SYNOPSIS
#include <nng/nng.h>
int nng_pipe_getopt(nng_pipe p, const char *opt, void *val, size_t *valszp);
int nng_pipe_getopt_int(nng_pipe p, const char *opt, int *ivalp);
int nng_pipe_getopt_ms(nng_pipe p, const char *opt, nng_duration *durp);
int nng_pipe_getopt_size(nng_pipe p, const char *opt, size_t *zp);
int nng_pipe_getopt_uint64(nng_pipe p, const char *opt, uint64_t *u64p);DESCRIPTION
The nng_pipe_getopt() functions are used to retrieve option values for
the pipe p. 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, and some protocol-specific options are documented
with the protocol.
| All "options" on a pipe are read-only values, and intended to facilitate understanding the identity of an associated peer; modification of options must be done on the listener or dialer using either nng_listener_setopt(3) or nng_dialer_getopt(3) |
Any option that is set on an endpoint will be retrievable from pipes created by that endpoint.
In all of these forms, the option opt is retrieved from the pipe p.
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_pipe_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_pipe_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_pipe_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_pipe_getopt_size(), is used to retrieve a size
into the pointer zp, typically for buffer sizes, message maximum sizes, and
similar options.
The fifth form, nng_pipe_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 p does not refer to an open pipe.
NNG_ENOTSUP-
The option opt is not supported.
NNG_EWRITEONLY-
The option opt is write-only.