/*
* CS:APP Data Lab
*
* bits.c - Source file with your solutions to the Lab.
* This is the file you will hand in to your instructor.
*
* WARNING: Do not include the header; it confuses the dlc
* compiler. You can still use printf for debugging without including
* , although you might get a compiler warning. In general,
* it's not good practice to ignore compiler warnings, but in this
* case it's OK.
*/
#include "btest.h"
#include
/*
* Instructions to Students:
*
* STEP 1: Fill in the following struct with your identifying info.
*/
team_struct team = {
/* Team name: Replace with the identifying string you want to show
* up on the lab webpage with your results. It need not be your
* Route Y login(s) if you wish to remain anonymous */
"Bantha Fodder",
/* Student name 1: Replace with the full name of first team member */
"Brian Goodrich",
/* Login ID 1: Replace with the Route Y login ID of first team member */
"bg59",
/* The following should only be changed if there are two team members */
/* Student name 2: Full name of the second team member */
"James Stevenson",
/* Login ID 2: Route Y login ID of the second team member */
"jes84"
};
#if 0
/*
* STEP 2: Read the following instructions carefully.
*/
You will provide your solution to the Data Lab by
editing the collection of functions in this source file.
CODING RULES:Replace the "return" statement in each function with one
or more lines of C code that implements the function.Your code
must conform to the following style:int
Funct (arg1, arg2, ...)
{
/* brief description of how your implementation works */
int var1 = Expr1;
...int varM = ExprM;
varJ = ExprJ;
...varN = ExprN;
return ExprR;
}
Each "Expr" is an expression using ONLY the following:
1. Integer constants 0 through 255 (0xFF), inclusive.You are not allowed to use big constants such as 0xffffffff.2. Function arguments and local variables (no global variables).3. Unary integer operations ! ~4. Binary integer operations & ^|+<<>>Some of the problems restrict the set of allowed operators even further.Each "Expr" may consist of multiple operators.You are not restricted to one operator per line.You are expressly forbidden to:
1. Use any control constructs such as if,
do
, while, for, switch, etc
.2. Define or use any macros.3. Define any additional functions in this file.4. Call any functions.5. Use any other operations, such as &&, ||, -, or ? : 6. Use any form of casting.You may assume that your machine:
1. Uses 2 s complement, 32 - bit representations of integers.2. Performs right shifts arithmetically.3. Has unpredictable behavior when shifting an integer by more than the word size.EXAMPLES OF ACCEPTABLE CODING STYLE:
/*
* pow2plus1 - returns 2^x + 1, where 0 <= x <= 31
*/
int
pow2plus1 (int x)
{
/* exploit ability of shifts to compute powers of 2 */
return (1 << x) + 1;
}
/*
* pow2plus4 - returns 2^x + 4, where 0 <= x <= 31
*/
int pow2plus4 (int x)
{
/* exploit ability of shifts to compute powers of 2 */
int result = (1 << x);
result += 4;
return result;
}
NOTES:
1. Use the dlc (data lab checker) compiler (described in the handout) to
check the legality of your solutions.
2. Each function has a maximum number of operators (!~&^|+<<>>)that
you are allowed to use for your implementation of the function.
The max operator count is checked by dlc.
Note that '=' is not counted;
you may use as many of these as you want without penalty.
3. Use the btest test harness to check your functions for correctness.
4. The maximum number of ops for each function is given in the header
comment for each function.
If there are any inconsistencies between the maximum ops in the
writeup and in this file, consider this file the authoritative source.
#endif
/*
* STEP 3: Modify the following functions according the coding rules.
*
* IMPORTANT. TO AVOID GRADING SURPRISES:
* 1. Use the dlc compiler to check that your solutions conform
* to the coding rules.
* 2. Use the btest test harness to check that your solutions produce
* the correct answers. Watch out for corner cases around Tmin and Tmax.
