index-encoder

Encode multiple values into sorted keys

``
npm install index-encoder
`

Usage

` js
const IndexEncoder = require('index-encoder')

const idx = new IndexEncoder([
IndexEncoder.STRING,
IndexEncoder.UINT
])

const buf = idx.encode(['foo', 42])
console.log(idx.decode(buf)) // ['foo', 42]

// pass any compact encoding name to map it to the relevant encoding
const uintType = IndexEncoder.lookup('uint')
const bufferType = IndexEncoder.lookup('buffer')
const alsoBufferType = IndexEncoder.lookup('fixed32')
`

API

#### const idx = new IndexEncoder(encodings, { prefix = -1 })

Create an index encoder using the array of encodings. The index encoder will produce a buffer encoding in the same order as encodings. A prefix can be defined to differentiate encoded buffers with the same encodings.

#### const buf = idx.encode(keys)

Encode the provided keys as a buffer. keys must be in the same order as the encodings when constructing the index encoder. keys can have less elements than the defined encodings to create a prefix buffer. When used with hyperbee, this can be used to search for only a subset of the total keys.

#### const range = idx.encodeRange(query)

Encodes the query object values into their buffer equivalent values. Useful for creating range queries for hyperbee based on the index encoder.

The query specifies the range you want to read:

`
{
gt, // Return values only > than this
gte, // Return values >= than this
lt, // Return values < than this
lte: // Return values <= than this
}
`

Returned query will be bounded by the prefix if defined and the query is unbounded. This ensures ranges only query ranges with the same prefix.

#### const values = idx.decode(buffer)

Decode the buffer into the original values. values will be in the same order as the defined encodings. Buffers encoded with a subset of keys will return the values encoded with remaining values being 0 filled if encoded with UNIT else null:

`
const idx = new IndexEncoder([
IndexEncoder.STRING,
IndexEncoder.UINT,
IndexEncoder.STRING
])

const buf = idx.encode(['foo'])
console.log(idx.decode(buf)) // ['foo', 0, null]
`

Encoding Types

The following are the types for encodings are supported provided as static properties on the IndexEncoder class:

- IndexEncoder.BUFFER : Encodes a buffer.
- IndexEncoder.STRING : Encodes a string.
- IndexEncoder.UINT : Encodes an unsigned integer.

#### const enc = IndexEncoder.lookup(c)

Returns the encoding type for a given compact encoding name (c). If c is not supported, it will throw an Unknown type` error.

License

Apache 2.0