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</pre><pre class="rust ">
<span class="comment">// Copyright 2015 The Rust Project Developers. See the COPYRIGHT</span>
<span class="comment">// file at the top-level directory of this distribution and at</span>
<span class="comment">// http://rust-lang.org/COPYRIGHT.</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license</span>
<span class="comment">// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your</span>
<span class="comment">// option. This file may not be copied, modified, or distributed</span>
<span class="comment">// except according to those terms.</span>
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ptr</span>::<span class="ident">Unique</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">mem</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">slice</span>;
<span class="kw">use</span> <span class="ident">heap</span>;
<span class="kw">use</span> <span class="kw">super</span>::<span class="ident">oom</span>;
<span class="kw">use</span> <span class="kw">super</span>::<span class="ident">boxed</span>::<span class="ident">Box</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">ops</span>::<span class="ident">Drop</span>;
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">cmp</span>;
<span class="doccomment">/// A low-level utility for more ergonomically allocating, reallocating, and deallocating</span>
<span class="doccomment">/// a buffer of memory on the heap without having to worry about all the corner cases</span>
<span class="doccomment">/// involved. This type is excellent for building your own data structures like Vec and VecDeque.</span>
<span class="doccomment">/// In particular:</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Produces Unique::empty() on zero-sized types</span>
<span class="doccomment">/// * Produces Unique::empty() on zero-length allocations</span>
<span class="doccomment">/// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics)</span>
<span class="doccomment">/// * Guards against 32-bit systems allocating more than isize::MAX bytes</span>
<span class="doccomment">/// * Guards against overflowing your length</span>
<span class="doccomment">/// * Aborts on OOM</span>
<span class="doccomment">/// * Avoids freeing Unique::empty()</span>
<span class="doccomment">/// * Contains a ptr::Unique and thus endows the user with all related benefits</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This type does not in anyway inspect the memory that it manages. When dropped it *will*</span>
<span class="doccomment">/// free its memory, but it *won't* try to Drop its contents. It is up to the user of RawVec</span>
<span class="doccomment">/// to handle the actual things *stored* inside of a RawVec.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that a RawVec always forces its capacity to be usize::MAX for zero-sized types.</span>
<span class="doccomment">/// This enables you to use capacity growing logic catch the overflows in your length</span>
<span class="doccomment">/// that might occur with zero-sized types.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// However this means that you need to be careful when roundtripping this type</span>
<span class="doccomment">/// with a `Box<[T]>`: `cap()` won't yield the len. However `with_capacity`,</span>
<span class="doccomment">/// `shrink_to_fit`, and `from_box` will actually set RawVec's private capacity</span>
<span class="doccomment">/// field. This allows zero-sized types to not be special-cased by consumers of</span>
<span class="doccomment">/// this type.</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">RawVec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="ident">ptr</span>: <span class="ident">Unique</span><span class="op"><</span><span class="ident">T</span><span class="op">></span>,
<span class="ident">cap</span>: <span class="ident">usize</span>,
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">RawVec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Creates the biggest possible RawVec without allocating. If T has positive</span>
<span class="doccomment">/// size, then this makes a RawVec with capacity 0. If T has 0 size, then it</span>
<span class="doccomment">/// it makes a RawVec with capacity `usize::MAX`. Useful for implementing</span>
<span class="doccomment">/// delayed allocation.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>() <span class="op">-></span> <span class="self">Self</span> {
<span class="comment">// !0 is usize::MAX. This branch should be stripped at compile time.</span>
<span class="kw">let</span> <span class="ident">cap</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">==</span> <span class="number">0</span> { <span class="op">!</span><span class="number">0</span> } <span class="kw">else</span> { <span class="number">0</span> };
<span class="comment">// Unique::empty() doubles as "unallocated" and "zero-sized allocation"</span>
<span class="ident">RawVec</span> {
<span class="ident">ptr</span>: <span class="ident">Unique</span>::<span class="ident">empty</span>(),
<span class="ident">cap</span>: <span class="ident">cap</span>,
}
}
<span class="doccomment">/// Creates a RawVec with exactly the capacity and alignment requirements</span>
<span class="doccomment">/// for a `[T; cap]`. This is equivalent to calling RawVec::new when `cap` is 0</span>
<span class="doccomment">/// or T is zero-sized. Note that if `T` is zero-sized this means you will *not*</span>
<span class="doccomment">/// get a RawVec with the requested capacity!</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Panics if the requested capacity exceeds `usize::MAX` bytes.</span>
