximum number of characters for an IPV6 string with no scope
*/
private static final int IPV6_MAX_CHAR_COUNT = 39;
/**
* Number of bytes needed to represent and IPV6 value
*/
private static final int IPV6_BYTE_COUNT = 16;
/**
* Maximum amount of value adding characters in between IPV6 separators
*/
private static final int IPV6_MAX_CHAR_BETWEEN_SEPARATOR = 4;
/**
* Minimum number of separators that must be present in an IPv6 string
*/
private static final int IPV6_MIN_SEPARATORS = 2;
/**
* Maximum number of separators that must be present in an IPv6 string
*/
private static final int IPV6_MAX_SEPARATORS = 8;
/**
* Number of bytes needed to represent and IPV4 value
*/
private static final int IPV4_BYTE_COUNT = 4;
/**
* Maximum amount of value adding characters in between IPV4 separators
*/
private static final int IPV4_MAX_CHAR_BETWEEN_SEPARATOR = 3;
/**
* Number of separators that must be present in an IPv4 string
*/
private static final int IPV4_SEPARATORS = 3;
/**
* The logger being used by this class
*/
private static final InternalLogger logger = InternalLoggerFactory.getInstance(NetUtil.class);
/**
* Creates an byte[] based on an ipAddressString. No error handling is
* performed here.
*/
public static byte[] createByteArrayFromIpAddressString(String ipAddressString) {
if (isValidIpV4Address(ipAddressString)) {
StringTokenizer tokenizer = new StringTokenizer(ipAddressString, ".");
String token;
int tempInt;
byte[] byteAddress = new byte[IPV4_BYTE_COUNT];
for (int i = 0; i < IPV4_BYTE_COUNT; i ++) {
token = tokenizer.nextToken();
tempInt = Integer.parseInt(token);
byteAddress[i] = (byte) tempInt;
}
return byteAddress;
}
if (isValidIpV6Address(ipAddressString)) {
if (ipAddressString.charAt(0) == '[') {
ipAddressString = ipAddressString.substring(1, ipAddressString.length() - 1);
}
int percentPos = ipAddressString.indexOf('%');
if (percentPos >= 0) {
ipAddressString = ipAddressString.substring(0, percentPos);
}
StringTokenizer tokenizer = new StringTokenizer(ipAddressString, ":.", true);
ArrayList hexStrings = new ArrayList();
ArrayList decStrings = new ArrayList();
String token = "";
String prevToken = "";
int doubleColonIndex = -1; // If a double colon exists, we need to
// insert 0s.
// Go through the tokens, including the seperators ':' and '.'
// When we hit a : or . the previous token will be added to either
// the hex list or decimal list. In the case where we hit a ::
// we will save the index of the hexStrings so we can add zeros
// in to fill out the string
while (tokenizer.hasMoreTokens()) {
prevToken = token;
token = tokenizer.nextToken();
if (":".equals(token)) {
if (":".equals(prevToken)) {
doubleColonIndex = hexStrings.size();
} else if (prevToken.length() != 0) {
hexStrings.add(prevToken);
}
} else if (".".equals(token)) {
decStrings.add(prevToken);
}
}
if (":".equals(prevToken)) {
if (":".equals(token)) {
doubleColonIndex = hexStrings.size();
} else {
hexStrings.add(token);
}
} else if (".".equals(prevToken)) {
decStrings.add(token);
}
// figure out how many hexStrings we should have
// also check if it is a IPv4 address
int hexStringsLength = 8;
// If we have an IPv4 address tagged on at the end, subtract
// 4 bytes, or 2 hex words from the total
if (!decStrings.isEmpty()) {
hexStringsLength -= 2;
}
// if we hit a double Colon add the appropriate hex strings
if (doubleColonIndex != -1) {
int numberToInsert = hexStringsLength - hexStrings.size();
for (int i = 0; i < numberToInsert; i ++) {
hexStrings.add(doubleColonIndex, "0");
}
}
byte[] ipByteArray = new byte[IPV6_BYTE_COUNT];
// Finally convert these strings to bytes...
for (int i = 0; i < hexStrings.size(); i ++) {
convertToBytes(hexStrings.get(i), ipByteArray, i << 1);
}
// Now if there are any decimal values, we know where they go...
