From 6c2108e6bd19ffa47b33f61501f25db47ddb4cfb Mon Sep 17 00:00:00 2001
From: Xavier Del Campo Romero <xavi92@disroot.org>
Date: Sat, 15 Nov 2025 18:53:12 +0100
Subject: Add select operator

---
 src/op/select.c | 119 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 119 insertions(+)
 create mode 100644 src/op/select.c

(limited to 'src/op/select.c')

diff --git a/src/op/select.c b/src/op/select.c
new file mode 100644
index 0000000..7705af9
--- /dev/null
+++ b/src/op/select.c
@@ -0,0 +1,119 @@
+/*
+ * 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 <nw/interp.h>
+#include <nw/io.h>
+#include <nw/log.h>
+#include <nw/opcodes.h>
+#include <nw/ops.h>
+#include <nw/stack.h>
+#include <nw/types.h>
+
+static enum nw_state push(struct nw_interp *const i)
+{
+    struct nw_i_sm_select *const s = &i->sm.select;
+    const enum nw_state n = nwp_stack_push(i, &s->io);
+
+    if (n)
+        return n;
+
+    nwp_interp_resume(i);
+    return NW_AGAIN;
+}
+
+static enum nw_state pop_left(struct nw_interp *const i)
+{
+    struct nw_i_sm_select *const s = &i->sm.select;
+    const enum nw_state n = nwp_stack_pop(i, &s->io);
+    struct nw_sm_io io = {0};
+
+    if (n)
+        return n;
+
+    io.buf = s->condition ? &s->left : &s->right;
+    io.n = s->sz;
+    s->io = io;
+    i->next = push;
+    return NW_AGAIN;
+}
+
+static enum nw_state pop_right(struct nw_interp *const i)
+{
+    struct nw_i_sm_select *const s = &i->sm.select;
+    const enum nw_state n = nwp_stack_pop(i, &s->io);
+
+    if (n)
+        return n;
+    else
+    {
+        struct nw_sm_io io = {0};
+
+        io.buf = &s->left;
+        io.n = s->sz;
+        s->io = io;
+    }
+
+    i->next = pop_left;
+    return NW_AGAIN;
+}
+
+static enum nw_state pop_condition(struct nw_interp *const i)
+{
+    struct nw_i_sm_select *const s = &i->sm.select;
+    const enum nw_state n = nwp_stack_pop(i, &s->io);
+
+    if (n)
+        return n;
+    else
+    {
+        struct nw_sm_io io = {0};
+
+        io.buf = &s->right;
+        io.n = s->sz;
+        s->io = io;
+    }
+
+    i->next = pop_right;
+    return NW_AGAIN;
+}
+
+static enum nw_state check(struct nw_interp *const i)
+{
+    struct nw_i_sm_select *const s = &i->sm.select;
+
+    if (nwp_type_sz(i->push_type, &s->sz))
+    {
+        static const char *const exc = "invalid type";
+
+        i->exception = exc;
+#ifdef NW_LOG
+        nwp_log("%s: %#x\n", exc, (unsigned)i->push_type);
+#endif
+        return NW_FATAL;
+    }
+    else
+    {
+        struct nw_sm_io io = {0};
+
+        io.buf = &s->condition;
+        io.n = sizeof s->condition;
+        s->io = io;
+    }
+
+    i->next = pop_condition;
+    return NW_AGAIN;
+}
+
+void nwp_op_select(struct nw_interp *const i)
+{
+    const struct nw_i_sm_select s = {0};
+
+    i->sm.select = s;
+    i->next = check;
+}
-- 
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