Introduce nng_options, nng_setopt, nng_getopt manual pages.

This starts a new section 5 for generic topics, and sets up some links
for things like nng_duration and nng_socket types.  There will some day
be an nng_errors(5) page as well.

Some initial work towards indexing terms for these pages is done now too.
(Indexing will mostly be useful when generating book forms of this
documentation.)

1 files changed, 116 insertions, 0 deletions

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+= nng_setopt(3)
+//
+// 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
+
+nng_setopt - set socket option
+
+== SYNOPSIS
+
+[source, c]
+-----------
+#include <nng/nng.h>
+
+int nng_setopt(nng_socket s, const char *opt, const void *val, size_t valsz);
+
+int nng_setopt_int(nng_socket s, const char *opt, int ival);
+
+int nng_setopt_ms(nng_socket s, const char *opt, nng_duration dur);
+
+int nng_setopt_ptr(nng_socket s, const char *opt, void *ptr);
+
+int nng_setopt_size(nng_socket s, const char *opt, size_t z);
+
+int nng_setopt_string(nng_socket s, const char *opt, const char *str);
+
+int nng_setopt_uint64(nng_socket s, const char *opt, uint64_t u64);
+-----------
+
+== DESCRIPTION
+
+The `((nng_setopt))()` functions are used to configure options for
+the socket _s_.
+The actual options that may be configured in this way vary, and are
+specified by _opt_.
+A number of them are documented in <<nng_options#,nng_options(5)>>.
+
+Additionally some transport-specific and protocol-specific options are
+documented with the transports and protocols themselves.
+
+The details of the type, size, and semantics of the option will depend
+on the actual option, and will be documented with the option itself.
+
+TIP: Generally, it will be easier to use one of the typed versions
+of this function.
+
+NOTE: No validation that the option is actually of the associated
+type is performed, so the caller must take care to use the *correct* typed form.
+
+`nng_setopt()`::
+This function is untyped, and can be used to configure any arbitrary data.
+The _val_ pointer addresses the data to copy, and _valsz_ is the
+size of the objected located at _val_.
+
+`nng_setopt_int()`::
+This function is for options which take an integer (`int`) or boolean (`bool`).
+The _ival_ is passed to the option.
+For booleans pass either 0 (`false`) or 1 (`true`).
+
+`nng_setopt_ms()`::
+This function is used to configure time durations (such as timeouts).
+The duration _dur_ is an integer number of milliseconds.
+(The special value ((`NNG_DUR_INFINITE`)) means an infinite amount of time.)
+
+`nng_setopt_ptr()`::
+This function is used to pass a pointer, _ptr_, to structured data.
+The data referenced by _ptr_ is generally managed by other functions.
+For example, TLS configuration objects
+(<<nng_tls_config_alloc#,`nng_tls_config_alloc`(3)>>) can be passed this way.
+Note that this form is somewhat special in that the object is generally
+not copied, but instead the *pointer* to the object is copied.
+
+`nng_setopt_size()`::
+This function is used to configure a size, _z_, typically for buffer sizes,
+message maximum sizes, and similar options.
+
+`nng_setopt_string()`::
+This function is used to pass configure a string, _str_.
+Strings passed this way must be legal UTF-8 or ASCII strings, terminated
+with a `NUL` (`\0`) byte.
+(Other constraints may apply as well, see the documentation for each option
+for details.)
+
+`nng_setopt_uint64()`::
+This function is used to configure a 64-bit unsigned value, _u64_.
+This is typically used for options related to identifiers, network numbers,
+and similar.
+
+== RETURN VALUES
+
+This function returns 0 on success, and non-zero otherwise.
+
+== ERRORS
+
+`NNG_ECLOSED`:: Parameter _s_ does not refer to an open socket.
+`NNG_EINVAL`:: The value being passed is invalid.
+`NNG_ENOTSUP`:: The option _opt_ is not supported.
+`NNG_EREADONLY`:: The option _opt_ is read-only.
+`NNG_ESTATE`:: The socket is in an inappropriate state for setting this option.
+
+== SEE ALSO
+
+[.text-left]
+<<nng_getopt#,nng_getopt(3)>>,
+<<nng_dialer_setopt#,nng_dialer_setopt(3)>>,
+<<nng_listener_setopt#,nng_listener_setopt(3)>>,
+<<nng_strerror#,nng_strerror(3)>>,
+<<nng_options#,nng_options(5)>>,
+<<nng#,nng(7)>>