使用 Rust 创建 PHP 扩展

使用 Rust 创建 PHP 扩展

去年十月，我和 Etsy 的同事有过一个关于如何为像PHP样的解释性语言写拓展的讨论，Ruby或Python目前的状况应该会比PHP容易。我们谈到了写一个成功创建扩展的障碍是它们通常需要用C来写，但是如果你不擅长C这门语言的话很难有那个信心。

从那时起我便萌生了用Rust写一个的想法，过去的几天一直在尝试。今天上午我终于让它运行了。
C或PHP中的Rust

我的基本出发点就是写一些可以编译的Rust代码到一个库里面，并写为它一些C的头文件，在C中为被调用的PHP做一个拓展。虽然并不是很简单，但是很有趣。
Rust FFIforeign function interface）

我所做的第一件事情就是摆弄Rust与C连接的Rust的外部函数接口。我曾用简单的方法hello_from_rust）写过一个灵活的库，伴有单一的声明a pointer to a C char, otherwise known as a string），如下是输入后输出的“Hello from Rust”。

<ol class="dp-c"><li class="alt"><span><span class="comment">// hello_from_rust.rs</span><span> </span></span></li><li><span>#![crate_type = <span class="string">"staticlib"</span><span>] </span></span></li><li class="alt"><span> </span></li><li><span>#![feature(libc)] </span></li><li class="alt"><span>extern crate libc; </span></li><li><span><span class="keyword">use</span><span> std::ffi::CStr; </span></span></li><li class="alt"><span> </span></li><li><span>#[no_mangle] </span></li><li class="alt"><span>pub extern <span class="string">"C"</span><span> fn hello_from_rust(name: *</span><span class="keyword">const</span><span> libc::c_char) { </span></span></li><li><span>let buf_name = unsafe { CStr::from_ptr(name).to_bytes() }; </span></li><li class="alt"><span>let str_name = String::from_utf8(buf_name.to_vec()).unwrap(); </span></li><li><span>let c_name = format!(<span class="string">"Hello from Rust, {}"</span><span>, str_name); </span></span></li><li class="alt"><span>println!(<span class="string">"{}"</span><span>, c_name); </span></span></li><li><span>} </span></li></ol>

我从C或其它！）中调用的Rust库拆分它。这有一个接下来会怎样的很好的解释。

编译它会得到.a的一个文件，libhello_from_rust.a。这是一个静态的库，包含它自己所有的依赖关系，而且我们在编译一个C程序的时候链接它，这让我们能做后续的事情。注意：在我们编译后会得到如下输出：

<ol class="dp-c"><li class="alt"><span><span>note: link against the following native artifacts when linking against this </span><span class="keyword">static</span><span> library </span></span></li><li><span>note: the order <span class="keyword">and</span><span> any duplication can be significant on some platforms, </span><span class="keyword">and</span><span> so may need to be preserved </span></span></li><li class="alt"><span>note: library: Systemnote: library: pthread </span></li><li><span>note: library: c </span></li><li class="alt"><span>note: library: m </span></li></ol>

这就是Rust编译器在我们不使用这个依赖的时候所告诉我们需要链接什么。
从C中调用Rust

既然我们有了一个库，不得不做两件事来保证它从C中可调用。首先，我们需要为它创建一个C的头文件，hello_from_rust.h。然后在我们编译的时候链接到它。

下面是头文件：

<ol class="dp-c"><li class="alt"><span><span>note: link against the following native artifacts when linking against this </span><span class="keyword">static</span><span> library </span></span></li><li><span>note: the order <span class="keyword">and</span><span> any duplication can be significant on some platforms, </span><span class="keyword">and</span><span> so may need to be preserved </span></span></li><li class="alt"><span>note: library: Systemnote: library: pthread </span></li><li><span>note: library: c </span></li><li class="alt"><span>note: library: m </span></li></ol>

这是一个相当基础的头文件，仅仅为了一个简单的函数提供签名/定义。接着我们需要写一个C程序并使用它。

<ol class="dp-c"><li class="alt"><span><span class="comment">// hello.c</span><span> </span></span></li><li><span>#<span class="keyword">include</span><span> <stdio.h> </span></span></li><li class="alt"><span>#<span class="keyword">include</span><span> <stdlib.h> </span></span></li><li><span>#<span class="keyword">include</span><span> </span><span class="string">"hello_from_rust.h"</span><span> </span></span></li><li class="alt"><span> </span></li><li><span>int main(int argc, char *argv[]) { </span></li><li class="alt"><span>hello_from_rust(<span class="string">"Jared!"</span><span>); </span></span></li><li><span>} </span></li></ol>

