17.html

linux 0.11中文版 有注释

<a name='L73'>      <b>break</b>;
<a name='L74'><i><font color='green'>// origin 设置出错，返回出错码退出。</font></i>
<a name='L75'>    <b>default</b>:
<a name='L76'>      <b>return</b> -<a href='../S/28.html#L51' title='Defined at 51 in include/errno.h.'>EINVAL</a>;
<a name='L77'>    <font color='red'>}</font>
<a name='L78'>  <b>return</b> file-&gt;f_pos;           <i><font color='green'>// 返回重定位后的文件读写指针值。</font></i>
<a name='L79'><font color='red'>}</font>
<a name='L80'>
<a name='L81'><i><font color='green'>//// 读文件系统调用函数。</font></i>
<a name='L82'><i><font color='green'>// 参数fd 是文件句柄，buf 是缓冲区，count 是欲读字节数。</font></i>
<a name='L83'><b>int</b>
<a name='L84'><a href='../R/669.html' title='Multiple refered from 2 places.'>sys_read</a> (<b>unsigned</b> <b>int</b> fd, <b>char</b> *buf, <b>int</b> count)
<a name='L85'><font color='red'>{</font>
<a name='L86'>  <b>struct</b> file *file;
<a name='L87'>  <b>struct</b> m_inode *inode;
<a name='L88'>
<a name='L89'><i><font color='green'>// 如果文件句柄值大于程序最多打开文件数NR_OPEN，或者需要读取的字节计数值小于0，或者该句柄</font></i>
<a name='L90'><i><font color='green'>// 的文件结构指针为空，则返回出错码并退出。</font></i>
<a name='L91'>  <b>if</b> (fd &gt;= <a href='../S/31.html#L59' title='Defined at 59 in include/linux/fs.h.'>NR_OPEN</a> || <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a> &lt; 0 || !(file = current-&gt;filp[fd]))
<a name='L92'>    <b>return</b> -<a href='../S/28.html#L51' title='Defined at 51 in include/errno.h.'>EINVAL</a>;
<a name='L93'><i><font color='green'>// 若需读取的字节数count 等于0，则返回0，退出</font></i>
<a name='L94'>  <b>if</b> (!<a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>)
<a name='L95'>    <b>return</b> 0;
<a name='L96'><i><font color='green'>// 验证存放数据的缓冲区内存限制。</font></i>
<a name='L97'>  <a href='../S/68.html#L34' title='Defined at 34 in kernel/fork.c.'>verify_area</a> (<a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>);
<a name='L98'><i><font color='green'>// 取文件对应的i 节点。若是管道文件，并且是读管道文件模式，则进行读管道操作，若成功则返回</font></i>
<a name='L99'><i><font color='green'>// 读取的字节数，否则返回出错码，退出。</font></i>
<a name='L100'>  inode = file-&gt;f_inode;
<a name='L101'>  <b>if</b> (inode-&gt;i_pipe)
<a name='L102'>    <b>return</b> (file-&gt;f_mode &amp; 1) ? <a href='../S/16.html#L18' title='Defined at 18 in fs/pipe.c.'>read_pipe</a> (inode, <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>) : -<a href='../D/92.html' title='Multiple defined in 5 places.'>EIO</a>;
<a name='L103'><i><font color='green'>// 如果是字符型文件，则进行读字符设备操作，返回读取的字符数。</font></i>
<a name='L104'>  <b>if</b> (<a href='../S/43.html#L36' title='Defined at 36 in include/sys/stat.h.'>S_ISCHR</a> (inode-&gt;i_mode))
<a name='L105'>    <b>return</b> rw_char (<a href='../S/31.html#L42' title='Defined at 42 in include/linux/fs.h.'>READ</a>, inode-&gt;i_zone[0], <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>, &amp;file-&gt;f_pos);
<a name='L106'><i><font color='green'>// 如果是块设备文件，则执行块设备读操作，并返回读取的字节数。</font></i>
<a name='L107'>  <b>if</b> (<a href='../S/43.html#L37' title='Defined at 37 in include/sys/stat.h.'>S_ISBLK</a> (inode-&gt;i_mode))
<a name='L108'>    <b>return</b> <a href='../S/5.html#L70' title='Defined at 70 in fs/block_dev.c.'>block_read</a> (inode-&gt;i_zone[0], &amp;file-&gt;f_pos, <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>);
<a name='L109'><i><font color='green'>// 如果是目录文件或者是常规文件，则首先验证读取数count 的有效性并进行调整（若读取字节数加上</font></i>
<a name='L110'><i><font color='green'>// 文件当前读写指针值大于文件大小，则重新设置读取字节数为文件长度-当前读写指针值，若读取数</font></i>
<a name='L111'><i><font color='green'>// 等于0，则返回0 退出），然后执行文件读操作，返回读取的字节数并退出。</font></i>
<a name='L112'>  <b>if</b> (<a href='../S/43.html#L35' title='Defined at 35 in include/sys/stat.h.'>S_ISDIR</a> (inode-&gt;i_mode) || <a href='../S/43.html#L34' title='Defined at 34 in include/sys/stat.h.'>S_ISREG</a> (inode-&gt;i_mode))
<a name='L113'>    <font color='red'>{</font>
<a name='L114'>      <b>if</b> (<a href='../D/738.html' title='Multiple defined in 17 places.'>count</a> + file-&gt;f_pos &gt; inode-&gt;i_size)
<a name='L115'>        <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a> = inode-&gt;i_size - file-&gt;f_pos;
