Re: modularizing lua code

["Guido Sohne" <guido@...>]

Hi,

On 7/20/06, Diego Nehab <diego@tecgraf.puc-rio.br> wrote:
> > 1) It would be great if your build process could support being built
> > directly into the interpreter. My system doesn't have dynamic linking,
> > so I had to hack your Makefiles (needed in any way, because the
> > compiler flags have to be <just so> to get it to actually run on the
> > target system).
>
> You mean automatically? This is tough, isn't it? You have to
> change your interpreter, and LuaSocket doesn't have access
> to it. If you are building your own interpreter, on the
> otherh and, it is simple to link LuaSocket to it.
>
> Just add the obj files to your makefile, then make sure you
> populate package.preload with luaopen_socket_core and
> luaopen_mime_core.

It is not about being tough or not. It's a simple request that at
least have an option to be friendly to those who are building your
code directly into the interpreter. It shouldn't be a large change to
the makefile.

Here's the diff from my makefile to yours (src/makefile). I had to
create a config file that had the same parameters etc as I used to
build my Lua interpreter.

--- /opt/pose/bin/luasocket-2.0.1/src/makefile	2006-04-27
03:23:21.000000000 +0000
+++ makefile	2006-07-08 09:00:09.000000000 +0000
@@ -1,7 +1,7 @@
#------
# Load configuration
#
-include ../config
+include config

#------
# Hopefully no need to change anything below this line
@@ -12,7 +12,6 @@
#

SOCKET_OBJS:= \
-	$(COMPAT)/compat-5.1.o \
	luasocket.o \
	timeout.o \
	buffer.o \
@@ -30,7 +29,6 @@
# Modules belonging mime-core
#
MIME_OBJS:=\
-	$(COMPAT)/compat-5.1.o \
	mime.o


@@ -46,16 +44,24 @@
	usocket.o \
	unix.o

-all: $(SOCKET_SO) $(MIME_SO)
+EXPORT_SO=luasocket.a
+SOCKET_SO=socket.a
+MIME_SO=mime.a
+UNIX_SO=unix.a
+
+all: $(SOCKET_SO) $(MIME_SO)  $(EXPORT_SO)
+
+$(EXPORT_SO): $(SOCKET_OBJS) $(MIME_SO)
+	$(AR) $(EXPORT_SO) $(SOCKET_OBJS) $(MIME_OBJS)

$(SOCKET_SO): $(SOCKET_OBJS)
-	$(LD) $(LDFLAGS) -o $@ $(SOCKET_OBJS)
+	$(AR) $(SOCKET_SO) $(SOCKET_OBJS)

$(MIME_SO): $(MIME_OBJS)
-	$(LD) $(LDFLAGS) -o $@ $(MIME_OBJS)
+	$(AR) $(MIME_SO) $(MIME_OBJS)

$(UNIX_SO): $(UNIX_OBJS)
-	$(LD) $(LDFLAGS) -o $@ $(UNIX_OBJS)
+	$(AR) $(UNIX_SO) $@ $(UNIX_OBJS)

#------
# List of dependencies


> > 3) It doesn't have ping functionality, though it wouldn't be hard to
> > do that, but why not? Pings that timeout are basically the only way I
> > can think of to check if the network is available or not.
>
> I'd be happy to consider a patch for that. I believe it
> would require an API and some C code.

Here's some C code for that. It's derived from BusyBox ping (socket
timeout and not lingering added). The rest I found were quite bloated.
I'm sure you can work from it.

#define DEFDATALEN      56
#define	MAXIPLEN	60
#define	MAXICMPLEN	76

static int ping(lua_State *L)
{
	struct hostent *h;
	struct sockaddr_in pingaddr;
	struct icmp *pkt;
	struct timeval timeout;
	struct linger linger;
	int pingsock, c, secs, ret;
	const char *host;
	char packet[DEFDATALEN + MAXIPLEN + MAXICMPLEN];

	host = lua_tostring(L, 1);
	secs = (int) lua_tonumber(L, 2);

	if ((pingsock = socket(AF_INET, SOCK_RAW, 1)) < 0) {	/* 1 == ICMP */
		goto notreachable;
	}

	memset(&pingaddr, 0, sizeof(struct sockaddr_in));
	pingaddr.sin_family = AF_INET;	
	
	if (!(h = gethostbyname(host)))
		goto notreachable;
	
	memcpy(&pingaddr.sin_addr, h->h_addr, sizeof(pingaddr.sin_addr));

	pkt = (struct icmp *) packet;
	memset(pkt, 0, sizeof(packet));
	pkt->icmp_type = ICMP_ECHO;
	pkt->icmp_cksum = in_cksum((unsigned short *) pkt, sizeof(packet));

	/* set timeout to user supplied value */
	timeout.tv_sec = secs;
	timeout.tv_usec = 0;

	/* set socket to linger for user supplied time */
	linger.l_onoff = 1;
	linger.l_linger = secs;
	
   if (setsockopt (pingsock, SOL_SOCKET, SO_LINGER, (char *)&linger,
sizeof linger) < 0)
		goto notreachable;
	if (setsockopt (pingsock, SOL_SOCKET, SO_RCVTIMEO, (char *)&timeout,
sizeof timeout) < 0)
		goto notreachable;
	if (setsockopt (pingsock, SOL_SOCKET, SO_SNDTIMEO, (char *)&timeout,
sizeof timeout) < 0)
		goto notreachable;

	c = sendto(pingsock, packet, sizeof(packet), 0,
			   (struct sockaddr *) &pingaddr, sizeof(struct sockaddr_in));
	if (c < 0 || c != sizeof(packet))
		goto notreachable;

	/* listen for replies */
	while (1) {
		struct sockaddr_in from;
		socklen_t fromlen = sizeof(from);
		if ((c = recvfrom (pingsock, packet, sizeof(packet), 0,
						  (struct sockaddr *) &from, (socklen_t *)&fromlen )) < 0) {
			if(errno == EAGAIN || errno == ETIMEDOUT)
				goto notreachable;
			else
				continue;
		}
		if (c >= 76) {			/* ip + icmp */
			struct iphdr *iphdr = (struct iphdr *) packet;

			pkt = (struct icmp *) (packet + (iphdr->ihl << 2));	/* skip ip hdr */
			if (pkt->icmp_type == ICMP_ECHOREPLY)
				break;
		}
	}
	
	close(pingsock);
	lua_pushboolean(L, 1);
	return 1;
	
notreachable:
	ret = pusherror(L, NULL);
	close(pingsock);
	return ret;
}

static int in_cksum(unsigned short *buf, int sz)
{
	int nleft = sz;
	int sum = 0;
	unsigned short *w = buf;
	unsigned short ans = 0;

	while (nleft > 1) {
		sum += *w++;
		nleft -= 2;
	}

	if (nleft == 1) {
		*(unsigned char *) (&ans) = *(unsigned char *) w;
		sum += ans;
	}

	sum = (sum >> 16) + (sum & 0xFFFF);
	sum += (sum >> 16);
	ans = ~sum;
	return (ans);
}

> > I implemented my own (basic!) HTTP client instead. It fetches from a
> > URL and returns the response minus headers. Here's the implementation
> > (sans libhttpd which is a socket object built into the interpreter).
>
> If you are interested in the lowest possible number of lines
> of code, I would suggest using popen and wget...

It's not the lowest number of lines. I'm building for a embedded
system. Your library alone is bigger than my entire application
(including the functionality that I wanted from your library).

Is that too hard to understand?

-- G.