for (int i = 0; i < decStrings.size(); i ++) {
ipByteArray[i + 12] = (byte) (Integer.parseInt(decStrings.get(i)) & 255);
}
return ipByteArray;
}
return null;
}
/**
* Converts a 4 character hex word into a 2 byte word equivalent
*/
private static void convertToBytes(String hexWord, byte[] ipByteArray, int byteIndex) {
int hexWordLength = hexWord.length();
int hexWordIndex = 0;
ipByteArray[byteIndex] = 0;
ipByteArray[byteIndex + 1] = 0;
int charValue;
// high order 4 bits of first byte
if (hexWordLength > 3) {
charValue = getIntValue(hexWord.charAt(hexWordIndex ++));
ipByteArray[byteIndex] |= charValue << 4;
}
// low order 4 bits of the first byte
if (hexWordLength > 2) {
charValue = getIntValue(hexWord.charAt(hexWordIndex ++));
ipByteArray[byteIndex] |= charValue;
}
// high order 4 bits of second byte
if (hexWordLength > 1) {
charValue = getIntValue(hexWord.charAt(hexWordIndex ++));
ipByteArray[byteIndex + 1] |= charValue << 4;
}
// low order 4 bits of the first byte
charValue = getIntValue(hexWord.charAt(hexWordIndex));
ipByteArray[byteIndex + 1] |= charValue & 15;
}
static int getIntValue(char c) {
switch (c) {
case '0':
return 0;
case '1':
return 1;
case '2':
return 2;
case '3':
return 3;
case '4':
return 4;
case '5':
return 5;
case '6':
return 6;
case '7':
return 7;
case '8':
return 8;
case '9':
return 9;
}
c = Character.toLowerCase(c);
switch (c) {
case 'a':
return 10;
case 'b':
return 11;
case 'c':
return 12;
case 'd':
return 13;
case 'e':
return 14;
case 'f':
return 15;
}
return 0;
}
public static boolean isValidIpV6Address(String ipAddress) {
int length = ipAddress.length();
boolean doubleColon = false;
int numberOfColons = 0;
int numberOfPeriods = 0;
StringBuilder word = new StringBuilder();
char c = 0;
char prevChar;
int startOffset = 0; // offset for [] ip addresses
int endOffset = ipAddress.length();
if (endOffset < 2) {
return false;
}
// Strip []
if (ipAddress.charAt(0) == '[') {
if (ipAddress.charAt(endOffset - 1) != ']') {
return false; // must have a close ]
}
startOffset = 1;
endOffset --;
}
// Strip the interface name/index after the percent sign.
int percentIdx = ipAddress.indexOf('%', startOffset);
if (percentIdx >= 0) {
endOffset = percentIdx;
}
for (int i = startOffset; i < endOffset; i ++) {
prevChar = c;
c = ipAddress.charAt(i);
switch (c) {
// case for the last 32-bits represented as IPv4 x:x:x:x:x:x:d.d.d.d
case '.':
numberOfPeriods ++;
if (numberOfPeriods > 3) {
return false;
}
if (!isValidIp4Word(word.toString())) {
return false;
}
if (numberOfColons != 6 && !doubleColon) {
return false;
}
// a special case ::1:2:3:4:5:d.d.d.d allows 7 colons with an
// IPv4 ending, otherwise 7 :'s is bad
if (numberOfColons == 7 && ipAddress.charAt(startOffset) != ':' &&
ipAddress.charAt(1 + startOffset) != ':') {
return false;
}
word.delete(0, word.length());
break;
case ':':
// FIX "IP6 mechanism syntax #ip6-bad1"
// An IPV6 address cannot start with a single ":".
