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</pre><pre class="rust ">
<span class="comment">// Copyright 2014 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="doccomment">//! OS-based thread local storage</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This module provides an implementation of OS-based thread local storage,</span>
<span class="doccomment">//! using the native OS-provided facilities (think `TlsAlloc` or</span>
<span class="doccomment">//! `pthread_setspecific`). The interface of this differs from the other types</span>
<span class="doccomment">//! of thread-local-storage provided in this crate in that OS-based TLS can only</span>
<span class="doccomment">//! get/set pointers,</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This module also provides two flavors of TLS. One is intended for static</span>
<span class="doccomment">//! initialization, and does not contain a `Drop` implementation to deallocate</span>
<span class="doccomment">//! the OS-TLS key. The other is a type which does implement `Drop` and hence</span>
<span class="doccomment">//! has a safe interface.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Usage</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! This module should likely not be used directly unless other primitives are</span>
<span class="doccomment">//! being built on. types such as `thread_local::spawn::Key` are likely much</span>
<span class="doccomment">//! more useful in practice than this OS-based version which likely requires</span>
<span class="doccomment">//! unsafe code to interoperate with.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! # Examples</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Using a dynamically allocated TLS key. Note that this key can be shared</span>
<span class="doccomment">//! among many threads via an `Arc`.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```rust,ignore</span>
<span class="doccomment">//! let key = Key::new(None);</span>
<span class="doccomment">//! assert!(key.get().is_null());</span>
<span class="doccomment">//! key.set(1 as *mut u8);</span>
<span class="doccomment">//! assert!(!key.get().is_null());</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! drop(key); // deallocate this TLS slot.</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! Sometimes a statically allocated key is either required or easier to work</span>
<span class="doccomment">//! with, however.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```rust,ignore</span>
<span class="doccomment">//! static KEY: StaticKey = INIT;</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! unsafe {</span>
<span class="doccomment">//! assert!(KEY.get().is_null());</span>
<span class="doccomment">//! KEY.set(1 as *mut u8);</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="attribute">#<span class="op">!</span>[<span class="ident">allow</span>(<span class="ident">non_camel_case_types</span>)]</span>
<span class="attribute">#<span class="op">!</span>[<span class="ident">unstable</span>(<span class="ident">feature</span> <span class="op">=</span> <span class="string">"thread_local_internals"</span>, <span class="ident">issue</span> <span class="op">=</span> <span class="string">"0"</span>)]</span>
<span class="attribute">#<span class="op">!</span>[<span class="ident">allow</span>(<span class="ident">dead_code</span>)]</span> <span class="comment">// sys isn't exported yet</span>
<span class="kw">use</span> <span class="ident">sync</span>::<span class="ident">atomic</span>::{<span class="self">self</span>, <span class="ident">AtomicUsize</span>, <span class="ident">Ordering</span>};
<span class="kw">use</span> <span class="ident">sys</span>::<span class="ident">thread_local</span> <span class="kw">as</span> <span class="ident">imp</span>;
<span class="kw">use</span> <span class="ident">sys_common</span>::<span class="ident">mutex</span>::<span class="ident">Mutex</span>;
<span class="doccomment">/// A type for TLS keys that are statically allocated.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This type is entirely `unsafe` to use as it does not protect against</span>
<span class="doccomment">/// use-after-deallocation or use-during-deallocation.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The actual OS-TLS key is lazily allocated when this is used for the first</span>
<span class="doccomment">/// time. The key is also deallocated when the Rust runtime exits or `destroy`</span>
<span class="doccomment">/// is called, whichever comes first.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```ignore</span>
<span class="doccomment">/// use tls::os::{StaticKey, INIT};</span>
<span class="doccomment">///</span>
<span class="doccomment">/// static KEY: StaticKey = INIT;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// unsafe {</span>
<span class="doccomment">/// assert!(KEY.get().is_null());</span>
<span class="doccomment">/// KEY.set(1 as *mut u8);</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">StaticKey</span> {
<span class="doccomment">/// Inner static TLS key (internals).</span>
<span class="ident">key</span>: <span class="ident">AtomicUsize</span>,
<span class="doccomment">/// Destructor for the TLS value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// See `Key::new` for information about when the destructor runs and how</span>
