C++ 中 int、 char、 char*、 const char*、 string之间的转换

1. char* to string

 

string s(char *);
注：在不是初始化的地方最好用assign().
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2. string to const char*
string a="strte";
const char* r=a.c_str();
注意是const的。还要转到char*：
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2.2. const char* to char*
const char* r="123";
char   *p1   =   new   char[strlen(r)+1];
strcpy(p1,r);
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3. cstring to string
vs2005 Unicode下：
CStringW   str(L"test");  
CStringA   stra(str.GetBuffer(0));  
str.ReleaseBuffer();      
std::string   strs   (stra.GetBuffer(0));  
stra.ReleaseBuffer();

非Unicode下：
CString cs("test");
std::string str=cs.getBuffer(0);
cs.ReleaseBuffer();

注：GetBuffer()后一定要ReleaseBuffer(),否则就没有释放缓冲区所占的空间.
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4. double ,int to string
#include <sstream>
using namespace std;

stringstream ss;
string result;
long n=11111;
stream << n; //从long型数据输入
stream >>result; //转换为 string

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5.char* to int, double ,long

char *s; double x; int i; long l;

s = " -2309.12E-15";
x = atof( s );
printf( "atof test: ASCII string: %s\tfloat: %e\n", s, x );

s = "7.8912654773d210";
x = atof( s );
printf( "atof test: ASCII string: %s\tfloat: %e\n", s, x );

s = " -9885 pigs";
i = atoi( s );
printf( "atoi test: ASCII string: %s\t\tinteger: %d\n", s, i );

s = "98854 dollars";
l = atol( s );
printf( "atol test: ASCII string: %s\t\tlong: %ld\n", s, l );
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6. string to int ,long ,double            
int s;
string str="123";
stringstream ss;
ss<<str;//从str输入
ss>>s;//输出到int
ss.clear();

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7. date to string
#include <time>
using namespace std;

char dateStr [9];
char timeStr [9];
_strdate( dateStr);
printf( "The current date is %s \n", dateStr);
_strtime( timeStr );
printf( "The current time is %s \n", timeStr);

--------实践证明是正确的版本--------------------------------------------------------------

#include <iostream>
#include <ctime>
#include <cerrno>

int main()
{
     //Find the current time
     time_t curtime = time(0);
     
      //convert it to tm
      tm now=*localtime(&curtime);
    
     //BUFSIZ is standard macro that expands to a integer constant expression
     //that is greater then or equal to 256. It is the size of the stream buffer
     //used by setbuf()
     char dest[BUFSIZ]={0};
    
     //Format string determines the conversion specification's behaviour
     const char format[]="%A, %B %d %Y. The time is %X";
    
     //strftime - converts date and time to a string
     if (strftime(dest, sizeof(dest)-1, format, &now)>0)
       std::cout<<dest<<std::endl;

    else
       std::cerr<<"strftime failed. Errno code: "<<errno<<std::endl;
}

 

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8.string to cstring

+++++++++++++++++++++++++++++++++++++++++++++++++++++
非Unicode下：
int 转 CString：
CString.Format("%d",int);
...............................
string 转 CString
CString.format("%s", string.c_str());
用c_str()确实比data()要好.
.......................................
char* 转 CString
CString.format("%s", char*);
CString strtest;
char * charpoint;
charpoint="give string a value";
strtest=charpoint; //直接付值
.....................................................
CString 转 int
CString ss="1212.12";
int temp=atoi(ss); //atoi _atoi64或atol
...................................................................................................................................
9.在Unicode下的CString to double
CSting sTemp("123.567");
double dTemp = _wtof(