compact-encoding-bitfield

compact-encoding-bitfield

compact-encoding codec for bitfields. Uses a variable length encoding that is ABI compatible with cenc.uint.

npm install compact-encoding-bitfield

Usage

const cenc = require('compact-encoding')
const bitfield = require('compact-encoding-bitfield')

const buffer = cenc.encode(bitfield(8), 0b1110_1011)
// <Buffer fd eb 00>

cenc.decode(bitfield(8), buffer)
// <Buffer eb>

Bitfields are represented as buffers. For each byte, the least significant bit denotes the first bit and the most significant bit denotes the last bit. For example, bit 0 will be the least significant bit of the first byte and bit 15 will be the most significant bit of the second byte.

The encoding will convert numbers to buffers. Buffers may also be passed directly and will be returned on decode.

ABI

Depending on length, the bitfield is stored using a variable number of bytes:

1. length < 8: 1 byte with no prefix.
2. length <= 16: 2 bytes with a 0xfd prefix.
3. length <= 32: 4 bytes with a 0xfe prefix.
4. length <= 64: 8 bytes with a 0xff prefix.

length must not exceed 64 bits.

License

ISC