--- /dev/null
+# ipaddr.js — an IPv6 and IPv4 address manipulation library [](https://travis-ci.org/whitequark/ipaddr.js)
+
+ipaddr.js is a small (1.9K minified and gzipped) library for manipulating
+IP addresses in JavaScript environments. It runs on both CommonJS runtimes
+(e.g. [nodejs]) and in a web browser.
+
+ipaddr.js allows you to verify and parse string representation of an IP
+address, match it against a CIDR range or range list, determine if it falls
+into some reserved ranges (examples include loopback and private ranges),
+and convert between IPv4 and IPv4-mapped IPv6 addresses.
+
+[nodejs]: http://nodejs.org
+
+## Installation
+
+`npm install ipaddr.js`
+
+or
+
+`bower install ipaddr.js`
+
+## API
+
+ipaddr.js defines one object in the global scope: `ipaddr`. In CommonJS,
+it is exported from the module:
+
+```js
+var ipaddr = require('ipaddr.js');
+```
+
+The API consists of several global methods and two classes: ipaddr.IPv6 and ipaddr.IPv4.
+
+### Global methods
+
+There are three global methods defined: `ipaddr.isValid`, `ipaddr.parse` and
+`ipaddr.process`. All of them receive a string as a single parameter.
+
+The `ipaddr.isValid` method returns `true` if the address is a valid IPv4 or
+IPv6 address, and `false` otherwise. It does not throw any exceptions.
+
+The `ipaddr.parse` method returns an object representing the IP address,
+or throws an `Error` if the passed string is not a valid representation of an
+IP address.
+
+The `ipaddr.process` method works just like the `ipaddr.parse` one, but it
+automatically converts IPv4-mapped IPv6 addresses to their IPv4 counterparts
+before returning. It is useful when you have a Node.js instance listening
+on an IPv6 socket, and the `net.ivp6.bindv6only` sysctl parameter (or its
+equivalent on non-Linux OS) is set to 0. In this case, you can accept IPv4
+connections on your IPv6-only socket, but the remote address will be mangled.
+Use `ipaddr.process` method to automatically demangle it.
+
+### Object representation
+
+Parsing methods return an object which descends from `ipaddr.IPv6` or
+`ipaddr.IPv4`. These objects share some properties, but most of them differ.
+
+#### Shared properties
+
+One can determine the type of address by calling `addr.kind()`. It will return
+either `"ipv6"` or `"ipv4"`.
+
+An address can be converted back to its string representation with `addr.toString()`.
+Note that this method:
+ * does not return the original string used to create the object (in fact, there is
+ no way of getting that string)
+ * returns a compact representation (when it is applicable)
+
+A `match(range, bits)` method can be used to check if the address falls into a
+certain CIDR range.
+Note that an address can be (obviously) matched only against an address of the same type.
+
+For example:
+
+```js
+var addr = ipaddr.parse("2001:db8:1234::1");
+var range = ipaddr.parse("2001:db8::");
+
+addr.match(range, 32); // => true
+```
+
+Alternatively, `match` can also be called as `match([range, bits])`. In this way,
+it can be used together with the `parseCIDR(string)` method, which parses an IP
+address together with a CIDR range.
+
+For example:
+
+```js
+var addr = ipaddr.parse("2001:db8:1234::1");
+
+addr.match(ipaddr.parseCIDR("2001:db8::/32")); // => true
+```
+
+A `range()` method returns one of predefined names for several special ranges defined
+by IP protocols. The exact names (and their respective CIDR ranges) can be looked up
+in the source: [IPv6 ranges] and [IPv4 ranges]. Some common ones include `"unicast"`
+(the default one) and `"reserved"`.
+
+You can match against your own range list by using
+`ipaddr.subnetMatch(address, rangeList, defaultName)` method. It can work with a mix of IPv6 or IPv4 addresses, and accepts a name-to-subnet map as the range list. For example:
+
+```js
+var rangeList = {
+ documentationOnly: [ ipaddr.parse('2001:db8::'), 32 ],
+ tunnelProviders: [
+ [ ipaddr.parse('2001:470::'), 32 ], // he.net
+ [ ipaddr.parse('2001:5c0::'), 32 ] // freenet6
+ ]
+};
+ipaddr.subnetMatch(ipaddr.parse('2001:470:8:66::1'), rangeList, 'unknown'); // => "tunnelProviders"
+```
+
+The addresses can be converted to their byte representation with `toByteArray()`.
+(Actually, JavaScript mostly does not know about byte buffers. They are emulated with
+arrays of numbers, each in range of 0..255.)
+
+```js
+var bytes = ipaddr.parse('2a00:1450:8007::68').toByteArray(); // ipv6.google.com
+bytes // => [42, 0x00, 0x14, 0x50, 0x80, 0x07, 0x00, <zeroes...>, 0x00, 0x68 ]
+```
+
+The `ipaddr.IPv4` and `ipaddr.IPv6` objects have some methods defined, too. All of them
+have the same interface for both protocols, and are similar to global methods.
