read_field.coffee.md

Read field

Library imports

{add, always, applySpec, both, converge, identity, ifElse, invoker, length, lte, pipe, slice} = require 'ramda'

Relative imports

buffer_to = require './buffer_to'

Helper functions

get_data_size = buffer_to.int16(4)

get_field_name = pipe(slice(0, 4), buffer_to.ascii)

get_full_field_size = pipe(get_data_size, add(6))

has_name_and_size = pipe length, lte(6)

slice_from_buffer = invoker(2, 'slice')

Main functions

get_main_values = applySpec
	bytes: get_full_field_size
	name: get_field_name
	value: converge(slice_from_buffer, [always(6), get_full_field_size, identity])

First ensure that there are 6 bytes (to get the size bytes) then calculate and check the full size.

has_byte_length = both(
	pipe(length, lte(6)),
	converge(lte, [get_full_field_size, length]),
)

Exports

module.exports = ifElse(has_byte_length, get_main_values, always({bytes: 0}))