// Copyright 2020 Justine Alexandra Roberts Tunney
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package sip

func unhex(b byte) byte {
	switch {
	case '0' <= b && b <= '9':
		return b - '0'
	case 'a' <= b && b <= 'f':
		return b - 'a' + 10
	case 'A' <= b && b <= 'F':
		return b - 'A' + 10
	}
	return 0
}