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</pre><pre class="rust ">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">prelude</span>::<span class="ident">v1</span>::<span class="kw-2">*</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">TypeId</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">cell</span>::<span class="ident">RefCell</span>;
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">hash</span>::{<span class="ident">BuildHasherDefault</span>, <span class="ident">Hasher</span>};
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">collections</span>::<span class="ident">HashMap</span>;
<span class="kw">use</span> <span class="ident">task_impl</span>::<span class="ident">with</span>;
<span class="doccomment">/// A macro to create a `static` of type `LocalKey`</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This macro is intentionally similar to the `thread_local!`, and creates a</span>
<span class="doccomment">/// `static` which has a `with` method to access the data on a task.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The data associated with each task local is per-task, so different tasks</span>
<span class="doccomment">/// will contain different values.</span>
<span class="attribute">#[<span class="ident">macro_export</span>]</span>
<span class="macro">macro_rules</span><span class="macro">!</span> <span class="ident">task_local</span> {
(<span class="kw">static</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">NAME</span>:<span class="ident">ident</span>: <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span>:<span class="ident">ty</span> <span class="op">=</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span>:<span class="ident">expr</span>) <span class="op">=></span> (
<span class="kw">static</span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">NAME</span>: <span class="macro-nonterminal">$</span><span class="kw">crate</span>::<span class="macro-nonterminal">task</span>::<span class="ident">LocalKey</span><span class="op"><</span><span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span><span class="op">></span> <span class="op">=</span> {
<span class="kw">fn</span> <span class="ident">__init</span>() <span class="op">-></span> <span class="macro-nonterminal">$</span><span class="macro-nonterminal">t</span> { <span class="macro-nonterminal">$</span><span class="macro-nonterminal">e</span> }
<span class="kw">fn</span> <span class="ident">__key</span>() <span class="op">-></span> ::<span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">TypeId</span> {
<span class="kw">struct</span> <span class="ident">__A</span>;
::<span class="ident">std</span>::<span class="ident">any</span>::<span class="ident">TypeId</span>::<span class="ident">of</span>::<span class="op"><</span><span class="ident">__A</span><span class="op">></span>()
}
<span class="macro-nonterminal">$</span><span class="kw">crate</span>::<span class="macro-nonterminal">task</span>::<span class="ident">LocalKey</span> {
<span class="ident">__init</span>: <span class="ident">__init</span>,
<span class="ident">__key</span>: <span class="ident">__key</span>,
}
};
)
}
<span class="kw">pub</span> <span class="kw">type</span> <span class="ident">LocalMap</span> <span class="op">=</span> <span class="ident">RefCell</span><span class="op"><</span><span class="ident">HashMap</span><span class="op"><</span><span class="ident">TypeId</span>,
<span class="ident">Box</span><span class="op"><</span><span class="ident">Opaque</span><span class="op">></span>,
<span class="ident">BuildHasherDefault</span><span class="op"><</span><span class="ident">IdHasher</span><span class="op">>></span><span class="op">></span>;
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">local_map</span>() <span class="op">-></span> <span class="ident">LocalMap</span> {
<span class="ident">RefCell</span>::<span class="ident">new</span>(<span class="ident">HashMap</span>::<span class="ident">default</span>())
}
<span class="kw">pub</span> <span class="kw">trait</span> <span class="ident">Opaque</span>: <span class="ident">Send</span> {}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Send</span><span class="op">></span> <span class="ident">Opaque</span> <span class="kw">for</span> <span class="ident">T</span> {}
<span class="doccomment">/// A key for task-local data stored in a future's task.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This type is generated by the `task_local!` macro and performs very</span>
<span class="doccomment">/// similarly to the `thread_local!` macro and `std::thread::LocalKey` types.</span>
<span class="doccomment">/// Data associated with a `LocalKey<T>` is stored inside of a future's task,</span>
<span class="doccomment">/// and the data is destroyed when the future is completed and the task is</span>
<span class="doccomment">/// destroyed.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Task-local data can migrate between threads and hence requires a `Send`</span>
<span class="doccomment">/// bound. Additionally, task-local data also requires the `'static` bound to</span>
<span class="doccomment">/// ensure it lives long enough. When a key is accessed for the first time the</span>
<span class="doccomment">/// task's data is initialized with the provided initialization expression to</span>
<span class="doccomment">/// the macro.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">LocalKey</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="comment">// "private" fields which have to be public to get around macro hygiene, not</span>
