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- /*
- * Public Domain Software
- *
- * I (Matthias Ladkau) am the author of the source code in this file.
- * I have placed the source code in this file in the public domain.
- *
- * For further information see: http://creativecommons.org/publicdomain/zero/1.0/
- */
- /*
- Package fileutil contains file based utilities and helper functions.
- */
- package fileutil
- import (
- "crypto/sha256"
- "encoding/json"
- "errors"
- "fmt"
- "io"
- "io/ioutil"
- "os"
- "strings"
- "sync"
- "time"
- "devt.de/krotik/common/stringutil"
- )
- /*
- LoadConfig loads or creates a JSON based configuration file. Missing settings
- from the config file will be filled with default settings. This function provides
- a simple mechanism for programs to handle user-defined configuration files which
- should be loaded at start time.
- */
- func LoadConfig(filename string, defaultConfig map[string]interface{}) (map[string]interface{}, error) {
- var mdata []byte
- var data map[string]interface{}
- var err error
- var ok bool
- if ok, err = PathExists(filename); err != nil {
- return nil, err
- } else if ok {
- // Load config
- mdata, err = ioutil.ReadFile(filename)
- if err == nil {
- err = json.Unmarshal(mdata, &data)
- if err == nil {
- // Make sure all required configuration values are set
- for k, v := range defaultConfig {
- if dv, ok := data[k]; !ok || dv == nil {
- data[k] = v
- }
- }
- }
- }
- } else if err == nil {
- // Write config
- data = defaultConfig
- mdata, err = json.MarshalIndent(data, "", " ")
- if err == nil {
- err = ioutil.WriteFile(filename, mdata, 0644)
- }
- }
- if err != nil {
- return nil, err
- }
- return data, nil
- }
- /*
- ConfStr reads a config value as a string value.
- */
- func ConfStr(config map[string]interface{}, key string) string {
- return fmt.Sprint(config[key])
- }
- /*
- ConfBool reads a config value as a boolean value.
- */
- func ConfBool(config map[string]interface{}, key string) bool {
- return strings.ToLower(fmt.Sprint(config[key])) == "true"
- }
- // Watched Config
- // ==============
- /*
- WatchedConfigErrRetries is the number of times the code will try to
- read the disk configuration before overwriting it with the current
- (working) configuration. Set to -1 if it should never attempt to overwrite.
- */
- var WatchedConfigErrRetries = 10
- /*
- watchSleep is the sleep which is used by the watch thread
- */
- var watchSleep = time.Sleep
- /*
- Defined error codes for WatchedConfig
- */
- var (
- ErrClosed = errors.New("Config file was closed")
- )
- /*
- WatchedConfig is a helper object which continuously watches a given config file.
- The file and the memory config are kept in sync.
- */
- type WatchedConfig struct {
- config map[string]interface{} // Internal in memory config
- configLock *sync.RWMutex // Lock for config
- interval time.Duration // Interval with which the file should be watched
- filename string // File which stores the config
- SyncError error // Synchronization errors
- shutdown chan bool // Signal channel for thread shutdown
- }
- /*
- NewWatchedConfig returns a new watcher object for a given config file.
- */
- func NewWatchedConfig(filename string, defaultConfig map[string]interface{},
- interval time.Duration) (*WatchedConfig, error) {
- var ret *WatchedConfig
- config, err := LoadConfig(filename, defaultConfig)
- if err == nil {
- wc := &WatchedConfig{config, &sync.RWMutex{}, interval, filename, nil, nil}
- err = wc.start()
- if err == nil {
- ret = wc
- }
- }
- return ret, err
- }
- /*
- GetValue returns a single config value.
- */
- func (wc *WatchedConfig) GetValue(k string) (interface{}, bool, error) {
- wc.configLock.Lock()
- defer wc.configLock.Unlock()
- if wc.SyncError != nil {
- return nil, false, wc.SyncError
- }
- val, ok := wc.config[k]
- return val, ok, nil
- }
- /*
- GetConfig returns the current config.
- */
- func (wc *WatchedConfig) GetConfig() (map[string]interface{}, error) {
- wc.configLock.Lock()
- defer wc.configLock.Unlock()
- if wc.SyncError != nil {
- return nil, wc.SyncError
- }
- cconfig := make(map[string]interface{})
- for k, v := range wc.config {
- cconfig[k] = v
- }
- return cconfig, nil
- }
- /*
- start kicks off the file watcher background thread.
