tailscale/jsondb/db.go

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// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package jsondb provides a trivial "database": a Go object saved to
// disk as JSON.
package jsondb
import (
"encoding/json"
"errors"
"io/fs"
"os"
"tailscale.com/atomicfile"
)
// DB is a database backed by a JSON file.
type DB[T any] struct {
// Data is the contents of the database.
Data *T
path string
}
// Open opens the database at path, creating it with a zero value if
// necessary.
func Open[T any](path string) (*DB[T], error) {
bs, err := os.ReadFile(path)
if errors.Is(err, fs.ErrNotExist) {
return &DB[T]{
Data: new(T),
path: path,
}, nil
} else if err != nil {
return nil, err
}
var val T
if err := json.Unmarshal(bs, &val); err != nil {
return nil, err
}
return &DB[T]{
Data: &val,
path: path,
}, nil
}
// Save writes db.Data back to disk.
func (db *DB[T]) Save() error {
bs, err := json.Marshal(db.Data)
if err != nil {
return err
}
return atomicfile.WriteFile(db.path, bs, 0600)
}