1 files changed, 44 insertions, 0 deletions
diff --git a/crypto/sha256-select.c b/crypto/sha256-select.c
new file mode 100644
index 00000000..78e5b7e4
--- /dev/null
+++ b/crypto/sha256-select.c
@@ -0,0 +1,44 @@
+/*
+ * Top-level vtables to select a SHA-256 implementation.
+ */
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include "putty.h"
+#include "ssh.h"
+#include "sha256.h"
+
+static ssh_hash *sha256_select(const ssh_hashalg *alg)
+{
+    static const ssh_hashalg *const real_algs[] = {
+#if HAVE_SHA_NI
+        &ssh_sha256_ni,
+#endif
+#if HAVE_NEON_CRYPTO
+        &ssh_sha256_neon,
+#endif
+        &ssh_sha256_sw,
+        NULL,
+    };
+
+    for (size_t i = 0; real_algs[i]; i++) {
+        const ssh_hashalg *alg = real_algs[i];
+        const struct sha256_extra *alg_extra =
+            (const struct sha256_extra *)alg->extra;
+        if (check_availability(alg_extra))
+            return ssh_hash_new(alg);
+    }
+
+    /* We should never reach the NULL at the end of the list, because
+     * the last non-NULL entry should be software-only SHA-256, which
+     * is always available. */
+    unreachable("sha256_select ran off the end of its list");
+}
+
+const ssh_hashalg ssh_sha256 = {
+    .new = sha256_select,
+    .hlen = 32,
+    .blocklen = 64,
+    HASHALG_NAMES_ANNOTATED("SHA-256", "dummy selector vtable"),
+};