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NN_CMSG(3)                      nanomsg manual                      NN_CMSG(3)

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[1]>

NOTES
        1. sustrik@250bpm.com
           mailto:sustrik@250bpm.com

nanomsg Unknown                   12/23/2015                        NN_CMSG(3)