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</pre><div class="example-wrap"><pre class="rust ">
<span class="comment">// Copyright 2020 Shin Yoshida</span>
<span class="comment">//</span>
<span class="comment">// "LGPL-3.0-or-later OR Apache-2.0 OR BSD-2-Clause OR MIT"</span>
<span class="comment">//</span>
<span class="comment">// This is part of cpu-endian</span>
<span class="comment">//</span>
<span class="comment">// cpu-endian is free software: you can redistribute it and/or modify</span>
<span class="comment">// it under the terms of the GNU Lesser General Public License as published by</span>
<span class="comment">// the Free Software Foundation, either version 3 of the License, or</span>
<span class="comment">// any later version.</span>
<span class="comment">//</span>
<span class="comment">// cpu-endian is distributed in the hope that it will be useful,</span>
<span class="comment">// but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<span class="comment">// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span>
<span class="comment">// GNU Lesser General Public License for more details.</span>
<span class="comment">//</span>
<span class="comment">// You should have received a copy of the GNU Lesser General Public License</span>
<span class="comment">// along with cpu-endian. If not, see <http://www.gnu.org/licenses/>.</span>
<span class="comment">//</span>
<span class="comment">//</span>
<span class="comment">// Licensed under the Apache License, Version 2.0 (the "License");</span>
<span class="comment">// you may not use this file except in compliance with the License.</span>
<span class="comment">// You may obtain a copy of the License at</span>
<span class="comment">//</span>
<span class="comment">// http://www.apache.org/licenses/LICENSE-2.0</span>
<span class="comment">//</span>
<span class="comment">// Unless required by applicable law or agreed to in writing, software</span>
<span class="comment">// distributed under the License is distributed on an "AS IS" BASIS,</span>
<span class="comment">// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.</span>
<span class="comment">// See the License for the specific language governing permissions and</span>
<span class="comment">// limitations under the License.</span>
<span class="comment">//</span>
<span class="comment">//</span>
<span class="comment">// Redistribution and use in source and binary forms, with or without modification, are permitted</span>
<span class="comment">// provided that the following conditions are met:</span>
<span class="comment">//</span>
<span class="comment">// 1. Redistributions of source code must retain the above copyright notice, this list of</span>
<span class="comment">// conditions and the following disclaimer.</span>
<span class="comment">// 2. Redistributions in binary form must reproduce the above copyright notice, this</span>
<span class="comment">// list of conditions and the following disclaimer in the documentation and/or other</span>
<span class="comment">// materials provided with the distribution.</span>
<span class="comment">//</span>
<span class="comment">// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND</span>
<span class="comment">// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED</span>
<span class="comment">// WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.</span>
<span class="comment">// IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,</span>
<span class="comment">// INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT</span>
<span class="comment">// NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR</span>
<span class="comment">// PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,</span>
<span class="comment">// WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)</span>
<span class="comment">// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE</span>
<span class="comment">// POSSIBILITY OF SUCH DAMAGE.</span>
<span class="comment">//</span>
<span class="comment">//</span>
<span class="comment">// Permission is hereby granted, free of charge, to any person obtaining a copy of this software</span>
<span class="comment">// and associated documentation files (the "Software"), to deal in the Software without</span>
<span class="comment">// restriction, including without limitation the rights to use, copy, modify, merge, publish,</span>
<span class="comment">// distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the</span>
<span class="comment">// Software is furnished to do so, subject to the following conditions:</span>
<span class="comment">//</span>
<span class="comment">// The above copyright notice and this permission notice (including the next paragraph) shall be</span>
