SYNOPSIS
#include <nng/nng.h>
int nng_listener_getopt(nng_listener l, const char *opt, void *val,
size_t *valszp);
int nng_listener_getopt_int(nng_listener l, const char *opt, int *ivalp);
int nng_listener_getopt_ms(nng_listener l, const char *opt, nng_duration *durp);
int nng_listener_getopt_ptr(nng_listener l, const char *opt, void **ptr);
int nng_listener_setopt_size(nng_listener l, const char *opt, size_t *zp);
int nng_listener_getopt_uint64(nng_listener l, const char *opt, uint64_t *u64p);DESCRIPTION
The nng_listener_getopt() functions are used to retrieve option values for
the listener l. The actual options that may be retrieved in this way
vary, and are documented in the nng_getopt(3) manual.
Additionally some transport-specific options are documented with the
transports themselves.
In all of these forms, the option opt is retrieved from the listener l.
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.
The first form of this function, nng_listener_getopt(), can be used to
retrieve the value of any option. It is untyped. The caller must store
a pointer to a buffer to receive the value in val, and the size of the
buffer shall be stored at the location referenced by valszp.
When the function returns, the actual size of the data copied (or that would have been copied if sufficient space were present) is stored at the location referened by valszp. If the caller’s buffer is not large enough to hold the entire object, then the copy is truncated. Therefore the caller should validate that the returned size in valszp does not exceed the original buffer size to check for truncation.
It is acceptable to pass NULL for val if the value in valszp is zero.
This can be used to determine the size of the buffer needed to receive
the object.
Generally, it will be easier to use one of the typed forms instead. Note however that 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.
The second form, nng_listener_getopt_int(),
is for options which take an integer (or boolean). The value will
be stored at ivalp. For booleans the value will be eiher 0 (false) or 1 (true).
The third form, nng_listener_getopt_ms(), is used to retrieve time durations
(such as timeouts), stored in durp as a number of milliseconds.
(The special value NNG_DUR_INFINITE means an infinite amount of time, and
the special value NNG_DUR_DEFAULT means a context-specific default.)
The fourth form, nng_listener_getopt_ptr(), is used to retrieve a
pointer ptr to structured data. The data referenced by ptr is
generally managed using other functions.
Note that this form is somewhat special in that the object is generally
not copied, but instead the pointer to the object is copied.
The fifth form, nng_listener_getopt_size(), is used to retrieve a size
into the pointer zp, typically for buffer sizes, message maximum sizes, and
similar options.
The sixth form, nng_listener_getopt_uint64(), is used to retrieve a
64-bit unsigned value into the value referenced by u64p.
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 l does not refer to an open listener.
NNG_ENOTSUP-
The option opt is not supported.
NNG_EWRITEONLY-
The option opt is write-only.