certspotter/monitor/fileutils.go

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// Copyright (C) 2017, 2023 Opsmate, Inc.
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License, v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
//
// This software is distributed WITHOUT A WARRANTY OF ANY KIND.
// See the Mozilla Public License for details.
package monitor
import (
"crypto/rand"
"encoding/hex"
"fmt"
"os"
)
func randomFileSuffix() string {
var randomBytes [12]byte
if _, err := rand.Read(randomBytes[:]); err != nil {
panic(err)
}
return hex.EncodeToString(randomBytes[:])
}
func writeFile(filename string, data []byte, perm os.FileMode) error {
tempname := filename + ".tmp." + randomFileSuffix()
if err := os.WriteFile(tempname, data, perm); err != nil {
return fmt.Errorf("error writing %s: %w", filename, err)
}
if err := os.Rename(tempname, filename); err != nil {
os.Remove(tempname)
return fmt.Errorf("error writing %s: %w", filename, err)
}
return nil
}
func fileExists(filename string) bool {
_, err := os.Lstat(filename)
return err == nil
}