<span class="comment">// included in all copies or substantial portions of the Software.</span>
<span class="comment">//</span>
<span class="comment">// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING</span>
<span class="comment">// BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND</span>
<span class="comment">// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,</span>
<span class="comment">// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,</span>
<span class="comment">// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.</span>
<span class="attribute">#![<span class="ident">deny</span>(<span class="ident">missing_docs</span>)]</span>
<span class="doccomment">//! # cpu-endian</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! `cpu-endian` is a portable crate to detect CPU byte order.</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! It detects how CPU native scalar type is ordered; little-endian or big-endian, or something else (like PDP-endian, mixed-endian, middle-endian, and so on.)</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ## Examples</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! ```</span>
<span class="doccomment">//! use cpu_endian::{Endian, working};</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // Takes first octet of 0x00ff: u16.</span>
<span class="doccomment">//! let v: u16 = 0x00ff;</span>
<span class="doccomment">//! let first_octet: u8 = unsafe {</span>
<span class="doccomment">//! let ptr = &v as *const u16;</span>
<span class="doccomment">//! let ptr = ptr as *const u8;</span>
<span class="doccomment">//! *ptr</span>
<span class="doccomment">//! };</span>
<span class="doccomment">//!</span>
<span class="doccomment">//! // If the byte-order is little-endian, the first octet should be 0xff, or if big-endian,</span>
<span class="doccomment">//! // it should be 0x00.</span>
<span class="doccomment">//! match working() {</span>
<span class="doccomment">//! Endian::Little => assert_eq!(0xff, first_octet),</span>
<span class="doccomment">//! Endian::Big => assert_eq!(0x00, first_octet),</span>
<span class="doccomment">//! _ => {},</span>
<span class="doccomment">//! }</span>
<span class="doccomment">//! ```</span>
<span class="kw">use</span> <span class="ident">core</span>::<span class="ident">cell</span>::<span class="ident">Cell</span>;
<span class="doccomment">/// Byte order of scalar types.</span>
<span class="attribute">#[<span class="ident">derive</span>(<span class="ident">Debug</span>, <span class="ident">Clone</span>, <span class="ident">Copy</span>, <span class="ident">PartialEq</span>, <span class="ident">Eq</span>)]</span>
<span class="kw">pub</span> <span class="kw">enum</span> <span class="ident">Endian</span> {
<span class="doccomment">/// little-endian</span>
<span class="ident">Little</span>,
<span class="doccomment">/// big-endian</span>
<span class="ident">Big</span>,
<span class="doccomment">/// Neither little-endian nor big-endian. For example, PDP-endian, mixed-endian, middle-endian, and so on.</span>
<span class="doccomment">/// (Such endian is very rare today.)</span>
<span class="ident">Minor</span>,
}
<span class="macro">thread_local</span><span class="macro">!</span>(
<span class="doccomment">/// Cache of native_().</span>
<span class="doccomment">///</span>
<span class="doccomment">/// Some CPUs change the byte order, however I don't think none of them changes it after process started.</span>
<span class="kw">static</span> <span class="ident">CACHE</span>: <span class="ident">Cell</span><span class="op"><</span><span class="ident">u8</span><span class="op">></span> <span class="op">=</span> <span class="ident">Cell</span>::<span class="ident">new</span>(<span class="number">0</span>)
);
<span class="doccomment">/// Returns the CPU byte order.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// ```</span>
<span class="doccomment">/// use cpu_endian::*;</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // Takes first octet of 0x00ff: u16.</span>
<span class="doccomment">/// let v: u16 = 0x00ff;</span>
<span class="doccomment">/// let first_octet: u8 = unsafe {</span>
<span class="doccomment">/// let ptr = &v as *const u16;</span>
<span class="doccomment">/// let ptr = ptr as *const u8;</span>
<span class="doccomment">/// *ptr</span>
<span class="doccomment">/// };</span>
<span class="doccomment">///</span>
<span class="doccomment">/// // If the byte-order is little-endian, the first octet should be 0xff, or if big-endian,</span>
<span class="doccomment">/// // it should be 0x00.</span>
<span class="doccomment">/// match working() {</span>
<span class="doccomment">/// Endian::Little => assert_eq!(0xff, first_octet),</span>