我们通过运行一下代码来编译它：

gcc -Wall -o hello_c hello.c -L /Users/jmcfarland/code/rust/php-hello-rust -lhello_from_rust -lSystem -lpthread -lc -lm

注意在末尾的-lSystem -lpthread -lc -lm告诉gcc不要链接那些“本地的古董”，为了当编译我们的Rust库时Rust编译器可以提供出来。

经运行下面的代码我们可以得到一个二进制的文件：

<ol class="dp-c"><li class="alt"><span><span>$ ./hello_c </span></span></li><li><span>Hello from Rust, Jared! </span></li></ol>

漂亮！我们刚才从C中调用了Rust库。现在我们需要理解Rust库是如何进入一个PHP扩展的。

从 php 中调用 c

该部分花了我一些时间来弄明白，在这个世界上，该文档在 php 扩展中并不是最好的。最好的部分是来自绑定一个脚本 ext_skel 的 php 源大多数代表“扩展骨架”）即生成大多数你需要的样板代码。为了让代码运行，我十分努力地学习 php 文档，“扩展骨骼”。

你可以通过下载来开始，和未配额的 php 源，把代码写进 php 目录并且运行：

<ol class="dp-c"><li class="alt"><span><span>$ cd ext/ </span></span></li><li><span>$ ./ext_skel &ndash;extname=hello_from_rust </span></li></ol>

这将生成需要创建 php 扩展的基本骨架。现在，移动你处处想局部地保持你的扩展的文件夹。并且移动你的

.rust 源

.rust库

.c header

进入同一个目录。因此，现在你应该看看像这样的一个目录：

.
├── CREDITS
├── EXPERIMENTAL
├── config.m4
├── config.w32
├── hello_from_rust.c
├── hello_from_rust.h
├── hello_from_rust.php
├── hello_from_rust.rs
├── libhello_from_rust.a
├── php_hello_from_rust.h
└── tests
└── 001.phpt

一个目录，11个文件

你可以在 php docs 在上面看到关于这些文件很好的描述。建立一个扩展的文件。我们将通过编辑 config.m4 来开始吧。

不解释，下面就是我的成果：

<ol class="dp-c"><li class="alt"><span><span>PHP_ARG_WITH(hello_from_rust, </span><span class="keyword">for</span><span> hello_from_rust support, </span></span></li><li><span>[ --with-hello_from_rust Include hello_from_rust support]) </span></li><li class="alt"><span> </span></li><li><span><span class="keyword">if</span><span> test </span><span class="string">"$PHP_HELLO_FROM_RUST"</span><span> != </span><span class="string">"no"</span><span>; then </span></span></li><li class="alt"><span>PHP_SUBST(HELLO_FROM_RUST_SHARED_LIBADD) </span></li><li><span> </span></li><li class="alt"><span>PHP_ADD_LIBRARY_WITH_PATH(hello_from_rust, ., HELLO_FROM_RUST_SHARED_LIBADD) </span></li><li><span> </span></li><li class="alt"><span>PHP_NEW_EXTENSION(hello_from_rust, hello_from_rust.c, <span class="vars">$ext_shared</span><span>) </span></span></li><li><span>fi </span></li></ol>

正如我所理解的那样，这些是基本的宏命令。但是有关这些宏命令的文档是相当糟糕的比如：google”PHP_ADD_LIBRARY_WITH_PATH”并没有出现PHP团队所写的结果）。我偶然这个PHP_ADD_LIBRARY_PATH宏命令在有些人所谈论的在一个PHP拓展里链接一个静态库的先前的线程里。在评论中其它的推荐使用的宏命令是在我运行ext_skel后产生的。

既然我们进行了配置设置，我们需要从PHP脚本中实际地调用库。为此我们得修改自动生成的文件，hello_from_rust.c。首先我们添加hello_from_rust.h头文件到包含命令中。然后我们要修改confirm_hello_from_rust_compiled的定义方法。

