kaisne — Mon, 29 Jun 2009 03:50:00 GMT

��一个无�W�号数是不�ؓ2^n-1(^为幂)�Q?nbsp; x&(x+1)

  ��最右侧0位改�?位：   x   |   (x+1)

  二进制补码运��公式：
  -x   =   ~x   +   1   =   ~(x-1)
  ~x   =   -x-1
  -(~x)   =   x+1
  ~(-x)   =   x-1
  x+y   =   x   -   ~y   -   1   =   (x|y)+(x&y)
  x-y   =   x   +   ~y   +   1   =   (x|~y)-(~x&y)
  x^y   =   (x|y)-(x&y)
  x|y   =   (x&~y)+y
  x&y   =   (~x|y)-~x

  x==y:         ~(x-y|y-x)
  x!=y:         x-y|y-x
  x<   y:         (x-y)^((x^y)&((x-y)^x))
  x<=y:         (x|~y)&((x^y)|~(y-x))
  x<   y:         (~x&y)|((~x|y)&(x-y))//无符号x,y比较
  x<=y:         (~x|y)&((x^y)|~(y-x))//无符号x,y比较


  使用位运��的无分支代码：

  计算�l�对�?nbsp;
  int   abs(   int   x   )
  {
  int   y   ;
  y   =   x   >>   31   ;
  return   (x^y)-y   ;//or:   (x+y)^y
  }

  �W�号函数�Q�sign(x)   =   -1,   x<0;   0,   x   ==   0   ;   1,   x   >   0
  int   sign(int   x)
  {
  return   (x>>31)   |   (unsigned(-x))>>31   ;//x=-2^31时失�?^为幂)
  }

  三值比较：cmp(x,y)   =   -1,   x   y
  int   cmp(   int   x,   int   y   )
  {
  return   (x>y)-(x-y)   ;
  }

  doz=x-y,   x>=y;   0,   x  int   doz(int   x,   int   y   )
  {
  int   d   ;
  d   =   x-y   ;
  return   d   &   ((~(d^((x^y)&(d^x))))>>31)   ;
  }

  int   max(int   x,   int   y   )
  {
  int   m   ;
  m   =   (x-y)>>31   ;
  return   y   &   m   |   x   &   ~m   ;
  }

  不��用第三方交换x,y:
  1.x   ^=   y   ;   y   ^=   x   ;   x   ^=   y   ;
  2.x   =   x+y   ;   y   =   x-y   ;   x   =   x-y   ;
  3.x   =   x-y   ;   y   =   y+x   ;   x   =   y-x   ;
  4.x   =   y-x   ;   x   =   y-x   ;   x   =   x+y   ;

  双��g��?x   =   a,   x==b;   b,   x==a//常规�~�码为x   =   x==a   ?   b   :a   ;
  1.x   =   a+b-x   ;
  2.x   =   a^b^x   ;

  下舍入到2的k�ơ方的倍数:
  1.x   &   ((-1)<  2.(((unsigned)x)>>k)<  上舍入：
  1.   t   =   (1<  2.t   =   (-1)<
  位计�?�l�计1位的数量�Q?nbsp;
  1.
  int   pop(unsigned   x)
  {
  x   =   x-((x>>1)&0x55555555)   ;
  x   =   (x&0x33333333)   +   ((x>>2)   &   0x33333333   )   ;
  x   =   (x+(x>>4))   &   0x0f0f0f0f   ;
  x   =   x   +   (x>>8)   ;
  x   =   x   +   (x>>16)   ;
  return   x   &   0x0000003f   ;
  }
  2.
  int   pop(unsigned   x)   {
  static   char   table[256]   =   {   0,1,1,2,   1,2,2,3,   ....,   6,7,7,8   }   ;
  return   table[x&0xff]+table[(x>>8)&0xff]+table[(x>>16)&0xff]+table[(x>>24)]   ;
  }

  奇偶性计��?
  x   =   x   ^   (   x>>1   )   ;
  x   =   x   ^   (   x>>2   )   ;
  x   =   x   ^   (   x>>4   )   ;
  x   =   x   ^   (   x>>8   )   ;
  x   =   x   ^   (   x>>16   )   ;
  �l�果中位于x最低位�Q�对无符号x,�l�果的第i位是原数�W�i位到最左侧位的奇偶�?nbsp;


  位反转：
  unsigned   rev(unsigned   x)
  {
  x   =   (x   &   0x55555555)   <<   1   |   (x>>1)   &   0x55555555   ;
  x   =   (x   &   0x33333333)   <<   2   |   (x>>2)   &   0x33333333   ;
  x   =   (x   &   0x0f0f0f0f)   <<   4   |   (x>>4)   &   0x0f0f0f0f   ;
  x   =   (x<<24)   |   ((x&0xff00)<<8)   |   ((x>>8)   &   0xff00)   |   (x>>24)   ;
  return   x   ;
  }

