1 files changed, 48 insertions, 0 deletions
diff --git a/src/routines/check_magic.c b/src/routines/check_magic.c
new file mode 100644
index 0000000..868d669
--- /dev/null
+++ b/src/routines/check_magic.c
@@ -0,0 +1,48 @@
+/*
+ * nanowasm, a tiny WebAssembly/Wasm interpreter
+ * Copyright (C) 2023-2025  Xavier Del Campo Romero
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+#include <nanowasm/nw.h>
+#include <nw/io.h>
+#include <nw/log.h>
+#include <nw/routines.h>
+#include <string.h>
+
+static enum nw_state run(struct nw_mod *const m)
+{
+    static const unsigned char magic[] = {'\0', 'a', 's', 'm'};
+    struct nw_sm_cm *const cm = &m->sm.check_magic;
+    const struct nw_io_cfg *const cfg = &m->cfg.io;
+    const enum nw_state n = nwp_io_read(cfg, &cm->io, cfg->user);
+
+    if (n)
+        return n;
+
+    if (memcmp(cm->buf, magic, sizeof cm->buf))
+    {
+#ifdef NW_LOG
+        nwp_log("wrong magic bytes\n");
+#endif
+        return NW_FATAL;
+    }
+
+    nwp_check_version(m);
+    return NW_AGAIN;
+}
+
+void nwp_check_magic(struct nw_mod *const m)
+{
+    const struct nw_sm_cm cm = {0};
+    struct nw_sm_cm *const pcm = &m->sm.check_magic;
+    struct nw_sm_io *const io = &pcm->io;
+
+    *pcm = cm;
+    io->buf = &pcm->buf;
+    io->n = sizeof pcm->buf;
+    m->next = run;
+}