<ol class="dp-c"><li class="alt"><span><span>#</span><span class="keyword">include</span><span> </span><span class="string">"hello_from_rust.h"</span><span> </span></span></li><li><span> </span></li><li class="alt"><span><span class="comment">// a bunch of comments and code removed...</span><span> </span></span></li><li><span> </span></li><li class="alt"><span>PHP_FUNCTION(confirm_hello_from_rust_compiled) </span></li><li><span>{ </span></li><li class="alt"><span>char *arg = NULL; </span></li><li><span>int arg_len, len; </span></li><li class="alt"><span>char *strg; </span></li><li><span> </span></li><li class="alt"><span><span class="keyword">if</span><span> (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, </span><span class="string">"s"</span><span>, &arg, &arg_len) == FAILURE) { </span></span></li><li><span><span class="keyword">return</span><span>; </span></span></li><li class="alt"><span>} </span></li><li><span> </span></li><li class="alt"><span>hello_from_rust(<span class="string">"Jared (from PHP!!)!"</span><span>); </span></span></li><li><span> </span></li><li class="alt"><span>len = spprintf(&strg, 0, <span class="string">"Congratulations! You have successfully modified ext/%.78s/config.m4. Module %.78s is now compiled into PHP."</span><span>, </span><span class="string">"hello_from_rust"</span><span>, arg); </span></span></li><li><span>RETURN_STRINGL(strg, len, 0); </span></li><li class="alt"><span>} </span></li></ol>

注意：我添加了hello_from_rust(“Jared (fromPHP!!)!”);。

现在，我们可以试着建立我们的扩展：

<ol class="dp-c"><li class="alt"><span><span>$ phpize </span></span></li><li><span>$ ./configure </span></li><li class="alt"><span>$ sudo make install </span></li></ol>

就是它，生成我们的元配置，运行生成的配置命令，然后安装该扩展。安装时，我必须亲自使用sudo，因为我的用户并不拥有安装目录的 php 扩展。

现在，我们可以运行它啦！

<ol class="dp-c"><li class="alt"><span><span>$ php hello_from_rust.php </span></span></li><li><span>Functions available in the test extension: </span></li><li class="alt"><span>confirm_hello_from_rust_compiled </span></li><li><span> </span></li><li class="alt"><span>Hello from Rust, Jared (from PHP!!)! </span></li><li><span>Congratulations! You have successfully modified ext/hello_from_rust/config.m4. Module hello_from_rust is now compiled into PHP. </span></li><li class="alt"><span>Segmentation fault: 11 </span></li></ol>

还不错，php 已进入我们的 c 扩展，看到我们的应用方法列表并且调用。接着，c 扩展已进入我们的 rust 库，开始打印我们的字符串。那很有趣！但是……那段错误的结局发生了什么？

正如我所提到的，这里是使用了 Rust 相关的 println! 宏，但是我没有对它做进一步的调试。如果我们从我们的 Rust 库中删除并返回一个 char* 替代，段错误就会消失。

这里是 Rust 的代码：

<ol class="dp-c"><li class="alt"><span><span>#![crate_type = </span><span class="string">"staticlib"</span><span>] </span></span></li><li><span> </span></li><li class="alt"><span>#![feature(libc)] </span></li><li><span>extern crate libc; </span></li><li class="alt"><span><span class="keyword">use</span><span> std::ffi::{CStr, CString}; </span></span></li><li><span> </span></li><li class="alt"><span>#[no_mangle] </span></li><li><span>pub extern <span class="string">"C"</span><span> fn hello_from_rust(name: *</span><span class="keyword">const</span><span> libc::c_char) -> *</span><span class="keyword">const</span><span> libc::c_char { </span></span></li><li class="alt"><span>let buf_name = unsafe { CStr::from_ptr(name).to_bytes() }; </span></li><li><span>let str_name = String::from_utf8(buf_name.to_vec()).unwrap(); </span></li><li class="alt"><span>let c_name = format!(<span class="string">"Hello from Rust, {}"</span><span>, str_name); </span></span></li><li><span> </span></li><li class="alt"><span>CString::<span class="keyword">new</span><span>(c_name).unwrap().as_ptr() </span></span></li><li><span>} </span></li></ol>

并变更 C 头文件：

<ol class="dp-c"><li class="alt"><span><span>#ifndef __HELLO </span></span></li><li><span>#define __HELLO </span></li><li><span><span class="keyword">const</span><span> char * hello_from_rust(</span><span class="keyword">const</span><span> char *name); </span></span></li><li><span>#<span class="keyword">endif</span><span> </span></span></li></ol>

