bitmap.c

#include "bitmap.h"
#include <stdio.h>
#define byte_dim 8

BitMapEntryKey BitMap_blockToIndex(int num){
// converts a block index to an index in the array,
// and a char that indicates the offset of the bit inside the array
	BitMapEntryKey map;
	int pos = num / 8;
	int offset = num % 8;
	map.entry_num = pos;
	map.bit_num = offset;
	return map;
}

int BitMap_indexToBlock(int entry, uint8_t bit_num){
	// converts a bit to a linear index
	if( entry<0 || bit_num < 0 ) return -1;
	return (entry * byte_dim) + bit_num;
}

int BitMap_get(BitMap* bmap, int start, int status ){
// returns the index of the first bit having status "status"
// in the bitmap bmap, and starts looking from position start
	if (start > bmap->num_bits){
		printf("Bitmap_get bad parameters (start > num_bits)\n");
	 return -1; //start maggiore dal numero dei bit all'interno della bitmap
	 }
	int i = 0;
	int j = 0;
	for(i = start; i < bmap->num_bits; i++){
		BitMapEntryKey map = BitMap_blockToIndex(start);
		if(((bmap->entries[map.entry_num] >> map.bit_num) & 0x01) == status)
		 	return BitMap_indexToBlock(map.entry_num,map.bit_num);
		start++;

	}
	printf("ATTENTION: No more free blocks!\n");
	return -1;
}

int BitMap_set(BitMap* bmap, int pos, int status){
	// sets the bit at index pos in bmap to status
	//posso fare uno shift, inserire il bit nella posizione richiesta
	// e poi fare un'or col numero
	//precedente in modo che sostituisco solo il numero in questione
	//se va sostituito(non sono sicuro che la or funzioni però)
	if(pos > bmap->num_bits) return -1;
	BitMapEntryKey map = BitMap_blockToIndex(pos);
	unsigned char flag = 1 << map.bit_num; // flag = 0000...010...000   (shifted k positions)
	if(status == 1){
		bmap->entries[map.entry_num] = bmap->entries[map.entry_num] | flag;
		return bmap->entries[map.entry_num] | flag;
	}else{
		bmap->entries[map.entry_num] = bmap->entries[map.entry_num] & (~flag);
		return bmap->entries[map.entry_num] & (~flag); //~ NOT OPERATOR
	}
	return 0;
}

void BitMap_print(BitMap* bmap){
	int i = 0;
	for(i = 0; i < bmap->num_bits; i++){
		BitMapEntryKey key = BitMap_blockToIndex(i);
		printf("Entry Num -> %d | bit_num -> %d | status -> %d\n",key.entry_num,key.bit_num,bmap->entries[key.entry_num] >> key.bit_num & 1);
	}

}