text: /*=========================================================================*\
  * UDP object 
  * LuaSocket toolkit
  *
  * RCS ID: $Id: udp.c,v 1.29 2005/10/07 04:40:59 diego Exp $
  \*=========================================================================*/
  #include <string.h> 
  #define LUA_LIB
  #include "lua.h"
  #include "lauxlib.h"
  
  #include "auxiliar.h"
  #include "socket.h"
  #include "inet.h"
  #include "options.h"
  #include "udp.h"
  
  /* min and max macros */
  #ifndef MIN
  #define MIN(x, y) ((x) < (y) ? x : y)
  #endif 
  #ifndef MAX
  #define MAX(x, y) ((x) > (y) ? x : y)
  #endif 
  
  /*=========================================================================*\
  * Internal function prototypes
  \*=========================================================================*/
  static int global_create(lua_State *L);
  static int meth_send(lua_State *L);
  static int meth_sendto(lua_State *L);
  static int meth_receive(lua_State *L);
  static int meth_receivefrom(lua_State *L);
  static int meth_getsockname(lua_State *L);
  static int meth_getpeername(lua_State *L);
  static int meth_setsockname(lua_State *L);
  static int meth_setpeername(lua_State *L);
  static int meth_close(lua_State *L);
  static int meth_setoption(lua_State *L);
  static int meth_settimeout(lua_State *L);
  static int meth_getfd(lua_State *L);
  static int meth_setfd(lua_State *L);
  static int meth_dirty(lua_State *L);
  
  /* udp object methods */
  static luaL_reg udp[] = {
      {"__gc",        meth_close},
      {"__tostring",  auxiliar_tostring},
      {"close",       meth_close},
      {"dirty",       meth_dirty},
      {"getfd",       meth_getfd},
      {"getpeername", meth_getpeername},
      {"getsockname", meth_getsockname},
      {"receive",     meth_receive},
      {"receivefrom", meth_receivefrom},
      {"send",        meth_send},
      {"sendto",      meth_sendto},
      {"setfd",       meth_setfd},
      {"setoption",   meth_setoption},
      {"setpeername", meth_setpeername},
      {"setsockname", meth_setsockname},
      {"settimeout",  meth_settimeout},
      {NULL,          NULL}
  };
  
  /* socket options */
  static t_opt opt[] = {
      {"dontroute",          opt_dontroute},
      {"broadcast",          opt_broadcast},
      {"reuseaddr",          opt_reuseaddr},
      {"ip-multicast-ttl",   opt_ip_multicast_ttl},
      {"ip-multicast-loop",  opt_ip_multicast_loop},
      {"ip-add-membership",  opt_ip_add_membership},
      {"ip-drop-membership", opt_ip_drop_membersip},
      {NULL,          NULL}
  };
  
  /* functions in library namespace */
  static luaL_reg func[] = {
      {"udp", global_create},
      {NULL, NULL}
  };
  
  /*-------------------------------------------------------------------------*\
  * Initializes module
  \*-------------------------------------------------------------------------*/
  int udp_open(lua_State *L)
  {
      /* create classes */
      auxiliar_newclass(L, "udp{connected}", udp);
      auxiliar_newclass(L, "udp{unconnected}", udp);
      /* create class groups */
      auxiliar_add2group(L, "udp{connected}",   "udp{any}");
      auxiliar_add2group(L, "udp{unconnected}", "udp{any}");
      auxiliar_add2group(L, "udp{connected}",   "select{able}");
      auxiliar_add2group(L, "udp{unconnected}", "select{able}");
      /* define library functions */
      luaL_openlib(L, NULL, func, 0); 
      return 0;
  }
  
  /*=========================================================================*\
  * Lua methods
  \*=========================================================================*/
  const char *udp_strerror(int err) {
      /* a 'closed' error on an unconnected means the target address was not
       * accepted by the transport layer */
      if (err == IO_CLOSED) return "refused";
      else return socket_strerror(err);
  }
  
