/*
DESCRIPTION
  helpers.go provides general helper utilities.

AUTHORS
  Saxon Nelson-Milton <saxon@ausocean.org>, The Australian Ocean Laboratory (AusOcean)
*/
package h264dec

import "errors"

// binToSlice is a helper function to convert a string of binary into a
// corresponding byte slice, e.g. "0100 0001 1000 1100" => {0x41,0x8c}.
// Spaces in the string are ignored.
func binToSlice(s string) ([]byte, error) {
	var (
		a     byte = 0x80
		cur   byte
		bytes []byte
	)

	for i, c := range s {
		switch c {
		case ' ':
			continue
		case '1':
			cur |= a
		case '0':
		default:
			return nil, errors.New("invalid binary string")
		}

		a >>= 1
		if a == 0 || i == (len(s)-1) {
			bytes = append(bytes, cur)
			cur = 0
			a = 0x80
		}
	}
	return bytes, nil
}