Merge pull request #16 from prysmaticlabs/divide

Divide by 32 on HashByteSlice

.github/workflows/go.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go: [ '1.14', '1.19', '1.20' ]
+        go: [ '1.20', '1.21' ]
     name: Go ${{ matrix.go }} test
     steps:
       - name: Set up Go 1.x
@@ -30,4 +30,4 @@ jobs:
         run: go build -v ./...
 
       - name: Test
-        run: go test -v ./...
+        run: go test -v ./...

go.mod

@@ -1,6 +1,6 @@
 module github.com/prysmaticlabs/gohashtree
 
-go 1.17
+go 1.20
 
 require (
 	github.com/klauspost/cpuid/v2 v2.0.9

hash.go

@@ -25,12 +25,13 @@ package gohashtree
 
 import (
 	"fmt"
-	"reflect"
 	"unsafe"
 )
 
 func _hash(digests *byte, p [][32]byte, count uint32)
 
+// Hash hashes the chunks two at the time and outputs the digests on the first
+// argument. It does check for lengths on the inputs.
 func Hash(digests [][32]byte, chunks [][32]byte) error {
 	if len(chunks) == 0 {
 		return nil
@@ -50,8 +51,13 @@ func Hash(digests [][32]byte, chunks [][32]byte) error {
 	return nil
 }
 
+// HashChunks is the same as Hash, but does not do error checking on the lengths of the slices
 func HashChunks(digests [][32]byte, chunks [][32]byte) {
-	_hash(&digests[0][0], chunks, uint32(len(chunks)/2))
+	if supportedCPU {
+		_hash(&digests[0][0], chunks, uint32(len(chunks)/2))
+	} else {
+		sha256_1_generic(digests, chunks)
+	}
 }
 
 func HashByteSlice(digests []byte, chunks []byte) error {
@@ -69,18 +75,14 @@ func HashByteSlice(digests []byte, chunks []byte) error {
 	}
 	// We use an unsafe pointer to cast []byte to [][32]byte. The length and
 	// capacity of the slice need to be divided accordingly by 32.
-	header := *(*reflect.SliceHeader)(unsafe.Pointer(&chunks))
-	header.Len <<= 5
-	header.Cap <<= 5
-	chunkedChunks := *(*[][32]byte)(unsafe.Pointer(&header))
+	sizeChunks := (len(chunks) >> 5)
+	chunkedChunks := unsafe.Slice((*[32]byte)(unsafe.Pointer(&chunks[0])), sizeChunks)
 
+	sizeDigests := (len(digests) >> 5)
+	chunkedDigest := unsafe.Slice((*[32]byte)(unsafe.Pointer(&digests[0])), sizeDigests)
 	if supportedCPU {
-		_hash(&digests[0], chunkedChunks, uint32(len(chunks)/64))
+		Hash(chunkedDigest, chunkedChunks)
 	} else {
-		headerDigest := *(*reflect.SliceHeader)(unsafe.Pointer(&digests))
-		headerDigest.Len <<= 5
-		headerDigest.Cap <<= 5
-		chunkedDigest := *(*[][32]byte)(unsafe.Pointer(&headerDigest))
 		sha256_1_generic(chunkedDigest, chunkedChunks)
 	}
 	return nil