From c83e5d2713334d39bf0718f626cab387f7331a98 Mon Sep 17 00:00:00 2001
From: Mitja Felicijan <mitja.felicijan@gmail.com>
Date: Thu, 17 Jul 2025 17:13:45 +0200
Subject: Added exposed C functions to Lua embed

---
 c-embed-lua/hi.h   | 13 +++++++++++--
 c-embed-lua/hi.lua |  7 +++++++
 c-embed-lua/main.c | 11 +++++++++++
 3 files changed, 29 insertions(+), 2 deletions(-)

(limited to 'c-embed-lua')

diff --git a/c-embed-lua/hi.h b/c-embed-lua/hi.h
index c339ac6..630da70 100644
--- a/c-embed-lua/hi.h
+++ b/c-embed-lua/hi.h
@@ -169,6 +169,15 @@ unsigned char hi[] = {
   0x28, 0x29, 0x20, 0x64, 0x6f, 0x0a, 0x09, 0x70, 0x72, 0x69, 0x6e, 0x74,
   0x28, 0x6c, 0x69, 0x6e, 0x65, 0x29, 0x0a, 0x65, 0x6e, 0x64, 0x0a, 0x0a,
   0x66, 0x69, 0x6c, 0x65, 0x3a, 0x63, 0x6c, 0x6f, 0x73, 0x65, 0x28, 0x29,
-  0x0a
+  0x0a, 0x0a, 0x2d, 0x2d, 0x20, 0x45, 0x78, 0x70, 0x6f, 0x73, 0x69, 0x6e,
+  0x67, 0x20, 0x43, 0x20, 0x66, 0x75, 0x6e, 0x63, 0x74, 0x69, 0x6f, 0x6e,
+  0x73, 0x2e, 0x0a, 0x0a, 0x68, 0x65, 0x61, 0x64, 0x65, 0x72, 0x28, 0x22,
+  0x45, 0x78, 0x70, 0x6f, 0x73, 0x69, 0x6e, 0x67, 0x20, 0x43, 0x20, 0x66,
+  0x75, 0x6e, 0x63, 0x74, 0x69, 0x6f, 0x6e, 0x73, 0x22, 0x29, 0x0a, 0x0a,
+  0x6c, 0x6f, 0x63, 0x61, 0x6c, 0x20, 0x72, 0x65, 0x73, 0x75, 0x6c, 0x74,
+  0x20, 0x3d, 0x20, 0x63, 0x5f, 0x73, 0x75, 0x6d, 0x28, 0x33, 0x2c, 0x20,
+  0x35, 0x29, 0x0a, 0x70, 0x72, 0x69, 0x6e, 0x74, 0x28, 0x22, 0x53, 0x75,
+  0x6d, 0x20, 0x69, 0x73, 0x22, 0x2c, 0x20, 0x72, 0x65, 0x73, 0x75, 0x6c,
+  0x74, 0x29, 0x0a
 };
-unsigned int hi_len = 2041;
+unsigned int hi_len = 2151;
diff --git a/c-embed-lua/hi.lua b/c-embed-lua/hi.lua
index fb6621c..1f2c072 100644
--- a/c-embed-lua/hi.lua
+++ b/c-embed-lua/hi.lua
@@ -104,3 +104,10 @@ for line in file:lines() do
 end
 
 file:close()
+
+-- Exposing C functions.
+
+header("Exposing C functions")
+
+local result = c_sum(3, 5)
+print("Sum is", result)
diff --git a/c-embed-lua/main.c b/c-embed-lua/main.c
index 7ab678a..662ea70 100644
--- a/c-embed-lua/main.c
+++ b/c-embed-lua/main.c
@@ -4,10 +4,21 @@
 
 #include "hi.h"
 
+static int l_sum(lua_State *L) {
+	double a = luaL_checknumber(L, 1);
+	double b = luaL_checknumber(L, 2);
+	lua_pushnumber(L, a + b);
+	return 1;
+}
+
 int main(void) {
 	lua_State *L = luaL_newstate();
 	luaL_openlibs(L);
 
+	// You do not need to prefix name of the function with `c_`. I did it to
+	// make it clear in the lua script code that this is a custom function.
+	lua_register(L, "c_sum", l_sum);
+
 	// Not wise since this is not a null-terminated string.
 	/* luaL_dostring(L, (const char*)hi); */
 
-- 
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