rclone/dircache/dircache.go

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// Package dircache provides a simple cache for caching directory to path lookups
package dircache
// _methods are called without the lock
import (
"fmt"
"log"
"strings"
"sync"
)
// DirCache caches paths to directory IDs and vice versa
type DirCache struct {
mu sync.RWMutex
cache map[string]string
invCache map[string]string
fs DirCacher // Interface to find and make stuff
trueRootID string // ID of the absolute root
root string // the path we are working on
rootID string // ID of the root directory
rootParentID string // ID of the root's parent directory
foundRoot bool // Whether we have found the root or not
}
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// DirCacher describes an interface for doing the low level directory work
type DirCacher interface {
FindLeaf(pathID, leaf string) (pathIDOut string, found bool, err error)
CreateDir(pathID, leaf string) (newID string, err error)
}
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// New makes a DirCache
//
// The cache is safe for concurrent use
func New(root string, trueRootID string, fs DirCacher) *DirCache {
d := &DirCache{
trueRootID: trueRootID,
root: root,
fs: fs,
}
d.Flush()
d.ResetRoot()
return d
}
// _get an ID given a path - without lock
func (dc *DirCache) _get(path string) (id string, ok bool) {
id, ok = dc.cache[path]
return
}
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// Get an ID given a path
func (dc *DirCache) Get(path string) (id string, ok bool) {
dc.mu.RLock()
id, ok = dc._get(path)
dc.mu.RUnlock()
return
}
// GetInv gets a path given an ID
func (dc *DirCache) GetInv(path string) (id string, ok bool) {
dc.mu.RLock()
id, ok = dc.invCache[path]
dc.mu.RUnlock()
return
}
// _put a path, id into the map without lock
func (dc *DirCache) _put(path, id string) {
dc.cache[path] = id
dc.invCache[id] = path
}
// Put a path, id into the map
func (dc *DirCache) Put(path, id string) {
dc.mu.Lock()
dc._put(path, id)
dc.mu.Unlock()
}
// _flush the map of all data without lock
func (dc *DirCache) _flush() {
dc.cache = make(map[string]string)
dc.invCache = make(map[string]string)
}
// Flush the map of all data
func (dc *DirCache) Flush() {
dc.mu.Lock()
dc._flush()
dc.mu.Unlock()
}
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// SplitPath splits a path into directory, leaf
//
// Path shouldn't start or end with a /
//
// If there are no slashes then directory will be "" and leaf = path
func SplitPath(path string) (directory, leaf string) {
lastSlash := strings.LastIndex(path, "/")
if lastSlash >= 0 {
directory = path[:lastSlash]
leaf = path[lastSlash+1:]
} else {
directory = ""
leaf = path
}
return
}
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// FindDir finds the directory passed in returning the directory ID
// starting from pathID
//
// Path shouldn't start or end with a /
//
// If create is set it will make the directory if not found
//
// Algorithm:
// Look in the cache for the path, if found return the pathID
// If not found strip the last path off the path and recurse
// Now have a parent directory id, so look in the parent for self and return it
func (dc *DirCache) FindDir(path string, create bool) (pathID string, err error) {
dc.mu.RLock()
defer dc.mu.RUnlock()
return dc._findDir(path, create)
}
// Look for the root and in the cache - safe to call without the mu
func (dc *DirCache) _findDirInCache(path string) string {
// fmt.Println("Finding",path,"create",create,"cache",cache)
// If it is the root, then return it
if path == "" {
// fmt.Println("Root")
return dc.rootID
}
// If it is in the cache then return it
pathID, ok := dc._get(path)
if ok {
// fmt.Println("Cache hit on", path)
return pathID
}
return ""
}
// Unlocked findDir - must have mu
func (dc *DirCache) _findDir(path string, create bool) (pathID string, err error) {
// if !dc.foundRoot {
// return "", fmt.Errorf("FindDir called before FindRoot")
// }
pathID = dc._findDirInCache(path)
if pathID != "" {
return pathID, nil
}
// Split the path into directory, leaf
directory, leaf := SplitPath(path)
// Recurse and find pathID for parent directory
parentPathID, err := dc._findDir(directory, create)
if err != nil {
return "", err
}
// Find the leaf in parentPathID
pathID, found, err := dc.fs.FindLeaf(parentPathID, leaf)
if err != nil {
return "", err
}
// If not found create the directory if required or return an error
if !found {
if create {
pathID, err = dc.fs.CreateDir(parentPathID, leaf)
if err != nil {
return "", fmt.Errorf("Failed to make directory: %v", err)
}
} else {
return "", fmt.Errorf("Couldn't find directory: %q", path)
}
}
// Store the leaf directory in the cache
dc._put(path, pathID)
// fmt.Println("Dir", path, "is", pathID)
return pathID, nil
}
// FindPath finds the leaf and directoryID from a path
//
// If create is set parent directories will be created if they don't exist
func (dc *DirCache) FindPath(path string, create bool) (leaf, directoryID string, err error) {
dc.mu.Lock()
defer dc.mu.Unlock()
directory, leaf := SplitPath(path)
directoryID, err = dc._findDir(directory, create)
if err != nil {
if create {
err = fmt.Errorf("Couldn't find or make directory %q: %s", directory, err)
} else {
err = fmt.Errorf("Couldn't find directory %q: %s", directory, err)
}
}
return
}
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// FindRoot finds the root directory if not already found
//
// Resets the root directory
//
// If create is set it will make the directory if not found
func (dc *DirCache) FindRoot(create bool) error {
dc.mu.Lock()
defer dc.mu.Unlock()
if dc.foundRoot {
return nil
}
dc.foundRoot = true
rootID, err := dc._findDir(dc.root, create)
if err != nil {
dc.foundRoot = false
return err
}
dc.rootID = rootID
// Find the parent of the root while we still have the root
// directory tree cached
rootParentPath, _ := SplitPath(dc.root)
dc.rootParentID, _ = dc._get(rootParentPath)
// Reset the tree based on dc.root
dc._flush()
// Put the root directory in
dc._put("", dc.rootID)
return nil
}
// RootID returns the ID of the root directory
//
// This should be called after FindRoot
func (dc *DirCache) RootID() string {
dc.mu.Lock()
defer dc.mu.Unlock()
if !dc.foundRoot {
log.Fatalf("Internal Error: RootID() called before FindRoot")
}
return dc.rootID
}
// RootParentID returns the ID of the parent of the root directory
//
// This should be called after FindRoot
func (dc *DirCache) RootParentID() (string, error) {
dc.mu.Lock()
defer dc.mu.Unlock()
if !dc.foundRoot {
return "", fmt.Errorf("Internal Error: RootID() called before FindRoot")
}
if dc.rootParentID == "" {
return "", fmt.Errorf("Internal Error: Didn't find rootParentID")
}
if dc.rootID == dc.trueRootID {
return "", fmt.Errorf("Is root directory")
}
return dc.rootParentID, nil
}
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// ResetRoot resets the root directory to the absolute root and clears
// the DirCache
func (dc *DirCache) ResetRoot() {
dc.mu.Lock()
defer dc.mu.Unlock()
dc.foundRoot = false
dc._flush()
// Put the true root in
dc.rootID = dc.trueRootID
// Put the root directory in
dc._put("", dc.rootID)
}