The package was created before Go introduced their own "errors" package. Trade the better juju errors semantic for a smaller dependency tree.
187 lines
4.2 KiB
Go
187 lines
4.2 KiB
Go
package cache
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import (
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"context"
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"crypto/sha1"
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"encoding/base32"
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"errors"
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"fmt"
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"io/fs"
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"os"
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"path/filepath"
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"time"
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"github.com/adrg/xdg"
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"github.com/vmihailenco/msgpack/v5"
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bolt "go.etcd.io/bbolt"
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)
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const (
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modifiedBucket = "modified"
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)
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// Entry represents a cache entry, indicating the last size and modified time for a file path.
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type Entry struct {
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Size int64
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Modified time.Time
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}
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var db *bolt.DB
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// Open creates an instance of bolt.DB for a given treeRoot path.
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// If clean is true, Open will delete any existing data in the cache.
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//
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// The database will be located in `XDG_CACHE_DIR/treefmt/eval-cache/<id>.db`, where <id> is determined by hashing
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// the treeRoot path. This associates a given treeRoot with a given instance of the cache.
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func Open(treeRoot string, clean bool) (err error) {
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// determine a unique and consistent db name for the tree root
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h := sha1.New()
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h.Write([]byte(treeRoot))
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digest := h.Sum(nil)
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name := base32.StdEncoding.EncodeToString(digest)
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path, err := xdg.CacheFile(fmt.Sprintf("treefmt/eval-cache/%v.db", name))
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if err != nil {
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return fmt.Errorf("%w: could not resolve local path for the cache", err)
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}
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// force a clean of the cache if specified
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if clean {
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err := os.Remove(path)
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if errors.Is(err, os.ErrNotExist) {
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err = nil
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} else if err != nil {
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return fmt.Errorf("%w: failed to clear cache", err)
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}
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}
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db, err = bolt.Open(path, 0o600, nil)
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if err != nil {
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return fmt.Errorf("%w: failed to open cache", err)
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}
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err = db.Update(func(tx *bolt.Tx) error {
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_, err := tx.CreateBucket([]byte(modifiedBucket))
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if errors.Is(err, bolt.ErrBucketExists) {
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return nil
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}
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return err
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})
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return
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}
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// Close closes any open instance of the cache.
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func Close() error {
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if db == nil {
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return nil
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}
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return db.Close()
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}
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// getEntry is a helper for reading cache entries from bolt.
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func getEntry(bucket *bolt.Bucket, path string) (*Entry, error) {
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b := bucket.Get([]byte(path))
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if b != nil {
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var cached Entry
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if err := msgpack.Unmarshal(b, &cached); err != nil {
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return nil, fmt.Errorf("%w: failed to unmarshal cache info for path '%v'", err, path)
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}
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return &cached, nil
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} else {
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return nil, nil
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}
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}
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// ChangeSet is used to walk a filesystem, starting at root, and outputting any new or changed paths using pathsCh.
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// It determines if a path is new or has changed by comparing against cache entries.
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func ChangeSet(ctx context.Context, root string, pathsCh chan<- string) error {
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return db.Update(func(tx *bolt.Tx) error {
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bucket := tx.Bucket([]byte(modifiedBucket))
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return filepath.Walk(root, func(path string, info fs.FileInfo, err error) error {
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if err != nil {
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return fmt.Errorf("%w: failed to walk path", err)
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} else if ctx.Err() != nil {
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return ctx.Err()
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} else if info.IsDir() {
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// todo what about symlinks?
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return nil
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}
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if info.Mode()&os.ModeSymlink == os.ModeSymlink {
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// skip symlinks
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return nil
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}
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cached, err := getEntry(bucket, path)
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if err != nil {
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return err
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}
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changedOrNew := cached == nil || !(cached.Modified == info.ModTime() && cached.Size == info.Size())
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if !changedOrNew {
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// no change
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return nil
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}
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// pass on the path
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pathsCh <- path
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return nil
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})
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})
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}
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// Update is used to record updated cache information for the specified list of paths.
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func Update(paths []string) (int, error) {
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if len(paths) == 0 {
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return 0, nil
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}
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var changes int
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return changes, db.Update(func(tx *bolt.Tx) error {
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bucket := tx.Bucket([]byte(modifiedBucket))
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for _, path := range paths {
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if path == "" {
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continue
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}
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cached, err := getEntry(bucket, path)
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if err != nil {
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return err
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}
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pathInfo, err := os.Stat(path)
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if err != nil {
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return err
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}
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if cached == nil || !(cached.Modified == pathInfo.ModTime() && cached.Size == pathInfo.Size()) {
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changes += 1
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} else {
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// no change to write
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continue
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}
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cacheInfo := Entry{
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Size: pathInfo.Size(),
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Modified: pathInfo.ModTime(),
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}
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bytes, err := msgpack.Marshal(cacheInfo)
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if err != nil {
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return fmt.Errorf("%w: failed to marshal mod time", err)
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}
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if err = bucket.Put([]byte(path), bytes); err != nil {
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return fmt.Errorf("%w: failed to put mode time", err)
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}
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}
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return nil
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})
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}
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