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</pre><pre class="rust ">
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">collections</span>::<span class="ident">VecDeque</span>;
<span class="kw">use</span> {<span class="ident">Poll</span>, <span class="ident">Async</span>};
<span class="kw">use</span> {<span class="ident">StartSend</span>, <span class="ident">AsyncSink</span>};
<span class="kw">use</span> <span class="ident">sink</span>::<span class="ident">Sink</span>;
<span class="kw">use</span> <span class="ident">stream</span>::<span class="ident">Stream</span>;
<span class="doccomment">/// Sink for the `Sink::buffer` combinator, which buffers up to some fixed</span>
<span class="doccomment">/// number of values when the underlying sink is unable to accept them.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>)]</span>
<span class="attribute">#[<span class="ident">must_use</span> <span class="op">=</span> <span class="string">"sinks do nothing unless polled"</span>]</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Buffer</span><span class="op"><</span><span class="ident">S</span>: <span class="ident">Sink</span><span class="op">></span> {
<span class="ident">sink</span>: <span class="ident">S</span>,
<span class="ident">buf</span>: <span class="ident">VecDeque</span><span class="op"><</span><span class="ident">S</span>::<span class="ident">SinkItem</span><span class="op">></span>,
<span class="comment">// Track capacity separately from the `VecDeque`, which may be rounded up</span>
<span class="ident">cap</span>: <span class="ident">usize</span>,
}
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span><span class="op"><</span><span class="ident">S</span>: <span class="ident">Sink</span><span class="op">></span>(<span class="ident">sink</span>: <span class="ident">S</span>, <span class="ident">amt</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">Buffer</span><span class="op"><</span><span class="ident">S</span><span class="op">></span> {
<span class="ident">Buffer</span> {
<span class="ident">sink</span>: <span class="ident">sink</span>,
<span class="ident">buf</span>: <span class="ident">VecDeque</span>::<span class="ident">with_capacity</span>(<span class="ident">amt</span>),
<span class="ident">cap</span>: <span class="ident">amt</span>,
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">S</span>: <span class="ident">Sink</span><span class="op">></span> <span class="ident">Buffer</span><span class="op"><</span><span class="ident">S</span><span class="op">></span> {
<span class="doccomment">/// Get a shared reference to the inner sink.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_ref</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="ident">S</span> {
<span class="kw-2">&</span><span class="self">self</span>.<span class="ident">sink</span>
}
<span class="doccomment">/// Get a mutable reference to the inner sink.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get_mut</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="kw-2">&</span><span class="kw-2">mut</span> <span class="ident">S</span> {
<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>.<span class="ident">sink</span>
}
<span class="doccomment">/// Consumes this combinator, returning the underlying sink.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this may discard intermediate state of this combinator, so</span>
<span class="doccomment">/// care should be taken to avoid losing resources when this is called.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">into_inner</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">S</span> {
<span class="self">self</span>.<span class="ident">sink</span>
}
<span class="kw">fn</span> <span class="ident">try_empty_buffer</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span>(), <span class="ident">S</span>::<span class="ident">SinkError</span><span class="op">></span> {
<span class="kw">while</span> <span class="kw">let</span> <span class="prelude-val">Some</span>(<span class="ident">item</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">pop_front</span>() {
<span class="kw">if</span> <span class="kw">let</span> <span class="ident">AsyncSink</span>::<span class="ident">NotReady</span>(<span class="ident">item</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">sink</span>.<span class="ident">start_send</span>(<span class="ident">item</span>)<span class="question-mark">?</span> {
<span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">push_front</span>(<span class="ident">item</span>);
<span class="kw">return</span> <span class="prelude-val">Ok</span>(<span class="ident">Async</span>::<span class="ident">NotReady</span>);
}
}
<span class="prelude-val">Ok</span>(<span class="ident">Async</span>::<span class="ident">Ready</span>(()))
}
}
<span class="comment">// Forwarding impl of Stream from the underlying sink</span>
