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memchr, wmemchr

  • Άρθρο

Find characters in a buffer.

Syntax

void *memchr(
   const void *buffer,
   int c,
   size_t count
); // C only
void *memchr(
   void *buffer,
   int c,
   size_t count
); // C++ only
const void *memchr(
   const void *buffer,
   int c,
   size_t count
); // C++ only
wchar_t *wmemchr(
   const wchar_t * buffer,
   wchar_t c,
   size_t count
); // C only
wchar_t *wmemchr(
   wchar_t * buffer,
   wchar_t c,
   size_t count
); // C++ only
const wchar_t *wmemchr(
   const wchar_t * buffer,
   wchar_t c,
   size_t count
); // C++ only

Parameters

buffer
Pointer to buffer.

c
Character to look for.

count
Number of characters to check.

Return value

If successful, returns a pointer to the first location of c in buffer. Otherwise it returns NULL.

Remarks

memchr and wmemchr look for the first occurrence of c in the first count characters of buffer. It stops when it finds c or when it has checked the first count characters.

In C, these functions take a const pointer for the first argument. In C++, two overloads are available. The overload taking a pointer to const returns a pointer to const; the version that takes a pointer to non-const returns a pointer to non-const. The macro _CRT_CONST_CORRECT_OVERLOADS is defined if both the const and non-const versions of these functions are available. If you require the non-const behavior for both C++ overloads in C++, define the symbol _CONST_RETURN.

Requirements

Routine Required header
memchr <memory.h> or <string.h>
wmemchr <wchar.h>

For more information about compatibility, see Compatibility.

Libraries

All versions of the C run-time libraries.

Example

// crt_memchr.c

#include <memory.h>
#include <stdio.h>

int  ch = 'r';
char str[] =    "lazy";
char string[] = "The quick brown dog jumps over the lazy fox";
char fmt1[] =   "         1         2         3         4         5";
char fmt2[] =   "12345678901234567890123456789012345678901234567890";

int main( void )
{
   char *pdest;
   int result;
   printf( "String to be searched:\n             %s\n", string );
   printf( "             %s\n             %s\n\n", fmt1, fmt2 );

   printf( "Search char: %c\n", ch );
   pdest = memchr( string, ch, sizeof( string ) );
   result = (int)(pdest - string + 1);
   if ( pdest != NULL )
      printf( "Result:      %c found at position %d\n", ch, result );
   else
      printf( "Result:      %c not found\n" );
}

Output

String to be searched:
             The quick brown dog jumps over the lazy fox
                      1         2         3         4         5
             12345678901234567890123456789012345678901234567890

Search char: r
Result:      r found at position 12

See also

Buffer manipulation
_memccpy
memcmp, wmemcmp
memcpy, wmemcpy
memset, wmemset
strchr, wcschr, _mbschr, _mbschr_l