README

Overview

This simple package creates a Java Pattern from a list of IP addresses, including support for CIDR block notation and wildcards. Only IPv4 is supported, not IPv6.

Usage

The CidrPattern class exposes compile and matches methods similar to Java's built-in Pattern class:

public static Pattern compile(String cidrs) throws PatternSyntaxException;
public static Pattern compile(String cidrs, int flags) throws PatternSyntaxException;
public static boolean matches(String cidrs, CharSequence input) throws PatternSyntaxException;

The cidrs input is a comma-separated list of CIDR, wildcard or address range IPv4 expressions of the form:

• IP-Address/bits
• IP-Address-IP-Address
• IP-Address

where

• IP-Address is betwen one and four integers 0-255 (or *) separated by . and
• bits is a number between 1 and 32 (defaulting to 32 if /bits is omitted)

The following are valid CIDR patterns:

• 10/8,172.16/12,192.168/16 describes the RFC 1918 private address space.
• 10/24 and 10.0.0.* describe the same set of addresses starting with 10.0.0..
• 10.0.0.0-10.0.0.255 also describes the same set of addresses starting with 10.0.0.
• 142.250.72.196 matches a single IP Address.

import com.cleo.labs.cidr.CidrPattern;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

// ...

try {
    Pattern cidr = CidrPattern.compile("192.168.0/24, 10/8");
    if (cidr.matcher("192.168.0.33").matches()) {
        // success!
    }
} catch (PatternSyntaxException e) {
    System.err.println(e.getDescription());
}

RangePattern

A helper class RangePattern may also be used directly if needed. It builds a regex pattern designed to match a range of integers:

public static Pattern compile(int min, int max);
public static Pattern compile(int min, int max, int flags);

The compiled pattern checks that the input:

• is an integer (optional leading -, followed by 1 or more digits), and
• has a value >= min and <= max.

Note that min and max maybe negative, 0, or positive. If min is larger than max, the returned Pattern matches no inputs. But no PatternSyntaxException is ever thrown—all inputs produce a valid Pattern.

Interactive Explorer Tool

CidrPattern is packaged as an executable jar whose main class is an interactive explorer tool that supports interactive testing of patterns against inputs.

To launch the tool:

java -jar cidr-pattern-1.0.0.jar

The tool supports the following commands:

• cidr pattern — compile pattern as a list of CIDR patterns
• range min max — compile a RangePattern from min to max
• pattern pattern — compile pattern as a java.util.regex.Pattern directly
• test input — test input against the last cidr, range or pattern entered
• . — exit the tool

Maven

The cidr-pattern library is packaged as a single jar file with no additional dependencies. It is stored in the GitHub package repository and can be included in your project's pom.xml as follows:

<dependency>
  <groupId>com.cleo.labs</groupId>
  <artifactId>cidr-pattern</artifactId>
  <version>1.0.0</version>
</dependency>

License

The cidr-pattern library is released under the MIT License.