digest: use github.com/minio/sha256-simd

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

pkg/hasher/sha256.go

@@ -0,0 +1,28 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package hasher
+
+import (
+	"hash"
+
+	sha256simd "github.com/minio/sha256-simd"
+)
+
+func NewSHA256() hash.Hash {
+	// An equivalent of sha256-simd is expected to be merged in Go 1.20 (1.21?): https://go-review.googlesource.com/c/go/+/408795/1
+	return sha256simd.New()
+}