strtoul, wcstoul (Windows CE 5.0)

项目
09/14/2012

Developing an Application > Microsoft C Run-time Library for Windows CE > Run-time Library Reference

Convert strings to an unsigned long-integer value.

long strtol( const char *nptr, char **endptr, int base );unsigned long wcstoul( const wchar_t *nptr, wchar_t **endptr, intbase);

Parameters

nptr
Null-terminated string to convert.
endptr
Pointer to character that stops scan.
base
Number base to use.

Return Values

strtoul returns the value represented in the string nptr, except when the representation would cause an overflow, in which case it returns LONG_MAX or LONG_MIN. strtoul returns 0 if no conversion can be performed.

wcstoul returns the converted value, if any, or ULONG_MAX on overflow. wcstoul returns 0 if no conversion can be performed.

Remarks

These functions are supported by all versions of the C run-time libraries.

strtoul converts the input string nptr to an unsigned long.

strtoul stops reading the string nptr at the first character it cannot recognize as part of a number. This can be the terminating null character, or it can be the first numeric character greater than or equal to base.

The LC_NUMERIC category setting of the current locale determines recognition of the radix character in nptr.

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 nptr is stored at the location pointed to by endptr.

wcstoul is a wide-character version of strtoul; its nptr argument is a wide-character string. Otherwise these functions behave identically.

The following table shows generic-text routine mappings for this function.

TCHAR.H Routine	_UNICODE Defined
_tcstoul	wcstoul

For more information about TCHAR.H routines, see Generic Text Mappings.

stoul expects nptr to point to a string of the following form:

[whitespace] [{+ | –}] [0 [{ x | X }]] [digits]

A whitespace may consist of space and tab characters, which are ignored; digits are one or more decimal digits. 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 nptr 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; otherwise, it is interpreted as a decimal number.

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.

Example

Description

This program uses strtod to convert a string to a double-precision value; strtol to convert a string to long integer values; and strtoul to convert a string to unsigned long-integer values.

Code

#include <stdlib.h>
#include <stdio.h>

void main( void )
{
   char   *string, *stopstring;
   double x;
   long   l;
   int    base;
   unsigned long ul;
   string = "3.1415926This stopped it";
   x = strtod( string, &stopstring );
   printf( "string = %s\n", string );
   printf("   strtod = %f\n", x );
   printf("   Stopped scan at: %s\n\n", stopstring );
   string = "-10110134932This stopped it";
   l = strtol( string, &stopstring, 10 );
   printf( "string = %s", string );
   printf("   strtol = %ld", l );
   printf("   Stopped scan at: %s", stopstring );
   string = "10110134932";
   printf( "string = %s\n", string );
   /* Convert string using base 2, 4, and 8: */
   for( base = 2; base <= 8; base *= 2 )
   {
      /* Convert the string: */
      ul = strtoul( string, &stopstring, base );
      printf( "   strtol = %ld (base %d)\n", ul, base );
      printf( "   Stopped scan at: %s\n", stopstring );
   }
}
// Output
string = 3.1415926This stopped it
   strtod = 3.141593
   Stopped scan at: This stopped it

string = -10110134932This stopped it   strtol = -2147483647   Stopped scan at: This stopped itstring = 10110134932
   strtol = 45 (base 2)
   Stopped scan at: 34932
   strtol = 4423 (base 4)
   Stopped scan at: 4932
   strtol = 2134108 (base 8)
   Stopped scan at: 932

Requirements

OS Versions: Windows CE 2.0 and later.

Header: stdio.h, string.h.

Link Library: coredll.dll.

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