  /*-------------------------------------------------------------------------*\
  * Send data through connected udp socket
  \*-------------------------------------------------------------------------*/
  static int meth_send(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkclass(L, "udp{connected}", 1);
      p_timeout tm = &udp->tm;
      size_t count, sent = 0;
      int err;
      const char *data = luaL_checklstring(L, 2, &count);
      timeout_markstart(tm);
      err = socket_send(&udp->sock, data, count, &sent, tm);
      if (err != IO_DONE) {
          lua_pushnil(L);
          lua_pushstring(L, udp_strerror(err));
          return 2;
      }
      lua_pushnumber(L, sent);
      return 1;
  }
  
  /*-------------------------------------------------------------------------*\
  * Send data through unconnected udp socket
  \*-------------------------------------------------------------------------*/
  static int meth_sendto(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkclass(L, "udp{unconnected}", 1);
      size_t count, sent = 0;
      const char *data = luaL_checklstring(L, 2, &count);
      const char *ip = luaL_checkstring(L, 3);
      unsigned short port = (unsigned short) luaL_checknumber(L, 4);
      p_timeout tm = &udp->tm;
      struct sockaddr_in addr;
      int err;
      memset(&addr, 0, sizeof(addr));
      if (!inet_aton(ip, &addr.sin_addr)) 
          luaL_argerror(L, 3, "invalid ip address");
      addr.sin_family = AF_INET;
      addr.sin_port = htons(port);
      timeout_markstart(tm);
      err = socket_sendto(&udp->sock, data, count, &sent, 
              (SA *) &addr, sizeof(addr), tm);
      if (err != IO_DONE) {
          lua_pushnil(L);
          lua_pushstring(L, udp_strerror(err));
          return 2;
      }
      lua_pushnumber(L, sent);
      return 1;
  }
  
  /*-------------------------------------------------------------------------*\
  * Receives data from a UDP socket
  \*-------------------------------------------------------------------------*/
  static int meth_receive(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      char buffer[UDP_DATAGRAMSIZE];
      size_t got, count = (size_t) luaL_optnumber(L, 2, sizeof(buffer));
      int err;
      p_timeout tm = &udp->tm;
      count = MIN(count, sizeof(buffer));
      timeout_markstart(tm);
      err = socket_recv(&udp->sock, buffer, count, &got, tm);
      if (err != IO_DONE) {
          lua_pushnil(L);
          lua_pushstring(L, udp_strerror(err));
          return 2;
      }
      lua_pushlstring(L, buffer, got);
      return 1;
  }
  
  /*-------------------------------------------------------------------------*\
  * Receives data and sender from a UDP socket
  \*-------------------------------------------------------------------------*/
  static int meth_receivefrom(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkclass(L, "udp{unconnected}", 1);
      struct sockaddr_in addr;
      socklen_t addr_len = sizeof(addr);
      char buffer[UDP_DATAGRAMSIZE];
      size_t got, count = (size_t) luaL_optnumber(L, 2, sizeof(buffer));
      int err;
      p_timeout tm = &udp->tm;
      timeout_markstart(tm);
      count = MIN(count, sizeof(buffer));
      err = socket_recvfrom(&udp->sock, buffer, count, &got, 
              (SA *) &addr, &addr_len, tm);
      if (err == IO_DONE) {
          lua_pushlstring(L, buffer, got);
          lua_pushstring(L, inet_ntoa(addr.sin_addr));
          lua_pushnumber(L, ntohs(addr.sin_port));
          return 3;
      } else {
          lua_pushnil(L);
          lua_pushstring(L, udp_strerror(err));
          return 2;
      }
  }
  
  /*-------------------------------------------------------------------------*\
  * Select support methods
  \*-------------------------------------------------------------------------*/
  static int meth_getfd(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      lua_pushnumber(L, (int) udp->sock);
      return 1;
  }
  
