_strdec, _wcsdec, _mbsdec, _mbsdec_l

项目
04/28/2015

Moves a string pointer back one character.

Important

mbsdec and mbsdec_l cannot be used in applications that execute in the Windows Runtime. For more information, see CRT functions not supported with /ZW.

unsigned char *_strdec(
   const unsigned char *start,
   const unsigned char *current 
);
unsigned wchar_t *_wcsdec(
   const unsigned wchar_t *start,
   const unsigned wchar_t *current 
);
unsigned char *_mbsdec(
   const unsigned char *start,
   const unsigned char *current 
);
unsigned char *_mbsdec_l(
   const unsigned char *start,
   const unsigned char *current,
   _locale_t locale
);

Parameters

start
Pointer to any character (or for _mbsdec and _mbsdec_l, the first byte of any multibyte character) in the source string; start must precede current in the source string.
current
Pointer to any character (or for _mbsdec and _mbsdec_l, the first byte of any multibyte character) in the source string; current must follow start in the source string.
locale
Locale to use.

Return Value

_mbsdec, _mbsdec_l, _strdec, and _wcsdec each return a pointer to the character that immediately precedes current; _mbsdec returns NULL if the value of start is greater than or equal to that of current. _tcsdec maps to one of these functions and its return value depends on the mapping.

Remarks

The _mbsdec and _mbsdec_l functions return a pointer to the first byte of the multibyte character that immediately precedes current in the string that contains start.

The output value is affected by the setting of the LC_CTYPE category setting of the locale; see setlocale, _wsetlocale for more information. _mbsdec recognizes multibyte-character sequences according to the locale that's currently in use, while _mbsdec_l is identical except that it instead uses the locale parameter that's passed in. For more information, see Locale.

If start or current is NULL, the invalid parameter handler is invoked, as described in Parameter Validation. If execution is allowed to continue, this function returns EINVAL and sets errno to EINVAL.

Security Note
These functions might be vulnerable to buffer overrun threats. Buffer overruns can be used for system attacks because they can cause an unwarranted elevation of privilege. For more information, see Avoiding Buffer Overruns.

Generic-Text Routine Mappings

Tchar.h routine	_UNICODE and _MBCS not defined	_MBCS defined	_UNICODE defined
_tcsdec	_strdec	_mbsdec	_wcsdec

_strdec and _wcsdec are single-byte-character and wide-character versions of _mbsdec and _mbsdec_l. _strdec and _wcsdec are provided only for this mapping and should not be used otherwise.

For more information, see Using Generic-Text Mappings and Generic-Text Mappings.

Requirements

Routine	Required header	Optional header
_mbsdec	<mbstring.h>	<mbctype.h>
_mbsdec_l	<mbstring.h>	<mbctype.h>
_strdec	<tchar.h>
_wcsdec	<tchar.h>

For more compatibility information, see Compatibility.

Example

The following example shows a use of _tcsdec.

#include <iostream>
#include <tchar.h>
using namespace std;

int main()
{
   const TCHAR *str = _T("12345");
   cout << "str: " << str << endl;

   const TCHAR *str2;
   str2 = str + 2;
   cout << "str2: " << str2 << endl;

   TCHAR *answer;
   answer = _tcsdec( str, str2 );
   cout << "answer: " << answer << endl;

   return (0); 
}

The following example shows a use of _mbsdec.

#include <iostream>
#include <mbstring.h>
using namespace std;

int main() 
{ 
   char *str = "12345";
   cout << "str: " << str << endl;

   char *str2;
   str2 = str + 2; 
   cout << "str2: " << str2 << endl;

   unsigned char *answer;
   answer = _mbsdec( reinterpret_cast<unsigned char *>( str ), reinterpret_cast<unsigned char *>( str2 ));

   cout << "answer: " << answer << endl;

   return (0); 
}

.NET Framework Equivalent

Not applicable. To call the standard C function, use PInvoke. For more information, see Platform Invoke Examples.

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