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diff --git a/docs/ref/str/nng_stream_get.adoc b/docs/ref/str/nng_stream_get.adoc new file mode 100644 index 00000000..f527dc8a --- /dev/null +++ b/docs/ref/str/nng_stream_get.adoc @@ -0,0 +1,98 @@ +## nng_stream_get + +Get option from byte stream. + +### Synopsis + +```c +#include <nng/nng.h> + +int nng_stream_get(nng_stream *s, const char *opt, void *val, size_t *sizep); + +int nng_stream_get_bool(nng_stream *s, const char *opt, bool *valp); +int nng_stream_get_int(nng_stream *s, const char *opt, int *valp); +int nng_stream_get_ms(nng_stream *s, const char *opt, nng_duration *valp); +int nng_stream_get_ptr(nng_stream *s, const char *opt, void **valp); +int nng_stream_get_size(nng_stream *s, const char *opt, size_t *valp); +int nng_stream_get_addr(nng_stream *s, const char *opt, nng_sockaddr *valp); +int nng_stream_get_string(nng_stream *s, const char *opt, char **valp); +int nng_stream_get_uint64(nng_stream *s, const char *opt, uint64_t *valp); +``` + +### Description + +The `nng_stream_get` functions are used to retrieve option values for the byte stream _s_. + +The actual options that may be retrieved in this way vary. +A number of them are documented in xref:../opts/index.adoc[Options]. + +#### Forms +In all of these forms, the option _opt_ is retrieved from the connected +byte stream _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. + +TIP: It may be easier to use one of the typed forms of this function. + +`nng_stream_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 _sizep_. ++ +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 _sizep_. +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 _sizep_ does not exceed the original buffer size. ++ +It is acceptable to pass `NULL` for _val_ if the value in _sizep_ is zero. +This can be used to determine the size of the buffer needed to receive the object. + +`nng_stream_get_bool`:: +This function is for options which take a Boolean (`bool`). + +`nng_stream_get_int`:: +This function is for options which take an integer (`int`). + +`nng_stream_get_ms`:: +This function is used to retrieve time durations (`nng_duration`), stored 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_stream_get_ptr`:: +This function is used to retrieve a pointer to structured data. +The data referenced 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. ++ +Care must be taken to ensure that the application respects any considerations about the lifetime of the underyling object. +See the documentation for the option for more specific guidance. + +`nng_stream_get_size`:: +This function is used to retrieve a size option. + +`nng_stream_get_addr`:: +This function is used to retrieve a xref:../opts/nng_sockaddr.adoc[socket address]. + +`nng_stream_get_string`:: +This function is used to retrieve a `NUL`-terminated string. +This string is created from the source using xref:nng_strdup.adoc[`nng_strdup`]. +Consequently, it must be freed by the caller using xref:nng_strfree.adoc[`nng_strfree`] when it is no longer needed. + +`nng_stream_get_uint64`:: +This function is used to retrieve a 64-bit unsigned value. + +### Return Values + +This function returns 0 on success, and non-zero otherwise. + +### Errors + +[horizontal] +`NNG_ECLOSED`:: The connection is closed. +`NNG_EINVAL`:: There was insufficient space to receive the object. + The amount of data actually needed is returned in _sizep_. +`NNG_ENOTSUP`:: The option is not supported. +`NNG_EWRITEONLY`:: The option may not read. + +### See Also + +xref:../opts/index.adoc[Options], +xref:nng_stream_set.adoc[nng_stream_set] |