📄 [c++对象模型][4]指针与字符串 - itech's blog - 博客园.htm
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style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000"> strlen(c3);
</SPAN><SPAN style="COLOR: #008000">//</SPAN><SPAN style="COLOR: #008000">
3</SPAN><SPAN style="COLOR: #008000"> <BR></SPAN><SPAN
style="COLOR: #000000"> free(c3); </SPAN><SPAN
style="COLOR: #008000">//</SPAN><SPAN
style="COLOR: #008000">如果这里不free，会内存泄漏</SPAN><SPAN style="COLOR: #008000">
<BR></SPAN><SPAN style="COLOR: #000000"> c3 </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN style="COLOR: #800000">abc</SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN style="COLOR: #000000">; </SPAN><SPAN
style="COLOR: #008000">//</SPAN><SPAN style="COLOR: #008000"> abc\0
在常量区，c3指向了常量区 <BR> </SPAN><SPAN
style="COLOR: #008000">//</SPAN><SPAN style="COLOR: #008000">c3[1] = 'g';
</SPAN><SPAN style="COLOR: #008000">//</SPAN><SPAN style="COLOR: #008000">
常量不能修改</SPAN><SPAN style="COLOR: #008000"> <BR></SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #0000ff">int</SPAN><SPAN style="COLOR: #000000"> y </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000"> strlen(c3);
</SPAN><SPAN style="COLOR: #008000">//</SPAN><SPAN style="COLOR: #008000">
3</SPAN><SPAN style="COLOR: #008000"> <BR></SPAN><SPAN
style="COLOR: #000000">}</SPAN></SPAN></DIV>
<P> </P>
<P><SPAN style="COLOR: #ff0000">字符串都以\0结尾，所以例如：<SPAN
style="COLOR: #ff0000"><SPAN id=Code_Open_Text_145503><SPAN
style="COLOR: #000000"></SPAN><SPAN style="COLOR: #ff0000">char<SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">c1 </SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #800000">abc</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #000000">;</SPAN></SPAN></SPAN></SPAN><SPAN
style="COLOR: #ff0000"><SPAN id=Code_Open_Text_145503><SPAN
style="COLOR: #ff0000"><SPAN style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> c2[] </SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #800000">abc</SPAN><SPAN
style="COLOR: #800000">"</SPAN></SPAN><SPAN style="COLOR: #000000"><SPAN
style="COLOR: #ff0000">;，</SPAN><SPAN
style="COLOR: #ff0000">使用strlen得到长度都为3，但是实际的存储空间为strlen+1即3+1。</SPAN></SPAN></SPAN></SPAN></SPAN></P>
<P>二 C中字符串操作函数</P>
<P>C++的程序员对C中的字符串指针操作的函数却并不是相当的熟悉。而C中的这些字符串的指针操作函数有的时候也是必须要面对的，比如我们的库要提供C函数接口，保持向后兼容和跨平台，还有我们经常使用一些第三方的库中都或多或少的使用到了这些C中的指针操作函数，所以下面列出C的指针操作函数，帮助大家熟悉之。</P>
<P>1) memcpy/memset/memcmp</P>
<TABLE cellSpacing=0 cellPadding=2 width="80%" border=2>
<TBODY>
<TR>
<TD vAlign=top width=99>
<P> </P>
<P> memcpy</P></TD>
<TD vAlign=top width=454>
<P>原型：extern void *memcpy( void *to, const void *from, size_t count );
<BR>包含：#include <string.h> 或<string>或<cstring>
<BR>功能：由src所指内存区域复制count个字节到dest所指内存区域。
<BR>说明：src和dest所指内存区域不能重叠，函数返回指向dest的指针。</P></TD></TR>
<TR>
<TD vAlign=top width=104>
<P> </P>
<P> memset</P></TD>
<TD vAlign=top width=454>
<P>原型：extern void* memset( void* buffer, int ch, size_t count );
<BR>包含：#include <string.h> 或<string>或<cstring>
<BR>功能：把buffer所指内存区域的前count个字节设置成字符c。 <BR>说明：返回指向buffer的指针。</P></TD></TR>
<TR>
<TD vAlign=top width=108>
<P> </P>
<P> </P>
<P> memcmp</P></TD>
<TD vAlign=top width=454>
<P>原型：extern int memcmp(const void *buffer1, const void *buffer2, size_t
count ); <BR>包含：#include <string.h> 或<string>或<cstring>
<BR>功能：比较内存区域buf1和buf2的前count个字节。 <BR>说明：
<BR> 当buf1<buf2时，返回值<0
<BR> 当buf1=buf2时，返回值=0
<BR>
当buf1>buf2时，返回值>0</P></TD></TR>
<TR>
<TD vAlign=top width=112><BR><BR> memchr <BR></TD>
<TD vAlign=top width=454>原型： extern void *memchr( const void *buffer, int
ch, size_t count ); <BR>包含：#include <string.h>
或<string>或<cstring> <BR>功能：查找ch在buffer中第一次出现的位置。
<BR>说明：如果发现返回指针，如果没有返回NULL。 <BR></TD></TR></TBODY></TABLE>
<P> </P>
<P>实例：</P>
<P> </P>
<DIV class=cnblogs_code><IMG id=Code_Closed_Image_154053 style="DISPLAY: none"
