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moby--moby/pkg/truncindex/truncindex.go
unclejack 39fe2a3e4e pkg/truncindex: lint and add comments
Docker-DCO-1.1-Signed-off-by: Cristian Staretu <cristian.staretu@gmail.com> (github: unclejack)
2014-10-06 22:00:58 +03:00

114 lines
2.7 KiB
Go

package truncindex
import (
"errors"
"fmt"
"strings"
"sync"
"github.com/tchap/go-patricia/patricia"
)
var (
// ErrNoID is thrown when attempting to use empty prefixes
ErrNoID = errors.New("prefix can't be empty")
errDuplicateID = errors.New("multiple IDs were found")
)
func init() {
// Change patricia max prefix per node length,
// because our len(ID) always 64
patricia.MaxPrefixPerNode = 64
}
// TruncIndex allows the retrieval of string identifiers by any of their unique prefixes.
// This is used to retrieve image and container IDs by more convenient shorthand prefixes.
type TruncIndex struct {
sync.RWMutex
trie *patricia.Trie
ids map[string]struct{}
}
// NewTruncIndex creates a new TruncIndex and initializes with a list of IDs
func NewTruncIndex(ids []string) (idx *TruncIndex) {
idx = &TruncIndex{
ids: make(map[string]struct{}),
trie: patricia.NewTrie(),
}
for _, id := range ids {
idx.addID(id)
}
return
}
func (idx *TruncIndex) addID(id string) error {
if strings.Contains(id, " ") {
return fmt.Errorf("illegal character: ' '")
}
if id == "" {
return ErrNoID
}
if _, exists := idx.ids[id]; exists {
return fmt.Errorf("id already exists: '%s'", id)
}
idx.ids[id] = struct{}{}
if inserted := idx.trie.Insert(patricia.Prefix(id), struct{}{}); !inserted {
return fmt.Errorf("failed to insert id: %s", id)
}
return nil
}
// Add adds a new ID to the TruncIndex
func (idx *TruncIndex) Add(id string) error {
idx.Lock()
defer idx.Unlock()
if err := idx.addID(id); err != nil {
return err
}
return nil
}
// Delete removes an ID from the TruncIndex. If there are multiple IDs
// with the given prefix, an error is thrown.
func (idx *TruncIndex) Delete(id string) error {
idx.Lock()
defer idx.Unlock()
if _, exists := idx.ids[id]; !exists || id == "" {
return fmt.Errorf("no such id: '%s'", id)
}
delete(idx.ids, id)
if deleted := idx.trie.Delete(patricia.Prefix(id)); !deleted {
return fmt.Errorf("no such id: '%s'", id)
}
return nil
}
// Get retrieves an ID from the TruncIndex. If there are multiple IDs
// with the given prefix, an error is thrown.
func (idx *TruncIndex) Get(s string) (string, error) {
idx.RLock()
defer idx.RUnlock()
var (
id string
)
if s == "" {
return "", ErrNoID
}
subTreeVisitFunc := func(prefix patricia.Prefix, item patricia.Item) error {
if id != "" {
// we haven't found the ID if there are two or more IDs
id = ""
return errDuplicateID
}
id = string(prefix)
return nil
}
if err := idx.trie.VisitSubtree(patricia.Prefix(s), subTreeVisitFunc); err != nil {
return "", fmt.Errorf("no such id: %s", s)
}
if id != "" {
return id, nil
}
return "", fmt.Errorf("no such id: %s", s)
}