// Either it can starti with "::" or with a number.
if (i == startOffset && (ipAddress.length() <= i || ipAddress.charAt(i + 1) != ':')) {
return false;
}
// END FIX "IP6 mechanism syntax #ip6-bad1"
numberOfColons ++;
if (numberOfColons > 7) {
return false;
}
if (numberOfPeriods > 0) {
return false;
}
if (prevChar == ':') {
if (doubleColon) {
return false;
}
doubleColon = true;
}
word.delete(0, word.length());
break;
default:
if (word != null && word.length() > 3) {
return false;
}
if (!isValidHexChar(c)) {
return false;
}
word.append(c);
}
}
// Check if we have an IPv4 ending
if (numberOfPeriods > 0) {
// There is a test case with 7 colons and valid ipv4 this should resolve it
if (numberOfPeriods != 3 || !(isValidIp4Word(word.toString()) && numberOfColons < 7)) {
return false;
}
} else {
// If we're at then end and we haven't had 7 colons then there is a
// problem unless we encountered a doubleColon
if (numberOfColons != 7 && !doubleColon) {
return false;
}
// If we have an empty word at the end, it means we ended in either
// a : or a .
// If we did not end in :: then this is invalid
if (word.length() == 0 && ipAddress.charAt(length - 1 - startOffset) == ':' &&
ipAddress.charAt(length - 2 - startOffset) != ':') {
return false;
}
}
return true;
}
public static boolean isValidIp4Word(String word) {
char c;
if (word.length() < 1 || word.length() > 3) {
return false;
}
for (int i = 0; i < word.length(); i ++) {
c = word.charAt(i);
if (!(c >= '0' && c <= '9')) {
return false;
}
}
return Integer.parseInt(word) <= 255;
}
private static boolean isValidHexChar(char c) {
return c >= '0' && c <= '9' || c >= 'A' && c <= 'F' || c >= 'a' && c <= 'f';
}
private static boolean isValidNumericChar(char c) {
return c >= '0' && c <= '9';
}
/**
* Takes a string and parses it to see if it is a valid IPV4 address.
*
* @return true, if the string represents an IPV4 address in dotted
* notation, false otherwise
*/
public static boolean isValidIpV4Address(String value) {
int periods = 0;
int i;
int length = value.length();
if (length > 15) {
return false;
}
char c;
StringBuilder word = new StringBuilder();
for (i = 0; i < length; i ++) {
c = value.charAt(i);
if (c == '.') {
periods ++;
if (periods > 3) {
return false;
}
if (word.length() == 0) {
return false;
}
if (Integer.parseInt(word.toString()) > 255) {
return false;
}
word.delete(0, word.length());
} else if (!Character.isDigit(c)) {
return false;
} else {
if (word.length() > 2) {
return false;
}
word.append(c);
}
}
if (word.length() == 0 || Integer.parseInt(word.toString()) > 255) {
return false;
}
return periods == 3;
}
/**
* Returns the {@link Inet6Address} representation of a {@link CharSequence} IP address.
*
* This method will treat all IPv4 type addresses as "IPv4 mapped" (see {@link #getByName(CharSequence, boolean)})
* @param ip {@link CharSequence} IP address to be converted to a {@link Inet6Address}
* @return {@link Inet6Address} representation of the {@code ip} or {@code null} if not a valid IP address.
*/
public static Inet6Address getByName(CharSequence ip) {
return getByName(ip, true);
}
/**
* Returns the {@link Inet6Address} representation of a {@link CharSequence} IP address.
*
* The {@code ipv4Mapped} parameter specifies how IPv4 addresses should be treated.
* "IPv4 mapped" format as
* defined in rfc 4291 section 2 is supported.
* @param ip {@link CharSequence} IP address to be converted to a {@link Inet6Address}
* @param ipv4Mapped
*
* - {@code true} To allow IPv4 mapped inputs to be translated into {@link Inet6Address}
* - {@code false} Don't turn IPv4 addressed to mapped addresses
*
* @return {@link Inet6Address} representation of the {@code ip} or {@code null} if not a valid IP address.
*/
public static Inet6Address getByName(CharSequence ip, boolean ipv4Mapped) {
final byte[] bytes = new byte[IPV6_BYTE_COUNT];
final int ipLength = ip.length();
int compressBegin = 0;
int compressLength = 0;
int currentIndex = 0;
int value = 0;
int begin = -1;
int i = 0;
int ipv6Seperators = 0;
int ipv4Seperators = 0;
int tmp;
boolean needsShift = false;
for (; i < ipLength; ++i) {
final char c = ip.charAt(i);
switch (c) {
case ':':
++ipv6Seperators;
if (i - begin > IPV6_MAX_CHAR_BETWEEN_SEPARATOR ||
ipv4Seperators > 0 || ipv6Seperators > IPV6_MAX_SEPARATORS ||
currentIndex + 1 >= bytes.length) {
return null;
}
value <<= (IPV6_MAX_CHAR_BETWEEN_SEPARATOR - (i - begin)) << 2;
if (compressLength > 0) {
compressLength -= 2;
}
// The value integer holds at most 4 bytes from right (most significant) to left (least significant).
