posix

详细描述了线程的基本知识己在实际开发中的应用适合初学者的深入研究。

face=Verdana>&nbsp;</FONT></o:p></SPAN></P>
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">在单线程程序中，我们经常要用到</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>"</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">全局变量</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>"</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">以实现多个函数间共享数据。在多线程环境下，由于数据空间是共享的，因此全局变量也为所有线程所共有。但有时应用程序设计中有必要提供线程私有的全局变量，仅在某个线程中有效，但却可以跨多个函数访问，比如程序可能需要每个线程维护一个链表，而使用相同的函数操作，最简单的办法就是使用同名而不同变量地址的线程相关数据结构。这样的数据结构可以由</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>Posix</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">线程库维护，称为线程私有数据（</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>Thread-specific Data</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">，或</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>TSD</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">）。</SPAN></P>
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align=left><SPAN lang=EN-US><FONT face=Verdana>Posix</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">定义了两个</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>API</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">分别用来创建和注销</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>TSD</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">：</SPAN></P>
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      align=left><SPAN lang=EN-US 
      style="FONT-SIZE: 12pt; FONT-FAMILY: 'Lucida Console'; mso-bidi-font-size: 9.0pt">int 
      pthread_key_create(pthread_key_t *key, void (*destr_function) (void 
      *))</SPAN><SPAN lang=EN-US 
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face=Verdana>&nbsp;</FONT></o:p></SPAN></P>
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">该函数从</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>TSD</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">池中分配一项，将其值赋给</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>key</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">供以后访问使用。如果</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>destr_function</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">不为空，在线程退出（</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>pthread_exit()</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">）时将以</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>key</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">所关联的数据为参数调用</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>destr_function()</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">，以释放分配的缓冲区。</SPAN></P>
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">不论哪个线程调用</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>pthread_key_create()</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">，所创建的</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>key</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">都是所有线程可访问的，但各个线程可根据自己的需要往</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>key</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">中填入不同的值，这就相当于提供了一个同名而不同值的全局变量。在</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>LinuxThreads</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">的实现中，</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>TSD</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">池用一个结构数组表示：</SPAN></P>
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      align=left><SPAN lang=EN-US 
      style="FONT-SIZE: 12pt; FONT-FAMILY: 'Lucida Console'; mso-bidi-font-size: 9.0pt">static 
      struct pthread_key_struct pthread_keys[PTHREAD_KEYS_MAX] = { { 0, NULL } 
      };</SPAN><SPAN lang=EN-US 
      style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"><o:p></o:p></SPAN></P></TD></TR></TBODY></TABLE>
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face=Verdana>&nbsp;</FONT></o:p></SPAN></P>
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">创建一个</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>TSD</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">就相当于将结构数组中的某一项设置为</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>"in_use"</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">，并将其索引返回给</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>*key</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">，然后设置</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>destructor</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">函数为</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>destr_function</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">。</SPAN></P>
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style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">注销一个</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>TSD</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">采用如下</SPAN><SPAN 
lang=EN-US><FONT face=Verdana>API</FONT></SPAN><SPAN 
style="FONT-FAMILY: 宋体; mso-ascii-font-family: Verdana; mso-hansi-font-family: Verdana">：</SPAN></P>
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      <P class=MsoNormal 
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      style="FONT-SIZE: 12pt; FONT-FAMILY: 'Lucida Console'; mso-bidi-font-size: 9.0pt">int 
      pthread_key_delete(pthread_key_t key)</SPAN><SPAN lang=EN-US 
      style="FONT-SIZE: 12pt; FONT-FAMILY: 宋体"><o:p></o:p></SPAN></P></TD></TR></TBODY></TABLE>
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