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# dns-txt
Encode or decode the RDATA field in multicast DNS TXT records. For use with DNS-Based Service Discovery. For details see [RFC 6763](https://tools.ietf.org/html/rfc6763).
[![Build status](https://travis-ci.org/watson/dns-txt.svg?branch=master)](https://travis-ci.org/watson/dns-txt) [![js-standard-style](https://img.shields.io/badge/code%20style-standard-brightgreen.svg?style=flat)](https://github.com/feross/standard) [![abstract-encoding](https://img.shields.io/badge/abstract--encoding-compliant-brightgreen.svg?style=flat)](https://github.com/mafintosh/abstract-encoding)
## Installation
``` npm install dns-txt ```
## Usage
```js var txt = require('dns-txt')()
var obj = { foo: 1, bar: 2 }
var enc = txt.encode(obj) // <Buffer 05 66 6f 6f 3d 31 05 62 61 72 3d 32>
txt.decode(enc) // { foo: '1', bar: '2' } ```
## API
The encoder and decoder conforms to [RFC 6763](https://tools.ietf.org/html/rfc6763).
### Initialize
The module exposes a constructor function which can be called with an optional options object:
```js var txt = require('dns-txt')({ binary: true }) ```
The options are:
- `binary` - If set to `true` all values will be returned as `Buffer` objects. The default behavior is to turn all values into strings. But according to the RFC the values can be any binary data. If you expect binary data, use this option.
#### `txt.encode(obj, [buffer], [offset])`
Takes a key/value object and returns a buffer with the encoded TXT record. If a buffer is passed as the second argument the object should be encoded into that buffer. Otherwise a new buffer should be allocated If an offset is passed as the third argument the object should be encoded at that byte offset. The byte offset defaults to `0`.
This module does not actively validate the key/value pairs, but keep the following in rules in mind:
- To be RFC compliant, each key should conform with the rules as specified in [section 6.4](https://tools.ietf.org/html/rfc6763#section-6.4).
- To be RFC compliant, each value should conform with the rules as specified in [section 6.5](https://tools.ietf.org/html/rfc6763#section-6.5).
After encoding `txt.encode.bytes` is set to the amount of bytes used to encode the object.
#### `txt.decode(buffer, [offset], [length])`
Takes a buffer and returns a decoded key/value object. If an offset is passed as the second argument the object should be decoded from that byte offset. The byte offset defaults to `0`. Note that all keys will be lowercased and all values will be Buffer objects.
After decoding `txt.decode.bytes` is set to the amount of bytes used to decode the object.
#### `txt.encodingLength(obj)`
Takes a single key/value object and returns the number of bytes that the given object would require if encoded.
## License
MIT
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