_itoa_s, _i64toa_s, _ui64toa_s, _itow_s, _i64tow_s, _ui64tow_s

 

For the latest documentation on Visual Studio 2017 RC, see Visual Studio 2017 RC Documentation.

Converts an integer to a string. These are versions of _itoa, _i64toa, _ui64toa, _itow, _i64tow, _ui64tow with security enhancements as described in Security Features in the CRT.

errno_t _itoa_s(  
   int value,  
   char *buffer,  
   size_t sizeInCharacters,  
   int radix   
);  
errno_t _i64toa_s(  
   __int64 value,  
   char *buffer,  
   size_t sizeInCharacters,  
   int radix   
);  
errno_t _ui64toa_s(  
   unsigned _int64 value,  
   char *buffer,  
   size_t sizeInCharacters,  
   int radix   
);  
errno_t _itow_s(  
   int value,  
   wchar_t *buffer,  
   size_t sizeInCharacters,  
   int radix   
);  
errno_t _i64tow_s(  
   __int64 value,  
   wchar_t *buffer,  
   size_t sizeInCharacters,  
   int radix   
);  
errno_t _ui64tow_s(  
   unsigned __int64 value,  
   wchar_t *buffer,  
   size_t sizeInCharacters,  
   int radix   
);  
template <size_t size>  
errno_t _itoa_s(  
   int value,  
   char (&buffer)[size],  
   int radix   
); // C++ only  
template <size_t size>  
errno_t _itow_s(  
   int value,  
   wchar_t (&buffer)[size],  
   int radix   
); // C++ only  

Parameters

[in] value
Number to be converted.

[out] buffer
Filled with the result of the conversion.

[in] sizeInCharacters
Size of the buffer in single-byte characters or wide characters.

[in] radix
Base of value; which must be in the range 2–36.

Zero if successful; an error code on failure. If any of the following conditions applies, the function invokes an invalid parameter handler, as described in Parameter Validation.

Error Conditions

valuebuffersizeInCharactersradixReturn
anyNULLanyanyEINVAL
anyany<=0anyEINVAL
anyany<= length of the result string requiredanyEINVAL
anyanyanyradix < 2 or radix > 36EINVAL

Security Issues

These functions can generate an access violation if buffer does not point to valid memory and is not NULL, or if the length of the buffer is not long enough to hold the result string.

Except for the parameters and return value, the _itoa_s functions have the same behavior as the corresponding less secure versions.

In C++, using these functions is simplified by template overloads; the overloads can infer buffer length automatically (eliminating the need to specify a size argument) and they can automatically replace older, non-secure functions with their newer, secure counterparts. For more information, see Secure Template Overloads.

The debug versions of these functions first fill the buffer with 0xFD. To disable this behavior, use _CrtSetDebugFillThreshold.

Generic-Text Routine Mappings

Tchar.h routine_UNICODE and _MBCS not defined_MBCS defined_UNICODE defined
_itot_s_itoa_s_itoa_s_itow_s
_i64tot_s_i64toa_s_i64toa_s_i64tow_s
_ui64tot_s_ui64toa_s_ui64toa_s_ui64tow_s
RoutineRequired header
_itoa_s<stdlib.h>
_i64toa_s<stdlib.h>
_ui64toa_s<stdlib.h>
_itow_s<stdlib.h> or <wchar.h>
_i64tow_s<stdlib.h> or <wchar.h>
_ui64tow_s<stdlib.h> or <wchar.h>

For more compatibility information, see Compatibility in the Introduction.

// crt_itoa_s.c  
#include <stdlib.h>  
#include <string.h>  
  
int main( void )  
{  
    char buffer[65];  
    int r;  
    for( r=10; r>=2; --r )  
    {  
       _itoa_s( -1, buffer, 65, r );  
       printf( "base %d: %s (%d chars)\n", r, buffer, strnlen(buffer, _countof(buffer)) );  
    }  
    printf( "\n" );  
    for( r=10; r>=2; --r )  
    {  
       _i64toa_s( -1L, buffer, 65, r );  
       printf( "base %d: %s (%d chars)\n", r, buffer, strnlen(buffer, _countof(buffer)) );  
    }  
    printf( "\n" );  
    for( r=10; r>=2; --r )  
    {  
       _ui64toa_s( 0xffffffffffffffffL, buffer, 65, r );  
       printf( "base %d: %s (%d chars)\n", r, buffer, strnlen(buffer, _countof(buffer)) );  
    }  
}  

base 10: -1 (2 chars)  
base 9: 12068657453 (11 chars)  
base 8: 37777777777 (11 chars)  
base 7: 211301422353 (12 chars)  
base 6: 1550104015503 (13 chars)  
base 5: 32244002423140 (14 chars)  
base 4: 3333333333333333 (16 chars)  
base 3: 102002022201221111210 (21 chars)  
base 2: 11111111111111111111111111111111 (32 chars)  
  
base 10: -1 (2 chars)  
base 9: 145808576354216723756 (21 chars)  
base 8: 1777777777777777777777 (22 chars)  
base 7: 45012021522523134134601 (23 chars)  
base 6: 3520522010102100444244423 (25 chars)  
base 5: 2214220303114400424121122430 (28 chars)  
base 4: 33333333333333333333333333333333 (32 chars)  
base 3: 11112220022122120101211020120210210211220 (41 chars)  
base 2: 1111111111111111111111111111111111111111111111111111111111111111 (64 chars)  
  
base 10: 18446744073709551615 (20 chars)  
base 9: 145808576354216723756 (21 chars)  
base 8: 1777777777777777777777 (22 chars)  
base 7: 45012021522523134134601 (23 chars)  
base 6: 3520522010102100444244423 (25 chars)  
base 5: 2214220303114400424121122430 (28 chars)  
base 4: 33333333333333333333333333333333 (32 chars)  
base 3: 11112220022122120101211020120210210211220 (41 chars)  
base 2: 1111111111111111111111111111111111111111111111111111111111111111 (64 chars)  

System::Convert::ToString

Data Conversion
_ltoa, _ltow
_ultoa, _ultow

Show: