Home > Article > Backend Development > pack, unpack homemade binary "database", packunpack_PHP tutorial
pack、unpack函数,如果没有接触过socket,这个可能会比较陌生,这两个函数在socket交互的作用是组包,将数据装进一个二进制字符串,和对二进制字符串中的数据进行解包,这个里面有好多种格式,具体的格式可以去查查官方的手册(或者等看完本篇文章之后,去调用接口查看),我这里主要用了pack(“N”,int),pack(“a”,str)以及他们两个对应的解包函数,N在手册中的解释是下面这个,占4个字节,大端方式(其实就是低位在前还是在后的问题)。a是对字符串进行打包,不够指定的数值的时候用NULL(\0,或者说assic码0对应的字符)填充。
<p>N - unsigned long (always 32 bit, big endian byte order)</p>
<p>a - NUL-padded string</p>
我将用这个打包解包函数做一个函数手册查询小工具,或者可以说是一个自制小型二进制数据库。
在做这个二进制文件数据库的时候我会创建两个文件,一个是索引文件,一个是要查询的数据的文件,分别看看他们的结构:
说明中括号内的数字为所占字节(bytes)数,"~"波浪线表示所占字节数不确定
数据文件,第一个php是一个正式的字符串"php",占4个字节,后面跟着版本说明,长度不确定(这个长度可以从后面的index文件中获取),接下来后面是存储信息的主体了。首先是一个函数名长度lenName占4个字节,接下来是函数名称,长度不确定,有前面的lenName对应的值确定,接下来是lenVal占4个字节,后面跟的是具体的函数说明内容,长度有前面的lenVal对应的值确定。
<pre class="code"><span> 内容存储格式定义 </span>++++++++++++++++++++++++++++++++++++++ |php(<span>4</span>) |版本说明(~) | ++++++++++++++++++++++++++++++++++++++ |lenName(<span>4</span>) |函数名称(~) | ++++++++++++++++++++++++++++++++++++++ |lenVal(<span>4</span>) |函数内容(~) | ++++++++++++++++++++++++++++++++++++++<span> ......</span>
索引文件,索引文件就比较简单了,其中全部存储了上面的存储文件中每个函数开始的指针位置,每个位置占用4个字节。
<pre class="code"><span>索引格式定义 </span>++++++++++++++++++++++++++++++++++++++ |position(<span>4</span>) | ++++++++++++++++++++++++++++++++++++++<span> ......</span>
由于存储文件中的内容是按照函数名顺序排序存储的,索引也是按照函数存储的顺序存储的,所以获取起来很方便,直接使用二分法就可以很轻松的获取到想要的函数
在查询的时候主要使用了下面几个方法:
第一、从制定位置获取一条索引的值(也就是对应的函数存储文件的指针位置)
<pre class="code"><span>/*</span><span>* * 从索引文件中获取一条记录的位置 * @param 索引文件中的开始位置,从开始位置获取四个字节为一个函数说明的开始位置 * @return 返回该索引位置所对应的存储位置指针偏移量 </span><span>*/</span> <span>private</span> <span>function</span> _getOneIndex(<span>$pos</span><span>) { </span><span>fseek</span>(<span>$this</span>->_indexHandle, <span>$pos</span><span>); </span><span>$len</span> = <span>unpack</span>("Nlen", <span>fread</span>(<span>$this</span>->_indexHandle, 4<span>)); </span><span>return</span> <span>$len</span>['len'<span>]; }</span>
第二、从指定的指针偏移位置获取一条len(4)+val(~)格式的内容
<pre class="code"><span>/*</span><span>* * 从制定的指针偏移量获取一个len+val型的内容 * @param $pos 文件的指针偏移量 * @return 返回数组,包括长度和值 </span><span>*/</span> <span>private</span> <span>function</span> _getStoreLenValFormat(<span>$pos</span><span>){ </span><span>fseek</span>(<span>$this</span>->_storeHandle, <span>$pos</span><span>); </span><span>$len</span> = <span>unpack</span>("Nlen", <span>fread</span>(<span>$this</span>->_storeHandle, 4<span>)); </span><span>$len</span> = <span>$len</span>['len'<span>]; </span><span>$val</span> = <span>fread</span>(<span>$this</span>->_storeHandle, <span>$len</span><span>); </span><span>return</span> <span>array</span><span> ( </span>'len' => <span>$len</span>, 'value' => <span>$val</span>,<span> ); }</span>
第三、获取制定函数的说明,这个也是最主要的一部分,使用二分法从数据文件中获取一条记录
<pre class="code"><span>/*</span><span>* * 获取函数内容 * @param 要查找的函数名称 * @return 返回函数说明的json字符串 </span><span>*/</span> <span>public</span> <span>function</span> get(<span>$func</span><span>) { </span><span>if</span>(!