/
treehash.go
61 lines (55 loc) · 1.08 KB
/
treehash.go
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package aws
import (
"crypto/sha256"
)
const chunkSize = 1024 * 1024
func computeHashes(buffer []byte) [][]byte {
hashCount := len(buffer) / chunkSize
if len(buffer)%chunkSize != 0 {
hashCount += 1
}
hashes := make([][]byte, hashCount)
for i := 0; i < hashCount; i++ {
last := (i + 1) * chunkSize
if last > len(buffer) {
last = len(buffer)
}
h := sha256.Sum256(buffer[i*chunkSize : last])
hashes[i] = h[:]
}
return hashes
}
func computeTreeHash(hashes [][]byte) []byte {
hashCount := len(hashes)
switch hashCount {
case 0:
return nil
case 1:
return hashes[0]
}
leaves := make([][32]byte, hashCount)
for i := range leaves {
copy(leaves[i][:], hashes[i])
}
var (
queue = leaves[:0]
h256 = sha256.New()
buf [32]byte
)
for len(leaves) > 1 {
for i := 0; i < len(leaves); i += 2 {
if i+1 == len(leaves) {
queue = append(queue, leaves[i])
break
}
h256.Write(leaves[i][:])
h256.Write(leaves[i+1][:])
h256.Sum(buf[:0])
queue = append(queue, buf)
h256.Reset()
}
leaves = queue
queue = queue[:0]
}
return leaves[0][:]
}