130 lines
3.3 KiB
Go
130 lines
3.3 KiB
Go
// Package truncindex package provides a general 'index tree', used by Docker
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// in order to be able to reference containers by only a few unambiguous
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// characters of their id.
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package truncindex
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import (
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"errors"
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"fmt"
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"strings"
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"sync"
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"github.com/tchap/go-patricia/patricia"
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)
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var (
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// ErrEmptyPrefix is an error returned if the prefix was empty.
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ErrEmptyPrefix = errors.New("Prefix can't be empty")
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// ErrAmbiguousPrefix is returned if the prefix was ambiguous
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// (multiple ids for the prefix).
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ErrAmbiguousPrefix = errors.New("Multiple IDs found with provided prefix")
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// ErrIllegalChar is returned when a space is in the ID
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ErrIllegalChar = errors.New("illegal character: ' '")
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)
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// TruncIndex allows the retrieval of string identifiers by any of their unique prefixes.
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// This is used to retrieve image and container IDs by more convenient shorthand prefixes.
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type TruncIndex struct {
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sync.RWMutex
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trie *patricia.Trie
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ids map[string]struct{}
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}
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// NewTruncIndex creates a new TruncIndex and initializes with a list of IDs.
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func NewTruncIndex(ids []string) (idx *TruncIndex) {
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idx = &TruncIndex{
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ids: make(map[string]struct{}),
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// Change patricia max prefix per node length,
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// because our len(ID) always 64
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trie: patricia.NewTrie(patricia.MaxPrefixPerNode(64)),
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}
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for _, id := range ids {
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idx.addID(id)
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}
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return
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}
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func (idx *TruncIndex) addID(id string) error {
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if strings.Contains(id, " ") {
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return ErrIllegalChar
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}
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if id == "" {
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return ErrEmptyPrefix
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}
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if _, exists := idx.ids[id]; exists {
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return fmt.Errorf("id already exists: '%s'", id)
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}
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idx.ids[id] = struct{}{}
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if inserted := idx.trie.Insert(patricia.Prefix(id), struct{}{}); !inserted {
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return fmt.Errorf("failed to insert id: %s", id)
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}
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return nil
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}
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// Add adds a new ID to the TruncIndex.
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func (idx *TruncIndex) Add(id string) error {
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idx.Lock()
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defer idx.Unlock()
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if err := idx.addID(id); err != nil {
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return err
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}
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return nil
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}
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// Delete removes an ID from the TruncIndex. If there are multiple IDs
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// with the given prefix, an error is thrown.
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func (idx *TruncIndex) Delete(id string) error {
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idx.Lock()
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defer idx.Unlock()
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if _, exists := idx.ids[id]; !exists || id == "" {
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return fmt.Errorf("no such id: '%s'", id)
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}
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delete(idx.ids, id)
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if deleted := idx.trie.Delete(patricia.Prefix(id)); !deleted {
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return fmt.Errorf("no such id: '%s'", id)
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}
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return nil
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}
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// Get retrieves an ID from the TruncIndex. If there are multiple IDs
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// with the given prefix, an error is thrown.
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func (idx *TruncIndex) Get(s string) (string, error) {
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if s == "" {
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return "", ErrEmptyPrefix
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}
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var (
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id string
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)
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subTreeVisitFunc := func(prefix patricia.Prefix, item patricia.Item) error {
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if id != "" {
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// we haven't found the ID if there are two or more IDs
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id = ""
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return ErrAmbiguousPrefix
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}
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id = string(prefix)
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return nil
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}
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idx.RLock()
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defer idx.RUnlock()
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if err := idx.trie.VisitSubtree(patricia.Prefix(s), subTreeVisitFunc); err != nil {
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return "", err
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}
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if id != "" {
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return id, nil
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}
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return "", fmt.Errorf("no such id: %s", s)
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}
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// Iterate iterates over all stored IDs, and passes each of them to the given handler.
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func (idx *TruncIndex) Iterate(handler func(id string)) {
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idx.RLock()
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defer idx.RUnlock()
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idx.trie.Visit(func(prefix patricia.Prefix, item patricia.Item) error {
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handler(string(prefix))
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return nil
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})
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}
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