From e0b5a8152311769c559c9f2eb484db605b36f108 Mon Sep 17 00:00:00 2001
From: YAMAMOTO Takashi <imuwoto@gmail.com>
Date: Thu, 2 Nov 2023 20:47:12 +0900
Subject: [PATCH] examples/hostfunc: implement a host func version of load_call

---
 examples/hostfunc/hostfunc.c | 44 ++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/examples/hostfunc/hostfunc.c b/examples/hostfunc/hostfunc.c
index d086876f..d4388d1b 100644
--- a/examples/hostfunc/hostfunc.c
+++ b/examples/hostfunc/hostfunc.c
@@ -2,7 +2,9 @@
 #include <errno.h>
 #include <stdlib.h>
 
+#include <toywasm/cconv.h>
 #include <toywasm/endian.h>
+#include <toywasm/exec_context.h>
 #include <toywasm/host_instance.h>
 
 static int
@@ -39,8 +41,50 @@ my_host_inst_load(struct exec_context *ctx, struct host_instance *hi,
         return host_ret;
 }
 
+static int
+my_host_inst_load_call(struct exec_context *ctx, struct host_instance *hi,
+                       const struct functype *ft, const struct cell *params,
+                       struct cell *results)
+{
+        HOST_FUNC_CONVERT_PARAMS(ft, params);
+        uint32_t pp = HOST_FUNC_PARAM(ft, params, 0, i32);
+        int host_ret;
+        uint32_t le32;
+
+        host_ret = host_func_copyin(ctx, &le32, pp, 4, 4);
+        if (host_ret != 0) {
+                goto fail;
+        }
+        uint32_t p = le32_to_host(le32);
+        host_ret = host_func_copyin(ctx, &le32, p, 4, 4);
+        if (host_ret != 0) {
+                goto fail;
+        }
+        uint32_t funcptr = le32_to_host(le32);
+        p += 4;
+        le32 = host_to_le32(p);
+        host_ret = host_func_copyout(ctx, &le32, pp, 4, 4);
+        if (host_ret != 0) {
+                goto fail;
+        }
+        const struct funcinst *func;
+        host_ret =
+                cconv_deref_func_ptr(ctx, ctx->instance, funcptr, ft, &func);
+        if (host_ret != 0) {
+                goto fail;
+        }
+        /* tail call with the same argument */
+        ctx->event_u.call.func = func;
+        ctx->event = EXEC_EVENT_CALL;
+        host_ret = ETOYWASMRESTART;
+fail:
+        HOST_FUNC_FREE_CONVERTED_PARAMS();
+        return host_ret;
+}
+
 static const struct host_func my_host_inst_funcs[] = {
         HOST_FUNC(my_host_inst_, load, "(i)i"),
+        HOST_FUNC(my_host_inst_, load_call, "(i)i"),
 };
 
 static const struct name name_my_host_inst =