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refactor: pre calculate the empty hash to save cost #25358

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refactor: pre calculate the empty hash to save cost #25358

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21 changes: 14 additions & 7 deletions store/internal/tree/hash.go
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@ package tree

import (
"crypto/sha256"
"encoding/hex"
"hash"
"math/bits"
)
Expand All @@ -17,10 +18,22 @@ func HashFromByteSlices(items [][]byte) []byte {
return hashFromByteSlices(sha256.New(), items)
}

// generate from this code
//
// func emptyHash() []byte {
// h := sha256.Sum256([]byte{})
// return h[:]
// }
//
// func main() {
// println(hex.EncodeToString(emptyHash()))
// }
var emptyHash, _ = hex.DecodeString("e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855")

func hashFromByteSlices(sha hash.Hash, items [][]byte) []byte {
switch len(items) {
case 0:
return emptyHash()
return emptyHash
case 1:
return leafHashOpt(sha, items[0])
default:
Expand All @@ -47,12 +60,6 @@ func innerHashOpt(s hash.Hash, left, right []byte) []byte {
return s.Sum(nil)
}

// emptyHash returns tmhash(<empty>)
func emptyHash() []byte {
h := sha256.Sum256([]byte{})
return h[:]
}

// getSplitPoint returns the largest power of 2 less than length
func getSplitPoint(length int64) int64 {
if length < 1 {
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