还要变更 C 扩展文件：

<ol class="dp-c"><li class="alt"><span><span>PHP_FUNCTION(confirm_hello_from_rust_compiled) </span></span></li><li><span>{ </span></li><li class="alt"><span>char *arg = NULL; </span></li><li><span>int arg_len, len; </span></li><li class="alt"><span>char *strg; </span></li><li><span> </span></li><li class="alt"><span><span class="keyword">if</span><span> (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, </span><span class="string">"s"</span><span>, &arg, &arg_len) == FAILURE) { </span></span></li><li><span><span class="keyword">return</span><span>; </span></span></li><li class="alt"><span>} </span></li><li><span> </span></li><li class="alt"><span>char *str; </span></li><li><span>str = hello_from_rust(<span class="string">"Jared (from PHP!!)!"</span><span>); </span></span></li><li class="alt"><span>printf(<span class="string">"%s/n"</span><span>, str); </span></span></li><li><span> </span></li><li class="alt"><span>len = spprintf(&strg, 0, <span class="string">"Congratulations! You have successfully modified ext/%.78s/config.m4. Module %.78s is now compiled into PHP."</span><span>, </span><span class="string">"hello_from_rust"</span><span>, arg); </span></span></li><li><span>RETURN_STRINGL(strg, len, 0); </span></li><li class="alt"><span>} </span></li></ol>

无用的微基准

那么为什么你还要这样做？我还真的没有在现实世界里使用过这个。但是我真的认为斐波那契序列算法就是一个好的例子来说明一个PHP拓展如何很基本。通常是直截了当在Ruby中）：

<ol class="dp-c"><li class="alt"><span><span>def fib(at) </span><span class="keyword">do</span><span> </span></span></li><li><span><span class="keyword">if</span><span> (at == 1 || at == 0) </span></span></li><li class="alt"><span><span class="keyword">return</span><span> at </span></span></li><li><span><span class="keyword">else</span><span> </span></span></li><li class="alt"><span><span class="keyword">return</span><span> fib(at - 1) + fib(at - 2) </span></span></li><li><span><span class="func">end</span><span> </span></span></li><li class="alt"><span><span class="func">end</span><span> </span></span></li></ol>

而且可以通过不使用递归来改善这不好的性能：

<ol class="dp-c"><li class="alt"><span><span>def fib(at) </span><span class="keyword">do</span><span> </span></span></li><li><span><span class="keyword">if</span><span> (at == 1 || at == 0) </span></span></li><li class="alt"><span><span class="keyword">return</span><span> at </span></span></li><li><span>elsif (val = @cache[at]).present? </span></li><li class="alt"><span><span class="keyword">return</span><span> val </span></span></li><li><span><span class="func">end</span><span> </span></span></li><li class="alt"><span> </span></li><li><span>total = 1 </span></li><li class="alt"><span>parent = 1 </span></li><li><span>gp = 1 </span></li><li class="alt"><span> </span></li><li><span>(1..at).each <span class="keyword">do</span><span> |i| </span></span></li><li class="alt"><span>total = parent + gp </span></li><li><span>gp = parent </span></li><li class="alt"><span>parent = total </span></li><li><span><span class="func">end</span><span> </span></span></li><li class="alt"><span> </span></li><li><span><span class="keyword">return</span><span> total </span></span></li><li class="alt"><span><span class="func">end</span><span> </span></span></li></ol>

