📄 csdn_文档中心_屏幕取词核心内幕.htm
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<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>mov sp, offset stack;<SPAN
style="mso-tab-count: 1">
</SPAN></SPAN><SPAN lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">/* </SPAN><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">设置</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">16</SPAN><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">位堆栈指针</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">
*/</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>add sp, 8192;<SPAN style="mso-tab-count: 1">
</SPAN></SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN
lang=EN-US>}</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">/* </SPAN><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">此处加入</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">16</SPAN><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">位代码要实现的功能</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">
*/</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN
lang=EN-US>_asm{</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>mov ss, prev_seg;</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>mov esp, dword ptr prev_ofs;<SPAN style="mso-tab-count: 1">
</SPAN></SPAN><SPAN lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">/* </SPAN><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">恢复</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">32</SPAN><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">位堆栈指针</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">
*/</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>mov ds, prev_ds;</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>lea sp, word ptr [bp-2];</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-spacerun: yes"> </SPAN><SPAN
style="mso-tab-count: 1"> </SPAN>pop
ds;</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>pop<SPAN style="mso-tab-count: 1"> </SPAN>bp;</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-spacerun: yes"> </SPAN>dec
bp;</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>db 66h;</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN lang=EN-US><SPAN
style="mso-tab-count: 2">
</SPAN>retf;</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 18pt"><SPAN
lang=EN-US>}</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 18pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">由于调用中传递的参数有限，所以涉及的代码并不多，唯一比较复杂之处在</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位侧，它临时转向一个</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位堆栈，服务于来自</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位的调用者的请求。在</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位侧入口处，必须存放好</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位调用者的</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位堆栈的指针，并且在</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位侧返回时恢复它。由代码可见，这个过程是不可重入的，即一次只支持一个调用者，由于调用者只有</SPAN><SPAN
lang=EN-US>LTW32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">的</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位侧代码，所以此限制可以满足。另外，在</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位代码返回时，必须恢复</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位调用者的</SPAN><SPAN
lang=EN-US>48</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位堆栈指针（</SPAN><SPAN
lang=EN-US>SS:ESP</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）而不是</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位的</SPAN><SPAN
lang=EN-US>CS:SP</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">，而且必须用一个</SPAN><SPAN
lang=EN-US>48</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位地址（</SPAN><SPAN
lang=EN-US>16:32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）远返回（</SPAN><SPAN
lang=EN-US>66h RETF</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）到它的</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位调用者。</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 18pt"><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">处理好这些细节，实现</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位到</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位的形式替换实际上是很简单的。</SPAN></P>
<P class=MsoNormal
style="MARGIN-LEFT: 18pt; TEXT-INDENT: -18pt; mso-list: l31 level1 lfo7; tab-stops: list 18.0pt"><SPAN
lang=EN-US
style="FONT-SIZE: 12pt; mso-bidi-font-size: 10.0pt; mso-fareast-font-family: 黑体">2．<SPAN
style="FONT: 7pt 'Times New Roman'"> </SPAN></SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 12pt; mso-bidi-font-size: 10.0pt; mso-fareast-font-family: 黑体">32</SPAN><SPAN
style="FONT-FAMILY: 黑体; FONT-SIZE: 12pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">位代码与</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 12pt; mso-bidi-font-size: 10.0pt; mso-fareast-font-family: 黑体">16</SPAN><SPAN
style="FONT-FAMILY: 黑体; FONT-SIZE: 12pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">位代码的数据交换</SPAN></P>
<P class=MsoNormal style="TEXT-INDENT: 18pt"><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位代码使用</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位段地址加</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位线性地址（</SPAN><SPAN
lang=EN-US>16:32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）的地址形式，</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位代码使用</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位段选择符（</SPAN><SPAN
lang=EN-US>selector</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）加</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位偏移（</SPAN><SPAN
lang=EN-US>16:16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）的地址形式。在</SPAN><SPAN
lang=EN-US>Windows 95</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">的</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位侧，段址</SPAN><SPAN
lang=EN-US>28h</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">是系统段，即通过</SPAN><SPAN
lang=EN-US>CS=28h</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">或</SPAN><SPAN
lang=EN-US>DS=28h</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">可以访问系统的</SPAN><SPAN
lang=EN-US>4G</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">空间，其它应用程序的地址空间都是映射到</SPAN><SPAN
lang=EN-US>28h</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">段的</SPAN><SPAN
lang=EN-US>4G</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">空间中。</SPAN><SPAN
lang=EN-US>Windows95</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">中所有</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位进程的地址空间（共</SPAN><SPAN
lang=EN-US>4G</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）的高</SPAN><SPAN
lang=EN-US>2G</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">（</SPAN><SPAN
lang=EN-US>80000000H~FFFFFFFFH</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）全部映射到</SPAN><SPAN
lang=EN-US>28:80000000~28:FFFFFFFFH</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">。即这块区域是所有</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位程序共享的。这里一般存放系统</SPAN><SPAN
lang=EN-US>DLL</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">、虚拟设备驱动程序（</SPAN><SPAN
lang=EN-US>VxD</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">）、内存映射文件、</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位应用程序和</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位全局堆等。最后一项很重要，这为</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位代码与</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位代码交换数据提供了一个简便的方法。因为</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位程序的段选择符的基址即是其所映射的系统段中的线性地址，这样，只要能够得到这个线性地址，</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位代码就可以轻易地访问到</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位程序的数据（</SPAN><SPAN
lang=EN-US>LTW32 </SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">的</SPAN><SPAN
lang=EN-US>32</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位侧使用此方法从</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位侧获得屏幕截获的信息）。而</SPAN><SPAN
lang=EN-US>16</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">位段选择符的线性基址可以通过使用系统调用</SPAN><SPAN
lang=EN-US>GetSelectorBase()</SPAN><SPAN
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Arial">得到，具体实现可参考源程序。线性地址计算的例子如下：</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 42.5pt"><SPAN lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">16</SPAN><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">位地址：</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">07F2:1234H</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 42.5pt"><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">段选择符</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt"><SPAN
style="mso-tab-count: 1">
</SPAN>07F2H</SPAN><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">的线性基址为：</SPAN><SPAN
lang=EN-US
style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt">82F41300H</SPAN></P>
<P class=MsoNormal style="MARGIN-LEFT: 42.5pt"><SPAN
style="FONT-FAMILY: 宋体; FONT-SIZE: 9pt; mso-ascii-font-family: Arial; mso-bidi-font-size: 10.0pt">段选择符</SPAN><SPAN
lang=EN-US style="FONT-SIZE: 9pt; mso-bidi-font-size: 10.0pt"><SPAN
style="mso-tab-count: 1">
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