Reticulum-Go/internal/storage/atomic.go

// SPDX-License-Identifier: Apache-2.0
// Copyright (c) 2024-2026 Quad4.io

package storage

import (
	"fmt"
	"os"
	"path/filepath"
)

// AtomicWriteFile writes data to path using a temporary file and rename.
func AtomicWriteFile(path string, data []byte, perm os.FileMode) error {
	dir := filepath.Dir(path)
	if err := os.MkdirAll(dir, 0o700); err != nil {
		return fmt.Errorf("create directory %q: %w", dir, err)
	}

	tmp, err := os.CreateTemp(dir, filepath.Base(path)+".tmp.*")
	if err != nil {
		return fmt.Errorf("create temp file: %w", err)
	}
	tmpName := tmp.Name()

	cleanup := func() {
		_ = tmp.Close()
		_ = os.Remove(tmpName)
	}

	if _, err := tmp.Write(data); err != nil {
		cleanup()
		return fmt.Errorf("write temp file: %w", err)
	}
	if err := tmp.Chmod(perm); err != nil {
		cleanup()
		return fmt.Errorf("chmod temp file: %w", err)
	}
	if err := tmp.Close(); err != nil {
		cleanup()
		return fmt.Errorf("close temp file: %w", err)
	}
	if err := os.Rename(tmpName, path); err != nil {
		_ = os.Remove(tmpName)
		return fmt.Errorf("rename temp file: %w", err)
	}
	return nil
}