<span class="doccomment">/// it runs.</span>
<span class="ident">dtor</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw">unsafe</span> <span class="kw">extern</span> <span class="kw">fn</span>(<span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>)<span class="op">></span>,
}
<span class="doccomment">/// A type for a safely managed OS-based TLS slot.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This type allocates an OS TLS key when it is initialized and will deallocate</span>
<span class="doccomment">/// the key when it falls out of scope. When compared with `StaticKey`, this</span>
<span class="doccomment">/// type is entirely safe to use.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Implementations will likely, however, contain unsafe code as this type only</span>
<span class="doccomment">/// operates on `*mut u8`, a raw pointer.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// # Examples</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```rust,ignore</span>
<span class="doccomment">/// use tls::os::Key;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// let key = Key::new(None);</span>
<span class="doccomment">/// assert!(key.get().is_null());</span>
<span class="doccomment">/// key.set(1 as *mut u8);</span>
<span class="doccomment">/// assert!(!key.get().is_null());</span>
<span class="doccomment">///</span>
<span class="doccomment">/// drop(key); // deallocate this TLS slot.</span>
<span class="doccomment">/// ```</span>
<span class="kw">pub</span> <span class="kw">struct</span> <span class="ident">Key</span> {
<span class="ident">key</span>: <span class="ident">imp</span>::<span class="ident">Key</span>,
}
<span class="doccomment">/// Constant initialization value for static TLS keys.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This value specifies no destructor by default.</span>
<span class="kw">pub</span> <span class="kw">const</span> <span class="ident">INIT</span>: <span class="ident">StaticKey</span> <span class="op">=</span> <span class="ident">StaticKey</span>::<span class="ident">new</span>(<span class="prelude-val">None</span>);
<span class="kw">impl</span> <span class="ident">StaticKey</span> {
<span class="kw">pub</span> <span class="kw">const</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">dtor</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw">unsafe</span> <span class="kw">extern</span> <span class="kw">fn</span>(<span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>)<span class="op">></span>) <span class="op">-></span> <span class="ident">StaticKey</span> {
<span class="ident">StaticKey</span> {
<span class="ident">key</span>: <span class="ident">atomic</span>::<span class="ident">AtomicUsize</span>::<span class="ident">new</span>(<span class="number">0</span>),
<span class="ident">dtor</span>: <span class="ident">dtor</span>
}
}
<span class="doccomment">/// Gets the value associated with this TLS key</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This will lazily allocate a TLS key from the OS if one has not already</span>
<span class="doccomment">/// been allocated.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">get</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">u8</span> { <span class="ident">imp</span>::<span class="ident">get</span>(<span class="self">self</span>.<span class="ident">key</span>()) }
<span class="doccomment">/// Sets this TLS key to a new value.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This will lazily allocate a TLS key from the OS if one has not already</span>
<span class="doccomment">/// been allocated.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">val</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>) { <span class="ident">imp</span>::<span class="ident">set</span>(<span class="self">self</span>.<span class="ident">key</span>(), <span class="ident">val</span>) }
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">key</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">imp</span>::<span class="ident">Key</span> {
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">key</span>.<span class="ident">load</span>(<span class="ident">Ordering</span>::<span class="ident">Relaxed</span>) {
<span class="number">0</span> <span class="op">=></span> <span class="self">self</span>.<span class="ident">lazy_init</span>() <span class="kw">as</span> <span class="ident">imp</span>::<span class="ident">Key</span>,
<span class="ident">n</span> <span class="op">=></span> <span class="ident">n</span> <span class="kw">as</span> <span class="ident">imp</span>::<span class="ident">Key</span>
}
}
<span class="kw">unsafe</span> <span class="kw">fn</span> <span class="ident">lazy_init</span>(<span class="kw-2">&</span><span class="self">self</span>) <span class="op">-></span> <span class="ident">usize</span> {
<span class="comment">// Currently the Windows implementation of TLS is pretty hairy, and</span>
<span class="comment">// it greatly simplifies creation if we just synchronize everything.</span>
<span class="comment">//</span>
<span class="comment">// Additionally a 0-index of a tls key hasn't been seen on windows, so</span>
<span class="comment">// we just simplify the whole branch.</span>