onclick="this.style.display='none'; document.getElementById('Code_Closed_Text_154053').style.display='none'; document.getElementById('Code_Open_Image_154053').style.display='inline'; document.getElementById('Code_Open_Text_154053').style.display='inline';"
height=16
src="[C++对象模型][4]指针与字符串 - iTech's Blog - 博客园.files/ContractedBlock.gif" width=11
align=top><IMG id=Code_Open_Image_154053
onclick="this.style.display='none'; document.getElementById('Code_Open_Text_154053').style.display='none'; getElementById('Code_Closed_Image_154053').style.display='inline'; getElementById('Code_Closed_Text_154053').style.display='inline';"
height=16
src="[C++对象模型][4]指针与字符串 - iTech's Blog - 博客园.files/ExpandedBlockStart.gif"
width=11 align=top><SPAN class=cnblogs_code_Collapse
id=Code_Closed_Text_154053>Code</SPAN><SPAN id=Code_Open_Text_154053> <BR><!--<br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--><SPAN
style="COLOR: #0000ff">void</SPAN><SPAN style="COLOR: #000000">
TestMemFunction() <BR>{ <BR> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">s1</SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN style="COLOR: #800000">Hello!</SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN style="COLOR: #000000">; </SPAN><SPAN
style="COLOR: #008000">//</SPAN><SPAN style="COLOR: #008000">
Hello!\0</SPAN><SPAN style="COLOR: #008000"> <BR></SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #0000ff">int</SPAN><SPAN style="COLOR: #000000"> l </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000"> strlen(s1);
</SPAN><SPAN style="COLOR: #008000">//</SPAN><SPAN style="COLOR: #008000"> 6
</SPAN><SPAN style="COLOR: #008000"><BR></SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">d1 </SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #0000ff">new</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN style="COLOR: #000000">[l</SPAN><SPAN
style="COLOR: #000000">+</SPAN><SPAN style="COLOR: #800080">1</SPAN><SPAN
style="COLOR: #000000">]; </SPAN><SPAN style="COLOR: #008000">//</SPAN><SPAN
style="COLOR: #008000"> d1 需要strlen(s1) + 1 空间</SPAN><SPAN
style="COLOR: #008000"> <BR></SPAN><SPAN
style="COLOR: #000000"> memcpy(d1,s1,l</SPAN><SPAN
style="COLOR: #000000">+</SPAN><SPAN style="COLOR: #800080">1</SPAN><SPAN
style="COLOR: #000000">); <BR><BR> memcpy(d1,d1,l);
<BR><BR> memmove(d1 </SPAN><SPAN
style="COLOR: #000000">+</SPAN><SPAN style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #800080">1</SPAN><SPAN style="COLOR: #000000">,d1,l</SPAN><SPAN
style="COLOR: #000000">-</SPAN><SPAN style="COLOR: #800080">1</SPAN><SPAN
style="COLOR: #000000">); <BR><BR> </SPAN><SPAN
style="COLOR: #0000ff">const</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #0000ff">int</SPAN><SPAN
style="COLOR: #000000"> ARRAY_LENGTH </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #800080">5</SPAN><SPAN style="COLOR: #000000">;
<BR> </SPAN><SPAN style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> the_array[ARRAY_LENGTH]; <BR>
</SPAN><SPAN style="COLOR: #008000">//</SPAN><SPAN style="COLOR: #008000"> zero
out the contents of the_array</SPAN><SPAN style="COLOR: #008000">
<BR></SPAN><SPAN style="COLOR: #000000"> memset( the_array,
</SPAN><SPAN style="COLOR: #800000">'</SPAN><SPAN
style="COLOR: #800000">c</SPAN><SPAN style="COLOR: #800000">'</SPAN><SPAN
style="COLOR: #000000">, ARRAY_LENGTH ); <BR><BR> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">a1 </SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #800000">source1</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #000000">; <BR> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN style="COLOR: #000000">
arr1[</SPAN><SPAN style="COLOR: #800080">8</SPAN><SPAN style="COLOR: #000000">]
</SPAN><SPAN style="COLOR: #000000">=</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #800000">source2</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #000000">; <BR> </SPAN><SPAN
style="COLOR: #0000ff">int</SPAN><SPAN style="COLOR: #000000"> r </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000">
