isabella232 / varint-1

use msb to create integer values of varying sizes

@chainsafe/varint

encode whole numbers to an array of protobuf-style varint bytes and also decode them.

import { encode, decode } from '@chainsafe/varint'

const bytes = encode(300) // === [0xAC, 0x02]
decode(bytes) // 300
decode.bytes // 2 (the last decode() call required 2 bytes)

api

import * as varint from '@chainsafe/varint'

varint.encode(num[, buffer=[], offset=0]) -> buffer

Encodes num into buffer starting at offset. returns buffer, with the encoded varint written into it. If buffer is not provided, it will default to a new array.

varint.encode.bytes will now be set to the number of bytes modified.

varint.decode(data[, offset=0]) -> number

decodes data, which can be either a buffer or array of integers, from position offset or default 0 and returns the decoded original integer.

Throws a RangeError when data does not represent a valid encoding.

varint.decode.bytes

if you also require the length (number of bytes) that were required to decode the integer you can access it via varint.decode.bytes. this is an integer property that will tell you the number of bytes that the last .decode() call had to use to decode.

varint.encode.bytes

similar to decode.bytes when encoding a number it can be useful to know how many bytes where written (especially if you pass an output array). you can access this via varint.encode.bytes which holds the number of bytes written in the last encode.

varint.encodingLength(num)

returns the number of bytes this number will be encoded as, up to a maximum of 8.

usage notes

If varint is passed a buffer that does not contain a valid end byte, then decode will throw RangeError, and decode.bytes will be set to 0. If you are reading from a streaming source, it's okay to pass an incomplete buffer into decode, detect this case, and then concatenate the next buffer.

License

MIT