// The following bit shifting is used to extract and re-order the individual bytes to achieve a
// left (most significant) to right (least significant) ordering.
bytes[currentIndex++] = (byte) (((value & 0xf) << 4) | ((value >> 4) & 0xf));
bytes[currentIndex++] = (byte) ((((value >> 8) & 0xf) << 4) | ((value >> 12) & 0xf));
tmp = i + 1;
if (tmp < ipLength && ip.charAt(tmp) == ':') {
++tmp;
if (compressBegin != 0 || (tmp < ipLength && ip.charAt(tmp) == ':')) {
return null;
}
++ipv6Seperators;
needsShift = ipv6Seperators == 2 && value == 0;
compressBegin = currentIndex;
compressLength = bytes.length - compressBegin - 2;
++i;
}
value = 0;
begin = -1;
break;
case '.':
++ipv4Seperators;
if (i - begin > IPV4_MAX_CHAR_BETWEEN_SEPARATOR
|| ipv4Seperators > IPV4_SEPARATORS
|| (ipv6Seperators > 0 && (currentIndex + compressLength < 12))
|| i + 1 >= ipLength
|| currentIndex >= bytes.length
|| begin < 0
|| (begin == 0 && (i == 3 && (!isValidNumericChar(ip.charAt(2)) ||
!isValidNumericChar(ip.charAt(1)) ||
!isValidNumericChar(ip.charAt(0))) ||
i == 2 && (!isValidNumericChar(ip.charAt(1)) ||
!isValidNumericChar(ip.charAt(0))) ||
i == 1 && !isValidNumericChar(ip.charAt(0))))) {
return null;
}
value <<= (IPV4_MAX_CHAR_BETWEEN_SEPARATOR - (i - begin)) << 2;
// The value integer holds at most 3 bytes from right (most significant) to left (least significant).
// The following bit shifting is to restructure the bytes to be left (most significant) to
// right (least significant) while also accounting for each IPv4 digit is base 10.
begin = (value & 0xf) * 100 + ((value >> 4) & 0xf) * 10 + ((value >> 8) & 0xf);
if (begin < 0 || begin > 255) {
return null;
}
bytes[currentIndex++] = (byte) begin;
value = 0;
begin = -1;
break;
default:
if (!isValidHexChar(c) || (ipv4Seperators > 0 && !isValidNumericChar(c))) {
return null;
}
if (begin < 0) {
begin = i;
} else if (i - begin > IPV6_MAX_CHAR_BETWEEN_SEPARATOR) {
return null;
}
// The value is treated as a sort of array of numbers because we are dealing with
// at most 4 consecutive bytes we can use bit shifting to accomplish this.
// The most significant byte will be encountered first, and reside in the right most
// position of the following integer
value += getIntValue(c) << ((i - begin) << 2);
break;
}
}
final boolean isCompressed = compressBegin > 0;
// Finish up last set of data that was accumulated in the loop (or before the loop)
if (ipv4Seperators > 0) {
if (begin > 0 && i - begin > IPV4_MAX_CHAR_BETWEEN_SEPARATOR ||
ipv4Seperators != IPV4_SEPARATORS ||
currentIndex >= bytes.length) {
return null;
}
if (ipv6Seperators == 0) {
compressLength = 12;
} else if (ipv6Seperators >= IPV6_MIN_SEPARATORS &&
ip.charAt(ipLength - 1) != ':' &&
(!isCompressed && (ipv6Seperators == 6 && ip.charAt(0) != ':') ||
isCompressed && (ipv6Seperators + 1 < IPV6_MAX_SEPARATORS &&
(ip.charAt(0) != ':' || compressBegin <= 2)))) {
compressLength -= 2;
} else {
return null;
}
value <<= (IPV4_MAX_CHAR_BETWEEN_SEPARATOR - (i - begin)) << 2;
// The value integer holds at most 3 bytes from right (most significant) to left (least significant).
