libdill: Structured Concurrency for C


msend, msendl - send message to a socket


#include <libdill.h>

int msend(int s, const void *buf, size_t len, int64_t deadline);

int msendl(int s, struct iolist *first, struct iolist *last, int64_t deadline);


Function msend() sends a message to a socket. It is a blocking operation that unblocks only after entire message is sent. There is no such thing as partial send. If a problem, including timeout, occurs while sending the message error is returned to the user and the socket cannot be used for sending from that point on.

buf points to the buffer containing message len bytes long.

deadline is a point in time when the operation should time out. Use the now() function to get your current point in time. 0 means immediate timeout, i.e., perform the operation if possible or return without blocking if not. -1 means no deadline, i.e., the call will block forever if the operation cannot be performed.

Function msendl() accepts a linked list of buffers instead of a single buffer. first points to the first item in the list, last points to the last buffer in the list. The list represent a single message, not a message per element of the list. Structure iolist has following members:

void *iol_base;          /* Pointer to the buffer. */
size_t iol_len;          /* Size of the buffer. */
struct iolist *iol_next; /* Next buffer. */
int iol_rsvd;            /* Reserved. Must be set to zero. */

msendl() returns EINVAL error in case the list is malformed:

The list can be temporarily modified while the function is in progress. However, once the function returns the list is guaranteed to be the same as before the call.


The function returns 0 on success. On error, it returns -1 and sets errno to one of the values below.



int rc = msend(s, "ABC", 3, -1);