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linux 0.11中文版 有注释

<a name='L383'>        <font color='red'>{</font>
<a name='L384'>          <a href='../S/65.html#L153' title='Defined at 153 in kernel/chr_drv/tty_io.c.'>sleep_if_empty</a> (&amp;<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>-&gt;secondary);
<a name='L385'>          <b>continue</b>;
<a name='L386'>        <font color='red'>}</font>
<a name='L387'><i><font color='green'>// 执行以下操作，直到nr=0 或者辅助缓冲队列为空。</font></i>
<a name='L388'>      <b>do</b>
<a name='L389'>        <font color='red'>{</font>
<a name='L390'><i><font color='green'>// 取辅助缓冲队列字符c。</font></i>
<a name='L391'>          <a href='../S/38.html#L49' title='Defined at 49 in include/linux/tty.h.'>GETCH</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>-&gt;secondary, c);
<a name='L392'><i><font color='green'>// 如果该字符是文件结束符(^D)或者是换行符NL(10)，则辅助缓冲队列字符数减1。</font></i>
<a name='L393'>          <b>if</b> (c == <a href='../S/38.html#L60' title='Defined at 60 in include/linux/tty.h.'>EOF_CHAR</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>) || c == 10)
<a name='L394'>            <a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>-&gt;secondary.data--;
<a name='L395'><i><font color='green'>// 如果该字符是文件结束符(^D)并且规范模式标志置位，则返回已读字符数，并退出。</font></i>
<a name='L396'>          <b>if</b> (c == <a href='../S/38.html#L60' title='Defined at 60 in include/linux/tty.h.'>EOF_CHAR</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>) &amp;&amp; <a href='../S/65.html#L41' title='Defined at 41 in kernel/chr_drv/tty_io.c.'>L_CANON</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>))
<a name='L397'>            <b>return</b> (b - <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>);
<a name='L398'><i><font color='green'>// 否则将该字符放入用户数据段缓冲区buf 中，欲读字符数减1，如果欲读字符数已为0，则中断循环。</font></i>
<a name='L399'>          <b>else</b>
<a name='L400'>            <font color='red'>{</font>
<a name='L401'>              <a href='../S/24.html#L44' title='Defined at 44 in include/asm/segment.h.'>put_fs_byte</a> (c, b++);
<a name='L402'>              <b>if</b> (!--nr)
<a name='L403'>                <b>break</b>;
<a name='L404'>            <font color='red'>}</font>
<a name='L405'>        <font color='red'>}</font>
<a name='L406'>      <b>while</b> (nr &gt; 0 &amp;&amp; !<a href='../S/38.html#L39' title='Defined at 39 in include/linux/tty.h.'>EMPTY</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>-&gt;secondary));
<a name='L407'><i><font color='green'>// 如果超时定时值time 不为0 并且规范模式标志没有置位(非规范模式)，那么：</font></i>
<a name='L408'>      <b>if</b> (time &amp;&amp; !<a href='../S/65.html#L41' title='Defined at 41 in kernel/chr_drv/tty_io.c.'>L_CANON</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>))
<a name='L409'><i><font color='green'>// 如果进程原定时值是0 或者time+当前系统时间值小于进程原定时值的话，则置重新设置进程定时值</font></i>
<a name='L410'><i><font color='green'>// 为time+当前系统时间，并置flag 标志。否则让进程的定时值等于进程原定时值。</font></i>
<a name='L411'>        <b>if</b> (flag = (!oldalarm || time + jiffies &lt; oldalarm))
<a name='L412'>          current-&gt;alarm = time + jiffies;
<a name='L413'>        <b>else</b>
<a name='L414'>          current-&gt;alarm = oldalarm;
<a name='L415'><i><font color='green'>// 如果规范模式标志置位，那么若没有读到1 个字符则中断循环。否则若已读取数大于或等于最少要</font></i>
<a name='L416'><i><font color='green'>// 求读取的字符数，则也中断循环。</font></i>
<a name='L417'>      <b>if</b> (<a href='../S/65.html#L41' title='Defined at 41 in kernel/chr_drv/tty_io.c.'>L_CANON</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>))
<a name='L418'>        <font color='red'>{</font>
<a name='L419'>          <b>if</b> (b - <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>)
<a name='L420'>            <b>break</b>;
<a name='L421'>        <font color='red'>}</font>
<a name='L422'>      <b>else</b> <b>if</b> (b - <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a> &gt;= minimum)
<a name='L423'>        <b>break</b>;
<a name='L424'>    <font color='red'>}</font>
<a name='L425'><i><font color='green'>// 让进程的定时值等于进程原定时值。</font></i>
<a name='L426'>  current-&gt;alarm = oldalarm;
<a name='L427'><i><font color='green'>// 如果进程有信号并且没有读取任何字符，则返回出错号（超时）。</font></i>
<a name='L428'>  <b>if</b> (current-&gt;signal &amp;&amp; !(b - <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>))
<a name='L429'>    <b>return</b> -<a href='../S/28.html#L33' title='Defined at 33 in include/errno.h.'>EINTR</a>;
<a name='L430'>  <b>return</b> (b - <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>);             <i><font color='green'>// 返回已读取的字符数。</font></i>
