linux按位运算datalab-handout

进入bits.c ，根据bits.c中的具体要求补全以下13个函数：

•intbitXor(intx, int y);

•inttmin(void);

•intisTmax(intx);

•ntallOddBits(intx);

•intnegate(int x);

•intisAsciiDigit(intx);

•intconditional(int x, inty, int z);

•intisLessOrEqual(intx, int y);

•intlogicalNeg(intx);

•inthowManyBits(intx);

•unsignedfloat_twice(unsigneduf);

•unsignedfloat_i2f(int x);

•intfloat_f2i(unsigned uf);

代码如下

//1/*  * bitXor - x^y using only ~ and &  *   Example: bitXor(4, 5) = 1 *   Legal ops: ~ & *   Max ops: 14 *   Rating: 1 */int bitXor(int x, int y) {    return (~(~(~x&y)&(~(x&~y))));}/*  * tmin - return minimum two's complement integer  *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 4 *   Rating: 1 */int tmin(void) {  return 1<<31;}//2/* * isTmax - returns 1 if x is the maximum, two's complement number, *     and 0 otherwise  *   Legal ops: ! ~ & ^ | + *   Max ops: 10 *   Rating: 2 */int isTmax(int x) {  return !((x+x+2)|!(~x));}/*  * allOddBits - return 1 if all odd-numbered bits in word set to 1 *   Examples allOddBits(0xFFFFFFFD) = 0, allOddBits(0xAAAAAAAA) = 1 *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 12 *   Rating: 2 */int allOddBits(int x) {   int y=x>>16;x=x&y;   y=x>>8;x=x&y;   return !((x&0xAA)^0xAA);}/*  * negate - return -x  *   Example: negate(1) = -1. *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 5 *   Rating: 2 */int negate(int x) {  return (~x+1);}//3/*  * isAsciiDigit - return 1 if 0x30 <= x <= 0x39 (ASCII codes for characters '0' to '9') *   Example: isAsciiDigit(0x35) = 1. *            isAsciiDigit(0x3a) = 0. *            isAsciiDigit(0x05) = 0. *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 15 *   Rating: 3 */int isAsciiDigit(int x) {  int min=0x30;  int max=0x39;    return (!((x+(~min+1))>>31)) & (!((max+(~x+1))>>31));}/*  * conditional - same as x ? y : z  *   Example: conditional(2,4,5) = 4 *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 16 *   Rating: 3 */int conditional(int x, int y, int z) {  return ((~(~!x+1))&y)|((~!x+1)&z);}/*  * isLessOrEqual - if x <= y  then return 1, else return 0  *   Example: isLessOrEqual(4,5) = 1. *   Legal ops: ! ~ & ^ | + << >> *   Max ops: 24 *   Rating: 3 */int isLessOrEqual(int x, int y) {  int x1=x>>31;  int y1=y>>31;  int r=((x+(~y))>>31)&(!(x1^y1));  int s=x1&(!y1);  return r|s;}//4/*  * logicalNeg - implement the ! operator, using all of  *              the legal operators except ! *   Examples: logicalNeg(3) = 0, logicalNeg(0) = 1 *   Legal ops: ~ & ^ | + << >> *   Max ops: 12 *   Rating: 4  */int logicalNeg(int x) {  return ~(((~x+1)|x)>> 31)&1;}/* howManyBits - return the minimum number of bits required to represent x in *             two's complement *  Examples: howManyBits(12) = 5 *            howManyBits(298) = 10 *            howManyBits(-5) = 4 *            howManyBits(0)  = 1 *            howManyBits(-1) = 1 *            howManyBits(0x80000000) = 32 *  Legal ops: ! ~ & ^ | + << >> *  Max ops: 90 *  Rating: 4 */int howManyBits(int x) {  int shiftSign = x >> 31;    int operations = shiftSign ^ x;          int negateOps = !operations;    int oppSign =  (!(!operations) << 31) >> 31;    int shift16 = !(!(operations >> 16)) << 4;    operations = operations >> shift16;    int shift8 = !(!(operations >> 8)) << 3;    operations = operations >> shift8;    int shift4 = !(!(operations >> 4)) << 2;    operations = operations >> shift4;    int shift2 = !(!(operations >> 2)) << 1;    operations = operations >> shift2;    int shift1 = !(!(operations >> 1));    operations = shift16 + shift8 + shift4 + shift2 + shift1;    operations += 2;       return (negateOps | (operations & oppSign));}//float/*  * float_twice - Return bit-level equivalent of expression 2*f for *   floating point argument f. *   Both the argument and result are passed as unsigned int's, but *   they are to be interpreted as the bit-level representation of *   single-precision floating point values. *   When argument is NaN, return argument *   Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while *   Max ops: 30 *   Rating: 4 */unsigned float_twice(unsigned uf) {   unsigned temp = uf & 0x7F800000;      unsigned sign = uf & 0x80000000;      if (temp) {            if (  temp != 0x7F800000 ) {                  uf = uf + 0x00800000 ;                  if (temp == 0x7F000000) uf = (uf & 0xFF800000);            }      } else              uf = ( uf << 1) | sign ;       return uf;}/*  * float_i2f - Return bit-level equivalent of expression (float) x *   Result is returned as unsigned int, but *   it is to be interpreted as the bit-level representation of a *   single-precision floating point values. *   Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while *   Max ops: 30 *   Rating: 4 */unsigned float_i2f(int x) {   unsigned shiftLeft=0;     unsigned afterShift, tmp, flag;     unsigned absX=x;     unsigned sign=0;      if (x==0) return 0;      if (x<0)      {          sign=0x80000000;          absX=-x;      }      afterShift=absX;      while (1)          {          tmp=afterShift;          afterShift<<=1;          hiftLeft++;          if (tmp & 0x80000000) break;          }      if ((afterShift & 0x01ff)>0x0100)          flag=1;      else if ((afterShift & 0x03ff)==0x0300)          flag=1;      else          flag=0;      return sign + (afterShift>>9) + ((159-shiftLeft)<<23) + flag;  }/*  * float_f2i - Return bit-level equivalent of expression (int) f *   for floating point argument f. *   Argument is passed as unsigned int, but *   it is to be interpreted as the bit-level representation of a *   single-precision floating point value. *   Anything out of range (including NaN and infinity) should return *   0x80000000u. *   Legal ops: Any integer/unsigned operations incl. ||, &&. also if, while *   Max ops: 30 *   Rating: 4 */int float_f2i(unsigned uf) {        int flag = uf & (1 << 31);        uf = uf & ~(1 << 31);        int exp = (uf >> 23);        int num = exp + ~126;        if( !exp || (num & (1 << 31)))            return 0;        else if(!(exp ^ 0xFF))        {            return (1 << 31);        }        else        {            num = 1 << num;            if(flag)                return ~num + 1;            else                return num;        }}

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