drone-yaml/yaml/compiler/internal/rand/rand.go

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2019-02-10 19:00:16 +00:00
// Copyright 2019 Drone IO, Inc.
//
// 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.
2019-01-22 23:44:17 +00:00
package rand
import (
"crypto/rand"
)
var chars = []byte("abcdefghijklmnopqrstuvwxyz0123456789")
// random string length
const length = 32
// String returns a string value.
func String() string {
clen := len(chars)
maxrb := 255 - (256 % clen)
b := make([]byte, length)
r := make([]byte, length+(length/4)) // storage for random bytes.
i := 0
for {
if _, err := rand.Read(r); err != nil {
panic("rand: error reading random bytes")
}
for _, rb := range r {
c := int(rb)
if c > maxrb {
// Skip this number to avoid modulo bias.
continue
}
b[i] = chars[c%clen]
i++
if i == length {
return string(b)
}
}
}
}