ricochet-go/core/config.go

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package core
import (
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"encoding/json"
"io/ioutil"
"log"
"os"
"sync"
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)
// XXX This is partially but not fully compatible with Ricochet's JSON
// configs. It might be better to be explicitly not compatible, but have
// an automatic import function.
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type Config struct {
filePath string
root ConfigRoot
mutex sync.RWMutex
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}
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type ConfigRoot struct {
Contacts map[string]ConfigContact
Identity ConfigIdentity
// Not used by the permanent instance in Config
writable bool
config *Config
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}
type ConfigContact struct {
Hostname string
LastConnected string `json:",omitempty"`
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Nickname string
WhenCreated string
Request ConfigContactRequest `json:",omitempty"`
}
type ConfigContactRequest struct {
Pending bool
MyNickname string
Message string
WhenDelivered string `json:",omitempty"`
WhenRejected string `json:",omitempty"`
RemoteError string `json:",omitempty"`
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}
type ConfigIdentity struct {
DataDirectory string `json:",omitempty"`
ServiceKey string
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}
func LoadConfig(filePath string) (*Config, error) {
config := &Config{
filePath: filePath,
}
data, err := ioutil.ReadFile(config.filePath)
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if err != nil {
log.Printf("Config read error from %s: %v", config.filePath, err)
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return nil, err
}
if err := json.Unmarshal(data, &config.root); err != nil {
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log.Printf("Config parse error: %v", err)
return nil, err
}
return config, nil
}
// Return a read-only snapshot of the current configuration. This object
// _must not_ be stored, and you must call Close() when finished with it.
// This function may block.
func (c *Config) OpenRead() *ConfigRoot {
c.mutex.RLock()
root := c.root.Clone()
root.writable = false
root.config = c
return root
}
// Return a writable snapshot of the current configuration. This object
// _must not_ be stored, and you must call Save() or Discard() when
// finished with it. This function may block.
func (c *Config) OpenWrite() *ConfigRoot {
c.mutex.Lock()
root := c.root.Clone()
root.writable = true
root.config = c
return root
}
func (root *ConfigRoot) Clone() *ConfigRoot {
re := *root
re.Contacts = make(map[string]ConfigContact)
for k, v := range root.Contacts {
re.Contacts[k] = v
}
return &re
}
func (root *ConfigRoot) Close() {
if root.writable {
log.Panic("Close called on writable config object; use Save or Discard")
}
if root.config == nil {
log.Panic("Close called on closed config object")
}
root.config.mutex.RUnlock()
root.config = nil
}
// Save writes the state to disk, and updates the Config object if
// successful. Changes to the object are discarded on error.
func (root *ConfigRoot) Save() error {
if !root.writable {
log.Panic("Save called on read-only config object")
}
if root.config == nil {
log.Panic("Save called on closed config object")
}
c := root.config
root.writable = false
root.config = nil
err := c.save(root)
c.mutex.Unlock()
return err
}
// Discard closes a config write without saving any changes to disk
// or to the Config object.
func (root *ConfigRoot) Discard() {
if !root.writable {
log.Panic("Discard called on read-only config object")
}
if root.config == nil {
log.Panic("Discard called on closed config object")
}
c := root.config
root.config = nil
c.mutex.Unlock()
}
func (c *Config) save(newRoot *ConfigRoot) error {
data, err := json.MarshalIndent(newRoot, "", " ")
if err != nil {
log.Printf("Config encoding error: %v", err)
return err
}
// Make a pathetic attempt at atomic file write by writing into a
// temporary file and renaming over the original; this is probably
// imperfect as-implemented, but better than truncating and writing
// directly.
tempPath := c.filePath + ".new"
file, err := os.OpenFile(tempPath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0600)
if err != nil {
log.Printf("Config save error: %v", err)
return err
}
if _, err := file.Write(data); err != nil {
log.Printf("Config write error: %v", err)
file.Close()
return err
}
file.Close()
if err := os.Rename(tempPath, c.filePath); err != nil {
log.Printf("Config replace error: %v", err)
return err
}
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c.root = *newRoot
return nil
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}