fixes #303 Flesh out compatible API docs

1 files changed, 98 insertions, 0 deletions

diff --git a/docs/man/nn_recvmsg.3compat.adoc b/docs/man/nn_recvmsg.3compat.adoc
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+++ b/docs/man/nn_recvmsg.3compat.adoc
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+= nn_recvmsg(3compat)
+//
+// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitar.com>
+//
+// This document is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+== NAME
+
+nn_recvmsg - receive message (compatible API)
+
+== SYNOPSIS
+
+[source, c]
+----
+#include <nanomsg/nn.h>
+
+int nn_recvmsg(int sock, struct nn_msghdr *hdr, int flags);
+----
+
+== DESCRIPTION
+
+The `nn_recvmsg()` function receives a message into the heade described by
+_hdr_ using the socket _sock_.
+
+NOTE: This function is provided for API
+<<nng_compat.3compat#,compatibility>> with legacy _libnanomsg_.
+Consider using the relevant <<libnng.3#,modern API>> instead.
+
+The _flags_ field may contain the special flag `NN_DONTWAIT`.
+In this case, if no message is ready for receiving on _sock_,
+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:
+
+[source, 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 scatter 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.
+
+The last member of this array may have the `iov_len` field set to `NN_MSG`,
+in which case the function shall allocate a message buffer, and store the
+pointer to it at the address indicated by `iov_base`.
+This can help save an extra copy operation.
+The buffer should be deallocated by `<<nn_freemsg.3compat#,nn_freemsg()>>`
+or similar when it is no longer needed.
+
+The values of `msg_control` and `msg_controllen` describe a buffer
+of ancillary data associated with the message.
+This is currenly only useful to obtain the message headers
+used with <<nng.7#raw_mode,raw mode>> sockets.
+In all other circumstances these fields should be zero.
+Details about this structure are covered in
+`<<nn_cmsg.3compat#,nn_cmsg(3compat)>>`.
+
+== RETURN VALUES
+
+This function returns the number of bytes received on success, and -1 on error.
+
+== ERRORS
+
+[horizontal]
+`EAGAIN`:: The operation would block.
+`EBADF`:: The socket _sock_ is not open.
+`EFSM`:: The socket cannot receive in this state.
+`EINVAL`:: The _hdr_ is invalid.
+`ENOTSUP`:: This protocol cannot receive.
+`ETIMEDOUT`:: Operation timed out.
+
+== SEE ALSO
+
+<<nn_cmsg.3compat#,nn_cmsg(3compat)>>,
+<<nn_errno.3compat#,nn_errno(3compat)>>,
+<<nn_recv.3compat#,nn_recv(3compat)>>,
+<<nn_send.3compat#,nn_send(3compat)>>,
+<<nn_socket.3compat#,nn_socket(3compat)>>,
+<<nng_compat.3compat#,nn_compat(3compat)>>,
+<<nng.7#,nng(7)>>