<span>$this</span>-><span>isInit()) </span><span>return</span><span>; </span><span>$begin</span> = 0<span>; </span><span>$end</span> = <span>filesize</span>(<span>$this</span>->_indexFile)/4<span>; </span><span>$ret</span> = '[]'<span>; </span><span>while</span>(<span>$begin</span> < <span>$end</span><span>){ </span><span>$mid</span> = <span>floor</span>((<span>$begin</span> + <span>$end</span>)/2<span>); </span><span>$pos</span> = <span>$mid</span>*4<span>; //$mid只是指针变量的位置,还需要乘上指针的长度4 </span><span>$pos</span> = <span>$this</span>->_getOneIndex(<span>$pos</span><span>); </span><span>$name</span> = <span>$this</span>->_getStoreLenValFormat(<span>$pos</span><span>); </span><span>$flag</span> = <span>strcmp</span>(<span>$func</span>, <span>$name</span>['value'<span>]); </span><span>if</span>(<span>$flag</span> == 0<span>){ </span><span>$val</span> = <span>$this</span>->_getStoreLenValFormat(<span>$pos</span>+4+<span>$name</span>['len'<span>]); </span><span>$ret</span> = <span>$val</span>['value'<span>]; </span><span>break</span><span>; }</span><span>elseif</span>(<span>$flag</span> < 0<span>){ </span><span>$end</span> = <span>$end</span> == <span>$mid</span> ? <span>$mid</span>-1 : <span>$mid</span><span>; }</span><span>else</span><span>{ </span><span>$begin</span> = <span>$begin</span> == <span>$mid</span> ? <span>$mid</span>+1 : <span>$mid</span><span>; } } </span><span>return</span> <span>$ret</span><span>; }</span>
使用很简单,只需包含类库文件和存储文件数据库,然后调用几句代码就可以
<pre class="code"><?<span>php </span><span>include_once</span>("./manual/phpManual.php"<span>); </span><span>$t</span> = <span>new</span><span> phpManual(); </span><span>$t</span>->init('zh'<span>); </span><span>echo</span> <span>$t</span>->get("unpack");
输出的是json字符串,转化后如下所示,其中有详细的说明,以及简洁的例子
<pre class="code"><span>{ </span>"name": "unpack"<span>, </span>"desc": "Unpack data from binary string."<span>, </span>"long_desc": "Unpacks from a binary string into an array according to the given `format`.\\n\\nThe unpacked data is stored in an associative array. To accomplish this you have to name the different format codes and separate them by a slash /. If a repeater argument is present, then each of the array keys will have a sequence number behind the given name."<span>, </span>"ver": "PHP 4, PHP 5"<span>, </span>"ret_desc": "Returns an associative array containing unpacked elements of binary string."<span>, </span>"seealso"<span>: [ </span>"pack"<span> ], </span>"url": "function.unpack"<span>, </span>"class": <span>null</span><span>, </span>"params"<span>: [ { </span>"list"<span>: [ { </span>"type": "string"<span>, </span>"var": "$format"<span>, </span>"beh": 0<span>, </span>"desc": "See pack() for an explanation of the format codes."<span> }, { </span>"type": "string"<span>, </span>"var": "$data"<span>, </span>"beh": 0<span>, </span>"desc": "The packed data."<span> } ], </span>"ret_type": "array"<span> } ], </span>"examples"<span>: [ { </span>"title": "unpack() example"<span>, </span>"source": "$binarydata = \"\\x04\\x00\\xa0\\x00\";\n$array = unpack(\"cchars/nint\", $binarydata);"<span>, </span>"output": <span>null</span><span> }, { </span>"title": "unpack() example with a repeater"<span>, </span>"source": "$binarydata = \"\\x04\\x00\\xa0\\x00\";\n$array = unpack(\"c2chars/nint\", $binarydata);"<span>, </span>"output": <span>null</span><span> }, { </span>"title": "unpack() example with unnamed keys"<span>, </span>"source": "$binarydata = \"\\x32\\x42\\x00\\xa0\";\n$array = unpack(\"c2/n\", $binarydata);\nvar_dump($array);"<span>, </span>"output": <span>null</span><span> } ] }</span>
最后再附上目录结构:
<pre class="code">+<span>phpManual </span>+<span>manual </span>+<span>phpManual </span>+<span>zh </span>|<span>_manualIndex </span>|<span>_manualStore </span>|<span>_phpManual.php </span>|_test.php
这个是程序的完整地址:
完整例子地址
https://github.com/aizuyan/php-doc-parser 从这里拿到的phpmanual的全部数据
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