[프로그래밍] itoa 함수 소스

/**

* Ansi C "itoa" based on Kernighan & Ritchie's "Ansi C":

*/

void strreverse(char* begin, char* end) {

         char aux;

         while(end>begin)

         aux=*end, *end--=*begin, *begin++=aux;

}

void itoa(int value, char* str, int base) {

       static char num[] = "0123456789abcdefghijklmnopqrstuvwxyz";

       char* wstr=str;

       int sign;

       // Validate base

       if (base<2 || base>35){ *wstr='\0'; return; }

       // Take care of sign

       if ((sign=value) < 0) value = -value;

       // Conversion. Number is reversed.

       do *wstr++ = num[value%base]; while(value/=base);

       if(sign<0) *wstr++='-';

       *wstr='\0';

       // Reverse string

       strreverse(str,wstr-1);

}

/**

 * Ansi C "itoa" based on Kernighan & Ritchie's "Ansi C"

 * with slight modification to optimize for specific architecture:

 */

void strreverse(char* begin, char* end) {

char aux;

while(end>begin)

aux=*end, *end--=*begin, *begin++=aux;

}

void itoa(int value, char* str, int base) {

static char num[] = "0123456789abcdefghijklmnopqrstuvwxyz";

char* wstr=str;

int sign;

div_t res;

// Validate base

if (base<2 || base>35){ *wstr='\0'; return; }

// Take care of sign

if ((sign=value) < 0) value = -value;

// Conversion. Number is reversed.

do {

res = div(value,base);

*wstr++ = num[res.rem];

}while(value=res.quot);

if(sign<0) *wstr++='-'; *wstr='\0';

// Reverse string

strreverse(str,wstr-1);

}

/**

 * C++ version std::string style "itoa":

 */

std::string itoa(int value, int base) {

enum { kMaxDigits = 35 };

std::string buf;

buf.reserve( kMaxDigits ); // Pre-allocate enough space.

// check that the base if valid

if (base < 2 || base > 16) return buf;

int quotient = value;

// Translating number to string with base:

do {

buf += "0123456789abcdef"[ std::abs( quotient % base ) ];

quotient /= base;

} while ( quotient );

// Append the negative sign for base 10

if ( value < 0 && base == 10) buf += '-';

std::reverse( buf.begin(), buf.end() );

return buf;

}

/**

 * C++ version char* style "itoa":

 */

char* itoa( int value, char* result, int base ) {

// check that the base if valid

if (base < 2 || base > 16) { 

*result = 0; return result; 

}

char* out = result;

int quotient = value;

do {

*out = "0123456789abcdef"[ std::abs( quotient % base ) ];

++out;

quotient /= base;

} while ( quotient );

// Only apply negative sign for base 10

if ( value < 0 && base == 10) *out++ = '-';

std::reverse( result, out );

*out = 0;

return result;

}