stpcpy.c

Newlib 嵌入式 C库 标准实现代码

/*
FUNCTION
	<<stpcpy>>---copy string returning a pointer to its end

INDEX
	stpcpy

ANSI_SYNOPSIS
	#include <string.h>
	char *stpcpy(char *<[dst]>, const char *<[src]>);

TRAD_SYNOPSIS
	#include <string.h>
	char *stpcpy(<[dst]>, <[src]>)
	char *<[dst]>;
	char *<[src]>;

DESCRIPTION
	<<stpcpy>> copies the string pointed to by <[src]>
	(including the terminating null character) to the array
	pointed to by <[dst]>.

RETURNS
	This function returns a pointer to the end of the destination string,
	thus pointing to the trailing '\0'.

PORTABILITY
<<stpcpy>> is a GNU extension, candidate for inclusion into POSIX/SUSv4.

<<stpcpy>> requires no supporting OS subroutines.

QUICKREF
	stpcpy gnu
*/

#include <string.h>
#include <limits.h>

/*SUPPRESS 560*/
/*SUPPRESS 530*/

/* Nonzero if either X or Y is not aligned on a "long" boundary.  */
#define UNALIGNED(X, Y) \
  (((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))

#if LONG_MAX == 2147483647L
#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
#else
#if LONG_MAX == 9223372036854775807L
/* Nonzero if X (a long int) contains a NULL byte. */
#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
#else
#error long int is not a 32bit or 64bit type.
#endif
#endif

#ifndef DETECTNULL
#error long int is not a 32bit or 64bit byte
#endif

char*
_DEFUN (stpcpy, (dst, src),
	char *dst _AND
	_CONST char *src)
{
#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
  long *aligned_dst;
  _CONST long *aligned_src;

  /* If SRC or DEST is unaligned, then copy bytes.  */
  if (!UNALIGNED (src, dst))
    {
      aligned_dst = (long*)dst;
      aligned_src = (long*)src;

      /* SRC and DEST are both "long int" aligned, try to do "long int"
         sized copies.  */
      while (!DETECTNULL(*aligned_src))
        {
          *aligned_dst++ = *aligned_src++;
        }

      dst = (char*)aligned_dst;
      src = (char*)aligned_src;
    }
#endif /* not PREFER_SIZE_OVER_SPEED */

  while ((*dst++ = *src++))
    ;
  return --dst;
}