<span class="doccomment">/// Endian::Big => assert_eq!(0x00, first_octet),</span>
<span class="doccomment">/// _ => {},</span>
<span class="doccomment">/// }</span>
<span class="doccomment">/// ```</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">pub</span> <span class="kw">fn</span> <span class="ident">working</span>() <span class="op">-</span><span class="op">></span> <span class="ident">Endian</span> {
<span class="ident">inner_working</span>()
}
<span class="doccomment">/// Implementation for `working` .</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is only for `x86` and `x86_64` architecture, and const function to return</span>
<span class="doccomment">/// `Endian::Little` . ( `x86` and `x86_64` are typical little-endian CPU.)</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>))]</span>
<span class="kw">const</span> <span class="kw">fn</span> <span class="ident">inner_working</span>() <span class="op">-</span><span class="op">></span> <span class="ident">Endian</span> {
<span class="ident">Endian</span>::<span class="ident">Little</span>
}
<span class="doccomment">/// Implementation for `working` .</span>
<span class="doccomment">///</span>
<span class="doccomment">/// This function is for CPUs but `x86` nor `x86_64` and calls C function to detect the endian.</span>
<span class="doccomment">/// (Some CPUs can switch the endian, so it is difficult to hard cord.)</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>)))]</span>
<span class="attribute">#[<span class="ident">inline</span>]</span>
<span class="kw">fn</span> <span class="ident">inner_working</span>() <span class="op">-</span><span class="op">></span> <span class="ident">Endian</span> {
<span class="comment">// No cache is hit.</span>
<span class="comment">// Because native()_ always returns the same value, Ordering::Relaxed will do.</span>
<span class="kw">if</span> <span class="ident">CACHE</span>.<span class="ident">with</span>(<span class="op">|</span><span class="ident">c</span><span class="op">|</span> <span class="ident">c</span>.<span class="ident">get</span>()) <span class="op">=</span><span class="op">=</span> <span class="number">0</span> {
<span class="kw">let</span> <span class="ident">order</span> <span class="op">=</span> <span class="kw">unsafe</span> { <span class="ident">native_</span>() };
<span class="macro">debug_assert_ne</span><span class="macro">!</span>(<span class="number">0</span>, <span class="ident">order</span>);
<span class="ident">CACHE</span>.<span class="ident">with</span>(<span class="op">|</span><span class="ident">c</span><span class="op">|</span> <span class="ident">c</span>.<span class="ident">set</span>(<span class="ident">order</span> <span class="kw">as</span> <span class="ident">u8</span>));
}
<span class="kw">match</span> <span class="ident">CACHE</span>.<span class="ident">with</span>(<span class="op">|</span><span class="ident">c</span><span class="op">|</span> <span class="ident">c</span>.<span class="ident">get</span>()) {
<span class="number">1</span> <span class="op">=</span><span class="op">></span> <span class="ident">Endian</span>::<span class="ident">Little</span>,
<span class="number">2</span> <span class="op">=</span><span class="op">></span> <span class="ident">Endian</span>::<span class="ident">Big</span>,
<span class="kw">_</span> <span class="op">=</span><span class="op">></span> <span class="ident">Endian</span>::<span class="ident">Minor</span>,
}
}
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>)))]</span>
<span class="kw">use</span> <span class="ident">std</span>::<span class="ident">os</span>::<span class="ident">raw</span>::<span class="ident">c_int</span>;
<span class="attribute">#[<span class="ident">link</span>(<span class="ident">name</span> <span class="op">=</span> <span class="string">"native_endian_"</span>)]</span>
<span class="attribute">#[<span class="ident">cfg</span>(<span class="ident">not</span>(<span class="ident">any</span>(<span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86"</span>, <span class="ident">target_arch</span> <span class="op">=</span> <span class="string">"x86_64"</span>)))]</span>
<span class="kw">extern</span> <span class="string">"C"</span> {
<span class="doccomment">/// Returns the cpu native endian.</span>
<span class="doccomment">///</span>
<span class="doccomment">/// - Little endian: 1</span>
<span class="doccomment">/// - Big endian: 2</span>
<span class="doccomment">/// - Other: 3</span>
<span class="kw">fn</span> <span class="ident">native_</span>() <span class="op">-</span><span class="op">></span> <span class="ident">c_int</span>;
}
</pre></div>
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