_strtoui64, _wcstoui64, _strtoui64_l, _wcstoui64_l

Convert a string to an unsigned __int64 value.

Syntax

unsigned __int64 _strtoui64(
   const char *strSource,
   char **endptr,
   int base
);
unsigned __int64 _wcstoui64(
   const wchar_t *strSource,
   wchar_t **endptr,
   int base
);
unsigned __int64 _strtoui64_l(
   const char *strSource,
   char **endptr,
   int base,
   _locale_t locale
);
unsigned __int64 _wcstoui64_l(
   const wchar_t *strSource,
   wchar_t **endptr,
   int base,
   _locale_t locale
);

Parameters

strSource
Null-terminated string to convert.

endptr
Pointer to character that stops scan.

base
Number base to use.

locale
Locale to use.

Return value

_strtoui64 returns the value represented in the string strSource, except when the representation would cause an overflow, in which case it returns _UI64_MAX. _strtoui64 returns 0 if no conversion can be performed.

_UI64_MAX is defined in LIMITS.H.

If strSource is NULL or the base is nonzero and either less than 2 or greater than 36, errno is set to EINVAL.

For more information on return codes, see errno, _doserrno, _sys_errlist, and _sys_nerr.

Remarks

The _strtoui64 function converts strSource to an unsigned __int64. _wcstoui64 is a wide-character version of _strtoui64; its strSource argument is a wide-character string. Otherwise these functions behave identically.

Both functions stop reading the string strSource at the first character they can't recognize as part of a number. It may be the terminating null character, or it may be the first numeric character greater than or equal to base.

By default, this function's global state is scoped to the application. To change it, see Global state in the CRT.

Generic-text routine mappings

TCHAR.H routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_tcstoui64	_strtoui64	_strtoui64	_wcstoui64
_tcstoui64_l	_strtoui64_l	_strtoui64_l	_wcstoui64_l

The current locale's LC_NUMERIC category setting determines recognition of the radix character in strSource; for more information, see setlocale. The functions without the _l suffix use the current locale; _strtoui64_l and _wcstoui64_l are identical to the corresponding functions without the _l suffix except that they use the locale passed in instead. For more information, see Locale.

If endptr isn't NULL, a pointer to the character that stopped the scan is stored at the location pointed to by endptr. If no conversion can be performed (no valid digits were found or an invalid base was specified), the value of strSource is stored at the location pointed to by endptr.

_strtoui64 expects strSource to point to a string of the following form:

[whitespace] [{+ | -}] [0 [{ x | X }]] [digits | letters]

A whitespace may consist of space and tab characters, which are ignored. digits are one or more decimal digits. letters are one or more of the letters 'a' through 'z' (or 'A' through 'Z'). The first character that doesn't fit this form stops the scan. If base is between 2 and 36, then it's used as the base of the number. If base is 0, the initial characters of the string pointed to by strSource are used to determine the base. If the first character is '0' and the second character isn't 'x' or 'X', the string is interpreted as an octal integer. If the first character is '0' and the second character is 'x' or 'X', the string is interpreted as a hexadecimal integer. If the first character is '1' through '9', the string is interpreted as a decimal integer. The letters 'a' through 'z' (or 'A' through 'Z') are assigned the values 10 through 35; only letters whose assigned values are less than base are permitted. The first character outside the range of the base stops the scan. For example, if base is 0 and the first character scanned is '0', an octal integer is assumed and an '8' or '9' character will stop the scan.

Requirements

Function	Required header
_strtoui64	<stdlib.h>
_wcstoui64	<stdlib.h> or <wchar.h>
_strtoui64_l	<stdlib.h>
_wcstoui64_l	<stdlib.h> or <wchar.h>

For more compatibility information, see Compatibility.

Example

// crt_strtoui64.c
#include <stdio.h>

unsigned __int64 atoui64(const char *szUnsignedInt) {
   return _strtoui64(szUnsignedInt, NULL, 10);
}

int main() {
   unsigned __int64 u = atoui64("18446744073709551615");
   printf( "u = %I64u\n", u );
}

u = 18446744073709551615

See also

Data conversion
Locale
localeconv
setlocale, _wsetlocale
String to numeric value functions
strtod, _strtod_l, wcstod, _wcstod_l
strtoul, _strtoul_l, wcstoul, _wcstoul_l
atof, _atof_l, _wtof, _wtof_l