<span class="doccomment">/// * Panics on 32-bit platforms if the requested capacity exceeds</span>
<span class="doccomment">/// `isize::MAX` bytes.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Aborts</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Aborts on OOM</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">with_capacity</span>(<span class="ident">cap</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="ident">RawVec</span>::<span class="ident">allocate</span>(<span class="ident">cap</span>, <span class="bool-val">false</span>)
}
<span class="doccomment">/// Like `with_capacity` but guarantees the buffer is zeroed.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">with_capacity_zeroed</span>(<span class="ident">cap</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="ident">RawVec</span>::<span class="ident">allocate</span>(<span class="ident">cap</span>, <span class="bool-val">true</span>)
}
<span class="kw">fn</span> <span class="ident">allocate</span>(<span class="ident">cap</span>: <span class="ident">usize</span>, <span class="ident">zeroed</span>: <span class="ident">bool</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">alloc_size</span> <span class="op">=</span> <span class="ident">cap</span>.<span class="ident">checked_mul</span>(<span class="ident">elem_size</span>).<span class="ident">expect</span>(<span class="string">"capacity overflow"</span>);
<span class="ident">alloc_guard</span>(<span class="ident">alloc_size</span>);
<span class="comment">// handles ZSTs and `cap = 0` alike</span>
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">alloc_size</span> <span class="op">==</span> <span class="number">0</span> {
<span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>
} <span class="kw">else</span> {
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">zeroed</span> {
<span class="ident">heap</span>::<span class="ident">allocate_zeroed</span>(<span class="ident">alloc_size</span>, <span class="ident">align</span>)
} <span class="kw">else</span> {
<span class="ident">heap</span>::<span class="ident">allocate</span>(<span class="ident">alloc_size</span>, <span class="ident">align</span>)
};
<span class="kw">if</span> <span class="ident">ptr</span>.<span class="ident">is_null</span>() {
<span class="ident">oom</span>()
}
<span class="ident">ptr</span>
};
<span class="ident">RawVec</span> {
<span class="ident">ptr</span>: <span class="ident">Unique</span>::<span class="ident">new</span>(<span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _),
<span class="ident">cap</span>: <span class="ident">cap</span>,
}
}
}
<span class="doccomment">/// Reconstitutes a RawVec from a pointer and capacity.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Undefined Behavior</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The ptr must be allocated, and with the given capacity. The</span>
<span class="doccomment">/// capacity cannot exceed `isize::MAX` (only a concern on 32-bit systems).</span>
<span class="doccomment">/// If the ptr and capacity come from a RawVec, then this is guaranteed.</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">from_raw_parts</span>(<span class="ident">ptr</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span>, <span class="ident">cap</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="ident">RawVec</span> {
<span class="ident">ptr</span>: <span class="ident">Unique</span>::<span class="ident">new</span>(<span class="ident">ptr</span>),
<span class="ident">cap</span>: <span class="ident">cap</span>,
}
}
<span class="doccomment">/// Converts a `Box<[T]>` into a `RawVec<T>`.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">from_box</span>(<span class="kw-2">mut</span> <span class="ident">slice</span>: <span class="ident">Box</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span>) <span class="op">-></span> <span class="self">Self</span> {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">result</span> <span class="op">=</span> <span class="ident">RawVec</span>::<span class="ident">from_raw_parts</span>(<span class="ident">slice</span>.<span class="ident">as_mut_ptr</span>(), <span class="ident">slice</span>.<span class="ident">len</span>());
<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="ident">slice</span>);
<span class="ident">result</span>
}
}
}
<span class="kw">impl</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> <span class="ident">RawVec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Gets a raw pointer to the start of the allocation. Note that this is</span>
<span class="doccomment">/// Unique::empty() if `cap = 0` or T is zero-sized. In the former case, you must</span>
<span class="doccomment">/// be careful.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">ptr</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">T</span> {
<span class="self">self</span>.<span class="ident">ptr</span>.<span class="ident">as_ptr</span>()
}
<span class="doccomment">/// Gets the capacity of the allocation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This will always be `usize::MAX` if `T` is zero-sized.</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">always</span>)]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">cap</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="kw">if</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>() <span class="op">==</span> <span class="number">0</span> {
<span class="op">!</span><span class="number">0</span>
} <span class="kw">else</span> {
<span class="self">self</span>.<span class="ident">cap</span>