<span class="kw">impl</span><span class="op"><</span><span class="ident">S</span><span class="op">></span> <span class="ident">Stream</span> <span class="kw">for</span> <span class="ident">Buffer</span><span class="op"><</span><span class="ident">S</span><span class="op">></span> <span class="kw">where</span> <span class="ident">S</span>: <span class="ident">Sink</span> <span class="op">+</span> <span class="ident">Stream</span> {
<span class="kw">type</span> <span class="ident">Item</span> <span class="op">=</span> <span class="ident">S</span>::<span class="ident">Item</span>;
<span class="kw">type</span> <span class="ident">Error</span> <span class="op">=</span> <span class="ident">S</span>::<span class="ident">Error</span>;
<span class="kw">fn</span> <span class="ident">poll</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span><span class="prelude-ty">Option</span><span class="op"><</span><span class="ident">S</span>::<span class="ident">Item</span><span class="op">></span>, <span class="ident">S</span>::<span class="ident">Error</span><span class="op">></span> {
<span class="self">self</span>.<span class="ident">sink</span>.<span class="ident">poll</span>()
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">S</span>: <span class="ident">Sink</span><span class="op">></span> <span class="ident">Sink</span> <span class="kw">for</span> <span class="ident">Buffer</span><span class="op"><</span><span class="ident">S</span><span class="op">></span> {
<span class="kw">type</span> <span class="ident">SinkItem</span> <span class="op">=</span> <span class="ident">S</span>::<span class="ident">SinkItem</span>;
<span class="kw">type</span> <span class="ident">SinkError</span> <span class="op">=</span> <span class="ident">S</span>::<span class="ident">SinkError</span>;
<span class="kw">fn</span> <span class="ident">start_send</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">item</span>: <span class="self">Self</span>::<span class="ident">SinkItem</span>) <span class="op">-></span> <span class="ident">StartSend</span><span class="op"><</span><span class="self">Self</span>::<span class="ident">SinkItem</span>, <span class="self">Self</span>::<span class="ident">SinkError</span><span class="op">></span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">cap</span> <span class="op">==</span> <span class="number">0</span> {
<span class="kw">return</span> <span class="self">self</span>.<span class="ident">sink</span>.<span class="ident">start_send</span>(<span class="ident">item</span>);
}
<span class="self">self</span>.<span class="ident">try_empty_buffer</span>()<span class="question-mark">?</span>;
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">len</span>() <span class="op">==</span> <span class="self">self</span>.<span class="ident">cap</span> {
<span class="kw">return</span> <span class="prelude-val">Ok</span>(<span class="ident">AsyncSink</span>::<span class="ident">NotReady</span>(<span class="ident">item</span>));
}
<span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">push_back</span>(<span class="ident">item</span>);
<span class="prelude-val">Ok</span>(<span class="ident">AsyncSink</span>::<span class="ident">Ready</span>)
}
<span class="kw">fn</span> <span class="ident">poll_complete</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span>(), <span class="self">Self</span>::<span class="ident">SinkError</span><span class="op">></span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">cap</span> <span class="op">==</span> <span class="number">0</span> {
<span class="kw">return</span> <span class="self">self</span>.<span class="ident">sink</span>.<span class="ident">poll_complete</span>();
}
<span class="macro">try_ready</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">try_empty_buffer</span>());
<span class="macro">debug_assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">is_empty</span>());
<span class="self">self</span>.<span class="ident">sink</span>.<span class="ident">poll_complete</span>()
}
<span class="kw">fn</span> <span class="ident">close</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">Poll</span><span class="op"><</span>(), <span class="self">Self</span>::<span class="ident">SinkError</span><span class="op">></span> {
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">cap</span> <span class="op">==</span> <span class="number">0</span> {
<span class="kw">return</span> <span class="self">self</span>.<span class="ident">sink</span>.<span class="ident">close</span>();
}
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">len</span>() <span class="op">></span> <span class="number">0</span> {
<span class="macro">try_ready</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">try_empty_buffer</span>());
}
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">buf</span>.<span class="ident">len</span>(), <span class="number">0</span>);
<span class="self">self</span>.<span class="ident">sink</span>.<span class="ident">close</span>()
}
}
</pre>
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