libdill: Structured Concurrency for C


brecv, brecvl - receive data from bytestream socket


#include <libdill.h>

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

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


Function brecv() receives data from a bytestream socket. It is a blocking operation that unblocks only after the requested amount of data is received. There is no such thing as partial receive. If a problem, including timeout, occurs while receiving the data error is returned to the user and the socket cannot be used for receiving from that point on.

buf points to the buffer len bytes long to write the received data to. If buf is NULL the len bytes will be received but they will be dropped rather than returned to the user.

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 brecvl() 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. 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. */

brecvl() 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.



char buf[100];
int rc = brecv(s, buf, sizeof(buf), -1);