*/
/*
* bitNor - ~(x|y) using only ~ and &
* Example: bitNor(0x6, 0x5) = 0xFFFFFFF8
* Legal ops: ~ &
* Max ops: 8
* Rating: 1
*/
int bitNor (int x, int y)
{
return (~x & ~y);
}
/*
* bitXor - x^y using only ~ and &
* Example: bitXor(4, 5) = 1
* Legal ops: ~ &
* Max ops: 14
* Rating: 2
*/
int bitXor (int x, int y)
{
return ~((~(~x & y)) & (~(x & ~y)));
}
/*
* isNotEqual - return 0 if x == y, and 1 otherwise
* Examples: isNotEqual(5,5) = 0, isNotEqual(4,5) = 1
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 6
* Rating: 2
*/
int isNotEqual (int x, int y)
{
//Subtract x from y using twos complement
//The result is zero if they are equal
return !(!((~x+1)+y));
}
/*
* getByte - Extract byte n from word x
* Bytes numbered from 0 (LSB) to 3 (MSB)
* Examples: getByte(0x12345678,1) = 0x56
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 6
* Rating: 2
*/
int getByte (int x, int n)
{
return (x >> (n << 3)) & ((0x00 << 0x31) | 0xff);
}
/*
* copyLSB - set all bits of result to least significant bit of x
* Example: copyLSB(5) = 0xFFFFFFFF, copyLSB(6) = 0x00000000
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 5
* Rating: 2
*/
int copyLSB (int x)
{
return ((x << 30) >> 30);
}
/*
* logicalShift - shift x to the right by n, using a logical shift
* Can assume that 1 <= n <= 31
* Examples: logicalShift(0x87654321,4) = 0x08765432
* Legal ops: ~ & ^ | + << >>
* Max ops: 16
* Rating: 3
*/
int logicalShift (int x, int n)
{
return 2;
}
/*
* bitCount - returns count of number of 1's in word
* Examples: bitCount(5) = 2, bitCount(7) = 3
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 40
* Rating: 4
*/
int bitCount (int x)
{
return 2;
}
/*
* bang - Compute !x without using !
* Examples: bang(3) = 0, bang(0) = 1
* Legal ops: ~ & ^ | + << >>
* Max ops: 12
* Rating: 4
*/
int bang (int x)
{
return 2;
}
/*
* leastBitPos - return a mask that marks the position of the
* least significant 1 bit. If x == 0, return 0
* Example: leastBitPos(96) = 0x20
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 6
* Rating: 4
*/
int leastBitPos (int x)
{
return 2;
}
/*
* TMax - return maximum two's complement integer
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 4
* Rating: 1
*/
int tmax (void)
{
return 2;
}
/*
* isNonNegative - return 1 if x >= 0, return 0 otherwise
* Example: isNonNegative(-1) = 0. isNonNegative(0) = 1.
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 6
* Rating: 3
*/
int isNonNegative (int x)
{
return 2;
}
/*
* isGreater - if x > y then return 1, else return 0
* Example: isGreater(4,5) = 0, isGreater(5,4) = 1
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 24
* Rating: 3
*/
int isGreater (int x, int y)
{
return 2;
}
/*
* divpwr2 - Compute x/(2^n), for 0 <= n <= 30
* Round toward zero
* Examples: divpwr2(15,1) = 7, divpwr2(-33,4) = -2
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 15
* Rating: 2
*/
int divpwr2 (int x, int n)
{
return 2;
}
/*
* abs - absolute value of x (except returns TMin for TMin)
* Example: abs(-1) = 1.
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 10
* Rating: 4
*/
int abs (int x)
{
return 2;
}
/*
* addOK - Determine if can compute x+y without overflow
* Example: addOK(0x80000000,0x80000000) = 0,
* addOK(0x80000000,0x70000000) = 1,
* Legal ops: ! ~ & ^ | + << >>
* Max ops: 20
* Rating: 3
*/
int addOK (int x, int y)
{
return 2;
}