<a name='L116'>      <b>if</b> (<a href='../D/738.html' title='Multiple defined in 17 places.'>count</a> &lt;= 0)
<a name='L117'>        <b>return</b> 0;
<a name='L118'>      <b>return</b> <a href='../S/10.html#L22' title='Defined at 22 in fs/file_dev.c.'>file_read</a> (inode, file, <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>);
<a name='L119'>    <font color='red'>}</font>
<a name='L120'><i><font color='green'>// 否则打印节点文件属性，并返回出错码退出。</font></i>
<a name='L121'>  <a href='../S/73.html#L30' title='Defined at 30 in kernel/printk.c.'>printk</a> ("(Read)inode-&gt;i_mode=%06o\n\r", inode-&gt;i_mode);
<a name='L122'>  <b>return</b> -<a href='../S/28.html#L51' title='Defined at 51 in include/errno.h.'>EINVAL</a>;
<a name='L123'><font color='red'>}</font>
<a name='L124'>
<a name='L125'><b>int</b>
<a name='L126'><a href='../R/697.html' title='Multiple refered from 2 places.'>sys_write</a> (<b>unsigned</b> <b>int</b> fd, <b>char</b> *buf, <b>int</b> count)
<a name='L127'><font color='red'>{</font>
<a name='L128'>  <b>struct</b> file *file;
<a name='L129'>  <b>struct</b> m_inode *inode;
<a name='L130'>
<a name='L131'><i><font color='green'>// 如果文件句柄值大于程序最多打开文件数NR_OPEN，或者需要写入的字节计数小于0，或者该句柄</font></i>
<a name='L132'><i><font color='green'>// 的文件结构指针为空，则返回出错码并退出。</font></i>
<a name='L133'>  <b>if</b> (fd &gt;= <a href='../S/31.html#L59' title='Defined at 59 in include/linux/fs.h.'>NR_OPEN</a> || <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a> &lt; 0 || !(file = current-&gt;filp[fd]))
<a name='L134'>    <b>return</b> -<a href='../S/28.html#L51' title='Defined at 51 in include/errno.h.'>EINVAL</a>;
<a name='L135'><i><font color='green'>// 若需读取的字节数count 等于0，则返回0，退出</font></i>
<a name='L136'>  <b>if</b> (!<a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>)
<a name='L137'>    <b>return</b> 0;
<a name='L138'><i><font color='green'>// 取文件对应的i 节点。若是管道文件，并且是写管道文件模式，则进行写管道操作，若成功则返回</font></i>
<a name='L139'><i><font color='green'>// 写入的字节数，否则返回出错码，退出。</font></i>
<a name='L140'>  inode = file-&gt;f_inode;
<a name='L141'>  <b>if</b> (inode-&gt;i_pipe)
<a name='L142'>    <b>return</b> (file-&gt;f_mode &amp; 2) ? <a href='../S/16.html#L60' title='Defined at 60 in fs/pipe.c.'>write_pipe</a> (inode, <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>) : -<a href='../D/92.html' title='Multiple defined in 5 places.'>EIO</a>;
<a name='L143'><i><font color='green'>// 如果是字符型文件，则进行写字符设备操作，返回写入的字符数，退出。</font></i>
<a name='L144'>  <b>if</b> (<a href='../S/43.html#L36' title='Defined at 36 in include/sys/stat.h.'>S_ISCHR</a> (inode-&gt;i_mode))
<a name='L145'>    <b>return</b> rw_char (<a href='../S/31.html#L43' title='Defined at 43 in include/linux/fs.h.'>WRITE</a>, inode-&gt;i_zone[0], <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>, &amp;file-&gt;f_pos);
<a name='L146'><i><font color='green'>// 如果是块设备文件，则进行块设备写操作，并返回写入的字节数，退出。</font></i>
<a name='L147'>  <b>if</b> (<a href='../S/43.html#L37' title='Defined at 37 in include/sys/stat.h.'>S_ISBLK</a> (inode-&gt;i_mode))
<a name='L148'>    <b>return</b> <a href='../S/5.html#L23' title='Defined at 23 in fs/block_dev.c.'>block_write</a> (inode-&gt;i_zone[0], &amp;file-&gt;f_pos, <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>);
<a name='L149'><i><font color='green'>// 若是常规文件，则执行文件写操作，并返回写入的字节数，退出。</font></i>
<a name='L150'>  <b>if</b> (<a href='../S/43.html#L34' title='Defined at 34 in include/sys/stat.h.'>S_ISREG</a> (inode-&gt;i_mode))
<a name='L151'>    <b>return</b> <a href='../S/10.html#L75' title='Defined at 75 in fs/file_dev.c.'>file_write</a> (inode, file, <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>, <a href='../D/738.html' title='Multiple defined in 17 places.'>count</a>);
<a name='L152'><i><font color='green'>// 否则，显示对应节点的文件模式，返回出错码，退出。</font></i>
<a name='L153'>  <a href='../S/73.html#L30' title='Defined at 30 in kernel/printk.c.'>printk</a> ("(Write)inode-&gt;i_mode=%06o\n\r", inode-&gt;i_mode);
<a name='L154'>  <b>return</b> -<a href='../S/28.html#L51' title='Defined at 51 in include/errno.h.'>EINVAL</a>;
<a name='L155'><font color='red'>}</font>
</pre>
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