1 files changed, 391 insertions, 0 deletions
diff --git a/mod/udp.c b/mod/udp.c
new file mode 100644
index 0000000..6448a56
--- /dev/null
+++ b/mod/udp.c
@@ -0,0 +1,391 @@
+/*
+ * 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 <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <assert.h>
+
+#include <unistd.h>
+#include <sys/eventfd.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <netinet/in.h>
+#include <arpa/inet.h>
+
+#include <lauxlib.h>
+
+#include "melisma.h"
+#include "melisma/ring.h"
+
+#define SOCKADDR_TYPENAME   "sockaddr"
+#define UDP_SOCKET_TYPENAME "udp socket"
+#define UDP_PACKET_SIZE     65536
+
+struct udp_socket
+{
+	int              fd;
+	int              family;
+	int              event;
+	int              bound;
+	int              callb;
+	lua_State       *state;
+	ml_ring         *recvring;
+	ml_ring         *sendring;
+	uint8_t          pollbuf[UDP_PACKET_SIZE];
+	uint8_t          procbuf[UDP_PACKET_SIZE];
+};
+
+// TODO: CHECK BUFFER SIZES FOR ADDRESSES
+
+static int l_sockaddr_unix(lua_State *s)
+{
+	size_t len;
+	const char *path = luaL_checklstring(s,1,&len);
+
+	struct sockaddr_storage *sa = lua_newuserdata(s,sizeof *sa);
+	luaL_setmetatable(s,SOCKADDR_TYPENAME);
+	memset(sa,0,sizeof *sa);
+
+	((struct sockaddr_un*)sa)->sun_family = AF_UNIX;
+	memcpy(((struct sockaddr_un*)sa)->sun_path,path,len);
+
+	return 1;
+}
+
+static int l_sockaddr_inet(lua_State *s)
+{
+	const char *addr = luaL_checkstring(s,1);
+	int port = luaL_checkinteger(s,2);
+
+	struct in_addr in_addr;
+	if (inet_pton(AF_INET,addr,&in_addr) != 1)
+	{
+		luaL_error(s,"invalid ipv4 address '%s'",addr);
+	}
+
+	struct sockaddr_storage *sa = lua_newuserdata(s,sizeof *sa);
+	luaL_setmetatable(s,SOCKADDR_TYPENAME);
+	memset(sa,0,sizeof *sa);
+
+	((struct sockaddr_in*)sa)->sin_family = AF_INET;
+	((struct sockaddr_in*)sa)->sin_port = htons(port);
+	memcpy(&((struct sockaddr_in*)sa)->sin_addr,&in_addr,sizeof in_addr);
+
+	return 1;
+}
+
+static void recv_handler(int fd, int flags, void *args)
+{
+	struct udp_socket *us = args;
+	ssize_t len = recvfrom(fd,us->pollbuf,sizeof us->pollbuf,0,NULL,NULL);
+
+	if (len < 0)
+	{
+		perror("recvfrom");
+		return;
+	}
+
+	if (!ml_ring_has_space(us->recvring,len + sizeof len))
+	{
+		fprintf(stderr,"dropped udp packet");
+	}
+
+	ml_ring_write_blocking(us->recvring,&len,sizeof len);
+	ml_ring_write_blocking(us->recvring,us->pollbuf,len);
+}
+
+static void send_handler(int fd, int flags, void *args)
+{
+	struct udp_socket *us = args;
+
+	size_t sa_len,len;
+	struct sockaddr_storage storage = {0};
+
+	ml_ring_read_blocking(us->sendring,&sa_len,sizeof sa_len);
+	ml_ring_read_blocking(us->sendring,&storage,sa_len);
+	ml_ring_read_blocking(us->sendring,&len,sizeof len);
+	ml_ring_read_blocking(us->sendring,us->pollbuf,len);
+
+	if (sendto(us->fd,us->pollbuf,len,0,(struct sockaddr*) &storage,sa_len) < 0)
+	{
+		perror("sendto");
+	}
+
+	uint64_t x;
+	if (read(us->event,&x,sizeof x) != sizeof x)
+		;
+}
+
+static int l_socket(lua_State *s)
+{
+	int family = lua_tointeger(s,lua_upvalueindex(1));
+	int fd = socket(family,SOCK_DGRAM,0);
+
+	if (fd < 0)
+	{
+		const char *err = strerror(errno);
+		luaL_error(s,"failed to create socket: %s",err);
+	}
+
+	struct udp_socket *us = calloc(1,sizeof(*us));
+	us->fd = fd;
+	us->family = family;
+	us->sendring = ml_ring_init(UDP_PACKET_SIZE);
