NetMask (Apache Tomcat 8.5.56 API Documentation)

org.apache.catalina.util

## Class NetMask

- java.lang.Object
- - org.apache.catalina.util.NetMask

-     public final class NetMask
      extends Object

  A class representing a CIDR netmask.

  The constructor takes a string as an argument which represents a netmask, as per the CIDR notation -- whether this netmask be IPv4 or IPv6. It then extracts the network address (before the /) and the CIDR prefix (after the /), and tells through the #matches() method whether a candidate `InetAddress` object fits in the recorded range.

  As byte arrays as returned by `InetAddress.getByName()` are always in network byte order, finding a match is therefore as simple as testing whether the n first bits (where n is the CIDR) are the same in both byte arrays (the one of the network address and the one of the candidate address). We do that by first doing byte comparisons, then testing the last bits if any (that is, if the remainder of the integer division of the CIDR by 8 is not 0).

  As a bonus, if no '/' is found in the input, it is assumed that an exact address match is required.

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `NetMask(String input)` Constructor

  - ### Method Summary

    Methods
    Modifier and Type | Method and Description
    --- | ---
    `boolean` | `matches(InetAddress addr)` Test if a given address matches this netmask.
    `String` | `toString()`

    - ### Methods inherited from class java.lang.Object

      `clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

- - ### Constructor Detail

    - #### NetMask

          public NetMask(String input)

      Constructor
      Parameters:
        `input` - the CIDR netmask
      Throws:
        `IllegalArgumentException` - if the netmask is not correct (invalid address specification, malformed CIDR prefix, etc)

  - ### Method Detail

    - #### matches

          public boolean matches(InetAddress addr)

      Test if a given address matches this netmask.
      Parameters:
        `addr` - The `InetAddress` to test
      Returns:
        true on match, false otherwise

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `Object`

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