bits.c

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// bits.c ... functions on bit-strings
// part of Multi-attribute Linear-hashed Files
// Bit-strings are 32-bit unsigned quantities
// Last modified by John Shepherd, July 2019

#include <assert.h>
#include "bits.h"

// check if the bit at position is 1

int bitIsSet(Bits val, int position)
{
	assert(0 <= position && position <= 31);
	Bits mask = (1 << position);
	return ((val & mask) != 0);
}

// set the bit at position to 1

Bits setBit(Bits val, int position)
{
	assert(0 <= position && position <= 31);
	Bits mask = (1 << position);
	return (val | mask);
}

// set the bit at position to 0

Bits unsetBit(Bits val, int position)
{
	assert(0 <= position && position <= 31);
	Bits mask = (~(1 << position));
	return (val & mask);
}

// extract just lower-order n bits

Bits getLower(Bits b, int n)
{
	assert(1 <= n && n <= 32);
	int i; Bits mask = 0;
	for (i = 0; i < n; i++) mask |= (1<<i);
	return b&mask;
}

// convert 32-bit unsigned quantity to string
// place in a user-supplied buffer of length > 36

void bitsString(Bits val, char *buf)
{
	int i,j; char ch;
	Bits bit = 0x80000000;

	i = j = 0;
	while (bit != 0) {
		ch = ((val & bit) != 0) ? '1' : '0';
		buf[i++] = ch;
		j++;
		if (j%8 == 0) buf[i++] = ' ';
		bit = bit >> 1;
	}
	buf[--i] = '\0';
}