}
}
<span class="doccomment">/// Doubles the size of the type's backing allocation. This is common enough</span>
<span class="doccomment">/// to want to do that it's easiest to just have a dedicated method. Slightly</span>
<span class="doccomment">/// more efficient logic can be provided for this than the general case.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is ideal for when pushing elements one-at-a-time because</span>
<span class="doccomment">/// you don't need to incur the costs of the more general computations</span>
<span class="doccomment">/// reserve needs to do to guard against overflow. You do however need to</span>
<span class="doccomment">/// manually check if your `len == cap`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Panics if T is zero-sized on the assumption that you managed to exhaust</span>
<span class="doccomment">/// all `usize::MAX` slots in your imaginary buffer.</span>
<span class="doccomment">/// * Panics on 32-bit platforms if the requested capacity exceeds</span>
<span class="doccomment">/// `isize::MAX` bytes.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Aborts</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Aborts on OOM</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```ignore</span>
<span class="doccomment">/// struct MyVec<T> {</span>
<span class="doccomment">/// buf: RawVec<T>,</span>
<span class="doccomment">/// len: usize,</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// impl<T> MyVec<T> {</span>
<span class="doccomment">/// pub fn push(&mut self, elem: T) {</span>
<span class="doccomment">/// if self.len == self.buf.cap() { self.buf.double(); }</span>
<span class="doccomment">/// // double would have aborted or panicked if the len exceeded</span>
<span class="doccomment">/// // `isize::MAX` so this is safe to do unchecked now.</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// ptr::write(self.buf.ptr().offset(self.len as isize), elem);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// self.len += 1;</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">never</span>)]</span>
<span class="attribute">#[<span class="ident">cold</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">double</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="comment">// since we set the capacity to usize::MAX when elem_size is</span>
<span class="comment">// 0, getting to here necessarily means the RawVec is overfull.</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">elem_size</span> <span class="op">!=</span> <span class="number">0</span>, <span class="string">"capacity overflow"</span>);
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> (<span class="ident">new_cap</span>, <span class="ident">ptr</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="comment">// skip to 4 because tiny Vec's are dumb; but not if that would cause overflow</span>
<span class="kw">let</span> <span class="ident">new_cap</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">elem_size</span> <span class="op">></span> (<span class="op">!</span><span class="number">0</span>) <span class="op">/</span> <span class="number">8</span> { <span class="number">1</span> } <span class="kw">else</span> { <span class="number">4</span> };
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="ident">heap</span>::<span class="ident">allocate</span>(<span class="ident">new_cap</span> <span class="op">*</span> <span class="ident">elem_size</span>, <span class="ident">align</span>);
(<span class="ident">new_cap</span>, <span class="ident">ptr</span>)
} <span class="kw">else</span> {
<span class="comment">// Since we guarantee that we never allocate more than isize::MAX bytes,</span>
<span class="comment">// `elem_size * self.cap <= isize::MAX` as a precondition, so this can't overflow</span>
<span class="kw">let</span> <span class="ident">new_cap</span> <span class="op">=</span> <span class="number">2</span> <span class="op">*</span> <span class="self">self</span>.<span class="ident">cap</span>;
<span class="kw">let</span> <span class="ident">new_alloc_size</span> <span class="op">=</span> <span class="ident">new_cap</span> <span class="op">*</span> <span class="ident">elem_size</span>;
<span class="ident">alloc_guard</span>(<span class="ident">new_alloc_size</span>);
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="ident">heap</span>::<span class="ident">reallocate</span>(<span class="self">self</span>.<span class="ident">ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _,
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">*</span> <span class="ident">elem_size</span>,
<span class="ident">new_alloc_size</span>,
<span class="ident">align</span>);
(<span class="ident">new_cap</span>, <span class="ident">ptr</span>)
};
<span class="comment">// If allocate or reallocate fail, we'll get `null` back</span>
<span class="kw">if</span> <span class="ident">ptr</span>.<span class="ident">is_null</span>() {
<span class="ident">oom</span>()
}
<span class="self">self</span>.<span class="ident">ptr</span> <span class="op">=</span> <span class="ident">Unique</span>::<span class="ident">new</span>(<span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _);
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">=</span> <span class="ident">new_cap</span>;
}
}
<span class="doccomment">/// Attempts to double the size of the type's backing allocation in place. This is common</span>
<span class="doccomment">/// enough to want to do that it's easiest to just have a dedicated method. Slightly</span>
