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multimap.go
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multimap.go
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package adt
import (
"github.com/ipfs/go-cid"
cbg "github.com/whyrusleeping/cbor-gen"
)
// Multimap stores multiple values per key in a HAMT of AMTs.
// The order of insertion of values for each key is retained.
type Multimap struct {
mp *Map
innerBitwidth int
}
// Interprets a store as a HAMT-based map of AMTs with root `r`.
// The outer map is interpreted with a branching factor of 2^bitwidth.
func AsMultimap(s Store, r cid.Cid, outerBitwidth, innerBitwidth int) (*Multimap, error) {
m, err := AsMap(s, r, outerBitwidth)
if err != nil {
return nil, err
}
return &Multimap{m, innerBitwidth}, nil
}
// Creates a new map backed by an empty HAMT and flushes it to the store.
// The outer map has a branching factor of 2^bitwidth.
func MakeEmptyMultimap(s Store, outerBitwidth, innerBitwidth int) (*Multimap, error) {
m, err := MakeEmptyMap(s, outerBitwidth)
if err != nil {
return nil, err
}
return &Multimap{m, innerBitwidth}, nil
}
// Creates and stores a new empty multimap, returning its CID.
func StoreEmptyMultimap(store Store, outerBitwidth, innerBitwidth int) (cid.Cid, error) {
mmap, err := MakeEmptyMultimap(store, outerBitwidth, innerBitwidth)
if err != nil {
return cid.Undef, err
}
return mmap.Root()
}
// Returns the root cid of the underlying HAMT.
func (mm *Multimap) Root() (cid.Cid, error) {
return mm.mp.Root()
}
func (mm *Multimap) ForAll(fn func(k string, arr *Array) error) error {
var arrRoot cbg.CborCid
if err := mm.mp.ForEach(&arrRoot, func(k string) error {
arr, err := AsArray(mm.mp.store, cid.Cid(arrRoot), mm.innerBitwidth)
if err != nil {
return err
}
return fn(k, arr)
}); err != nil {
return err
}
return nil
}