+	us->event = eventfd(0,EFD_SEMAPHORE);
+
+	ml_add_io_handler(us->event,POLLIN,send_handler,us);
+
+	*(struct udp_socket**) lua_newuserdata(s,sizeof(struct udp_socket*)) = us;
+	luaL_setmetatable(s,UDP_SOCKET_TYPENAME);
+
+	return 1;
+}
+
+static const char *family_name(int family)
+{
+	switch (family)
+	{
+	case AF_UNIX: return "unix";
+	case AF_INET: return "inet";
+	default:      assert(0);
+	}
+}
+
+static void proc(const ml_proc_args *args)
+{
+	struct udp_socket *us = args->userp;
+	ssize_t len;
+
+	while (!ml_ring_empty(us->recvring))
+	{
+		ml_ring_read_blocking(us->recvring,&len,sizeof len);
+		ml_ring_read_blocking(us->recvring,us->procbuf,len);
+
+		lua_pushlstring(us->state,(const char*)us->procbuf,len);
+		int arg = luaL_ref(us->state,LUA_REGISTRYINDEX);
+
+		ml_schedule_event(0,us->callb,arg);
+	}
+}
+
+static size_t get_sockaddr_len(struct sockaddr *sa)
+{
+	if (sa->sa_family == AF_UNIX)
+	{
+		const char *path = ((struct sockaddr_un*)sa)->sun_path;
+
+		if (path[0] == 0 && path[1] != 0)
+		{
+			return offsetof(struct sockaddr_un,sun_path) + strlen(path+1) + 1;
+		}
+
+		return offsetof(struct sockaddr_un,sun_path) + strlen(path);
+	}
+	else
+	{
+		return sizeof(struct sockaddr_in);
+	}
+}
+
+static void check_family(lua_State *s, struct udp_socket *us, struct sockaddr *sa)
+{
+	if (us->family != sa->sa_family)
+	{
+		luaL_error(s,"sockaddr address family (%s) does not match socket address family (%s)",
+		           family_name(sa->sa_family), family_name(us->family));
+	}
+}
+
+static int l_bind(lua_State *s)
+{
+	struct udp_socket *us = *(struct udp_socket**) luaL_checkudata(s,1,UDP_SOCKET_TYPENAME);
+	struct sockaddr *sa = luaL_checkudata(s,2,SOCKADDR_TYPENAME);
+
+	luaL_checktype(s,3,LUA_TFUNCTION);
+
+	if (us->bound)
+	{
+		luaL_error(s,"socket is already bound");
+	}
+
+	check_family(s,us,sa);
+
+	size_t len = get_sockaddr_len(sa);
+
+	if (bind(us->fd,sa,len) < 0)
+	{
+		const char *err = strerror(errno);
+		luaL_error(s,"failed to bind socket: %s",err);
+	}
+
+	us->bound = 1;
+	us->recvring = ml_ring_init(UDP_PACKET_SIZE);
+	us->state = s;
+
+	ml_add_io_handler(us->fd,POLLIN,recv_handler,us);
+
+	lua_pushvalue(s,3);
+	us->callb = luaL_ref(s,LUA_REGISTRYINDEX);
+
+	ml_node *node = ml_create_node(proc,us);
+	ml_channel *src = ml_add_output(node);
+	ml_channel *dst = ml_add_input(ml_get_root_node());
+	ml_connect(src,dst);
+
+	return 0;
+}
+
+static int l_send(lua_State *s)
+{
+	struct udp_socket *us = *(struct udp_socket**) luaL_checkudata(s,1,UDP_SOCKET_TYPENAME);
+	struct sockaddr *sa = luaL_checkudata(s,2,SOCKADDR_TYPENAME);
+	size_t len;
+	const char *data = luaL_checklstring(s,3,&len);
+
+	check_family(s,us,sa);
+
+	size_t sa_len = get_sockaddr_len(sa);
+	size_t full_len = sizeof len + len + sizeof sa_len + sa_len;
+
+	if (!ml_ring_has_space(us->sendring,full_len))
+	{
+		lua_pushboolean(s,0);
+		return 1;
+	}
+
+	ml_ring_write_blocking(us->sendring,&sa_len,sizeof sa_len);
+	ml_ring_write_blocking(us->sendring,sa,sa_len);
+	ml_ring_write_blocking(us->sendring,&len,sizeof len);
+	ml_ring_write_blocking(us->sendring,data,len);
+
+	uint64_t x = 1;
+	if (write(us->event,&x,sizeof x) < sizeof x)
+		;
+
+	lua_pushboolean(s,1);
+	return 1;
+}
+
+int luaopen_melisma_udp(lua_State *s)
+{
+	lua_newtable(s);
+	int tbl = lua_gettop(s);
+
+/*** UDP support.