<span class="comment">// included in the stability story for this type. Can change at any time.</span>
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="kw">pub</span> <span class="ident">__key</span>: <span class="kw">fn</span>() <span class="op">-></span> <span class="ident">TypeId</span>,
<span class="attribute">#[<span class="ident">doc</span>(<span class="ident">hidden</span>)]</span>
<span class="kw">pub</span> <span class="ident">__init</span>: <span class="kw">fn</span>() <span class="op">-></span> <span class="ident">T</span>,
}
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">IdHasher</span> {
<span class="ident">id</span>: <span class="ident">u64</span>,
}
<span class="kw">impl</span> <span class="ident">Default</span> <span class="kw">for</span> <span class="ident">IdHasher</span> {
<span class="kw">fn</span> <span class="ident">default</span>() <span class="op">-></span> <span class="ident">IdHasher</span> {
<span class="ident">IdHasher</span> { <span class="ident">id</span>: <span class="number">0</span> }
}
}
<span class="kw">impl</span> <span class="ident">Hasher</span> <span class="kw">for</span> <span class="ident">IdHasher</span> {
<span class="kw">fn</span> <span class="ident">write</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">_bytes</span>: <span class="kw-2">&</span>[<span class="ident">u8</span>]) {
<span class="comment">// TODO: need to do something sensible</span>
<span class="macro">panic</span><span class="macro">!</span>(<span class="string">"can only hash u64"</span>);
}
<span class="kw">fn</span> <span class="ident">write_u64</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">u</span>: <span class="ident">u64</span>) {
<span class="self">self</span>.<span class="ident">id</span> <span class="op">=</span> <span class="ident">u</span>;
}
<span class="kw">fn</span> <span class="ident">finish</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">u64</span> {
<span class="self">self</span>.<span class="ident">id</span>
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Send</span> <span class="op">+</span> <span class="lifetime">'static</span><span class="op">></span> <span class="ident">LocalKey</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Access this task-local key, running the provided closure with a</span>
<span class="doccomment">/// reference to the value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function will access this task-local key to retrieve the data</span>
<span class="doccomment">/// associated with the current task and this key. If this is the first time</span>
<span class="doccomment">/// this key has been accessed on this task, then the key will be</span>
<span class="doccomment">/// initialized with the initialization expression provided at the time the</span>
<span class="doccomment">/// `task_local!` macro was called.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The provided closure will be provided a shared reference to the</span>
<span class="doccomment">/// underlying data associated with this task-local-key. The data itself is</span>
<span class="doccomment">/// stored inside of the current task.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function can possibly panic for a number of reasons:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * If there is not a current task.</span>
<span class="doccomment">/// * If the initialization expression is run and it panics</span>
<span class="doccomment">/// * If the closure provided panics</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">with</span><span class="op"><</span><span class="ident">F</span>, <span class="ident">R</span><span class="op">></span>(<span class="kw-2">&</span><span class="lifetime">'static</span> <span class="self">self</span>, <span class="ident">f</span>: <span class="ident">F</span>) <span class="op">-></span> <span class="ident">R</span>
<span class="kw">where</span> <span class="ident">F</span>: <span class="ident">FnOnce</span>(<span class="kw-2">&</span><span class="ident">T</span>) <span class="op">-></span> <span class="ident">R</span>
{
<span class="kw">let</span> <span class="ident">key</span> <span class="op">=</span> (<span class="self">self</span>.<span class="ident">__key</span>)();
<span class="ident">with</span>(<span class="op">|</span><span class="ident">task</span><span class="op">|</span> {
<span class="kw">let</span> <span class="ident">raw_pointer</span> <span class="op">=</span> {
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">data</span> <span class="op">=</span> <span class="ident">task</span>.<span class="ident">map</span>.<span class="ident">borrow_mut</span>();
<span class="kw">let</span> <span class="ident">entry</span> <span class="op">=</span> <span class="ident">data</span>.<span class="ident">entry</span>(<span class="ident">key</span>).<span class="ident">or_insert_with</span>(<span class="op">||</span> {
<span class="ident">Box</span>::<span class="ident">new</span>((<span class="self">self</span>.<span class="ident">__init</span>)())
});
<span class="kw-2">&</span><span class="kw-2">*</span><span class="kw-2">*</span><span class="ident">entry</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">Opaque</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw">const</span> <span class="ident">T</span>
};
<span class="kw">unsafe</span> {
<span class="ident">f</span>(<span class="kw-2">&</span><span class="kw-2">*</span><span class="ident">raw_pointer</span>)
}
})
}
}
</pre>
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