// The following bit shifting is to restructure the bytes to be left (most significant) to
// right (least significant) while also accounting for each IPv4 digit is base 10.
begin = (value & 0xf) * 100 + ((value >> 4) & 0xf) * 10 + ((value >> 8) & 0xf);
if (begin < 0 || begin > 255) {
return null;
}
bytes[currentIndex++] = (byte) begin;
} else {
tmp = ipLength - 1;
if (begin > 0 && i - begin > IPV6_MAX_CHAR_BETWEEN_SEPARATOR ||
ipv6Seperators < IPV6_MIN_SEPARATORS ||
!isCompressed && (ipv6Seperators + 1 != IPV6_MAX_SEPARATORS ||
ip.charAt(0) == ':' || ip.charAt(tmp) == ':') ||
isCompressed && (ipv6Seperators > IPV6_MAX_SEPARATORS ||
(ipv6Seperators == IPV6_MAX_SEPARATORS &&
(compressBegin <= 2 && ip.charAt(0) != ':' ||
compressBegin >= 14 && ip.charAt(tmp) != ':'))) ||
currentIndex + 1 >= bytes.length) {
return null;
}
if (begin >= 0 && i - begin <= IPV6_MAX_CHAR_BETWEEN_SEPARATOR) {
value <<= (IPV6_MAX_CHAR_BETWEEN_SEPARATOR - (i - begin)) << 2;
}
// The value integer holds at most 4 bytes from right (most significant) to left (least significant).
// The following bit shifting is used to extract and re-order the individual bytes to achieve a
// left (most significant) to right (least significant) ordering.
bytes[currentIndex++] = (byte) (((value & 0xf) << 4) | ((value >> 4) & 0xf));
bytes[currentIndex++] = (byte) ((((value >> 8) & 0xf) << 4) | ((value >> 12) & 0xf));
}
i = currentIndex + compressLength;
if (needsShift || i >= bytes.length) {
// Right shift array
if (i >= bytes.length) {
++compressBegin;
}
for (i = currentIndex; i < bytes.length; ++i) {
for (begin = bytes.length - 1; begin >= compressBegin; --begin) {
bytes[begin] = bytes[begin - 1];
}
bytes[begin] = 0;
++compressBegin;
}
} else {
// Selectively move elements
for (i = 0; i < compressLength; ++i) {
begin = i + compressBegin;
currentIndex = begin + compressLength;
if (currentIndex < bytes.length) {
bytes[currentIndex] = bytes[begin];
bytes[begin] = 0;
} else {
break;
}
}
}
if (ipv4Mapped && ipv4Seperators > 0 &&
bytes[0] == 0 && bytes[1] == 0 && bytes[2] == 0 && bytes[3] == 0 && bytes[4] == 0 &&
bytes[5] == 0 && bytes[6] == 0 && bytes[7] == 0 && bytes[8] == 0 && bytes[9] == 0) {
bytes[10] = bytes[11] = (byte) 0xff;
}
try {
return Inet6Address.getByAddress(null, bytes, -1);
} catch (UnknownHostException e) {
throw new RuntimeException(e); // Should never happen
}
}
/**
* Returns the {@link String} representation of an {@link InetAddress}.
*
* - Inet4Address results are identical to {@link InetAddress#getHostAddress()}
* - Inet6Address results adhere to
* rfc 5952 section 4
*
*
* The output does not include Scope ID.
* @param ip {@link InetAddress} to be converted to an address string
* @return {@code String} containing the text-formatted IP address
*/
public static String toAddressString(InetAddress ip) {
return toAddressString(ip, false);
}
/**
* Returns the {@link String} representation of an {@link InetAddress}.
*
* - Inet4Address results are identical to {@link InetAddress#getHostAddress()}
* - Inet6Address results adhere to
* rfc 5952 section 4 if
* {@code ipv4Mapped} is false. If {@code ipv4Mapped} is true then "IPv4 mapped" format
* from rfc 4291 section 2 will be supported.
* The compressed result will always obey the compression rules defined in
* rfc 5952 section 4
*
*
* The output does not include Scope ID.
