1 files changed, 114 insertions, 0 deletions
diff --git a/mod/mixer.c b/mod/mixer.c
new file mode 100644
index 0000000..ab5ade2
--- /dev/null
+++ b/mod/mixer.c
@@ -0,0 +1,114 @@
+/*
+ * melisma - extensible and scriptable audio engine
+ * Copyright (C) 2026  Ludvig Gunne Lindström
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <string.h>
+#include <lauxlib.h>
+#include "melisma.h"
+#include "mutil.h"
+
+#define MIXER_TYPENAME "mixer"
+
+static void proc(const ml_proc_args *args)
+{
+	float *out = args->out[0];
+
+	memset(out,0,args->nframes * sizeof(out[0]));
+
+	for (size_t i = 0; i < args->icnt; i++)
+	{
+		const float *in = args->in[i];
+
+		for (size_t j = 0; j < args->nframes; j++)
+		{
+			out[j] += in[j];
+		}
+	}
+}
+
+static int l_init(lua_State *s)
+{
+	int n = lua_gettop(s);
+
+	if (n == 0)
+	{
+		luaL_error(s,"need at least one input channel");
+	}
+
+	ml_node *node = ml_create_node(proc,NULL);
+	ml_label_node(node,"mix");
+
+	for (int i = 0; i < n; i++)
+	{
+		ml_channel *src = mutil_get_channel(s,i+1);
+		ml_channel *dst = ml_add_input(node);
+		ml_connect(src,dst);
+	}
+
+	ml_channel *out = ml_add_output(node);
+
+	*(void**) lua_newuserdata(s,sizeof(void*)) = out;
+	luaL_setmetatable(s,MIXER_TYPENAME);
+
+	return 1;
+}
+
+static int l_out(lua_State *s)
+{
+	ml_channel *c = *(void**) luaL_checkudata(s,1,MIXER_TYPENAME);
+	*(void**) lua_newuserdata(s,sizeof(void*)) = c;
+	luaL_setmetatable(s,MELISMA_OUTPUT_CHANNEL_TYPENAME);
+	return 1;
+}
+
+int luaopen_melisma_mixer(lua_State *s)
+{
+	ml_check_version();
+
+/*** Mix signals.
+
+	local mmixer = require 'melisma.mixer'
+
+	local signals = ...
+	local mixer = mmixer.init(table.unpack(signals))
+
+@classmod mixer
+*/
+	lua_newtable(s);
+	int tbl = lua_gettop(s);
+
+/*** Mix input signals in to a single output signal.
+@static
+@function init
+@tparam channel ... Input signals.
+@treturn mixer The newly created mixer unit.
+*/
+	lua_pushcfunction(s,l_init);
+	lua_setfield(s,tbl,"init");
+
+	lua_pushcfunction(s,l_out);
+	lua_setfield(s,tbl,MUTIL_OUTPUT_CHANNEL_FUNCTION);
+
+	luaL_newmetatable(s,MIXER_TYPENAME);
+	int mt = lua_gettop(s);
+
+	lua_pushvalue(s,tbl);
+	lua_setfield(s,mt,"__index");
+
+	lua_settop(s,tbl);
+	return 1;
+}