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<h1 id="urls"><a class="header" href="#urls">URLs</a></h1>
<p><a name="a001"></a>Universal Resource Locators, or <a name="a002"></a>URLs for short, are a standardized
way of representing a network resource,
defined in <a href="https://datatracker.ietf.org/doc/html/rfc1738">RFC 1738</a>,
and <a href="https://datatracker.ietf.org/doc/html/rfc3986">RFC 3968</a>.</p>
<p>In Scalability Protocols, this concept is extended, although it includes schemes
that are not part of the IETF standards.</p>
<h2 id="url-structure"><a class="header" href="#url-structure">URL Structure</a></h2>
<pre><code class="language-c">typedef struct nng_url {
const char *u_scheme;
char *u_userinfo;
char *u_hostname;
uint16_t u_port;
char *u_path;
char *u_query;
char *u_fragment;
} nng_url;
</code></pre>
<h3 id="url-fields"><a class="header" href="#url-fields">URL Fields</a></h3>
<p>Applications may access individual fields, but must not free or
alter them, as the underlying memory is managed by the library.</p>
<p>Additionally applications must not depend on the size of this structure.
Obtain one using <code>nng_parse_url</code>.</p>
<p>The fields of an <code>nng_url</code> object are as follows:</p>
<ul>
<li><code>u_scheme</code>: The URL scheme, such as “http” or “inproc”. Always lower case. This will never be <code>NULL</code>.</li>
<li><code>u_userinfo</code>: This username and password if supplied in the URL string. Will be <code>NULL</code> when not present.</li>
<li><code>u_hostname</code>: The name of the host, and may be the empty string in some cases.</li>
<li><code>u_port</code>: The port. May be zero if irrelevant or not specified.</li>
<li><code>u_path</code>: The path, typically used with HTTP or WebSockets. Will be empty string if not specified.</li>
<li><code>u_query</code>: The query info (typically following <code>?</code> in the URL.) Will be <code>NULL</code> if not present.</li>
<li><code>u_fragment</code>: This is used for specifying an anchor, the part after <code>#</code> in a URL. Will be <code>NULL</code> if not present.</li>
</ul>
<div class="mdbook-alerts mdbook-alerts-note">
<p class="mdbook-alerts-title">
<span class="mdbook-alerts-icon"></span>
note
</p>
<p>Other fields may also be present, but only those documented here are safe for application use.</p>
</div>
<h2 id="format-a-url"><a class="header" href="#format-a-url">Format a URL</a></h2>
<pre><code class="language-c">int nng_url_sprintf(char *buf, size_t bufsz, const nng_url *url);
</code></pre>
<p>The <a name="a003"></a><code>nng_url_sprintf</code> function formats the <em>url</em> to the <em>buf</em>,
which must have <code>bufsz</code> bytes of free space associated with it.</p>
<p>This function returns the number of bytes formatted to <em>buf</em>, excludng
the terminating zero byte, or if <em>bufsz</em> is too small, then it returns
the number of bytes that would have been formatted if there was sufficient
space. The semantics are similar to the <code>snprintf</code> function from C99.</p>
<div class="mdbook-alerts mdbook-alerts-tip">
<p class="mdbook-alerts-title">
<span class="mdbook-alerts-icon"></span>
tip
</p>
<p>If <em>bufsz</em> is 0, then <em>buf</em> can be <code>NULL</code>, and the return value
can be used to determine the amount of space to allocate for a dynamically
sized buffer.</p>
</div>
<h2 id="parse-a-url"><a class="header" href="#parse-a-url">Parse a URL</a></h2>
<pre><code class="language-c">int nng_url_parse(nng_url **urlp, const char *str);
</code></pre>
<p>The <a name="a004"></a><code>nng_url_parse</code> function parses a URL string (in <em>str</em>),
and creates a dynamically allocated <code>nng_url</code>, returning it in <em>urlp</em>.</p>
<div class="mdbook-alerts mdbook-alerts-important">
<p class="mdbook-alerts-title">
<span class="mdbook-alerts-icon"></span>
important
</p>
<p>Only <a href="/api/url.html#destroy-a-url"><code>nng_url_free</code></a> should be used to deallocate <code>nng_url</code> objects.</p>
</div>
<h2 id="clone-a-url"><a class="header" href="#clone-a-url">Clone a URL</a></h2>
<pre><code class="language-c">int nng_url_clone(nng_url **dup, nng_url *url);
</code></pre>
<p>The <a name="a005"></a><code>nng_url_clone</code> function creates a copy of <em>url</em>, and returns it in <em>dup</em>.</p>
<h2 id="destroy-a-url"><a class="header" href="#destroy-a-url">Destroy a URL</a></h2>
<pre><code class="language-c">void nng_url_free(nng_url *url);
</code></pre>
<p>The <a name="a006"></a><code>nng_url_free</code> function destroy an <code>nng_url</code> object created with
either <a href="/api/url.html#parse-a-url"><code>nng_url_parse</code></a> or <a href="/api/url.html#destroy-a-url"><code>nng_url_free</code></a>.</p>
<p>This is the only correct way to destroy an <a href="/api/url.html#url-structure"><code>nng_url</code></a> object.</p>
<h2 id="see-also"><a class="header" href="#see-also">See Also</a></h2>
<p>More information about Universal Resource Locators can be found in
<a href="https://tools.ietf.org/html/rfc3986">RFC 3986</a>.</p>
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