/
namespace.go
83 lines (68 loc) · 1.94 KB
/
namespace.go
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package namespace
import (
"fmt"
"strings"
ds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
ktds "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/keytransform"
dsq "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore/query"
)
// PrefixTransform constructs a KeyTransform with a pair of functions that
// add or remove the given prefix key.
//
// Warning: will panic if prefix not found when it should be there. This is
// to avoid insidious data inconsistency errors.
func PrefixTransform(prefix ds.Key) ktds.KeyTransform {
return &ktds.Pair{
// Convert adds the prefix
Convert: func(k ds.Key) ds.Key {
return prefix.Child(k)
},
// Invert removes the prefix. panics if prefix not found.
Invert: func(k ds.Key) ds.Key {
if !prefix.IsAncestorOf(k) {
fmt.Errorf("Expected prefix (%s) in key (%s)", prefix, k)
panic("expected prefix not found")
}
s := strings.TrimPrefix(k.String(), prefix.String())
return ds.NewKey(s)
},
}
}
// Wrap wraps a given datastore with a key-prefix.
func Wrap(child ds.Datastore, prefix ds.Key) ktds.Datastore {
if child == nil {
panic("child (ds.Datastore) is nil")
}
d := ktds.Wrap(child, PrefixTransform(prefix))
return &datastore{Datastore: d, raw: child, prefix: prefix}
}
type datastore struct {
prefix ds.Key
raw ds.Datastore
ktds.Datastore
}
// Query implements Query, inverting keys on the way back out.
func (d *datastore) Query(q dsq.Query) (dsq.Results, error) {
qr, err := d.raw.Query(q)
if err != nil {
return nil, err
}
ch := make(chan dsq.Result)
go func() {
defer close(ch)
defer qr.Close()
for r := range qr.Next() {
if r.Error != nil {
ch <- r
continue
}
k := ds.NewKey(r.Entry.Key)
if !d.prefix.IsAncestorOf(k) {
continue
}
r.Entry.Key = d.Datastore.InvertKey(k).String()
ch <- r
}
}()
return dsq.DerivedResults(qr, ch), nil
}