Delete a character set present in a given string

char* strdel(char* s1, int len1, char* s2, int len2)
{
int bitmapvec[8]; //bit[n] = 1 if s1[i] == n else 0
for(int i=0; i<8; i++)
bitmapvec[i] = 0;

for(int i=0; i {
bitmapvec[ (s1[i] / 32) ] |= (1 << (s1[i] % 32)) ;
}

int j=0;
for(int i=0; i< len2; i++)
{
if(!(bitmapvec[s2[i]/32] & (1 << (s2[i] % 32))))
{
s2[j] = s2[i];
j++;
}
}

s2[j] = '\0';

return s2;
}