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// Copyright (c) 2020 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 ipn
import (
"encoding/json"
"errors"
"io/ioutil"
"os"
"path/filepath"
"sync"
"tailscale.com/atomicfile"
)
// ErrStateNotExist is returned by StateStore.ReadState when the
// requested state ID doesn't exist.
var ErrStateNotExist = errors.New("no state with given ID")
// StateStore persists state, and produces it back on request.
type StateStore interface {
// ReadState returns the bytes associated with ID. Returns (nil,
// ErrStateNotExist) if the ID doesn't have associated state.
ReadState(id StateKey) ([]byte, error)
// WriteState saves bs as the state associated with ID.
WriteState(id StateKey, bs []byte) error
}
// MemoryStore is a store that keeps state in memory only.
type MemoryStore struct {
mu sync.Mutex
cache map[StateKey][]byte
}
// ReadState implements the StateStore interface.
func (s *MemoryStore) ReadState(id StateKey) ([]byte, error) {
s.mu.Lock()
defer s.mu.Unlock()
if s.cache == nil {
s.cache = map[StateKey][]byte{}
}
bs, ok := s.cache[id]
if !ok {
return nil, ErrStateNotExist
}
return bs, nil
}
// WriteState implements the StateStore interface.
func (s *MemoryStore) WriteState(id StateKey, bs []byte) error {
s.mu.Lock()
defer s.mu.Unlock()
if s.cache == nil {
s.cache = map[StateKey][]byte{}
}
s.cache[id] = append([]byte(nil), bs...)
return nil
}
// FileStore is a StateStore that uses a JSON file for persistence.
type FileStore struct {
path string
mu sync.RWMutex
cache map[StateKey][]byte
}
// NewFileStore returns a new file store that persists to path.
func NewFileStore(path string) (*FileStore, error) {
bs, err := ioutil.ReadFile(path)
if err != nil {
if os.IsNotExist(err) {
// Write out an initial file, to verify that we can write
// to the path.
os.MkdirAll(filepath.Dir(path), 0755) // best effort
if err = atomicfile.WriteFile(path, []byte("{}"), 0600); err != nil {
return nil, err
}
return &FileStore{
path: path,
cache: map[StateKey][]byte{},
}, nil
}
return nil, err
}
ret := &FileStore{
path: path,
cache: map[StateKey][]byte{},
}
if err := json.Unmarshal(bs, &ret.cache); err != nil {
return nil, err
}
return ret, nil
}
// ReadState implements the StateStore interface.
func (s *FileStore) ReadState(id StateKey) ([]byte, error) {
s.mu.RLock()
defer s.mu.RUnlock()
bs, ok := s.cache[id]
if !ok {
return nil, ErrStateNotExist
}
return bs, nil
}
// WriteState implements the StateStore interface.
func (s *FileStore) WriteState(id StateKey, bs []byte) error {
s.mu.Lock()
defer s.mu.Unlock()
s.cache[id] = append([]byte(nil), bs...)
bs, err := json.MarshalIndent(s.cache, "", " ")
if err != nil {
return err
}
return atomicfile.WriteFile(s.path, bs, 0600)
}
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