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_sendmsg.adoc | 71 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+) create mode 100644 docs/ref/compat/nn_sendmsg.adoc (limited to 'docs/ref/compat/nn_sendmsg.adoc') diff --git a/docs/ref/compat/nn_sendmsg.adoc b/docs/ref/compat/nn_sendmsg.adoc new file mode 100644 index 00000000..f3f3ebea --- /dev/null +++ b/docs/ref/compat/nn_sendmsg.adoc @@ -0,0 +1,71 @@ +## nn_sendmsg + +Send message (compatible API). + +### Synopsis + +```c +#include + +int nn_sendmsg(int sock, const struct nn_msghdr *hdr, int flags); +``` + +### Description + +The `nn_sendmsg` function sends the message described by _hdr_ using the socket _sock_. + +The _flags_ field may contain the special flag `NN_DONTWAIT`. +In this case, if the socket is unable to accept more data for sending, the operation shall not block, but instead will fail with the error `EAGAIN`. + +The _hdr_ points to a structure of type `struct nn_msghdr`, which has the following definition: + +```c +struct nn_iovec { + void * iov_base; + size_t iov_len; +}; + +struct nn_msghdr { + struct nn_iovec *msg_iov; + int msg_iovlen; + void * msg_control; + size_t msg_controllen; +}; +``` + +The `msg_iov` is an array of gather items, permitting the message to be spread into different memory blocks. +There are `msg_iovlen` elements in this array, each of which has the base address (`iov_base`) and length (`iov_len`) indicated. + +For buffers allocated for zero copy (such as by xref:nn_allocmsg.adoc[`nn_allocmsg`]), the value of `iov_base` should be the address of the pointer to the buffer, rather than the address of the buffer itself. +In this case, the value of `iov_len` should be `NN_MSG`, as the length is inferred from the allocated message. +If the `msg_iovlen` field is `NN_MSG`, then this function will free the associated buffer after it is done with it, if it returns successfully. +(If the function returns with an error, then the caller retains ownership of the associated buffer and may retry the operation or free the buffer at its choice.) + +The values of `msg_control` and `msg_controllen` describe a buffer of ancillary data to send the message. +This is only useful to provide the message headers used with raw mode sockets. +In all other circumstances these fields should be zero. +Details about this structure are covered in xref:nn_cmsg.adoc[`nn_cmsg`]. + +NOTE: The send operation is performed asynchronously, and may not have completed before this function returns control to the caller. + +### Return Values + +This function returns the number of bytes sent on success, and -1 on error. + +### Errors + +[horizontal] +`EAGAIN`:: The operation would block. +`EBADF`:: The socket _sock_ is not open. +`EFSM`:: The socket cannot send in this state. +`EINVAL`:: The _hdr_ is invalid. +`ENOTSUP`:: This protocol cannot send. +`ETIMEDOUT`:: Operation timed out. + +### See Also + +xref:nn_cmsg.adoc[nn_cmsg], +xref:nn_errno.adoc[nn_errno], +xref:nn_recv.adoc[nn_recv], +xref:nn_send.adoc[nn_send], +xref:nn_socket.adoc[nn_socket] -- cgit v1.2.3-70-g09d2