sequence.go

/*
 * Copyright © 2015-2018 Aeneas Rekkas <aeneas+oss@aeneas.io>
 *
 * 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.
 *
 * @author		Aeneas Rekkas <aeneas+oss@aeneas.io>
 * @copyright 	2015-2018 Aeneas Rekkas <aeneas+oss@aeneas.io>
 * @license 	Apache-2.0
 */

package sequence

import (
	"crypto/rand"
	"math/big"
)

var rander = rand.Reader // random function

var (
	AlphaNum      = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
	Alpha         = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
	AlphaLowerNum = []rune("abcdefghijklmnopqrstuvwxyz0123456789")
	AlphaUpperNum = []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
	AlphaLower    = []rune("abcdefghijklmnopqrstuvwxyz")
	AlphaUpper    = []rune("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
	Numeric       = []rune("0123456789")
)

func RuneSequence(l int, allowedRunes []rune) (seq []rune, err error) {
	c := big.NewInt(int64(len(allowedRunes)))
	seq = make([]rune, l)

	for i := 0; i < l; i++ {
		r, err := rand.Int(rander, c)
		if err != nil {
			return seq, err
		}
		rn := allowedRunes[r.Uint64()]
		seq[i] = rn
	}

	return seq, nil
}