[Caml-list] camlIDL and callbacks

[Jonathan Heusser <jonny@drugphish.ch>]

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Hello,

I'm trying to implement libpcap bindings for ocaml using CamlIDL.

Currently, I'm running into trouble with C libpcap functions which are 
using
callbacks. Those are: pcap_loop, pcap_dispatch and indirectly pcap_next 
(which calls pcap_dispatch)

When using e.g. pcap_next in ocaml, defined by the idl code attached, it 
returns a
correct pcap_pkthdr though the call to pcap_dispatch is not working due 
to the missing
callback functionality..

Can anyone give me an idea how to solve such C-to-ocaml callback issues 
in idl ?

thank you for any help,
jonathan heusser

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[-- Attachment #2: pcap.idl --]
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quote(C, "
	#include <pcap.h>

	typedef pcap_t *pcap_handle;
	typedef struct pcap_pkthdr pcap_pkthdr;

	typedef void (*pcap_callback)(u_char *, const struct pcap_pkthdr *,
			 const u_char *);

")

/* type defitions */
/* .............. */

typedef [abstract, ptr] void * pcap_handle;

struct timeval {
	int tv_sec;
	int tv_usec;
};

typedef struct {
	struct timeval ts;
	int caplen;
	int len;
} pcap_pkthdr;

/* function definitions */
/* .................... */

/* experimental callback handler */
typedef [ptr,mltype("string -> pcap_pkthdr -> string -> unit")] void *pcap_callback;

/* tested, OK */
pcap_handle pcap_open_live([in,string] char *dev, [in] int snaplen, 
		[in] int promisc, [in] int to_ms, [in,out,string] char *err);

/* tested, OK */
[string] char *pcap_lookupdev([in,out,string] char *errbuf);

/* broken ! */
[string] unsigned char *pcap_next([in] pcap_handle p, [in,out] pcap_pkthdr * h)
	quote(call, "_res = (char*) pcap_next(p,h); 
	");

/* tested, OK */
void pcap_close(pcap_handle p);

/* broken ! */
int pcap_loop([in] pcap_handle p, [in] int cnt, [in] pcap_callback callback, 
		[in,string] char *user);

int pcap_dispatch([in] pcap_handle p, [in] int cnt, [in] pcap_callback callback,
	[in,string] char *user);