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<section id='main' class="content"><h1 class='fqn'><span class='in-band'>Macro <a href='index.html'>memoffset</a>::<wbr><a class="macro" href=''>span_of</a></span><span class='out-of-band'><span id='render-detail'>
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</span><a class='srclink' href='../src/memoffset/span_of.rs.html#83-131' title='goto source code'>[src]</a></span></h1><div class="docblock type-decl"><pre class="rust macro">
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">span_of</span> {
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, [] ..=) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, [] ..) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, [] ..= $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">tt</span>)<span class="op">+</span>) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, [] .. $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">field</span>:<span class="ident">tt</span>)<span class="op">+</span>) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, $(# <span class="macro-nonterminal">$</span><span class="macro-nonterminal">begin</span>:<span class="ident">tt</span>)<span class="op">+</span> [] ..= $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">end</span>:<span class="ident">tt</span>)<span class="op">+</span>) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, $(# <span class="macro-nonterminal">$</span><span class="macro-nonterminal">begin</span>:<span class="ident">tt</span>)<span class="op">+</span> [] .. $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">end</span>:<span class="ident">tt</span>)<span class="op">+</span>) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, $(# <span class="macro-nonterminal">$</span><span class="macro-nonterminal">begin</span>:<span class="ident">tt</span>)<span class="op">+</span> [] ..) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, $(# <span class="macro-nonterminal">$</span><span class="macro-nonterminal">begin</span>:<span class="ident">tt</span>)<span class="op">+</span> [] ..=) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, $(# <span class="macro-nonterminal">$</span><span class="macro-nonterminal">begin</span>:<span class="ident">tt</span>)<span class="op">+</span> []) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, $(# <span class="macro-nonterminal">$</span><span class="macro-nonterminal">begin</span>:<span class="ident">tt</span>)<span class="op">+</span> [] <span class="macro-nonterminal">$</span><span class="macro-nonterminal">tt</span>:<span class="ident">tt</span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=&gt;</span> { ... };
(@<span class="ident">helper</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">root</span>:<span class="ident">ident</span>, [] <span class="macro-nonterminal">$</span><span class="macro-nonterminal">tt</span>:<span class="ident">tt</span> $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">rest</span>:<span class="ident">tt</span>)<span class="kw-2">*</span>) <span class="op">=&gt;</span> { ... };
(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">sty</span>:<span class="ident">ty</span>, $(<span class="macro-nonterminal">$</span><span class="macro-nonterminal">exp</span>:<span class="ident">tt</span>)<span class="op">+</span>) <span class="op">=&gt;</span> { ... };
}</pre>
</div><div class='docblock'><p>Produces a range instance representing the sub-slice containing the specified member.</p>
<p>This macro provides 2 forms of differing functionalities.</p>
<p>The first form is identical to the appearance of the <code>offset_of!</code> macro,
and just like <code>offset_of!</code>, it has no limit on the depth of fields / subscripts used.</p>
<div class='information'><div class='tooltip ignore'><span class='tooltiptext'>This example is not tested</span></div></div><pre class="rust rust-example-rendered ignore">
<span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Struct</span>, <span class="ident">member</span>[<span class="ident">index</span>].<span class="ident">field</span>)</pre>
<p>The second form of <code>span_of!</code> returns a sub-slice which starts at one field, and ends at another.
The general pattern of this form is:</p>
<div class='information'><div class='tooltip ignore'><span class='tooltiptext'>This example is not tested</span></div></div><pre class="rust rust-example-rendered ignore">
<span class="comment">// Exclusive</span>
<span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Struct</span>, <span class="ident">member_a</span> .. <span class="ident">member_b</span>)
<span class="comment">// Inclusive</span>
<span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Struct</span>, <span class="ident">member_a</span> ..= <span class="ident">member_b</span>)
<span class="comment">// Open-ended ranges</span>
<span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Struct</span>, .. <span class="ident">end</span>)
<span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Struct</span>, <span class="ident">start</span> ..)</pre>
<p><em>Note</em>:
This macro uses recursion in order to resolve the range expressions, so there is a limit to the complexity of the expression.
In order to raise the limit, the compiler's recursion limit should be lifted.</p>
<p><em>Note</em>:
This macro may not make much sense when used on structs that are not <code>#[repr(C, packed)]</code></p>
<h2 id="examples" class="section-header"><a href="#examples">Examples</a></h2>
<pre class="rust rust-example-rendered">
<span class="attribute">#[<span class="ident">macro_use</span>]</span>
<span class="kw">extern</span> <span class="kw">crate</span> <span class="ident">memoffset</span>;
<span class="attribute">#[<span class="ident">repr</span>(<span class="ident">C</span>, <span class="ident">packed</span>)]</span>
<span class="kw">struct</span> <span class="ident">Florp</span> {
<span class="ident">a</span>: <span class="ident">u32</span>
}
<span class="attribute">#[<span class="ident">repr</span>(<span class="ident">C</span>, <span class="ident">packed</span>)]</span>
<span class="kw">struct</span> <span class="ident">Blarg</span> {
<span class="ident">x</span>: <span class="ident">u64</span>,
<span class="ident">y</span>: [<span class="ident">u8</span>; <span class="number">56</span>],
<span class="ident">z</span>: <span class="ident">Florp</span>,
<span class="ident">egg</span>: [[<span class="ident">u8</span>; <span class="number">4</span>]; <span class="number">4</span>]
}
<span class="kw">fn</span> <span class="ident">main</span>() {
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>..<span class="number">8</span>, <span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Blarg</span>, <span class="ident">x</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">64</span>..<span class="number">68</span>, <span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Blarg</span>, <span class="ident">z</span>.<span class="ident">a</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">79</span>..<span class="number">80</span>, <span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Blarg</span>, <span class="ident">egg</span>[<span class="number">2</span>][<span class="number">3</span>]));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">8</span>..<span class="number">64</span>, <span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Blarg</span>, <span class="ident">y</span>[<span class="number">0</span>] .. <span class="ident">z</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>..<span class="number">42</span>, <span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Blarg</span>, <span class="ident">x</span> .. <span class="ident">y</span>[<span class="number">34</span>]));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">0</span>..<span class="number">64</span>, <span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Blarg</span>, <span class="ident">x</span> ..= <span class="ident">y</span>));
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">58</span>..<span class="number">68</span>, <span class="macro">span_of</span><span class="macro">!</span>(<span class="ident">Blarg</span>, <span class="ident">y</span>[<span class="number">50</span>] ..= <span class="ident">z</span>));
}</pre>
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