<span class="kw">if</span> <span class="ident">imp</span>::<span class="ident">requires_synchronized_create</span>() {
<span class="kw">static</span> <span class="ident">INIT_LOCK</span>: <span class="ident">Mutex</span> <span class="op">=</span> <span class="ident">Mutex</span>::<span class="ident">new</span>();
<span class="ident">INIT_LOCK</span>.<span class="ident">lock</span>();
<span class="kw">let</span> <span class="kw-2">mut</span> <span class="ident">key</span> <span class="op">=</span> <span class="self">self</span>.<span class="ident">key</span>.<span class="ident">load</span>(<span class="ident">Ordering</span>::<span class="ident">SeqCst</span>);
<span class="kw">if</span> <span class="ident">key</span> <span class="op">==</span> <span class="number">0</span> {
<span class="ident">key</span> <span class="op">=</span> <span class="ident">imp</span>::<span class="ident">create</span>(<span class="self">self</span>.<span class="ident">dtor</span>) <span class="kw">as</span> <span class="ident">usize</span>;
<span class="self">self</span>.<span class="ident">key</span>.<span class="ident">store</span>(<span class="ident">key</span>, <span class="ident">Ordering</span>::<span class="ident">SeqCst</span>);
}
<span class="ident">INIT_LOCK</span>.<span class="ident">unlock</span>();
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">key</span> <span class="op">!=</span> <span class="number">0</span>);
<span class="kw">return</span> <span class="ident">key</span>
}
<span class="comment">// POSIX allows the key created here to be 0, but the compare_and_swap</span>
<span class="comment">// below relies on using 0 as a sentinel value to check who won the</span>
<span class="comment">// race to set the shared TLS key. As far as I know, there is no</span>
<span class="comment">// guaranteed value that cannot be returned as a posix_key_create key,</span>
<span class="comment">// so there is no value we can initialize the inner key with to</span>
<span class="comment">// prove that it has not yet been set. As such, we'll continue using a</span>
<span class="comment">// value of 0, but with some gyrations to make sure we have a non-0</span>
<span class="comment">// value returned from the creation routine.</span>
<span class="comment">// FIXME: this is clearly a hack, and should be cleaned up.</span>
<span class="kw">let</span> <span class="ident">key1</span> <span class="op">=</span> <span class="ident">imp</span>::<span class="ident">create</span>(<span class="self">self</span>.<span class="ident">dtor</span>);
<span class="kw">let</span> <span class="ident">key</span> <span class="op">=</span> <span class="kw">if</span> <span class="ident">key1</span> <span class="op">!=</span> <span class="number">0</span> {
<span class="ident">key1</span>
} <span class="kw">else</span> {
<span class="kw">let</span> <span class="ident">key2</span> <span class="op">=</span> <span class="ident">imp</span>::<span class="ident">create</span>(<span class="self">self</span>.<span class="ident">dtor</span>);
<span class="ident">imp</span>::<span class="ident">destroy</span>(<span class="ident">key1</span>);
<span class="ident">key2</span>
};
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">key</span> <span class="op">!=</span> <span class="number">0</span>);
<span class="kw">match</span> <span class="self">self</span>.<span class="ident">key</span>.<span class="ident">compare_and_swap</span>(<span class="number">0</span>, <span class="ident">key</span> <span class="kw">as</span> <span class="ident">usize</span>, <span class="ident">Ordering</span>::<span class="ident">SeqCst</span>) {
<span class="comment">// The CAS succeeded, so we've created the actual key</span>
<span class="number">0</span> <span class="op">=></span> <span class="ident">key</span> <span class="kw">as</span> <span class="ident">usize</span>,
<span class="comment">// If someone beat us to the punch, use their key instead</span>
<span class="ident">n</span> <span class="op">=></span> { <span class="ident">imp</span>::<span class="ident">destroy</span>(<span class="ident">key</span>); <span class="ident">n</span> }
}
}
}
<span class="kw">impl</span> <span class="ident">Key</span> {
<span class="doccomment">/// Creates a new managed OS TLS key.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This key will be deallocated when the key falls out of scope.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// The argument provided is an optionally-specified destructor for the</span>
<span class="doccomment">/// value of this TLS key. When a thread exits and the value for this key</span>
<span class="doccomment">/// is non-null the destructor will be invoked. The TLS value will be reset</span>
<span class="doccomment">/// to null before the destructor is invoked.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Note that the destructor will not be run when the `Key` goes out of</span>
<span class="doccomment">/// scope.</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">new</span>(<span class="ident">dtor</span>: <span class="prelude-ty">Option</span><span class="op"><</span><span class="kw">unsafe</span> <span class="kw">extern</span> <span class="kw">fn</span>(<span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>)<span class="op">></span>) <span class="op">-></span> <span class="ident">Key</span> {