<span class="doccomment">/// more efficient logic can be provided for this than the general case.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns true if the reallocation attempt has succeeded, or false otherwise.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Panics if T is zero-sized on the assumption that you managed to exhaust</span>
<span class="doccomment">/// all `usize::MAX` slots in your imaginary buffer.</span>
<span class="doccomment">/// * Panics on 32-bit platforms if the requested capacity exceeds</span>
<span class="doccomment">/// `isize::MAX` bytes.</span>
<span class="attribute">#[<span class="ident">inline</span>(<span class="ident">never</span>)]</span>
<span class="attribute">#[<span class="ident">cold</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">double_in_place</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="comment">// since we set the capacity to usize::MAX when elem_size is</span>
<span class="comment">// 0, getting to here necessarily means the RawVec is overfull.</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">elem_size</span> <span class="op">!=</span> <span class="number">0</span>, <span class="string">"capacity overflow"</span>);
<span class="comment">// Since we guarantee that we never allocate more than isize::MAX bytes,</span>
<span class="comment">// `elem_size * self.cap <= isize::MAX` as a precondition, so this can't overflow</span>
<span class="kw">let</span> <span class="ident">new_cap</span> <span class="op">=</span> <span class="number">2</span> <span class="op">*</span> <span class="self">self</span>.<span class="ident">cap</span>;
<span class="kw">let</span> <span class="ident">new_alloc_size</span> <span class="op">=</span> <span class="ident">new_cap</span> <span class="op">*</span> <span class="ident">elem_size</span>;
<span class="ident">alloc_guard</span>(<span class="ident">new_alloc_size</span>);
<span class="kw">let</span> <span class="ident">size</span> <span class="op">=</span> <span class="ident">heap</span>::<span class="ident">reallocate_inplace</span>(<span class="self">self</span>.<span class="ident">ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _,
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">*</span> <span class="ident">elem_size</span>,
<span class="ident">new_alloc_size</span>,
<span class="ident">align</span>);
<span class="kw">if</span> <span class="ident">size</span> <span class="op">>=</span> <span class="ident">new_alloc_size</span> {
<span class="comment">// We can't directly divide `size`.</span>
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">=</span> <span class="ident">new_cap</span>;
}
<span class="ident">size</span> <span class="op">>=</span> <span class="ident">new_alloc_size</span>
}
}
<span class="doccomment">/// Ensures that the buffer contains at least enough space to hold</span>
<span class="doccomment">/// `used_cap + needed_extra_cap` elements. If it doesn't already,</span>
<span class="doccomment">/// will reallocate the minimum possible amount of memory necessary.</span>
<span class="doccomment">/// Generally this will be exactly the amount of memory necessary,</span>
<span class="doccomment">/// but in principle the allocator is free to give back more than</span>
<span class="doccomment">/// we asked for.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate</span>
<span class="doccomment">/// the requested space. This is not really unsafe, but the unsafe</span>
<span class="doccomment">/// code *you* write that relies on the behavior of this function may break.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Panics if the requested capacity exceeds `usize::MAX` bytes.</span>
<span class="doccomment">/// * Panics on 32-bit platforms if the requested capacity exceeds</span>
<span class="doccomment">/// `isize::MAX` bytes.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Aborts</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Aborts on OOM</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">reserve_exact</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">used_cap</span>: <span class="ident">usize</span>, <span class="ident">needed_extra_cap</span>: <span class="ident">usize</span>) {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="comment">// NOTE: we don't early branch on ZSTs here because we want this</span>
<span class="comment">// to actually catch "asking for more than usize::MAX" in that case.</span>
<span class="comment">// If we make it past the first branch then we are guaranteed to</span>
<span class="comment">// panic.</span>
<span class="comment">// Don't actually need any more capacity.</span>
<span class="comment">// Wrapping in case they gave a bad `used_cap`.</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">cap</span>().<span class="ident">wrapping_sub</span>(<span class="ident">used_cap</span>) <span class="op">>=</span> <span class="ident">needed_extra_cap</span> {
<span class="kw">return</span>;
}
<span class="comment">// Nothing we can really do about these checks :(</span>
<span class="kw">let</span> <span class="ident">new_cap</span> <span class="op">=</span> <span class="ident">used_cap</span>.<span class="ident">checked_add</span>(<span class="ident">needed_extra_cap</span>).<span class="ident">expect</span>(<span class="string">"capacity overflow"</span>);
<span class="kw">let</span> <span class="ident">new_alloc_size</span> <span class="op">=</span> <span class="ident">new_cap</span>.<span class="ident">checked_mul</span>(<span class="ident">elem_size</span>).<span class="ident">expect</span>(<span class="string">"capacity overflow"</span>);
<span class="ident">alloc_guard</span>(<span class="ident">new_alloc_size</span>);
<span class="kw">let</span> <span class="ident">ptr</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="ident">heap</span>::<span class="ident">allocate</span>(<span class="ident">new_alloc_size</span>, <span class="ident">align</span>)
} <span class="kw">else</span> {
<span class="ident">heap</span>::<span class="ident">reallocate</span>(<span class="self">self</span>.<span class="ident">ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _,
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">*</span> <span class="ident">elem_size</span>,
<span class="ident">new_alloc_size</span>,
<span class="ident">align</span>)
};
<span class="comment">// If allocate or reallocate fail, we'll get `null` back</span>
<span class="kw">if</span> <span class="ident">ptr</span>.<span class="ident">is_null</span>() {
<span class="ident">oom</span>()
}
<span class="self">self</span>.<span class="ident">ptr</span> <span class="op">=</span> <span class="ident">Unique</span>::<span class="ident">new</span>(<span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _);
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">=</span> <span class="ident">new_cap</span>;
}
}
<span class="doccomment">/// Calculates the buffer's new size given that it'll hold `used_cap +</span>
<span class="doccomment">/// needed_extra_cap` elements. This logic is used in amortized reserve methods.</span>
<span class="doccomment">/// Returns `(new_capacity, new_alloc_size)`.</span>
<span class="kw">fn</span> <span class="ident">amortized_new_size</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">used_cap</span>: <span class="ident">usize</span>, <span class="ident">needed_extra_cap</span>: <span class="ident">usize</span>) <span class="op">-></span> (<span class="ident">usize</span>, <span class="ident">usize</span>) {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="comment">// Nothing we can really do about these checks :(</span>
<span class="kw">let</span> <span class="ident">required_cap</span> <span class="op">=</span> <span class="ident">used_cap</span>.<span class="ident">checked_add</span>(<span class="ident">needed_extra_cap</span>)
.<span class="ident">expect</span>(<span class="string">"capacity overflow"</span>);
<span class="comment">// Cannot overflow, because `cap <= isize::MAX`, and type of `cap` is `usize`.</span>
<span class="kw">let</span> <span class="ident">double_cap</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">cap</span> <span class="op">*</span> <span class="number">2</span>;
<span class="comment">// `double_cap` guarantees exponential growth.</span>
<span class="kw">let</span> <span class="ident">new_cap</span> <span class="op">=</span> <span class="ident">cmp</span>::<span class="ident">max</span>(<span class="ident">double_cap</span>, <span class="ident">required_cap</span>);
<span class="kw">let</span> <span class="ident">new_alloc_size</span> <span class="op">=</span> <span class="ident">new_cap</span>.<span class="ident">checked_mul</span>(<span class="ident">elem_size</span>).<span class="ident">expect</span>(<span class="string">"capacity overflow"</span>);
(<span class="ident">new_cap</span>, <span class="ident">new_alloc_size</span>)
}
<span class="doccomment">/// Ensures that the buffer contains at least enough space to hold</span>
<span class="doccomment">/// `used_cap + needed_extra_cap` elements. If it doesn't already have</span>
<span class="doccomment">/// enough capacity, will reallocate enough space plus comfortable slack</span>
<span class="doccomment">/// space to get amortized `O(1)` behavior. Will limit this behavior</span>
<span class="doccomment">/// if it would needlessly cause itself to panic.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate</span>
<span class="doccomment">/// the requested space. This is not really unsafe, but the unsafe</span>
<span class="doccomment">/// code *you* write that relies on the behavior of this function may break.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This is ideal for implementing a bulk-push operation like `extend`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Panics if the requested capacity exceeds `usize::MAX` bytes.</span>
<span class="doccomment">/// * Panics on 32-bit platforms if the requested capacity exceeds</span>
<span class="doccomment">/// `isize::MAX` bytes.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Aborts</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Aborts on OOM</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```ignore</span>
<span class="doccomment">/// struct MyVec<T> {</span>
<span class="doccomment">/// buf: RawVec<T>,</span>
<span class="doccomment">/// len: usize,</span>
<span class="doccomment">/// }</span>
<span class="doccomment">///</span>
<span class="doccomment">/// impl<T> MyVec<T> {</span>
<span class="doccomment">/// pub fn push_all(&mut self, elems: &[T]) {</span>
<span class="doccomment">/// self.buf.reserve(self.len, elems.len());</span>
<span class="doccomment">/// // reserve would have aborted or panicked if the len exceeded</span>
<span class="doccomment">/// // `isize::MAX` so this is safe to do unchecked now.</span>
<span class="doccomment">/// for x in elems {</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// ptr::write(self.buf.ptr().offset(self.len as isize), x.clone());</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// self.len += 1;</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">reserve</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">used_cap</span>: <span class="ident">usize</span>, <span class="ident">needed_extra_cap</span>: <span class="ident">usize</span>) {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="comment">// NOTE: we don't early branch on ZSTs here because we want this</span>
<span class="comment">// to actually catch "asking for more than usize::MAX" in that case.</span>
<span class="comment">// If we make it past the first branch then we are guaranteed to</span>
<span class="comment">// panic.</span>
<span class="comment">// Don't actually need any more capacity.</span>
<span class="comment">// Wrapping in case they give a bad `used_cap`</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">cap</span>().<span class="ident">wrapping_sub</span>(<span class="ident">used_cap</span>) <span class="op">>=</span> <span class="ident">needed_extra_cap</span> {
<span class="kw">return</span>;
}
<span class="kw">let</span> (<span class="ident">new_cap</span>, <span class="ident">new_alloc_size</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">amortized_new_size</span>(<span class="ident">used_cap</span>, <span class="ident">needed_extra_cap</span>);
<span class="comment">// FIXME: may crash and burn on over-reserve</span>
<span class="ident">alloc_guard</span>(<span class="ident">new_alloc_size</span>);
<span class="kw">let</span> <span class="ident">ptr</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="ident">heap</span>::<span class="ident">allocate</span>(<span class="ident">new_alloc_size</span>, <span class="ident">align</span>)
} <span class="kw">else</span> {
<span class="ident">heap</span>::<span class="ident">reallocate</span>(<span class="self">self</span>.<span class="ident">ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _,
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">*</span> <span class="ident">elem_size</span>,
<span class="ident">new_alloc_size</span>,
<span class="ident">align</span>)
};
<span class="comment">// If allocate or reallocate fail, we'll get `null` back</span>
<span class="kw">if</span> <span class="ident">ptr</span>.<span class="ident">is_null</span>() {
<span class="ident">oom</span>()
}
<span class="self">self</span>.<span class="ident">ptr</span> <span class="op">=</span> <span class="ident">Unique</span>::<span class="ident">new</span>(<span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _);
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">=</span> <span class="ident">new_cap</span>;
}
}
<span class="doccomment">/// Attempts to ensure that the buffer contains at least enough space to hold</span>
<span class="doccomment">/// `used_cap + needed_extra_cap` elements. If it doesn't already have</span>
<span class="doccomment">/// enough capacity, will reallocate in place enough space plus comfortable slack</span>
<span class="doccomment">/// space to get amortized `O(1)` behaviour. Will limit this behaviour</span>
<span class="doccomment">/// if it would needlessly cause itself to panic.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate</span>
<span class="doccomment">/// the requested space. This is not really unsafe, but the unsafe</span>
<span class="doccomment">/// code *you* write that relies on the behaviour of this function may break.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Returns true if the reallocation attempt has succeeded, or false otherwise.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// * Panics if the requested capacity exceeds `usize::MAX` bytes.</span>
<span class="doccomment">/// * Panics on 32-bit platforms if the requested capacity exceeds</span>
<span class="doccomment">/// `isize::MAX` bytes.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">reserve_in_place</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">used_cap</span>: <span class="ident">usize</span>, <span class="ident">needed_extra_cap</span>: <span class="ident">usize</span>) <span class="op">-></span> <span class="ident">bool</span> {
<span class="kw">unsafe</span> {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="comment">// NOTE: we don't early branch on ZSTs here because we want this</span>
<span class="comment">// to actually catch "asking for more than usize::MAX" in that case.</span>
<span class="comment">// If we make it past the first branch then we are guaranteed to</span>
<span class="comment">// panic.</span>
<span class="comment">// Don't actually need any more capacity. If the current `cap` is 0, we can't</span>
<span class="comment">// reallocate in place.</span>
<span class="comment">// Wrapping in case they give a bad `used_cap`</span>
<span class="kw">if</span> <span class="self">self</span>.<span class="ident">cap</span>().<span class="ident">wrapping_sub</span>(<span class="ident">used_cap</span>) <span class="op">>=</span> <span class="ident">needed_extra_cap</span> <span class="op">||</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="bool-val">false</span>;
}
<span class="kw">let</span> (_, <span class="ident">new_alloc_size</span>) <span class="op">=</span> <span class="self">self</span>.<span class="ident">amortized_new_size</span>(<span class="ident">used_cap</span>, <span class="ident">needed_extra_cap</span>);
<span class="comment">// FIXME: may crash and burn on over-reserve</span>
<span class="ident">alloc_guard</span>(<span class="ident">new_alloc_size</span>);
<span class="kw">let</span> <span class="ident">size</span> <span class="op">=</span> <span class="ident">heap</span>::<span class="ident">reallocate_inplace</span>(<span class="self">self</span>.<span class="ident">ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _,
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">*</span> <span class="ident">elem_size</span>,
<span class="ident">new_alloc_size</span>,
<span class="ident">align</span>);
<span class="kw">if</span> <span class="ident">size</span> <span class="op">>=</span> <span class="ident">new_alloc_size</span> {
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">=</span> <span class="ident">new_alloc_size</span> <span class="op">/</span> <span class="ident">elem_size</span>;
}
<span class="ident">size</span> <span class="op">>=</span> <span class="ident">new_alloc_size</span>
}
}
<span class="doccomment">/// Shrinks the allocation down to the specified amount. If the given amount</span>
<span class="doccomment">/// is 0, actually completely deallocates.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Panics</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Panics if the given amount is *larger* than the current capacity.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Aborts</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Aborts on OOM.</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">shrink_to_fit</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>, <span class="ident">amount</span>: <span class="ident">usize</span>) {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="comment">// Set the `cap` because they might be about to promote to a `Box<[T]>`</span>
<span class="kw">if</span> <span class="ident">elem_size</span> <span class="op">==</span> <span class="number">0</span> {
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">=</span> <span class="ident">amount</span>;
<span class="kw">return</span>;
}
<span class="comment">// This check is my waterloo; it's the only thing Vec wouldn't have to do.</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="self">self</span>.<span class="ident">cap</span> <span class="op">>=</span> <span class="ident">amount</span>, <span class="string">"Tried to shrink to a larger capacity"</span>);
<span class="kw">if</span> <span class="ident">amount</span> <span class="op">==</span> <span class="number">0</span> {
<span class="ident">mem</span>::<span class="ident">replace</span>(<span class="self">self</span>, <span class="ident">RawVec</span>::<span class="ident">new</span>());
} <span class="kw">else</span> <span class="kw">if</span> <span class="self">self</span>.<span class="ident">cap</span> <span class="op">!=</span> <span class="ident">amount</span> {
<span class="kw">unsafe</span> {
<span class="comment">// Overflow check is unnecessary as the vector is already at</span>
<span class="comment">// least this large.</span>
<span class="kw">let</span> <span class="ident">ptr</span> <span class="op">=</span> <span class="ident">heap</span>::<span class="ident">reallocate</span>(<span class="self">self</span>.<span class="ident">ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _,
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">*</span> <span class="ident">elem_size</span>,
<span class="ident">amount</span> <span class="op">*</span> <span class="ident">elem_size</span>,
<span class="ident">align</span>);
<span class="kw">if</span> <span class="ident">ptr</span>.<span class="ident">is_null</span>() {
<span class="ident">oom</span>()
}
<span class="self">self</span>.<span class="ident">ptr</span> <span class="op">=</span> <span class="ident">Unique</span>::<span class="ident">new</span>(<span class="ident">ptr</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _);
}
<span class="self">self</span>.<span class="ident">cap</span> <span class="op">=</span> <span class="ident">amount</span>;
}
}
<span class="doccomment">/// Converts the entire buffer into `Box<[T]>`.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// While it is not *strictly* Undefined Behavior to call</span>
<span class="doccomment">/// this procedure while some of the RawVec is uninitialized,</span>
<span class="doccomment">/// it certainly makes it trivial to trigger it.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that this will correctly reconstitute any `cap` changes</span>
<span class="doccomment">/// that may have been performed. (see description of type for details)</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">into_box</span>(<span class="self">self</span>) <span class="op">-></span> <span class="ident">Box</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> {
<span class="comment">// NOTE: not calling `cap()` here, actually using the real `cap` field!</span>
<span class="kw">let</span> <span class="ident">slice</span> <span class="op">=</span> <span class="ident">slice</span>::<span class="ident">from_raw_parts_mut</span>(<span class="self">self</span>.<span class="ident">ptr</span>(), <span class="self">self</span>.<span class="ident">cap</span>);
<span class="kw">let</span> <span class="ident">output</span>: <span class="ident">Box</span><span class="op"><</span>[<span class="ident">T</span>]<span class="op">></span> <span class="op">=</span> <span class="ident">Box</span>::<span class="ident">from_raw</span>(<span class="ident">slice</span>);
<span class="ident">mem</span>::<span class="ident">forget</span>(<span class="self">self</span>);
<span class="ident">output</span>
}
}
<span class="kw">unsafe</span> <span class="kw">impl</span><span class="op"><</span><span class="attribute">#[<span class="ident">may_dangle</span>]</span> <span class="ident">T</span><span class="op">></span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">RawVec</span><span class="op"><</span><span class="ident">T</span><span class="op">></span> {
<span class="doccomment">/// Frees the memory owned by the RawVec *without* trying to Drop its contents.</span>
