fixes #303 Flesh out compatible API docs

1 files changed, 66 insertions, 0 deletions

diff --git a/docs/man/nn_allocmsg.3compat.adoc b/docs/man/nn_allocmsg.3compat.adoc
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index 00000000..943ecf4b
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+++ b/docs/man/nn_allocmsg.3compat.adoc
@@ -0,0 +1,66 @@
+= nn_allocmsg(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_allocmsg - allocate message (compatible API)
+
+== SYNOPSIS
+
+[source,c]
+----
+#include <nanomsg/nn.h>
+
+void *nn_allocmsg(size_t size, int type);
+----
+
+== DESCRIPTION
+
+The `nn_allocmsg()` allocates a message structure of size _size_, and is
+primarily used to support zero-copy send operations, making use of the
+`NNG_MSG` special size indicator.
+The value returned is a pointer ot the start of the message payload buffer.
+
+The value of _size_ must be positive, and small enough to hold reasonable
+message data plus book-keeping information.
+
+NOTE: This function is provided for API
+<<nng_compat.3compat#,compatibility>> with legacy _libnanomsg_.
+Consider using the relevant <<libnng.3#,modern API>> instead.
+
+The value of _type_ *must* be zero.
+(This argument was reserved to support different kinds of memory spaces
+for RDMA devices, but this was never developed in the legacy API.)
+
+The returned message must be disposed of by either
+`<<nn_freemsg.3compat#,nn_freemsg()>>` or
+`<<nn_send.3compat#,nn_send()>>` when the caller is finished with it.
+
+== RETURN VALUES
+
+This function returns a pointer to message buffer space, or `NULL`
+on failure.
+
+== ERRORS
+
+[horizontal]
+`ENOMEM`:: Insufficient memory is available.
+`EINVAL`:: An invalid _size_ or _type_ was specified.
+`ETERM`:: The library is shutting down.
+
+== SEE ALSO
+
+<<nn_errno.3compat#,nn_errno(3compat)>>,
+<<nn_freemsg.3compat#,nn_freemsg(3compat)>>,
+<<nn_reallocmsg.3compat#,nn_reallocmsg(3compat)>>,
+<<nn_send.3compat#,nn_send(3compat)>>,
+<<nng_compat.3compat#,nng_compat(3compat)>>,
+<<nng.7#,nng(7)>>