memcmp(a1,arr1,strlen(a1) </SPAN><SPAN style="COLOR: #000000">-</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #800080">1</SPAN><SPAN
style="COLOR: #000000">); </SPAN><SPAN style="COLOR: #008000">//</SPAN><SPAN
style="COLOR: #008000"> 仅比较source，所以相等</SPAN><SPAN style="COLOR: #008000">
<BR></SPAN><SPAN style="COLOR: #000000"><BR> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN style="COLOR: #000000"> str[</SPAN><SPAN
style="COLOR: #800080">17</SPAN><SPAN style="COLOR: #000000">];
<BR> </SPAN><SPAN style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">ptr; <BR> strcpy(str, </SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN style="COLOR: #800000">This is a
string</SPAN><SPAN style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #000000">); <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">)memchr(str, </SPAN><SPAN
style="COLOR: #800000">'</SPAN><SPAN style="COLOR: #800000">r</SPAN><SPAN
style="COLOR: #800000">'</SPAN><SPAN style="COLOR: #000000">, strlen(str));
<BR>}</SPAN></SPAN></DIV>
<P> </P>
<P>2) strlen/strcpy/strcat/strcmp/strchr/strcoll/strstr/strtok/strtod/strtol</P>
<TABLE cellSpacing=0 cellPadding=2 width=400 border=2>
<TBODY>
<TR>
<TD vAlign=top width=81><BR>strcpy</TD>
<TD vAlign=top width=319>
<P>char *strcpy(char *s1, const char *s2)
将字符串s2复制到字符串数组s1中，返回s1的值</P></TD></TR>
<TR>
<TD vAlign=top width=81><BR>strcat</TD>
<TD vAlign=top width=319>
<P>char *strcat(char *s1, const char *s2)
<BR>将字符串s2添加到字符串s1的后面。s2的第一个字符重定义s1的null终止符。返回s1的值</P></TD></TR>
<TR>
<TD vAlign=top width=81><BR><BR>strcmp</TD>
<TD vAlign=top width=319>
<P>int strcmp(const char *s1, const char *s2)
<BR>比较字符串s1和字符串s2。函数在s1等于、小于或大于s2时分别返回0、小于0或者大于0的值</P></TD></TR>
<TR>
<TD vAlign=top width=81>strchr</TD>
<TD vAlign=top width=319>
<P>char *strchr(char * str,int c ); 在str中查找c第一次出现的位置。</P></TD></TR>
<TR>
<TD vAlign=top width=81>strstr</TD>
<TD vAlign=top width=319>char *strstr(char *str,const char *strSearch
);在string1中查找string2第一次出现的位置。</TD></TR>
<TR>
<TD vAlign=top width=81>strtok</TD>
<TD vAlign=top width=319>char *strtok(char *strToken,const char
*strDelimit ); 分割字符串。</TD></TR></TBODY></TABLE>
<P> </P>
<P>实例：</P>
<P> </P>
<DIV class=cnblogs_code><IMG id=Code_Closed_Image_163224 style="DISPLAY: none"
onclick="this.style.display='none'; document.getElementById('Code_Closed_Text_163224').style.display='none'; document.getElementById('Code_Open_Image_163224').style.display='inline'; document.getElementById('Code_Open_Text_163224').style.display='inline';"
height=16
src="[C++对象模型][4]指针与字符串 - iTech's Blog - 博客园.files/ContractedBlock.gif" width=11
align=top><IMG id=Code_Open_Image_163224
onclick="this.style.display='none'; document.getElementById('Code_Open_Text_163224').style.display='none'; getElementById('Code_Closed_Image_163224').style.display='inline'; getElementById('Code_Closed_Text_163224').style.display='inline';"
height=16
src="[C++对象模型][4]指针与字符串 - iTech's Blog - 博客园.files/ExpandedBlockStart.gif"
width=11 align=top><SPAN class=cnblogs_code_Collapse
id=Code_Closed_Text_163224>Code</SPAN><SPAN id=Code_Open_Text_163224><BR><!--<br /><br />Code highlighting produced by Actipro CodeHighlighter (freeware)<br />http://www.CodeHighlighter.com/<br /><br />--><SPAN
style="COLOR: #0000ff">void</SPAN><SPAN
style="COLOR: #000000"> TestStrFunction()<BR>{<BR> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #0000ff">string</SPAN><SPAN style="COLOR: #000000">[</SPAN><SPAN
style="COLOR: #800080">11</SPAN><SPAN
style="COLOR: #000000">];<BR> </SPAN><SPAN
style="COLOR: #0000ff">char</SPAN><SPAN
style="COLOR: #000000"> </SPAN><SPAN style="COLOR: #000000">*</SPAN><SPAN
style="COLOR: #000000">str1 </SPAN><SPAN
style="COLOR: #000000">=</SPAN><SPAN style="COLOR: #000000"> </SPAN><SPAN
style="COLOR: #800000">"</SPAN><SPAN
style="COLOR: #800000">123456789</SPAN><SPAN
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