+
+`ipaddr.IPvX.isValid(string)` can be used to check if the string is a valid address
+for particular protocol, and `ipaddr.IPvX.parse(string)` is the error-throwing parser.
+
+`ipaddr.IPvX.isValid(string)` uses the same format for parsing as the POSIX `inet_ntoa` function, which accepts unusual formats like `0xc0.168.1.1` or `0x10000000`. The function `ipaddr.IPv4.isValidFourPartDecimal(string)` validates the IPv4 address and also ensures that it is written in four-part decimal format.
+
+[IPv6 ranges]: https://github.com/whitequark/ipaddr.js/blob/master/src/ipaddr.coffee#L186
+[IPv4 ranges]: https://github.com/whitequark/ipaddr.js/blob/master/src/ipaddr.coffee#L71
+
+#### IPv6 properties
+
+Sometimes you will want to convert IPv6 not to a compact string representation (with
+the `::` substitution); the `toNormalizedString()` method will return an address where
+all zeroes are explicit.
+
+For example:
+
+```js
+var addr = ipaddr.parse("2001:0db8::0001");
+addr.toString(); // => "2001:db8::1"
+addr.toNormalizedString(); // => "2001:db8:0:0:0:0:0:1"
+```
+
+The `isIPv4MappedAddress()` method will return `true` if this address is an IPv4-mapped
+one, and `toIPv4Address()` will return an IPv4 object address.
+
+To access the underlying binary representation of the address, use `addr.parts`.
+
+```js
+var addr = ipaddr.parse("2001:db8:10::1234:DEAD");
+addr.parts // => [0x2001, 0xdb8, 0x10, 0, 0, 0, 0x1234, 0xdead]
+```
+
+A IPv6 zone index can be accessed via `addr.zoneId`:
+
+```js
+var addr = ipaddr.parse("2001:db8::%eth0");
+addr.zoneId // => 'eth0'
+```
+
+#### IPv4 properties
+
+`toIPv4MappedAddress()` will return a corresponding IPv4-mapped IPv6 address.
+
+To access the underlying representation of the address, use `addr.octets`.
+
+```js
+var addr = ipaddr.parse("192.168.1.1");
+addr.octets // => [192, 168, 1, 1]
+```
+
+`prefixLengthFromSubnetMask()` will return a CIDR prefix length for a valid IPv4 netmask or
+null if the netmask is not valid.
+
+```js
+ipaddr.IPv4.parse('255.255.255.240').prefixLengthFromSubnetMask() == 28
+ipaddr.IPv4.parse('255.192.164.0').prefixLengthFromSubnetMask() == null
+```
+
+`subnetMaskFromPrefixLength()` will return an IPv4 netmask for a valid CIDR prefix length.
+
+```js
+ipaddr.IPv4.subnetMaskFromPrefixLength(24) == "255.255.255.0"
+ipaddr.IPv4.subnetMaskFromPrefixLength(29) == "255.255.255.248"
+```
+
+`broadcastAddressFromCIDR()` will return the broadcast address for a given IPv4 interface and netmask in CIDR notation.
+```js
+ipaddr.IPv4.broadcastAddressFromCIDR("172.0.0.1/24") == "172.0.0.255"
+```
+`networkAddressFromCIDR()` will return the network address for a given IPv4 interface and netmask in CIDR notation.
+```js
+ipaddr.IPv4.networkAddressFromCIDR("172.0.0.1/24") == "172.0.0.0"
+```
+
+#### Conversion
+
+IPv4 and IPv6 can be converted bidirectionally to and from network byte order (MSB) byte arrays.
+
+The `fromByteArray()` method will take an array and create an appropriate IPv4 or IPv6 object
+if the input satisfies the requirements. For IPv4 it has to be an array of four 8-bit values,
+while for IPv6 it has to be an array of sixteen 8-bit values.
+
+For example:
+```js
+var addr = ipaddr.fromByteArray([0x7f, 0, 0, 1]);
+addr.toString(); // => "127.0.0.1"
+```
+
+or
+
+```js
+var addr = ipaddr.fromByteArray([0x20, 1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1])
+addr.toString(); // => "2001:db8::1"
+```
+
+Both objects also offer a `toByteArray()` method, which returns an array in network byte order (MSB).
+
+For example:
+```js
+var addr = ipaddr.parse("127.0.0.1");
+addr.toByteArray(); // => [0x7f, 0, 0, 1]
+```
+
+or
+
+```js
+var addr = ipaddr.parse("2001:db8::1");
+addr.toByteArray(); // => [0x20, 1, 0xd, 0xb8, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1]
+```
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