bit-vect.c

用于汇编领域的,运用于OS的MAIN函数.基于硬件基础的源代码

#include "fs.h"
// member functions for BitVect
#define BVSIZE BLKSIZE
void BitVect_init(struct BitVect *v){
//make all bits free initially
   int i;
   for(i=0;i<BVSIZE;i++)
      v->vect[i]=0;
}

static int find_free_loc(char vect){
// ret loc of the first 0 in vect
   int i; char mask;
   
   for(i=0;i<8;i++){
      mask = (1 << i);
	  if ( (vect & mask) == 0) return i;
   }
   panic("no free loc");
}

static void set_bit(char vect, int fbit){
// mark fbit position in vect
   vect = vect | (1 << fbit);
}

int BitVect_get_free_bit(struct BitVect *v){// find free bit 
   int i,fbit;
   for(i=0;i<BVSIZE;i++) // 
      if (v->vect[i]!= 0xff) { // found a byte with free bit
	      fbit=find_free_loc(v->vect[i]); // find its loc
		  set_bit(v->vect[i], fbit); // mark it
		  return fbit;
	  }
   panic("no more free bit");
}

void BitVect_set_bit(struct BitVect *v,int x){
   // first compute vect and offset
   int vector, offset;
   vector = x / 8; // vect is a byte
   offset = x % 8;
   set_bit(v->vect[vector], offset);
}