redis-字符串

hyzqb

/* Return the length of the null-terminated string STR.  Scan for　　
   the null terminator quickly by testing four bytes at a time.  */size_tstrlen (str)     const char *str;
　　
{  const char *char_ptr;  const unsigned long int *longword_ptr;  unsigned long int longword, himagic, lomagic;  /* Handle the first few characters by reading one character at a time.
　　
     Do this until CHAR_PTR is aligned on a longword boundary.  */
　　
  for (char_ptr = str;
　　
        ((unsigned long int) char_ptr & (sizeof (longword) - 1)) != 0;
　　
            ++char_ptr)    if (*char_ptr == '\0')      return char_ptr - str;  /* All these elucidatory comments refer to 4-byte longwords,
　　
     but the theory applies equally well to 8-byte longwords.  */
　　

　　
  longword_ptr = (unsigned long int *) char_ptr;  /* Bits 31, 24, 16, and 8 of this number are zero.  Call these bits
　　
     the "holes."  Note that there is a hole just to the left of
　　
     each byte, with an extra at the end:
　　

　　
     bits:  01111110 11111110 11111110 11111111
　　
     bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
　　

　　
     The 1-bits make sure that carries propagate to the next 0-bit.
　　
     The 0-bits provide holes for carries to fall into.  */
　　
  himagic = 0x80808080L;
　　
  lomagic = 0x01010101L;  if (sizeof (longword) > 4)
　　
  {      /* 64-bit version of the magic.  */
　　
      /* Do the shift in two steps to avoid a warning if long has 32 bits.  */
　　
      himagic = ((himagic