<a name='L431'><font color='red'>}</font>
<a name='L432'>
<a name='L433'><i><font color='green'>//// tty 写函数。</font></i>
<a name='L434'><i><font color='green'>// 参数：channel - 子设备号；buf - 缓冲区指针；nr - 写字节数。</font></i>
<a name='L435'><i><font color='green'>// 返回已写字节数。</font></i>
<a name='L436'><b>int</b>
<a name='L437'><a href='../R/715.html' title='Multiple refered from 4 places.'>tty_write</a> (<b>unsigned</b> channel, <b>char</b> *buf, <b>int</b> nr)
<a name='L438'><font color='red'>{</font>
<a name='L439'>  <b>static</b> cr_flag = 0;
<a name='L440'>  <b>struct</b> tty_struct *<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>;
<a name='L441'>  <b>char</b> c, *b = <a href='../D/716.html' title='Multiple defined in 16 places.'>buf</a>;
<a name='L442'>
<a name='L443'><i><font color='green'>// 本版本linux 内核的终端只有3 个子设备，分别是控制台(0)、串口终端1(1)和串口终端2(2)。</font></i>
<a name='L444'><i><font color='green'>// 所以任何大于2 的子设备号都是非法的。写的字节数当然也不能小于0 的。</font></i>
<a name='L445'>  <b>if</b> (channel &gt; 2 || nr &lt; 0)
<a name='L446'>    <b>return</b> -1;
<a name='L447'><i><font color='green'>// tty 指针指向子设备号对应ttb_table 表中的tty 结构。</font></i>
<a name='L448'>  <a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a> = channel + tty_table;
<a name='L449'><i><font color='green'>// 字符设备是一个一个字符进行处理的，所以这里对于nr 大于0 时对每个字符进行循环处理。</font></i>
<a name='L450'>  <b>while</b> (nr &gt; 0)
<a name='L451'>    <font color='red'>{</font>
<a name='L452'><i><font color='green'>// 如果此时tty 的写队列已满，则当前进程进入可中断的睡眠状态。</font></i>
<a name='L453'>      <a href='../S/65.html#L167' title='Defined at 167 in kernel/chr_drv/tty_io.c.'>sleep_if_full</a> (&amp;<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>-&gt;write_q);
<a name='L454'><i><font color='green'>// 如果当前进程有信号要处理，则退出，返回0。</font></i>
<a name='L455'>      <b>if</b> (current-&gt;signal)
<a name='L456'>        <b>break</b>;
<a name='L457'><i><font color='green'>// 当要写的字节数&gt;0 并且tty 的写队列不满时，循环执行以下操作。</font></i>
<a name='L458'>      <b>while</b> (nr &gt; 0 &amp;&amp; !<a href='../S/38.html#L45' title='Defined at 45 in include/linux/tty.h.'>FULL</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>-&gt;write_q))
<a name='L459'>        <font color='red'>{</font>
<a name='L460'><i><font color='green'>// 从用户数据段内存中取一字节c。</font></i>
<a name='L461'>          c = <a href='../D/821.html' title='Multiple defined in 2 places.'>get_fs_byte</a> (b);
<a name='L462'><i><font color='green'>// 如果终端输出模式标志集中的执行输出处理标志OPOST 置位，则执行下列输出时处理过程。</font></i>
<a name='L463'>          <b>if</b> (<a href='../S/65.html#L56' title='Defined at 56 in kernel/chr_drv/tty_io.c.'>O_POST</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>))
<a name='L464'>            <font color='red'>{</font>
<a name='L465'><i><font color='green'>// 如果该字符是回车符'\r'(CR，13)并且回车符转换行符标志OCRNL 置位，则将该字符换成换行符</font></i>
<a name='L466'><i><font color='green'>// '\n'(NL，10)；否则如果该字符是换行符'\n'(NL，10)并且换行转回车功能标志ONLRET 置位的话，</font></i>
<a name='L467'><i><font color='green'>// 则将该字符换成回车符'\r'(CR，13)。</font></i>
<a name='L468'>              <b>if</b> (c == '\r' &amp;&amp; <a href='../S/65.html#L58' title='Defined at 58 in kernel/chr_drv/tty_io.c.'>O_CRNL</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>))
<a name='L469'>                c = '\n';
<a name='L470'>              <b>else</b> <b>if</b> (c == '\n' &amp;&amp; <a href='../S/65.html#L59' title='Defined at 59 in kernel/chr_drv/tty_io.c.'>O_NLRET</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>))
<a name='L471'>                c = '\r';
<a name='L472'><i><font color='green'>// 如果该字符是换行符'\n'并且回车标志cr_flag 没有置位，换行转回车-换行标志ONLCR 置位的话，</font></i>
<a name='L473'><i><font color='green'>// 则将cr_flag 置位，并将一回车符放入写队列中。然后继续处理下一个字符。</font></i>
<a name='L474'>              <b>if</b> (c == '\n' &amp;&amp; !cr_flag &amp;&amp; <a href='../S/65.html#L57' title='Defined at 57 in kernel/chr_drv/tty_io.c.'>O_NLCR</a> (<a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>))
<a name='L475'>                <font color='red'>{</font>
<a name='L476'>                  cr_flag = 1;
<a name='L477'>                  <a href='../S/38.html#L52' title='Defined at 52 in include/linux/tty.h.'>PUTCH</a> (13, <a href='../S/7.html#L44' title='Defined at 44 in fs/char_dev.c.'>tty</a>-&gt;write_q);
<a name='L478'>                  <b>continue</b>;
<a name='L479'>                <font color='red'>}</font>
<a name='L480'><i><font color='green'>// 如果小写转大写标志OLCUC 置位的话，就将该字符转成大写字符。</font></i>
<a name='L481'>              <b>if</b> (<a href='../S/65.html#L60' title='Defined at 60 in kernel/chr_