SYNOPSIS
#include <nng/nng.h>
int nng_pipe_getopt(nng_pipe p, const char *opt, void *val, size_t *valszp);
int nng_pipe_getopt_bool(nng_pipe p, const char *opt, int *bvalp);
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_dialer_getopt_ptr(nng_pipe p, const char *opt, void **ptr);
int nng_pipe_getopt_sockaddr(nng_pipe p, const char *opt, nng_sockaddr *sap);
int nng_pipe_getopt_string(nng_pipe p, const char *opt, char **strp);
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 many are documented in nng_options(5).
Additionally some transport-specific options and protocol-specific options are
documented with the transports and protocols themselves.
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() or
nng_dialer_setopt().
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Any option that is set on a dialer or listener will normally be retrievable from pipes created by that dialer or listener.
Forms
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.
nng_pipe_getopt()
This is untyped, and can be used to retrieve the value of any option. 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 referenced 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 check for truncation by verifying that the size returned in valszp does not exceed the original buffer size.
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. |
nng_pipe_getopt_bool()
This function is for options which take a Boolean (bool).
The value will be stored at bvalp.
nng_pipe_getopt_int()
This function is for options which take an integer (int).
The value will be stored at ivalp.
nng_pipe_getopt_ms()
This function is used to retrieve time durations
(nng_duration) in milliseconds, which are stored in
durp.
nng_pipe_getopt_ptr()
This function 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.
nng_pipe_getopt_size()
This function is used to retrieve a size into the pointer zp, typically for buffer sizes, message maximum sizes, and similar options.
nng_pipe_getopt_sockaddr()
This function is used to retrieve an nng_sockaddr
into sap.
nng_pipe_getopt_string()
This function is used to retrieve a string into strp.
This string is created from the source using nng_strdup()
and consequently must be freed by the caller using
nng_strfree() when it is no longer needed.
nng_pipe_getopt_uint64()
This function 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
These functions return 0 on success, and non-zero otherwise.
ERRORS
NNG_EBADTYPE
|
Incorrect type for option. |
NNG_ECLOSED
|
Parameter p does not refer to an open pipe. |
NNG_ENOTSUP
|
The option opt is not supported. |
NNG_ENOMEM
|
Insufficient memory exists. |
NNG_EINVAL
|
Size of destination val too small for object. |
NNG_EWRITEONLY
|
The option opt is write-only. |