<span class="kw">fn</span> <span class="ident">drop</span>(<span class="kw-2">&</span><span class="kw-2">mut</span> <span class="self">self</span>) {
<span class="kw">let</span> <span class="ident">elem_size</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">if</span> <span class="ident">elem_size</span> <span class="op">!=</span> <span class="number">0</span> <span class="op">&&</span> <span class="self">self</span>.<span class="ident">cap</span> <span class="op">!=</span> <span class="number">0</span> {
<span class="kw">let</span> <span class="ident">align</span> <span class="op">=</span> <span class="ident">mem</span>::<span class="ident">align_of</span>::<span class="op"><</span><span class="ident">T</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">num_bytes</span> <span class="op">=</span> <span class="ident">elem_size</span> <span class="op">*</span> <span class="self">self</span>.<span class="ident">cap</span>;
<span class="kw">unsafe</span> {
<span class="ident">heap</span>::<span class="ident">deallocate</span>(<span class="self">self</span>.<span class="ident">ptr</span>() <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>, <span class="ident">num_bytes</span>, <span class="ident">align</span>);
}
}
}
}
<span class="comment">// We need to guarantee the following:</span>
<span class="comment">// * We don't ever allocate `> isize::MAX` byte-size objects</span>
<span class="comment">// * We don't overflow `usize::MAX` and actually allocate too little</span>
<span class="comment">//</span>
<span class="comment">// On 64-bit we just need to check for overflow since trying to allocate</span>
<span class="comment">// `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add</span>
<span class="comment">// an extra guard for this in case we're running on a platform which can use</span>
<span class="comment">// all 4GB in user-space. e.g. PAE or x32</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">alloc_guard</span>(<span class="ident">alloc_size</span>: <span class="ident">usize</span>) {
<span class="kw">if</span> <span class="ident">mem</span>::<span class="ident">size_of</span>::<span class="op"><</span><span class="ident">usize</span><span class="op">></span>() <span class="op"><</span> <span class="number">8</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">alloc_size</span> <span class="op"><=</span> ::<span class="ident">core</span>::<span class="ident">isize</span>::<span class="ident">MAX</span> <span class="kw">as</span> <span class="ident">usize</span>,
<span class="string">"capacity overflow"</span>);
}
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">test</span>)]</span>
<span class="kw">mod</span> <span class="ident">tests</span> {
<span class="kw">use</span> <span class="kw">super</span>::<span class="kw-2">*</span>;
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">reserve_does_not_overallocate</span>() {
{
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">v</span>: <span class="ident">RawVec</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">RawVec</span>::<span class="ident">new</span>();
<span class="comment">// First `reserve` allocates like `reserve_exact`</span>
<span class="ident">v</span>.<span class="ident">reserve</span>(<span class="number">0</span>, <span class="number">9</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">9</span>, <span class="ident">v</span>.<span class="ident">cap</span>());
}
{
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">v</span>: <span class="ident">RawVec</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">RawVec</span>::<span class="ident">new</span>();
<span class="ident">v</span>.<span class="ident">reserve</span>(<span class="number">0</span>, <span class="number">7</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">7</span>, <span class="ident">v</span>.<span class="ident">cap</span>());
<span class="comment">// 97 if more than double of 7, so `reserve` should work</span>
<span class="comment">// like `reserve_exact`.</span>
<span class="ident">v</span>.<span class="ident">reserve</span>(<span class="number">7</span>, <span class="number">90</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">97</span>, <span class="ident">v</span>.<span class="ident">cap</span>());
}
{
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">v</span>: <span class="ident">RawVec</span><span class="op"><</span><span class="ident">u32</span><span class="op">></span> <span class="op">=</span> <span class="ident">RawVec</span>::<span class="ident">new</span>();
<span class="ident">v</span>.<span class="ident">reserve</span>(<span class="number">0</span>, <span class="number">12</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="number">12</span>, <span class="ident">v</span>.<span class="ident">cap</span>());
<span class="ident">v</span>.<span class="ident">reserve</span>(<span class="number">12</span>, <span class="number">3</span>);
<span class="comment">// 3 is less than half of 12, so `reserve` must grow</span>
<span class="comment">// exponentially. At the time of writing this test grow</span>
<span class="comment">// factor is 2, so new capacity is 24, however, grow factor</span>
<span class="comment">// of 1.5 is OK too. Hence `>= 18` in assert.</span>
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">v</span>.<span class="ident">cap</span>() <span class="op">>=</span> <span class="number">12</span> <span class="op">+</span> <span class="number">12</span> <span class="op">/</span> <span class="number">2</span>);
}
}
}
</pre>
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