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_atoi64, _atoi64_l, _wtoi64, _wtoi64_l

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Converts a string to a 64-bit integer.

Syntax

__int64 _atoi64(
   const char *str
);
__int64 _wtoi64(
   const wchar_t *str
);
__int64 _atoi64_l(
   const char *str,
   _locale_t locale
);
__int64 _wtoi64_l(
   const wchar_t *str,
   _locale_t locale
);

Parameters

str
String to be converted.

locale
Locale to use.

Return value

Each function returns the __int64 value produced by interpreting the input characters as a number. The return value is 0 for _atoi64 if the input can't be converted to a value of that type.

If the functions overflow with large positive integral values, they return I64_MAX. The functions return I64_MIN if they overflow with large negative integral values.

In all out-of-range cases, errno is set to ERANGE. If the parameter passed in is NULL, the invalid parameter handler is invoked, as described in Parameter validation. If execution is allowed to continue, these functions set errno to EINVAL and return 0.

Remarks

These functions convert a character string to a 64-bit integer value.

The input string is a sequence of characters that can be interpreted as a numerical value of the specified type. The function stops reading the input string at the first character that it can't recognize as part of a number. This character might be the null character ('\0' or L'\0') terminating the string.

The str argument to _atoi64 has the following form:

[whitespace] [sign] [digits]

A whitespace consists of space or tab characters, which are ignored; sign is either plus (+) or minus (-); and digits are one or more digits.

_wtoi64 is identical to _atoi64 except that it takes a wide character string as a parameter.

The versions of these functions with the _l suffix are identical except that they use the locale parameter passed in instead of the current locale. For more information, see Locale.

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

Generic-text routine mappings

Tchar.h routine _UNICODE and _MBCS not defined _MBCS defined _UNICODE defined
_tstoi64 _atoi64 _atoi64 _wtoi64
_ttoi64 _atoi64 _atoi64 _wtoi64

Requirements

Routines Required header
_atoi64, _atoi64_l <stdlib.h>
_wtoi64, _wtoi64_l <stdlib.h> or <wchar.h>

Example

This program shows how numbers stored as strings can be converted to numeric values using the _atoi64 functions.

// crt_atoi64.c
// This program shows how numbers stored as
// strings can be converted to numeric values
// using the _atoi64 functions.
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>

int main( void )
{
    char    *str = NULL;
    __int64 value = 0;

    // An example of the _atoi64 function
    // with leading and trailing white spaces.
    str = "  -2309 ";
    value = _atoi64( str );
    printf( "Function: _atoi64( \"%s\" ) = %d\n", str, value );

    // Another example of the _atoi64 function
    // with an arbitrary decimal point.
    str = "314127.64";
    value = _atoi64( str );
    printf( "Function: _atoi64( \"%s\" ) = %d\n", str, value );

    // Another example of the _atoi64 function
    // with an overflow condition occurring.
    str = "3336402735171707160320";
    value = _atoi64( str );
    printf( "Function: _atoi64( \"%s\" ) = %d\n", str, value );
    if (errno == ERANGE)
    {
       printf("Overflow condition occurred.\n");
    }
}

Function: _atoi64( "  -2309 " ) = -2309
Function: _atoi64( "314127.64" ) = 314127
Function: _atoi64( "3336402735171707160320" ) = -1
Overflow condition occurred.

See also

Data conversion
Math and floating-point support
Locale
_ecvt
_fcvt
_gcvt
setlocale, _wsetlocale
_atodbl, _atodbl_l, _atoldbl, _atoldbl_l, _atoflt, _atoflt_l