blob: 61cf410d32a19b7939850c9ccb17beff257abe41 [file] [log] [blame]
nn_cmsg - access control information
*#include <nanomsg/nn.h>*
*struct nn_cmsghdr *NN_CMSG_FIRSTHDR(struct nn_msghdr '*hdr');*
*struct nn_cmsghdr *NN_CMSG_NXTHDR(struct nn_msghdr '*hdr', struct nn_cmsghdr '*cmsg');*
*unsigned char *NN_CMSG_DATA(struct nn_cmsghdr '*cmsg');*
*size_t NN_CMSG_SPACE(size_t 'len');*
*size_t NN_CMSG_LEN(size_t 'len');*
These functions can be used to iterate over ancillary data attached to a message.
Structure 'nn_cmsghdr' represents a single ancillary property and contains following members:
size_t cmsg_len;
int cmsg_level;
int cmsg_type;
'cmsg_len' is the size of the property data, including the preceding nn_cmsghdr structure.
'cmsg_level' is the level of the property; same values can be used as with <<nn_getsockopt#,nn_getsockopt(3)>> and <<nn_setsockopt#,nn_setsockopt(3)>>.
'cmsg_type' is the name of the property. These names are specific for each level.
_NN_CMSG_FIRSTHDR_ returns a pointer to the first nn_cmsghdr in the control buffer in the supplied nn_msghdr structure.
_NN_CMSG_NXTHDR_ returns the next nn_cmsghdr after the supplied nn_cmsghdr. Returns NULL if there isn't enough space in the buffer.
_NN_CMSG_DATA_ returns a pointer to the data associated with supplied nn_cmsghdr.
_NN_CMSG_SPACE_ returns the number of bytes occupied by nn_cmsghdr with payload of the specified length.
_NN_CMSG_LEN_ returns the value to store in the cmsg_len member of the cmsghdr structure, taking into account any necessary alignment.
Iterating over ancillary properties:
struct nn_cmsghdr *hdr = NN_CMSG_FIRSTHDR (&msg);
while (hdr != NULL) {
size_t len = hdr->cmsg_len - sizeof (nn_cmsghdr);
printf ("level: %d property: %d length: %dB data: ",
(int) hdr->cmsg_level,
(int) hdr->cmsg_type,
(int) len);
unsigned char *data = NN_CMSG_DATA(hdr);
while (len) {
printf ("%02X", *data);
printf ("\n");
hdr = NN_CMSG_NXTHDR (&msg, hdr);
-------[Martin Sustrik]