From 1b825b063da65fe3d88c1ca97afded0d6f6ccc14 Mon Sep 17 00:00:00 2001 From: Garrett D'Amore Date: Fri, 5 Apr 2024 08:40:25 -0700 Subject: Compat pages converted. --- docs/ref/compat/nn_cmsg.adoc | 55 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 55 insertions(+) create mode 100644 docs/ref/compat/nn_cmsg.adoc (limited to 'docs/ref/compat/nn_cmsg.adoc') diff --git a/docs/ref/compat/nn_cmsg.adoc b/docs/ref/compat/nn_cmsg.adoc new file mode 100644 index 00000000..82b48966 --- /dev/null +++ b/docs/ref/compat/nn_cmsg.adoc @@ -0,0 +1,55 @@ +## nn_cmsg + +Message control data (compatible API). + +### Synopsis + +[source,c] +``` +#include + +struct nn_cmsghdr { + size_t cmsg_len; + int cmsg_level; + int cmsg_type; +}; +``` + +### Description + +The `nn_cmsghdr` structure describes a block of control data that is associated with a message either sent by xref:nn_sendmsg.adoc[`nn_sendmsg`] or received by xref:nn_recvmsg.adoc[`nn_recvmsg`]. + +Each header is followed by `cmsg_len` bytes of data, plus any padding required to align the structure. + +The only defined ancillary data at this time is the protocol headers used by the protocols. +This uses `cmsg_level` set to `PROTO_SP` and the `cmsg_type` set to `SP_HDR`. +The actual data for this will vary from depending on the protocol used. + +Convenience macros are provided to make working with these fields easier. + +`struct nn_cmsghdr *NN_CMSG_FIRSTHDR(struct nn_msghdr *__hdr__)`:: +This macro returns the first `struct nn_cmsghdr` header in _hdr_. + +`struct nn_cmsghdr *NN_CMSG_NXTHDR(struct nn_msghdr *__hdr__, struct nn_cmsghdr *__ch__)`:: +This macro returns a pointer to the next `struct nn_cmsghdr` in _hdr_ after _ch_. + +`void *NN_CMSG_DATA(struct nn_cmsghdr *__ch__)`:: +This macro returns a pointer to the header-specific data for _ch_. + +`size_t NN_CMSG_ALIGN(size_t __len__)`:: +This macro returns the length specified by _len_, plus any padding required to +provide the necessary alignment for another structure. + +`size_t NN_CMSG_SPACE(size_t __len__)`:: +This macro returns the amount of space required for a header, with _len_ +bytes of following data, and any necessary padding. + +`size_t NN_CMSG_LEN(size_t __len__)`:: +This macro evaluates to the length of the header (including alignment), +and the associated data of length _len_, but without any trailing padding +to align for another header. + +### See Also + +xref:nn_recvmsg.adoc[nn_recvmsg], +xref:nn_sendmsg.adoc[nn_sendmsg] -- cgit v1.2.3-70-g09d2