'\" t
.\"     Title: nn_cmsg
.\"    Author: [see the "AUTHOR(S)" section]
.\" Generator: Asciidoctor 2.0.20
.\"      Date: 2024-02-21
.\"    Manual: nanomsg 1.2.1
.\"    Source: \ \&
.\"  Language: English
.\"
.TH "NN_CMSG" "3" "2024-02-21" "\ \&" "nanomsg 1.2.1"
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.SH "NAME"
nn_cmsg \- access control information
.SH "SYNOPSIS"
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\fB#include <nanomsg/nn.h>\fP
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\fBstruct nn_cmsghdr *NN_CMSG_FIRSTHDR(struct nn_msghdr \fI*hdr\fP);\fP
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\fBstruct nn_cmsghdr *NN_CMSG_NXTHDR(struct nn_msghdr \fI*hdr\fP, struct nn_cmsghdr \fI*cmsg\fP);\fP
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\fBunsigned char *NN_CMSG_DATA(struct nn_cmsghdr \fI*cmsg\fP);\fP
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\fBsize_t NN_CMSG_SPACE(size_t \fIlen\fP);\fP
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\fBsize_t NN_CMSG_LEN(size_t \fIlen\fP);\fP
.SH "DESCRIPTION"
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These functions can be used to iterate over ancillary data attached to a message.
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Structure \fInn_cmsghdr\fP represents a single ancillary property and contains following members:
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size_t cmsg_len;
int cmsg_level;
int cmsg_type;
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\fIcmsg_len\fP is the size of the property data, including the preceding nn_cmsghdr structure.
\fIcmsg_level\fP is the level of the property; same values can be used as with nn_getsockopt(3) and nn_setsockopt(3).
\fIcmsg_type\fP is the name of the property. These names are specific for each level.
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\fINN_CMSG_FIRSTHDR\fP returns a pointer to the first nn_cmsghdr in the control buffer in the supplied nn_msghdr structure.
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\fINN_CMSG_NXTHDR\fP returns the next nn_cmsghdr after the supplied nn_cmsghdr. Returns NULL if there isn\(cqt enough space in the buffer.
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\fINN_CMSG_DATA\fP returns a pointer to the data associated with supplied nn_cmsghdr.
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\fINN_CMSG_SPACE\fP returns the number of bytes occupied by nn_cmsghdr with payload of the specified length.
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\fINN_CMSG_LEN\fP returns the value to store in the cmsg_len member of the cmsghdr structure, taking into account any  necessary  alignment.
.SH "EXAMPLE"
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Iterating over ancillary properties:
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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 ("\(rsn");
    hdr = NN_CMSG_NXTHDR (&msg, hdr);
}
.fam
.fi
.if n .RE
.SH "SEE ALSO"
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nn_sendmsg(3)
nn_recvmsg(3)
nn_getsockopt(3)
nn_setsockopt(3)
nanomsg(7)
.SH "AUTHORS"
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.MTO "sustrik\(at250bpm.com" "Martin Sustrik" ""