mount.go 3.82 KB
Newer Older
Tommi Virtanen's avatar
Tommi Virtanen committed
1 2 3 4 5 6 7 8 9
// Package mount provides a Datastore that has other Datastores
// mounted at various key prefixes.
package mount

import (
	"errors"
	"strings"

	"github.com/jbenet/go-datastore"
10
	"github.com/jbenet/go-datastore/keytransform"
Tommi Virtanen's avatar
Tommi Virtanen committed
11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
	"github.com/jbenet/go-datastore/query"
)

var (
	ErrNoMount = errors.New("no datastore mounted for this key")
)

type Mount struct {
	Prefix    datastore.Key
	Datastore datastore.Datastore
}

func New(mounts []Mount) *Datastore {
	// make a copy so we're sure it doesn't mutate
	m := make([]Mount, len(mounts))
	for i, v := range mounts {
		m[i] = v
	}
	return &Datastore{mounts: m}
}

type Datastore struct {
	mounts []Mount
}

var _ datastore.Datastore = (*Datastore)(nil)

38
func (d *Datastore) lookup(key datastore.Key) (ds datastore.Datastore, mountpoint, rest datastore.Key) {
Tommi Virtanen's avatar
Tommi Virtanen committed
39
	for _, m := range d.mounts {
40
		if m.Prefix.Equal(key) || m.Prefix.IsAncestorOf(key) {
Tommi Virtanen's avatar
Tommi Virtanen committed
41 42
			s := strings.TrimPrefix(key.String(), m.Prefix.String())
			k := datastore.NewKey(s)
43
			return m.Datastore, m.Prefix, k
Tommi Virtanen's avatar
Tommi Virtanen committed
44 45
		}
	}
46
	return nil, datastore.NewKey("/"), key
Tommi Virtanen's avatar
Tommi Virtanen committed
47 48 49
}

func (d *Datastore) Put(key datastore.Key, value interface{}) error {
50
	ds, _, k := d.lookup(key)
Tommi Virtanen's avatar
Tommi Virtanen committed
51 52 53 54 55 56 57
	if ds == nil {
		return ErrNoMount
	}
	return ds.Put(k, value)
}

func (d *Datastore) Get(key datastore.Key) (value interface{}, err error) {
58
	ds, _, k := d.lookup(key)
Tommi Virtanen's avatar
Tommi Virtanen committed
59 60 61 62 63 64 65
	if ds == nil {
		return nil, datastore.ErrNotFound
	}
	return ds.Get(k)
}

func (d *Datastore) Has(key datastore.Key) (exists bool, err error) {
66
	ds, _, k := d.lookup(key)
Tommi Virtanen's avatar
Tommi Virtanen committed
67 68 69 70
	if ds == nil {
		return false, nil
	}
	return ds.Has(k)
Tommi Virtanen's avatar
Tommi Virtanen committed
71 72 73
}

func (d *Datastore) Delete(key datastore.Key) error {
74
	ds, _, k := d.lookup(key)
Tommi Virtanen's avatar
Tommi Virtanen committed
75 76 77 78
	if ds == nil {
		return datastore.ErrNotFound
	}
	return ds.Delete(k)
Tommi Virtanen's avatar
Tommi Virtanen committed
79 80 81
}

func (d *Datastore) Query(q query.Query) (query.Results, error) {
82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115
	if len(q.Filters) > 0 ||
		len(q.Orders) > 0 ||
		q.Limit > 0 ||
		q.Offset > 0 {
		// TODO this is overly simplistic, but the only caller is
		// `ipfs refs local` for now, and this gets us moving.
		return nil, errors.New("mount only supports listing all prefixed keys in random order")
	}
	key := datastore.NewKey(q.Prefix)
	ds, mount, k := d.lookup(key)
	if ds == nil {
		return nil, errors.New("mount only supports listing a mount point")
	}
	// TODO support listing cross mount points too

	// delegate the query to the mounted datastore, while adjusting
	// keys in and out
	q2 := q
	q2.Prefix = k.String()
	wrapDS := keytransform.Wrap(ds, &keytransform.Pair{
		Convert: func(datastore.Key) datastore.Key {
			panic("this should never be called")
		},
		Invert: func(k datastore.Key) datastore.Key {
			return mount.Child(k)
		},
	})

	r, err := wrapDS.Query(q2)
	if err != nil {
		return nil, err
	}
	r = query.ResultsReplaceQuery(r, q)
	return r, nil
Tommi Virtanen's avatar
Tommi Virtanen committed
116
}
Jeromy's avatar
Jeromy committed
117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175

type mountBatch struct {
	mounts map[string]datastore.Batch

	d *Datastore
}

func (d *Datastore) Batch() (datastore.Batch, error) {
	return &mountBatch{
		mounts: make(map[string]datastore.Batch),
		d:      d,
	}, nil
}

func (mt *mountBatch) lookupBatch(key datastore.Key) (datastore.Batch, datastore.Key, error) {
	child, loc, rest := mt.d.lookup(key)
	t, ok := mt.mounts[loc.String()]
	if !ok {
		bds, ok := child.(datastore.BatchingDatastore)
		if !ok {
			return nil, datastore.NewKey(""), datastore.ErrBatchUnsupported
		}
		var err error
		t, err = bds.Batch()
		if err != nil {
			return nil, datastore.NewKey(""), err
		}
		mt.mounts[loc.String()] = t
	}
	return t, rest, nil
}

func (mt *mountBatch) Put(key datastore.Key, val interface{}) error {
	t, rest, err := mt.lookupBatch(key)
	if err != nil {
		return err
	}

	return t.Put(rest, val)
}

func (mt *mountBatch) Delete(key datastore.Key) error {
	t, rest, err := mt.lookupBatch(key)
	if err != nil {
		return err
	}

	return t.Delete(rest)
}

func (mt *mountBatch) Commit() error {
	for _, t := range mt.mounts {
		err := t.Commit()
		if err != nil {
			return err
		}
	}
	return nil
}