_strtoi64, _wcstoi64, _strtoi64_l, _wcstoi64_l

Convert a string to an __int64 value.


__int64 _strtoi64(
   const char *strSource,
   char **endptr,
   int base
__int64 _wcstoi64(
   const wchar_t *strSource,
   wchar_t **endptr,
   int base
__int64 _strtoi64_l(
   const char *strSource,
   char **endptr,
   int base,
   _locale_t locale
__int64 _wcstoi64_l(
   const wchar_t *strSource,
   wchar_t **endptr,
   int base,
   _locale_t locale


Null-terminated string to convert.

Pointer to character that stops scan.

Number base to use.

The locale to use.

Return Value

_strtoi64 returns the value represented in the string strSource, except when the representation would cause an overflow, in which case it returns _I64_MAX or _I64_MIN. The function will return 0 if no conversion can be performed. _wcstoi64 returns values analogously to strtoi64.

_I64_MAX and _I64_MIN are 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.

See _doserrno, errno, _sys_errlist, and _sys_nerr for more information on these, and other, return codes.


The _strtoi64 function converts strSource to an __int64. Both functions stop reading the string strSource at the first character they cannot recognize as part of a number. This may be the terminating null character, or it may be the first numeric character greater than or equal to base. _wcstoi64 is a wide-character version of _strtoi64; its strSource argument is a wide-character string. These functions behave identically otherwise.

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

Generic-Text Routine Mappings

TCHAR.H routine _UNICODE & _MBCS not defined _MBCS defined _UNICODE defined
_tcstoi64 _strtoi64 _strtoi64 _wcstoi64
_tcstoi64_l _strtoi64_l _strtoi64_l _wcstoi64_l

The 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; _strtoi64_l and _wcstoi64_l are identical to the corresponding function without the _l suffix except that they use the locale passed in instead. For more information, see Locale.

If endptr is not 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.

_strtoi64 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 does not fit this form stops the scan. If base is between 2 and 36, then it is 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 is not '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.


Routine Required header
_strtoi64, _strtoi64_l <stdlib.h>
_wcstoi64, _wcstoi64_l <stdlib.h> or <wchar.h>

For additional compatibility information, see Compatibility.

See also

Data Conversion
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