+
+	local mudp = require 'melisma.udp'
+
+	local addr = mudp.sockaddr.inet('127.0.0.1',8000)
+	local sock = mudp.socket.inet()
+
+	sock:send(addr,'hello')
+	sock:bind(addr,print)
+
+@module udp
+*/
+
+/*** Socket address description.
+@type sockaddr
+*/
+	lua_newtable(s);
+	int sockaddr_tbl = lua_gettop(s);
+
+/*** Create a unix domain address description.
+@static
+@function unix
+@tparam string path
+@treturn sockaddr
+*/
+	lua_pushcfunction(s,l_sockaddr_unix);
+	lua_setfield(s,sockaddr_tbl,"unix");
+
+
+/*** Create a internet domain address description.
+@static
+@function inet
+@tparam string host
+@tparam integer port
+@treturn sockaddr
+*/
+	lua_pushcfunction(s,l_sockaddr_inet);
+	lua_setfield(s,sockaddr_tbl,"inet");
+
+	lua_pushvalue(s,sockaddr_tbl);
+	lua_setfield(s,tbl,"sockaddr");
+
+	luaL_newmetatable(s,SOCKADDR_TYPENAME);
+	int sockaddr_mt = lua_gettop(s);
+
+	lua_pushvalue(s,sockaddr_tbl);
+	lua_setfield(s,sockaddr_mt,"__index");
+
+/*** Handle to a socket.
+@type socket
+*/
+
+	lua_newtable(s);
+	int socket_tbl = lua_gettop(s);
+
+/*** Create a unix domain socket.
+@static
+@function unix
+@treturn socket
+*/
+	lua_pushinteger(s,AF_UNIX);
+	lua_pushcclosure(s,l_socket,1);
+	lua_setfield(s,socket_tbl,"unix");
+
+
+/*** Create an internet domain socket.
+@static
+@function inet
+@treturn socket
+*/
+	lua_pushinteger(s,AF_INET);
+	lua_pushcclosure(s,l_socket,1);
+	lua_setfield(s,socket_tbl,"inet");
+
+/*** Bind a socket to an address.
+@function bind
+@tparam sockaddr addr Address description.
+@tparam function fn Packet callback function.
+*/
+	lua_pushcfunction(s,l_bind);
+	lua_setfield(s,socket_tbl,"bind");
+
+/*** Send a packet on a socket.
+@function send
+@tparam sockaddr addr Address description.
+@tparam string pkt Packet to send.
+*/
+	lua_pushcfunction(s,l_send);
+	lua_setfield(s,socket_tbl,"send");
+
+	lua_pushvalue(s,socket_tbl);
+	lua_setfield(s,tbl,"socket");
+
+	luaL_newmetatable(s,UDP_SOCKET_TYPENAME);
+	int socket_mt = lua_gettop(s);
+
+	lua_pushvalue(s,socket_tbl);
+	lua_setfield(s,socket_mt,"__index");
+
+	lua_settop(s,tbl);
+	return 1;
+}