那么我们围绕它来写两个例子，一个在PHP中，一个在Rust中。看看哪个更快。下面是PHP版：

<ol class="dp-c"><li class="alt"><span><span>def fib(at) </span><span class="keyword">do</span><span> </span></span></li><li><span><span class="keyword">if</span><span> (at == 1 || at == 0) </span></span></li><li class="alt"><span><span class="keyword">return</span><span> at </span></span></li><li><span>elsif (val = @cache[at]).present? </span></li><li class="alt"><span><span class="keyword">return</span><span> val </span></span></li><li><span><span class="func">end</span><span> </span></span></li><li class="alt"><span> </span></li><li><span>total = 1 </span></li><li class="alt"><span>parent = 1 </span></li><li><span>gp = 1 </span></li><li class="alt"><span> </span></li><li><span>(1..at).each <span class="keyword">do</span><span> |i| </span></span></li><li class="alt"><span>total = parent + gp </span></li><li><span>gp = parent </span></li><li class="alt"><span>parent = total </span></li><li><span><span class="func">end</span><span> </span></span></li><li class="alt"><span> </span></li><li><span><span class="keyword">return</span><span> total </span></span></li><li class="alt"><span><span class="func">end</span><span> </span></span></li><li><span> </span></li><li class="alt"><span>这是它的运行结果： </span></li><li><span> </span></li><li class="alt"><span>$ time php php_fib.php </span></li><li><span> </span></li><li class="alt"><span>real 0m2.046s </span></li><li><span>user 0m1.823s </span></li><li class="alt"><span>sys 0m0.207s </span></li><li><span> </span></li><li class="alt"><span>现在我们来做Rust版。下面是库资源： </span></li><li><span> </span></li><li class="alt"><span>#![crate_type = <span class="string">"staticlib"</span><span>] </span></span></li><li><span> </span></li><li class="alt"><span>fn fib(at: usize) -> usize { </span></li><li><span><span class="keyword">if</span><span> at == 0 { </span></span></li><li class="alt"><span><span class="keyword">return</span><span> 0; </span></span></li><li><span>} <span class="keyword">else</span><span> </span><span class="keyword">if</span><span> at == 1 { </span></span></li><li class="alt"><span><span class="keyword">return</span><span> 1; </span></span></li><li><span>} </span></li><li class="alt"><span> </span></li><li><span>let mut total = 1; </span></li><li class="alt"><span>let mut parent = 1; </span></li><li><span>let mut gp = 0; </span></li><li class="alt"><span><span class="keyword">for</span><span> _ in 1 .. at { </span></span></li><li><span>total = parent + gp; </span></li><li class="alt"><span>gp = parent; </span></li><li><span>parent = total; </span></li><li class="alt"><span>} </span></li><li><span> </span></li><li class="alt"><span><span class="keyword">return</span><span> total; </span></span></li><li><span>} </span></li><li class="alt"><span> </span></li><li><span>#[no_mangle] </span></li><li class="alt"><span>pub extern <span class="string">"C"</span><span> fn rust_fib(at: usize) -> usize { </span></span></li><li><span>fib(at) </span></li><li class="alt"><span>} </span></li><li><span> </span></li><li class="alt"><span>注意，我编译的库rustc &ndash; O rust_lib.rs使编译器优化因为我们是这里的标准）。这里是C扩展源相关摘录）： </span></li><li><span> </span></li><li class="alt"><span>PHP_FUNCTION(confirm_rust_fib_compiled) </span></li><li><span>{ </span></li><li class="alt"><span>long number; </span></li><li><span> </span></li><li class="alt"><span><span class="keyword">if</span><span> (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, </span><span class="string">"l"</span><span>, &number) == FAILURE) { </span></span></li><li><span><span class="keyword">return</span><span>; </span></span></li><li class="alt"><span>} </span></li><li><span> </span></li><li class="alt"><span>RETURN_LONG(rust_fib(number)); </span></li><li><span>} </span></li></ol>

运行ＰＨＰ脚本：

<ol class="dp-c"><li class="alt"><span><span><?php </span></span></li><li><span><span class="vars">$br</span><span> = (php_sapi_name() == </span><span class="string">"cli"</span><span>)? </span><span class="string">""</span><span>:</span><span class="string">"<br>"</span><span>; </span></span></li><li class="alt"><span> </span></li><li><span><span class="keyword">if</span><span>(!</span><span class="func">extension_loaded</span><span>(</span><span class="string">'rust_fib'</span><span>)) { </span></span></li><li class="alt"><span>dl(<span class="string">'rust_fib.'</span><span> . PHP_SHLIB_SUFFIX); </span></span></li><li><span>} </span></li><li class="alt"><span> </span></li><li><span><span class="keyword">for</span><span> (</span><span class="vars">$i</span><span> = 0; </span><span class="vars">$i</span><span> < 100000; </span><span class="vars">$i</span><span> ++) { </span></span></li><li class="alt"><span>confirm_rust_fib_compiled(92); </span></li><li><span>} </span></li><li class="alt"><span>?> </span></li><li><span> </span></li><li class="alt"><span>这就是它的运行结果： </span></li><li><span> </span></li><li class="alt"><span>$ time php rust_fib.php </span></li><li><span> </span></li><li class="alt"><span>real 0m0.586s </span></li><li><span>user 0m0.342s </span></li><li class="alt"><span>sys 0m0.221s </span></li></ol>

你可以看见它比前者快了三倍！完美的Rust微基准！

总结

这里几乎没有得出什么结论。我不确定在Rust上写一个PHP的扩展是一个好的想法，但是花费一些时间去研究Rust，PHP和C，这是一个很好的方式。

如果你希望查看所有代码或者查看更改记录，可以访问GitHub Repo。

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