dircache: implement FindRootParent and unify locking
This commit is contained in:
Nick Craig-Wood
parent
ea12e446ca
commit
967fd2a778
1 changed files with 90 additions and 43 deletions
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@ -1,6 +1,8 @@
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// dircache provides a simple cache for caching directory to path lookups
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package dircache
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// _methods are called without the lock
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import (
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"fmt"
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"log"
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@ -10,16 +12,15 @@ import (
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// DirCache caches paths to directory IDs and vice versa
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type DirCache struct {
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cacheLock sync.RWMutex
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mu sync.RWMutex
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cache map[string]string
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invCache map[string]string
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fs DirCacher // Interface to find and make stuff
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trueRootID string // ID of the absolute root
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findDirLock sync.Mutex // Protect findDir from concurrent use
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root string // the path we are working on
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rootID string // ID of the root directory
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findRootLock sync.Mutex // Protect findRoot from concurrent use
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foundRoot bool // Whether we have found the root or not
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fs DirCacher // Interface to find and make stuff
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trueRootID string // ID of the absolute root
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root string // the path we are working on
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rootID string // ID of the root directory
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rootParentID string // ID of the root's parent directory
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foundRoot bool // Whether we have found the root or not
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}
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// DirCache describes an interface for doing the low level directory work
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@ -42,36 +43,52 @@ func New(root string, trueRootID string, fs DirCacher) *DirCache {
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return d
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}
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// _get an ID given a path - without lock
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func (dc *DirCache) _get(path string) (id string, ok bool) {
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id, ok = dc.cache[path]
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return
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}
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// Gets an ID given a path
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func (dc *DirCache) Get(path string) (id string, ok bool) {
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dc.cacheLock.RLock()
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id, ok = dc.cache[path]
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dc.cacheLock.RUnlock()
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dc.mu.RLock()
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id, ok = dc._get(path)
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dc.mu.RUnlock()
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return
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}
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// GetInv gets a path given an ID
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func (dc *DirCache) GetInv(path string) (id string, ok bool) {
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dc.cacheLock.RLock()
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dc.mu.RLock()
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id, ok = dc.invCache[path]
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dc.cacheLock.RUnlock()
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dc.mu.RUnlock()
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return
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}
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// _put a path, id into the map without lock
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func (dc *DirCache) _put(path, id string) {
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dc.cache[path] = id
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dc.invCache[id] = path
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}
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// Put a path, id into the map
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func (dc *DirCache) Put(path, id string) {
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dc.cacheLock.Lock()
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dc.cache[path] = id
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dc.invCache[id] = path
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dc.cacheLock.Unlock()
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dc.mu.Lock()
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dc._put(path, id)
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dc.mu.Unlock()
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}
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// _flush the map of all data without lock
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func (dc *DirCache) _flush() {
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dc.cache = make(map[string]string)
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dc.invCache = make(map[string]string)
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}
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// Flush the map of all data
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func (dc *DirCache) Flush() {
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dc.cacheLock.Lock()
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dc.cache = make(map[string]string)
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dc.invCache = make(map[string]string)
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dc.cacheLock.Unlock()
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dc.mu.Lock()
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dc._flush()
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dc.mu.Unlock()
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}
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// Splits a path into directory, leaf
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@ -102,16 +119,12 @@ func SplitPath(path string) (directory, leaf string) {
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// If not found strip the last path off the path and recurse
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// Now have a parent directory id, so look in the parent for self and return it
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func (dc *DirCache) FindDir(path string, create bool) (pathID string, err error) {
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pathID = dc._findDirInCache(path)
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if pathID != "" {
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return
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}
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dc.findDirLock.Lock()
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defer dc.findDirLock.Unlock()
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dc.mu.RLock()
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defer dc.mu.RUnlock()
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return dc._findDir(path, create)
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}
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// Look for the root and in the cache - safe to call without the findDirLock
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// Look for the root and in the cache - safe to call without the mu
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func (dc *DirCache) _findDirInCache(path string) string {
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// fmt.Println("Finding",path,"create",create,"cache",cache)
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// If it is the root, then return it
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@ -121,7 +134,7 @@ func (dc *DirCache) _findDirInCache(path string) string {
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}
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// If it is in the cache then return it
