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NNG_PIPE_GET(3) NNG Reference Manual NNG_PIPE_GET(3)

NAME

nng_pipe_get - get pipe option

SYNOPSIS

#include <nng/nng.h>
int nng_pipe_get(nng_pipe p, const char *opt, void *val, size_t *valszp);
int nng_pipe_get_bool(nng_pipe p, const char *opt, bool *bvalp);
int nng_pipe_get_int(nng_pipe p, const char *opt, int *ivalp);
int nng_pipe_get_ms(nng_pipe p, const char *opt, nng_duration *durp);
int nng_pipe_get_ptr(nng_pipe p, const char *opt, void **ptr);
int nng_pipe_get_addr(nng_pipe p, const char *opt, nng_sockaddr *sap);
int nng_pipe_get_string(nng_pipe p, const char *opt, char **strp);
int nng_pipe_get_size(nng_pipe p, const char *opt, size_t *zp);
int nng_pipe_get_uint64(nng_pipe p, const char *opt, uint64_t *u64p);

DESCRIPTION

The nng_pipe_get() 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.


Note

All options on a pipe are read-only values.
Modification of options may be done before the pipe is created using nng_listener_set() or nng_dialer_set().

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_get()

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.


Tip

It may be easier to use one of the typed forms of this function.

nng_pipe_get_bool()

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

nng_pipe_get_int()

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

nng_pipe_get_ms()

This function is used to retrieve time durations (nng_duration) in milliseconds, which are stored in durp.

nng_pipe_get_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_get_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_get_addr()

This function is used to retrieve an nng_sockaddr into sap.

nng_pipe_get_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_get_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.

SEE ALSO

nng_dialer_set(3) nng_socket_get(3), nng_listener_set(3) nng_msg_get_pipe(3) nng_strdup(3), nng_strerror(3), nng_strfree(3), nng_duration(5), nng_options(5), nng_pipe(5), nng_sockaddr(5), nng(7)

2024-10-11