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package merkle
import (
"github.com/tendermint/tendermint/crypto/tmhash"
cmn "github.com/tendermint/tendermint/libs/common"
)
// Merkle tree from a map.
// Leaves are `hash(key) | hash(value)`.
// Leaves are sorted before Merkle hashing.
type simpleMap struct {
kvs cmn.KVPairs
sorted bool
}
func newSimpleMap() *simpleMap {
return &simpleMap{
kvs: nil,
sorted: false,
}
}
// Set hashes the key and value and appends it to the kv pairs.
func (sm *simpleMap) Set(key string, value Hasher) {
sm.sorted = false
// The value is hashed, so you can
// check for equality with a cached value (say)
// and make a determination to fetch or not.
vhash := value.Hash()
sm.kvs = append(sm.kvs, cmn.KVPair{
Key: []byte(key),
Value: vhash,
})
}
// Hash Merkle root hash of items sorted by key
// (UNSTABLE: and by value too if duplicate key).
func (sm *simpleMap) Hash() []byte {
sm.Sort()
return hashKVPairs(sm.kvs)
}
func (sm *simpleMap) Sort() {
if sm.sorted {
return
}
sm.kvs.Sort()
sm.sorted = true
}
// Returns a copy of sorted KVPairs.
// NOTE these contain the hashed key and value.
func (sm *simpleMap) KVPairs() cmn.KVPairs {
sm.Sort()
kvs := make(cmn.KVPairs, len(sm.kvs))
copy(kvs, sm.kvs)
return kvs
}
//----------------------------------------
// A local extension to KVPair that can be hashed.
// Key and value are length prefixed and concatenated,
// then hashed.
type KVPair cmn.KVPair
func (kv KVPair) Hash() []byte {
hasher := tmhash.New()
err := encodeByteSlice(hasher, kv.Key)
if err != nil {
panic(err)
}
err = encodeByteSlice(hasher, kv.Value)
if err != nil {
panic(err)
}
return hasher.Sum(nil)
}
func hashKVPairs(kvs cmn.KVPairs) []byte {
kvsH := make([]Hasher, len(kvs))
for i, kvp := range kvs {
kvsH[i] = KVPair(kvp)
}
return SimpleHashFromHashers(kvsH)
}