<span class="ident">Key</span> { <span class="ident">key</span>: <span class="kw">unsafe</span> { <span class="ident">imp</span>::<span class="ident">create</span>(<span class="ident">dtor</span>) } }
}
<span class="doccomment">/// See StaticKey::get</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">get</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">u8</span> {
<span class="kw">unsafe</span> { <span class="ident">imp</span>::<span class="ident">get</span>(<span class="self">self</span>.<span class="ident">key</span>) }
}
<span class="doccomment">/// See StaticKey::set</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">set</span>(<span class="kw-2">&</span><span class="self">self</span>, <span class="ident">val</span>: <span class="kw-2">*</span><span class="kw-2">mut</span> <span class="ident">u8</span>) {
<span class="kw">unsafe</span> { <span class="ident">imp</span>::<span class="ident">set</span>(<span class="self">self</span>.<span class="ident">key</span>, <span class="ident">val</span>) }
}
}
<span class="kw">impl</span> <span class="ident">Drop</span> <span class="kw">for</span> <span class="ident">Key</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="comment">// Right now Windows doesn't support TLS key destruction, but this also</span>
<span class="comment">// isn't used anywhere other than tests, so just leak the TLS key.</span>
<span class="comment">// unsafe { imp::destroy(self.key) }</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="ident">Key</span>, <span class="ident">StaticKey</span>};
<span class="kw">fn</span> <span class="ident">assert_sync</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Sync</span><span class="op">></span>() {}
<span class="kw">fn</span> <span class="ident">assert_send</span><span class="op"><</span><span class="ident">T</span>: <span class="ident">Send</span><span class="op">></span>() {}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">smoke</span>() {
<span class="ident">assert_sync</span>::<span class="op"><</span><span class="ident">Key</span><span class="op">></span>();
<span class="ident">assert_send</span>::<span class="op"><</span><span class="ident">Key</span><span class="op">></span>();
<span class="kw">let</span> <span class="ident">k1</span> <span class="op">=</span> <span class="ident">Key</span>::<span class="ident">new</span>(<span class="prelude-val">None</span>);
<span class="kw">let</span> <span class="ident">k2</span> <span class="op">=</span> <span class="ident">Key</span>::<span class="ident">new</span>(<span class="prelude-val">None</span>);
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">k1</span>.<span class="ident">get</span>().<span class="ident">is_null</span>());
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">k2</span>.<span class="ident">get</span>().<span class="ident">is_null</span>());
<span class="ident">k1</span>.<span class="ident">set</span>(<span class="number">1</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _);
<span class="ident">k2</span>.<span class="ident">set</span>(<span class="number">2</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">k1</span>.<span class="ident">get</span>() <span class="kw">as</span> <span class="ident">usize</span>, <span class="number">1</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">k2</span>.<span class="ident">get</span>() <span class="kw">as</span> <span class="ident">usize</span>, <span class="number">2</span>);
}
<span class="attribute">#[<span class="ident">test</span>]</span>
<span class="kw">fn</span> <span class="ident">statik</span>() {
<span class="kw">static</span> <span class="ident">K1</span>: <span class="ident">StaticKey</span> <span class="op">=</span> <span class="ident">StaticKey</span>::<span class="ident">new</span>(<span class="prelude-val">None</span>);
<span class="kw">static</span> <span class="ident">K2</span>: <span class="ident">StaticKey</span> <span class="op">=</span> <span class="ident">StaticKey</span>::<span class="ident">new</span>(<span class="prelude-val">None</span>);
<span class="kw">unsafe</span> {
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">K1</span>.<span class="ident">get</span>().<span class="ident">is_null</span>());
<span class="macro">assert</span><span class="macro">!</span>(<span class="ident">K2</span>.<span class="ident">get</span>().<span class="ident">is_null</span>());
<span class="ident">K1</span>.<span class="ident">set</span>(<span class="number">1</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _);
<span class="ident">K2</span>.<span class="ident">set</span>(<span class="number">2</span> <span class="kw">as</span> <span class="kw-2">*</span><span class="kw-2">mut</span> _);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">K1</span>.<span class="ident">get</span>() <span class="kw">as</span> <span class="ident">usize</span>, <span class="number">1</span>);
<span class="macro">assert_eq</span><span class="macro">!</span>(<span class="ident">K2</span>.<span class="ident">get</span>() <span class="kw">as</span> <span class="ident">usize</span>, <span class="number">2</span>);
}
}
}
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