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pathID, ok := dc.Get(path)
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pathID, ok := dc._get(path)
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if ok {
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// fmt.Println("Cache hit on", path)
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return pathID
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@ -130,8 +143,12 @@ func (dc *DirCache) _findDirInCache(path string) string {
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return ""
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}
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// Unlocked findDir - must have findDirLock
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// Unlocked findDir - must have mu
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func (dc *DirCache) _findDir(path string, create bool) (pathID string, err error) {
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// if !dc.foundRoot {
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// return "", fmt.Errorf("FindDir called before FindRoot")
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// }
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pathID = dc._findDirInCache(path)
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if pathID != "" {
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return pathID, nil
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@ -166,7 +183,7 @@ func (dc *DirCache) _findDir(path string, create bool) (pathID string, err error
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}
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// Store the leaf directory in the cache
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dc.Put(path, pathID)
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dc._put(path, pathID)
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// fmt.Println("Dir", path, "is", pathID)
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return pathID, nil
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@ -176,8 +193,10 @@ func (dc *DirCache) _findDir(path string, create bool) (pathID string, err error
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//
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// If create is set parent directories will be created if they don't exist
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func (dc *DirCache) FindPath(path string, create bool) (leaf, directoryID string, err error) {
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dc.mu.Lock()
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defer dc.mu.Unlock()
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directory, leaf := SplitPath(path)
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directoryID, err = dc.FindDir(directory, create)
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directoryID, err = dc._findDir(directory, create)
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if err != nil {
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if create {
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err = fmt.Errorf("Couldn't find or make directory %q: %s", directory, err)
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@ -194,20 +213,28 @@ func (dc *DirCache) FindPath(path string, create bool) (leaf, directoryID string
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//
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// If create is set it will make the directory if not found
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func (dc *DirCache) FindRoot(create bool) error {
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dc.findRootLock.Lock()
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defer dc.findRootLock.Unlock()
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dc.mu.Lock()
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defer dc.mu.Unlock()
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if dc.foundRoot {
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return nil
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}
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rootID, err := dc.FindDir(dc.root, create)
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dc.foundRoot = true
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rootID, err := dc._findDir(dc.root, create)
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if err != nil {
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dc.foundRoot = false
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return err
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}
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dc.rootID = rootID
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dc.Flush()
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// Find the parent of the root while we still have the root
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// directory tree cached
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rootParentPath, _ := SplitPath(dc.root)
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dc.rootParentID, _ = dc._get(rootParentPath)
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// Reset the tree based on dc.root
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dc._flush()
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// Put the root directory in
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dc.Put("", dc.rootID)
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dc.foundRoot = true
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dc._put("", dc.rootID)
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return nil
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}
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@ -215,22 +242,42 @@ func (dc *DirCache) FindRoot(create bool) error {
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//
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// This should be called after FindRoot
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func (dc *DirCache) RootID() string {
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if dc.rootID == "" {
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dc.mu.Lock()
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defer dc.mu.Unlock()
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if !dc.foundRoot {
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log.Fatalf("Internal Error: RootID() called before FindRoot")
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}
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return dc.rootID
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}
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// RootParentID returns the ID of the parent of the root directory
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//
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// This should be called after FindRoot
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func (dc *DirCache) RootParentID() (string, error) {
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dc.mu.Lock()
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defer dc.mu.Unlock()
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if !dc.foundRoot {
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return "", fmt.Errorf("Internal Error: RootID() called before FindRoot")
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}
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if dc.rootParentID == "" {
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return "", fmt.Errorf("Internal Error: Didn't find rootParentID")
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}
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if dc.rootID == dc.trueRootID {
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return "", fmt.Errorf("Is root directory")
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}
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return dc.rootParentID, nil
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}
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// Resets the root directory to the absolute root and clears the DirCache
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func (dc *DirCache) ResetRoot() {
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dc.findRootLock.Lock()
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defer dc.findRootLock.Unlock()
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dc.mu.Lock()
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defer dc.mu.Unlock()
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dc.foundRoot = false
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dc.Flush()
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dc._flush()
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// Put the true root in
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dc.rootID = dc.trueRootID
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// Put the root directory in
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dc.Put("", dc.rootID)
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dc._put("", dc.rootID)
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}
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