pack, unpack homemade binary 'database', packunpack

pack、unpack自制二进制“数据库”，packunpack

引言

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>

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<p>a - NUL-padded string</p>

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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。

设计数据格式

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>

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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>

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查询的实现

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>

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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>

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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>

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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");

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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>

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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

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这个是程序的完整地址：

完整例子地址