- */
- func (wc *WatchedConfig) start() error {
- // Sync from file - if the file exists. No need to hold a lock since
- // we are in the startup
- err := wc.sync(true)
- if err == nil {
- // Kick off watcher
- wc.shutdown = make(chan bool)
- go wc.watch()
- }
- return err
- }
- /*
- watch is the internal file watch goroutine function.
- */
- func (wc *WatchedConfig) watch() {
- err := wc.SyncError
- errCnt := 0
- defer func() {
- wc.shutdown <- true
- }()
- for wc.SyncError != ErrClosed {
- // Wakeup every interval
- watchSleep(wc.interval)
- // Run the sync
- wc.configLock.Lock()
- // Sync from file
- if err = wc.sync(true); err != nil && wc.SyncError != ErrClosed {
- // Increase the error count
- err = fmt.Errorf("Could not sync config from disk: %v",
- err.Error())
- errCnt++
- } else {
- // Reset the error count
- errCnt = 0
- }
- // Update the sync error
- if wc.SyncError != ErrClosed {
- wc.SyncError = err
- }
- if errCnt == WatchedConfigErrRetries {
- // We can't read the disk configuration after
- // WatchedConfigErrRetries attempts - try to overwrite
- // it with the working memory configuration
- wc.sync(false)
- }
- wc.configLock.Unlock()
- }
- }
- /*
- Close closes this config watcher.
- */
- func (wc *WatchedConfig) Close() error {
- var err error
- wc.configLock.Lock()
- if wc.SyncError != nil {
- // Preserve any old error
- err = wc.SyncError
- }
- // Set the table into the closed state
- wc.SyncError = ErrClosed
- wc.configLock.Unlock()
- // Wait for watcher shutdown if it was started
- if wc.shutdown != nil {
- <-wc.shutdown
- wc.shutdown = nil
- }
- return err
- }
- /*
- Attempt to synchronize the memory config with the file. Depending on the
- checkFile flag either the file (true) or the memory config (false) is
- regarded as up-to-date.
- It is assumed that the configLock (write) is held before calling this
- function.
- The table is in an undefined state if an error is returned.
- */
- func (wc *WatchedConfig) sync(checkFile bool) error {
- var checksumFile, checksumMemory string
- stringMemoryTable := func() ([]byte, error) {
- return json.MarshalIndent(wc.config, "", " ")
- }
- writeMemoryTable := func() error {
- res, err := stringMemoryTable()
- if err == nil {
- err = ioutil.WriteFile(wc.filename, res, 0644)
- }
- return err
- }
- readMemoryTable := func() (map[string]interface{}, error) {
- var conf map[string]interface{}
- res, err := ioutil.ReadFile(wc.filename)
- if err == nil {
- err = json.Unmarshal(stringutil.StripCStyleComments(res), &conf)
- }
- return conf, err
- }
- // Check if the file can be opened
- file, err := os.OpenFile(wc.filename, os.O_RDONLY, 0660)
- if err != nil {
- if os.IsNotExist(err) {
- // Just ignore not found errors
- err = nil
- }
- // File does not exist - no checksum
- checksumFile = ""
- } else {
- hashFactory := sha256.New()
- if _, err = io.Copy(hashFactory, file); err == nil {
- // Create the checksum of the present file
- checksumFile = fmt.Sprintf("%x", hashFactory.Sum(nil))
- }
- file.Close()
- }
- if err == nil {
- // At this point we know everything about the file now check
- // the memory table
- var cString []byte
- if cString, err = stringMemoryTable(); err == nil {
- hashFactory := sha256.New()
- hashFactory.Write(cString)
- checksumMemory = fmt.Sprintf("%x", hashFactory.Sum(nil))
- }
- }
- if err == nil {
- // At this point we also know everything about the memory table
- if checkFile {
- // File is up-to-date - we should build the memory table
- if checksumFile != checksumMemory {
- var conf map[string]interface{}
- if conf, err = readMemoryTable(); err == nil {
- wc.config = conf
- }
- }
- } else {
- // Memory is up-to-date - we should write a new file
- if checksumFile != checksumMemory {
- err = writeMemoryTable()
- }
- }
- }
- return err
- }
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