JarCastinglevel-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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License
MIT © 2012-present Contributors.
