Level-codec NPM

level-codec

Encode keys, values and range options, with built-in or custom encodings.

Usage

If you are upgrading: please see UPGRADING.md.

const Codec = require('level-codec')
const codec = Codec({ keyEncoding: 'json' })
const key = codec.encodeKey({ foo: 'bar' })
console.log(key) // -> '{"foo":"bar"}'
console.log(codec.decodeKey(key)) // -> { foo: 'bar' }

API

`codec = Codec([opts])`

Create a new codec, with a global options object.

`codec.encodeKey(key[, opts])`

Encode key with given opts.

`codec.encodeValue(value[, opts])`

Encode value with given opts.

`codec.encodeBatch(batch[, opts])`

Encode batch ops with given opts.

`codec.encodeLtgt(ltgt)`

Encode the ltgt values of option object ltgt.

`codec.decodeKey(key[, opts])`

Decode key with given opts.

`codec.decodeValue(value[, opts])`

Decode value with given opts.

`codec.createStreamDecoder([opts])`

Create a function with signature (key, value), that for each key-value pair returned from a levelup read stream returns the decoded value to be emitted.

`codec.keyAsBuffer([opts])`

Check whether opts and the global opts call for a binary key encoding.

`codec.valueAsBuffer([opts])`

Check whether opts and the global opts call for a binary value encoding.

`codec.encodings`

The builtin encodings as object of form

{
  [type]: encoding
}

See below for a list and the format of encoding.

Builtin Encodings

Type	Input	Stored as	Output
`utf8`	String or Buffer	String or Buffer	String
`json`	Any JSON type	JSON string	Input
`binary`	Buffer, string or byte array	Buffer	As stored
`hexasciibase64ucs2utf16leutf-16le`	String or Buffer	Buffer	String
`none` a.k.a. `id`	Any type (bypass encoding)	Input*	As stored

* Stores may have their own type coercion. Whether type information is preserved depends on the abstract-leveldown implementation as well as the underlying storage (LevelDB, IndexedDB, etc).

Encoding Format

An encoding is an object of the form:

{
  encode: function (data) {
    return data
  },
  decode: function (data) {
    return data
  },
  buffer: Boolean,
  type: 'example'
}

All of these properties are required.

The buffer boolean tells consumers whether to fetch data as a Buffer, before calling your decode() function on that data. If buffer is true, it is assumed that decode() takes a Buffer. If false, it is assumed that decode takes any other type (usually a string).

To explain this in the grand scheme of things, consider a store like leveldown which has the ability to return either a Buffer or string, both sourced from the same byte array. Wrap this store with encoding-down and it'll select the most optimal data type based on the buffer property of the active encoding. If your decode() function needs a string (and the data can legitimately become a UTF8 string), you should set buffer to false. This avoids the cost of having to convert a Buffer to a string.

The type string should be a unique name.

Contributing

Level/codec is an OPEN Open Source Project. This means that:

Individuals making significant and valuable contributions are given commit-access to the project to contribute as they see fit. This project is more like an open wiki than a standard guarded open source project.

See the Contribution Guide for more details.

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