#include <stdio.h>
#include <limits.h>

typedef unsigned char byte;

void show_bytes(void * start, size_t len){

  printf("\t%lu bytes from %p:", len, start);

  int i;
  for(i = 0; i < len; i++){
    printf(" %.2x", ((byte *) start)[i]);
  }
  printf("\n");

}

void casting_demo_shorter(){
  printf("\nCasting from longer to shorter:\n");
  int x1 = -5;
  int x2 = 5;
  int x3 = 24967291;
  short y1 = (short) x1;
  short y2 = (short) x2;
  short y3 = (short) x3;
  
  printf("\t(short) -5 = %d\n",y1);
  show_bytes(&x1,4);
  show_bytes(&y1,2);

  printf("\n\t(short) 5 = %d\n",y2);
  show_bytes(&x2,4);
  show_bytes(&y2,2);

  printf("\n\t(short) 2294967291 = %d\n",y3);
  show_bytes(&x3,4);
  show_bytes(&y3,2);
}

void casting_demo_longer(){
  printf("\nCasting from shorter to longer:\n");
  short x1 = -5;
  short x2 = 5;
  int y1 = (int) x1;
  int y2 = (int) x2;

  printf("\t(int) -5 = %d\n",y1);
  show_bytes(&x1,2);
  show_bytes(&y1,4);

  printf("\n\t(int) 5 = %d\n",y2);
  show_bytes(&x2,2);
  show_bytes(&y2,4);
}


void casting_demo_signed_unsigned(){
  printf("Casting from signed to unsigned:\n");
    
  int x1 = -5;
  int x2 = 5;

  unsigned int y1 = (unsigned int) x1;
  unsigned int y2 = (unsigned int) x2;

  printf("\t(unsigned int) -5 = %u\n",y1);
  show_bytes(&x1,4);
  show_bytes(&y1,4);

  printf("\n\t(unsigned int) 5 = %u\n",y2);
  show_bytes(&x2,4);
  show_bytes(&y2,4);
}

void casting_demo_unsigned_signed(){
  printf("\nCasting from unsigned to signed:\n");

  unsigned int x1 = 5;
  unsigned int x2 = 4294967291;
  
  int y1 = (int) x1;
  int y2 = (int) x2;

  printf("\t(int) 5 = %d\n",y1);
  show_bytes(&x1,4);
  show_bytes(&y1,4);

  printf("\n\t(int) 4294967291 = %d\n",y2);
  show_bytes(&x2,4);
  show_bytes(&y2,4);
  
}


void why_unsigned_is_dangerous(){
  int cnt = 8;
  int a[cnt];
  for(int x = 0; x < cnt; x++){
    a[x] = x;
  }
  
  unsigned int i;
  for(i = cnt-2; i >= 0; i--){
    a[i] += a[i+1];
    printf("i = %u, a[%u] = %d\n",i,i,a[i]);
  }
}

void exercise3(){
  char a = -30;
  char b = 21;
  char x;

  x = ~a;
  printf("~(-30) = %d\n",x);
  x = !a;
  printf("!(-30) = %d\n",x);

  x = a & b;
  printf("-30 & 21 = %d\n",x);
  x = a && b;
  printf("-30 && 21 = %d\n",x);

  x = a << 2;
  printf("-30 << 2 = %d\n",x);
  x = a >> 2;
  printf("-30 >> 2 = %d\n",x);
  x = b >> 2;
  printf("21 >> 2 = %d\n",x);

}

int main(int argc, char ** argv){
  casting_demo_shorter();
  casting_demo_longer();

  casting_demo_signed_unsigned();
  casting_demo_unsigned_signed();

  
  //why_unsigned_is_dangerous();

  //exercise3();
  return 0;
}