  递增位反转后的数�Q?nbsp;
  unsigned   inc_r(unsigned   x)
  {
  unsigned   m   =   0x80000000   ;
  x   ^=   m   ;
  if(   (int)x   >=   0   )
  do   {   m   >>=   1   ;   x   ^=   m   ;   }   while(   x   <   m   )   ;
  return   x   ;
  }

  混选位�Q?nbsp;
  abcd   efgh   ijkl   mnop   ABCD   EFGH   IJKL   MNOP->aAbB   cCdD   eEfF   gGhH   iIjJ   kKlL   mMnN   oOpP
  unsigned   ps(unsigned   x)
  {
  unsigned   t   ;
  t   =   (x   ^   (x>>8))   &   0x0000ff00;   x   =   x   ^   t   ^   (t<<8)   ;
  t   =   (x   ^   (x>>4))   &   0x00f000f0;   x   =   x   ^   t   ^   (t<<4)   ;
  t   =   (x   ^   (x>>2))   &   0x0c0c0c0c;   x   =   x   ^   t   ^   (t<<2)   ;
  t   =   (x   ^   (x>>1))   &   0x22222222;   x   =   x   ^   t   ^   (t<<1)   ;
  return   x   ;
  }

  位压�~�：
  选择�q�右�U�d��x中对应于掩码m�?位的�?如：compress(abcdefgh,01010101)=0000bdfh
  compress_left(x,m)操作与此�c�M��Q�但�l�果位在左边:   bdfh0000.
  unsigned   compress(unsigned   x,   unsigned   m)
  {
  unsigned   mk,   mp,   mv,   t   ;
  int   i   ;

  x   &=   m   ;
  mk   =   ~m   <<   1   ;
  for(   i   =   0   ;   i   <   5   ;   ++i   )   {
  mp   =   mk   ^   (   mk   <<   1)   ;
  mp   ^=   (   mp   <<   2   )   ;
  mp   ^=   (   mp   <<   4   )   ;
  mp   ^=   (   mp   <<   8   )   ;
  mp   ^=   (   mp   <<   16   )   ;
  mv   =   mp   &   m   ;
  m   =   m   ^   mv   |   (mv   >>   (1<  t   =   x   &   mv   ;
  x     =   x   ^   t   |   (   t   >>   (   1<  mk   =   mk   &   ~mp   ;
  }
  return   x   ;
  }


  位置换：
  �?2�?位数表示从最低位开始的位的目标位置�Q�结果是一�?2*5的位矩阵�Q?nbsp;
  ��该矩阵沿次对角�U��{�|�后�?�?2位字p[5]存放�?nbsp;
  SAG(x,m)   =   compress_left(x,m)   |   compress(x,~m)   ;
  准备工作�Q?nbsp;
  void   init(   unsigned   *p   )   {
  p[1]   =   SAG(   p[1],   p[0]   )   ;
  p[2]   =   SAG(   SAG(   p[2],   p[0]),   p[1]   )   ;
  p[3]   =   SAG(   SAG(   SAG(   p[3],   p[0]   ),   p[1]),   p[2]   )   ;
  p[4]   =   SAG(   SAG(   SAG(   SAG(   p[4],   p[0]   ),   p[1])   ,p[2]),   p[3]   )   ;
  }
  实际�|�换�Q?nbsp;
  int   rep(   unsigned   x   )   {
  x   =   SAG(x,p[0]);
  x   =   SAG(x,p[1]);
  x   =   SAG(x,p[2]);
  x   =   SAG(x,p[3]);
  x   =   SAG(x,p[4]);
  return   x   ;
  }

  二进制码到GRAY码的转换:
  unsigned   B2G(unsigned   B   )
  {
  return   B   ^   (B>>1)   ;
  }
  GRAY码到二进制码:
  unsigned   G2B(unsigned   G)
  {
  unsigned   B   ;
  B   =   G   ^   (G>>1)   ;
  B   =   G   ^   (G>>2)   ;
  B   =   G   ^   (G>>4)   ;
  B   =   G   ^   (G>>8)   ;
  B   =   G   ^   (G>>16)   ;
  return   B   ;
  }

  扑և�最�?字节的位�|?
  int   zbytel(   unsigned   x   )
  {
  static   cahr   table[16]   =   {   4,3,2,2,   1,1,1,1,   0,0,0,0,   0,0,0,0   }   ;
  unsigned   y   ;
  y   =   (x&0x7f7f7f7f)   +   0x7f7f7f7f   ;
  y   =   ~(y|x|0x7f7f7f7f)   ;
  return   table[y*0x00204081   >>   28]   ;//乘法可用�U�M��和加完成
  }

转自�Q�http://www.x-boy.com/trackback.asp?tbID=64

kaisne 2009-06-29 11:50 发表评论

kaisne — Sat, 30 May 2009 18:29:00 GMT

摘要: 今天看看了symbian的活动对象介�l�，于是写一个有��x��动对象的��程序，该程序是一个GUI�E�序�Q�在view动态显�C�当前的旉��Q��用到的活动对象定义如下： /**//* ============================================================================ Name ... 阅读全文

kaisne 2009-05-31 02:29 发表评论

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