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NOTE: This documentation is for version 1.0.0 of nng, but the latest released version is 1.1.0. Please see the documentation for 1.1.0 for the most up-to-date information.
nng_getopt(3)

SYNOPSIS

#include <nng/nng.h>

int nng_getopt(nng_socket s, const char *opt, void *val, size_t *valszp);

int nng_getopt_bool(nng_socket s, const char *opt, bool *bvalp);

int nng_getopt_int(nng_socket s, const char *opt, int *ivalp);

int nng_getopt_ms(nng_socket s, const char *opt, nng_duration *durp);

int nng_getopt_ptr(nng_socket s, const char *opt, void **ptr);

int nng_getopt_size(nng_socket s, const char *opt, size_t *zp);

int nng_getopt_string(nng_socket s, const char *opt, char **strp);

int nng_getopt_uint64(nng_socket s, const char *opt, uint64_t *u64p);

DESCRIPTION

The nng_getopt() functions are used to retrieve option values for the socket s. The actual options that may be retrieved in this way vary. A number of them are documented in nng_options(5).

Additionally transport-specific options and protocol-specific options are documented with the transports and protocols themselves.

Forms

In all of these forms, the option opt is retrieved from the socket s. The forms vary based on the type of the option they take.

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.

Generally, it will be easier to use one of the typed forms instead.

nng_getopt()

This function is untyped and can be used to retrieve the value of any option. 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 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 returned size 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.

nng_getopt_bool()

This function is for options which take a Boolean (bool). The value will be stored at ivalp.

nng_getopt_int()

This function is for options which take an integer (int). The value will be stored at ivalp.

nng_getopt_ms()

This function 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.)

nng_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_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_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_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 s does not refer to an open socket.

NNG_EINVAL

Size of destination val too small for object.

NNG_ENOMEM

Insufficient memory exists.

NNG_ENOTSUP

The option opt is not supported.

NNG_EWRITEONLY

The option opt is write-only.

NNG Reference Manual v1.0.0 © 2018 Staysail Systems, Inc, © 2018 Capitar IT Group BV
This document is supplied under the MIT License.
nanomsg™ and nng™ are trademarks of Garrett D'Amore.