* @param ip {@link InetAddress} to be converted to an address string
* @param ipv4Mapped
*
* - {@code true} to stray from strict rfc 5952 and support the "IPv4 mapped" format
* defined in rfc 4291 section 2 while still
* following the updated guidelines in
* rfc 5952 section 4
* - {@code false} to strictly follow rfc 5952
*
* @return {@code String} containing the text-formatted IP address
*/
public static String toAddressString(InetAddress ip, boolean ipv4Mapped) {
if (ip instanceof Inet4Address) {
return ip.getHostAddress();
}
if (!(ip instanceof Inet6Address)) {
throw new IllegalArgumentException("Unhandled type: " + ip.getClass());
}
final byte[] bytes = ip.getAddress();
final int[] words = new int[IPV6_WORD_COUNT];
int i;
for (i = 0; i < words.length; ++i) {
words[i] = ((bytes[i << 1] & 0xff) << 8) | (bytes[(i << 1) + 1] & 0xff);
}
// Find longest run of 0s, tie goes to first found instance
int currentStart = -1;
int currentLength = 0;
int shortestStart = -1;
int shortestLength = 0;
for (i = 0; i < words.length; ++i) {
if (words[i] == 0) {
if (currentStart < 0) {
currentStart = i;
}
} else if (currentStart >= 0) {
currentLength = i - currentStart;
if (currentLength > shortestLength) {
shortestStart = currentStart;
shortestLength = currentLength;
}
currentStart = -1;
}
}
// If the array ends on a streak of zeros, make sure we account for it
if (currentStart >= 0) {
currentLength = i - currentStart;
if (currentLength > shortestLength) {
shortestStart = currentStart;
shortestLength = currentLength;
}
}
// Ignore the longest streak if it is only 1 long
if (shortestLength == 1) {
shortestLength = 0;
shortestStart = -1;
}
// Translate to string taking into account longest consecutive 0s
final int shortestEnd = shortestStart + shortestLength;
final StringBuilder b = new StringBuilder(IPV6_MAX_CHAR_COUNT);
if (shortestEnd < 0) { // Optimization when there is no compressing needed
b.append(Integer.toHexString(words[0]));
for (i = 1; i < words.length; ++i) {
b.append(':');
b.append(Integer.toHexString(words[i]));
}
} else { // General case that can handle compressing (and not compressing)
// Loop unroll the first index (so we don't constantly check i==0 cases in loop)
final boolean isIpv4Mapped;
if (inRangeEndExclusive(0, shortestStart, shortestEnd)) {
b.append("::");
isIpv4Mapped = ipv4Mapped && (shortestEnd == 5 && words[5] == 0xffff);
} else {
b.append(Integer.toHexString(words[0]));
isIpv4Mapped = false;
}
for (i = 1; i < words.length; ++i) {
if (!inRangeEndExclusive(i, shortestStart, shortestEnd)) {
if (!inRangeEndExclusive(i - 1, shortestStart, shortestEnd)) {
// If the last index was not part of the shortened sequence
if (!isIpv4Mapped || i == 6) {
b.append(':');
} else {
b.append('.');
}
}
if (isIpv4Mapped && i > 5) {
b.append(words[i] >> 8);
b.append('.');
b.append(words[i] & 0xff);
} else {
b.append(Integer.toHexString(words[i]));
}
} else if (!inRangeEndExclusive(i - 1, shortestStart, shortestEnd)) {
// If we are in the shortened sequence and the last index was not
b.append("::");
}
}
}
return b.toString();
}
/**
* Does a range check on {@code value} if is within {@code start} (inclusive) and {@code end} (exclusive).
* @param value The value to checked if is within {@code start} (inclusive) and {@code end} (exclusive)
* @param start The start of the range (inclusive)
* @param end The end of the range (exclusive)
* @return
*
* - {@code true} if {@code value} if is within {@code start} (inclusive) and {@code end} (exclusive)
* - {@code false} otherwise
*
*/
private static boolean inRangeEndExclusive(int value, int start, int end) {
return value >= start && value < end;
}
/**
* A constructor to stop this class being constructed.
*/
private NetUtil() {
// Unused
}
}