📄 [c++对象模型][3]指针与数组 - itech's blog - 博客园.htm
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<H1 class=postTitle><A class=postTitle2 id=AjaxHolder_ctl01_TitleUrl
href="http://www.cnblogs.com/itech/archive/2009/02/22/1395434.html">[C++对象模型][3]指针与数组</A>
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<P>一 C指针操作函数</P>
<P>new和delete对C++的程序员也许很熟悉，但是malloc和free被用来在C代码中用来内存分配和释放，很多C++开发者并不能游刃有余的使用，下面实例解析malloc和free的使用。</P>
<TABLE cellSpacing=0 cellPadding=2 width="80%" border=2>
<TBODY>
<TR>
<TD vAlign=top width=101> malloc</TD>
<TD vAlign=top width=434>void *malloc(long
NumBytes)：该函数分配了NumBytes个字节，并返回了指向这块内存的指针。如果分配失败，则返回一个空指针（NULL）。</TD></TR>
<TR>
<TD vAlign=top width=104> free</TD>
<TD vAlign=top width=431>void free(void *FirstByte)：
该函数是将之前用malloc分配的空间还给程序或者是操作系统，也就是释放了这块内存，让它重新得到自由。</TD></TR></TBODY></TABLE>
<P> </P>
<P>实例如下：</P>
<P> </P>
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height=16 src="[C++对象模型][3]指针与数组 - iTech's Blog - 博客园.files/ContractedBlock.gif"
width=11 align=top><IMG id=Code_Open_Image_130001
onclick="this.style.display='none'; document.getElementById('Code_Open_Text_130001').style.display='none'; getElementById('Code_Closed_Image_130001').style.display='inline'; getElementById('Code_Closed_Text_130001').style.display='inline';"
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src="[C++对象模型][3]指针与数组 - iTech's Blog - 博客园.files/ExpandedBlockStart.gif"
width=11 align=top><SPAN class=cnblogs_code_Collapse
id=Code_Closed_Text_130001>Code</SPAN><SPAN id=Code_Open_Text_130001><BR><!--<br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--><SPAN
style="COLOR: #0000ff">#pragma</SPAN><SPAN
style="COLOR: #000000"> once</SPAN><SPAN
style="COLOR: #000000"><BR>#include </SPAN><SPAN
style="COLOR: #000000"><</SPAN><SPAN
style="COLOR: #0000ff">string</SPAN><SPAN
style="COLOR: #000000">></SPAN><SPAN
style="COLOR: #000000"><BR><BR></SPAN><SPAN
style="COLOR: #0000ff">void</SPAN><SPAN
style="COLOR: #000000"> TestMallocAndFree()<BR>{<BR> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">ptr </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> NULL;<BR> ptr </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000"> (</SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">)malloc(</SPAN><SPAN
style="COLOR: #800080">100</SPAN><SPAN style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #000000">*</SPAN><SPAN style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #0000ff">sizeof</SPAN><SPAN style="COLOR: #000000">(</SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000">));<BR> </SPAN><SPAN
style="COLOR: #0000ff">if</SPAN><SPAN
style="COLOR: #000000"> (NULL </SPAN><SPAN
style="COLOR: #000000">==</SPAN><SPAN
style="COLOR: #000000"> ptr)<BR> {<BR> </SPAN><SPAN
style="COLOR: #0000ff">return</SPAN><SPAN
style="COLOR: #000000">;<BR> }<BR> memcpy(ptr,</SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN style="COLOR: #800000">Hello!</SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN style="COLOR: #000000">,strlen(</SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN style="COLOR: #800000">Hello!</SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #000000">));<BR> free(ptr);<BR> ptr </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> NULL;<BR><BR> typedef </SPAN><SPAN
style="COLOR: #0000ff">struct</SPAN><SPAN
style="COLOR: #000000"> data_type <BR> {<BR> </SPAN><SPAN
style="COLOR: #0000ff">int</SPAN><SPAN
style="COLOR: #000000"> age;<BR> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">name;<BR> } data;<BR> <BR> data </SPAN><SPAN
style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">willy </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> NULL;<BR> willy </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> (data</SPAN><SPAN
style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">) malloc( </SPAN><SPAN
style="COLOR: #0000ff">sizeof</SPAN><SPAN
style="COLOR: #000000">(data) );<BR> willy</SPAN><SPAN
style="COLOR: #000000">-></SPAN><SPAN
style="COLOR: #000000">age </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #800080">20</SPAN><SPAN
style="COLOR: #000000">;<BR> willy</SPAN><SPAN
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