oxmox
17f68cf8fe
git-subtree-dir: external/nng git-subtree-split: 169221da8d53b2ca4fda76f894bee8505887a7c6
134 lines
4.7 KiB
Text
134 lines
4.7 KiB
Text
= nng_ctx_getopt(3)
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//
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// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
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// Copyright 2018 Capitar IT Group BV <info@capitar.com>
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//
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// This document is supplied under the terms of the MIT License, a
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// copy of which should be located in the distribution where this
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// file was obtained (LICENSE.txt). A copy of the license may also be
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// found online at https://opensource.org/licenses/MIT.
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//
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== NAME
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nng_ctx_getopt - get context option
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== SYNOPSIS
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[source, c]
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----
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#include <nng/nng.h>
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int nng_ctx_getopt(nng_ctx ctx, const char *opt, void *val, size_t *valszp);
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int nng_ctx_getopt_bool(nng_ctx ctx, const char *opt, bool *bvalp);
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int nng_ctx_getopt_int(nng_ctx ctx, const char *opt, int *ivalp);
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int nng_ctx_getopt_ms(nng_ctx ctx, const char *opt, nng_duration *durp);
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int nng_ctx_getopt_size(nng_ctx ctx, const char *opt, size_t *zp);
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int nng_ctx_getopt_string(nng_ctx ctx, const char *opt, char **strp);
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int nng_ctx_getopt_uint64(nng_ctx ctx, const char *opt, uint64_t *u64p);
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----
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== DESCRIPTION
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IMPORTANT: These functions are deprecated. Please see xref:nng_ctx_get.3.adoc[nng_ctx_get].
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They may not be present if the library was built with `NNG_ELIDE_DEPRECATED`.
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(((options, context)))
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The `nng_ctx_getopt()` functions are used to retrieve option values for
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the xref:nng_ctx.5.adoc[context] _ctx_.
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The actual options that may be retrieved in this way vary.
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A number of them are documented in xref:nng_options.5.adoc[nng_options(5)].
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NOTE: Context options are protocol specific.
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The details will be documented with the protocol.
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=== Forms
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In all of these forms, the option _opt_ is retrieved from the context _ctx_.
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The forms vary based on the type of the option they take.
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The details of the type, size, and semantics of the option will depend
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on the actual option, and will be documented with the option itself.
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`nng_ctx_getopt()`::
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This function is untyped and can be used to retrieve the value of any option.
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The caller must store a pointer to a buffer to receive the value in _val_,
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and the size of the buffer shall be stored at the location referenced by
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_valszp_. +
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+
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When the function returns, the actual size of the data copied (or that
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would have been copied if sufficient space were present) is stored at
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the location referenced by _valszp_.
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If the caller's buffer is not large enough to hold the entire object,
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then the copy is truncated.
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Therefore the caller should check for truncation by verifying that the
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returned size in _valszp_ does not exceed the original buffer size. +
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+
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It is acceptable to pass `NULL` for _val_ if the value in _valszp_ is zero.
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This can be used to determine the size of the buffer needed to receive
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the object.
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TIP: It may be easier to use one of the typed forms of this function.
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`nng_ctx_getopt_bool()`::
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This function is for options which take a Boolean (`bool`).
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The value will be stored at _ivalp_.
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`nng_ctx_getopt_int()`::
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This function is for options which take an integer (`int`).
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The value will be stored at _ivalp_.
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`nng_ctx_getopt_ms()`::
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This function is used to retrieve time xref:nng_duration.5.adoc[durations]
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(such as timeouts), stored in _durp_ as a number of milliseconds.
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(The special value ((`NNG_DUR_INFINITE`)) means an infinite amount of time, and
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the special value ((`NNG_DUR_DEFAULT`)) means a context-specific default.)
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`nng_ctx_getopt_size()`::
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This function is used to retrieve a size into the pointer _zp_,
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typically for buffer sizes, message maximum sizes, and similar options.
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`nng_ctx_getopt_string()`::
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This function is used to retrieve a string into _strp_.
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This string is created from the source using xref:nng_strdup.3.adoc[`nng_strdup()`]
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and consequently must be freed by the caller using
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xref:nng_strfree.3.adoc[`nng_strfree()`] when it is no longer needed.
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`nng_ctx_getopt_uint64()`::
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This function is used to retrieve a 64-bit unsigned value into the value
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referenced by _u64p_.
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This is typically used for options related to identifiers, network
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numbers, and similar.
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== RETURN VALUES
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These functions return 0 on success, and non-zero otherwise.
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== ERRORS
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[horizontal]
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`NNG_EBADTYPE`:: Incorrect type for option.
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`NNG_ECLOSED`:: Parameter _s_ does not refer to an open socket.
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`NNG_EINVAL`:: Size of destination _val_ too small for object.
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`NNG_ENOMEM`:: Insufficient memory exists.
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`NNG_ENOTSUP`:: The option _opt_ is not supported.
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`NNG_EWRITEONLY`:: The option _opt_ is write-only.
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== SEE ALSO
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[.text-left]
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xref:nng_ctx_setopt.3.adoc[nng_ctx_setopt(3)],
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xref:nng_strdup.3.adoc[nng_strdup(3)],
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xref:nng_strerror.3.adoc[nng_strerror(3)],
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xref:nng_strfree.3.adoc[nng_strfree(3)],
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xref:nng_duration.5.adoc[nng_duration(5)],
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xref:nng_ctx.5.adoc[nng_ctx(5)],
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xref:nng_options.5.adoc[nng_options(5)],
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xref:nng.7.adoc[nng(7)]
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