NAME¶

nn_cmsg - access control information

SYNOPSIS¶

#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);

DESCRIPTION¶

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(3) and 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.

EXAMPLE¶

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);


        ++data;


        --len;


    }


    printf ("\n");


    hdr = NN_CMSG_NXTHDR (&msg, hdr);
}

SEE ALSO¶

nn_sendmsg(3) nn_recvmsg(3) nn_getsockopt(3) nn_setsockopt(3) nanomsg(7)

AUTHORS¶

Martin Sustrik <sustrik@250bpm.com>