new

static VALUE
ossl_digest_initialize(int argc, VALUE *argv, VALUE self)
{
    EVP_MD_CTX *ctx;
    const EVP_MD *md;
    VALUE type, data;

    rb_scan_args(argc, argv, "11", &type, &data);
    md = GetDigestPtr(type);
    if (!NIL_P(data)) StringValue(data);

    GetDigest(self, ctx);
    EVP_DigestInit_ex(ctx, md, NULL);
    
    if (!NIL_P(data)) return ossl_digest_update(self, data);
    return self;
}