// AccessMerkleTree opens the Merkle tree stored in the DB. There should never be two different
// MerkleTree objects accessing the same tree.
func AccessMerkleTree(db kv.DB, prefix []byte, treeNonce []byte) (*MerkleTree, error) {
// read the allocation count out of the DB
allocCounterKey := append(append([]byte(nil), prefix...), AllocCounterKey...)
val, err := db.Get(allocCounterKey)
var allocCount uint64
if err == db.ErrNotFound() {
allocCount = 0
} else if err != nil {
return nil, err
} else if len(val) != 8 {
log.Panicf("bad alloc counter")
} else {
allocCount = binary.LittleEndian.Uint64(val)
}
return &MerkleTree{
treeNonce: treeNonce,
db: db,
nodeKeyPrefix: append(append([]byte(nil), prefix...), NodePrefix),
allocCounterKey: allocCounterKey,
allocCounter: allocCount,
}, nil
}
