Adding minio-hash with streaming crypto hashes

pkgs/crypto/sha512/sha512.go

@@ -7,3 +7,23 @@ package sha512
 // void sha512_transform_ssse3(const void* M, void* D, uint64_t L);
 // void sha512_transform_rorx(const void* M, void* D, uint64_t L);
 import "C"
+import (
+	gosha512 "crypto/sha512"
+	"io"
+)
+
+func Sum(reader io.Reader) ([]byte, error) {
+	hash := gosha512.New()
+	var err error
+	for err == nil {
+		length := 0
+		byteBuffer := make([]byte, 1024*1024)
+		length, err = reader.Read(byteBuffer)
+		byteBuffer = byteBuffer[0:length]
+		hash.Write(byteBuffer)
+	}
+	if err != io.EOF {
+		return nil, err
+	}
+	return hash.Sum(nil), nil
+}