  /* this is very dangerous, but can be handy for those that are brave enough */
  static int meth_setfd(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      udp->sock = (t_socket) luaL_checknumber(L, 2);
      return 0;
  }
  
  static int meth_dirty(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      (void) udp;
      lua_pushboolean(L, 0);
      return 1;
  }
  
  /*-------------------------------------------------------------------------*\
  * Just call inet methods
  \*-------------------------------------------------------------------------*/
  static int meth_getpeername(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkclass(L, "udp{connected}", 1);
      return inet_meth_getpeername(L, &udp->sock);
  }
  
  static int meth_getsockname(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      return inet_meth_getsockname(L, &udp->sock);
  }
  
  /*-------------------------------------------------------------------------*\
  * Just call option handler
  \*-------------------------------------------------------------------------*/
  static int meth_setoption(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      return opt_meth_setoption(L, opt, &udp->sock);
  }
  
  /*-------------------------------------------------------------------------*\
  * Just call tm methods
  \*-------------------------------------------------------------------------*/
  static int meth_settimeout(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      return timeout_meth_settimeout(L, &udp->tm);
  }
  
  /*-------------------------------------------------------------------------*\
  * Turns a master udp object into a client object.
  \*-------------------------------------------------------------------------*/
  static int meth_setpeername(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      p_timeout tm = &udp->tm;
      const char *address =  luaL_checkstring(L, 2);
      int connecting = strcmp(address, "*");
      unsigned short port = connecting ? 
          (unsigned short) luaL_checknumber(L, 3) : 
          (unsigned short) luaL_optnumber(L, 3, 0);
      const char *err = inet_tryconnect(&udp->sock, address, port, tm);
      if (err) {
          lua_pushnil(L);
          lua_pushstring(L, err);
          return 2;
      }
      /* change class to connected or unconnected depending on address */
      if (connecting) auxiliar_setclass(L, "udp{connected}", 1);
      else auxiliar_setclass(L, "udp{unconnected}", 1);
      lua_pushnumber(L, 1);
      return 1;
  }
  
  /*-------------------------------------------------------------------------*\
  * Closes socket used by object 
  \*-------------------------------------------------------------------------*/
  static int meth_close(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkgroup(L, "udp{any}", 1);
      socket_destroy(&udp->sock);
      lua_pushnumber(L, 1);
      return 1;
  }
  
  /*-------------------------------------------------------------------------*\
  * Turns a master object into a server object
  \*-------------------------------------------------------------------------*/
  static int meth_setsockname(lua_State *L) {
      p_udp udp = (p_udp) auxiliar_checkclass(L, "udp{unconnected}", 1);
      const char *address =  luaL_checkstring(L, 2);
      unsigned short port = (unsigned short) luaL_checknumber(L, 3);
      const char *err = inet_trybind(&udp->sock, address, port);
      if (err) {
          lua_pushnil(L);
          lua_pushstring(L, err);
          return 2;
      }
      lua_pushnumber(L, 1);
      return 1;
  }
  
  /*=========================================================================*\
  * Library functions
  \*=========================================================================*/
  /*-------------------------------------------------------------------------*\
  * Creates a master udp object 
  \*-------------------------------------------------------------------------*/
  static int global_create(lua_State *L) {
      t_socket sock;
      const char *err = inet_trycreate(&sock, SOCK_DGRAM);
      /* try to allocate a system socket */
      if (!err) { 
          /* allocate tcp object */
          p_udp udp = (p_udp) lua_newuserdata(L, sizeof(t_udp));
          auxiliar_setclass(L, "udp{unconnected}", -1);
          /* initialize remaining structure fields */
          socket_setnonblocking(&sock);
          udp->sock = sock;
          timeout_init(&udp->tm, -1, -1);
          return 1;
      } else {
          lua_pushnil(L);
          lua_pushstring(L, err);
          return 2;
      }
  }
  