NAME

       nng_ctx_get - get context option

SYNOPSIS

           #include <nng/nng.h>

           int nng_ctx_get(nng_ctx ctx, const char *opt, void *val, size_t *valszp);

           int nng_ctx_get_bool(nng_ctx ctx, const char *opt, bool *bvalp);

           int nng_ctx_get_int(nng_ctx ctx, const char *opt, int *ivalp);

           int nng_ctx_get_ms(nng_ctx ctx, const char *opt, nng_duration *durp);

           int nng_ctx_get_size(nng_ctx ctx, const char *opt, size_t *zp);

           int nng_ctx_get_string(nng_ctx ctx, const char *opt, char **strp);

           int nng_ctx_get_uint64(nng_ctx ctx, const char *opt, uint64_t *u64p);

DESCRIPTION

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

           Note
           Context options are protocol specific. The details will be documented with the
           protocol.

   Forms
       In all of these forms, the option opt is retrieved from the context ctx. 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.

       nng_ctx_get()
           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.

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

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

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

       nng_ctx_get_ms()
           This function is used to retrieve time durations (such as timeouts), stored in durp as
           a number of milliseconds. (The special value NNG_DURATION_INFINITE means an infinite
           amount of time, and the special value NNG_DURATION_DEFAULT means a context-specific
           default.)

       nng_ctx_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_ctx_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_ctx_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 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.

SEE ALSO

       nng_ctx_set(3), nng_strdup(3), nng_strerror(3), nng_strfree(3), nng_duration(5),
       nng_ctx(5), nng_options(5), nng(7)

                                            2024-10-11                             NNG_CTX_GET(3)