9.12. 網路位址函式及運算子
Table 9.36shows the operators available for thecidrandinettypes. The operators<<,<<=,>>,>>=, and&&test for subnet inclusion. They consider only the network parts of the two addresses (ignoring any host part) and determine whether one network is identical to or a subnet of the other.
**Table 9.36. **cidrandinetOperators
| Operator | Description | Example | ||
|---|---|---|---|---|
| is less than |
| ||
| is less than or equal |
| ||
| equals |
| ||
| is greater or equal |
| ||
| is greater than |
| ||
| is not equal |
| ||
| is contained by |
| ||
| is contained by or equals |
| ||
| contains |
| ||
| contains or equals |
| ||
| contains or is contained by |
| ||
| bitwise NOT |
| ||
| bitwise AND |
| ||
` | ` | bitwise OR | `inet '192.168.1.6' | inet '0.0.0.255'` |
| addition |
| ||
| subtraction |
| ||
| subtraction |
|
Table 9.37shows the functions available for use with thecidrandinettypes. Theabbrev,host, andtextfunctions are primarily intended to offer alternative display formats.
**Table 9.37. **cidrandinetFunctions
| Function | Return Type | Description | Example | Result |
|---|---|---|---|---|
|
| abbreviated display format as text |
|
|
|
| abbreviated display format as text |
|
|
|
| broadcast address for network |
|
|
|
| extract family of address; |
|
|
|
| extract IP address as text |
|
|
|
| construct host mask for network |
|
|
|
| extract netmask length |
|
|
|
| construct netmask for network |
|
|
|
| extract network part of address |
|
|
|
| set netmask length for |
|
|
|
| set netmask length for |
|
|
|
| extract IP address and netmask length as text |
|
|
|
| are the addresses from the same family? |
|
|
|
| the smallest network which includes both of the given networks |
|
|
Anycidrvalue can be cast toinetimplicitly or explicitly; therefore, the functions shown above as operating oninetalso work oncidrvalues. (Where there are separate functions forinetandcidr, it is because the behavior should be different for the two cases.) Also, it is permitted to cast aninetvalue tocidr. When this is done, any bits to the right of the netmask are silently zeroed to create a validcidrvalue. In addition, you can cast a text value toinetorcidrusing normal casting syntax: for example,inet(expression)orcolname::cidr.
Table 9.38shows the functions available for use with themacaddrtype. The functiontrunc(macaddr)returns a MAC address with the last 3 bytes set to zero. This can be used to associate the remaining prefix with a manufacturer.
**Table 9.38. **macaddrFunctions
| Function | Return Type | Description | Example | Result |
|---|---|---|---|---|
|
| set last 3 bytes to zero |
|
|
Themacaddrtype also supports the standard relational operators (>,<=, etc.) for lexicographical ordering, and the bitwise arithmetic operators (~,&and|) for NOT, AND and OR.
Table 9.39shows the functions available for use with themacaddr8type. The functiontrunc(macaddr8)returns a MAC address with the last 5 bytes set to zero. This can be used to associate the remaining prefix with a manufacturer.
**Table 9.39. **macaddr8Functions
| Function | Return Type | Description | Example | Result |
|---|---|---|---|---|
|
| set last 5 bytes to zero |
|
|
|
| set 7th bit to one, also known as modified EUI-64, for inclusion in an IPv6 address |
|
|
Themacaddr8type also supports the standard relational operators (>,<=, etc.) for ordering, and the bitwise arithmetic operators (~,&and|) for NOT, AND and OR.