#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 exercise1(){
  char x1 = 47;
  char x2 = -47;
  char x3 = 0x86;
  char x4 = 0x25;

  printf("x1 = %d (0x%hhx)\n", x1, x1);
  printf("x2 = %d (0x%hhx)\n", x2, x2);
  printf("x3 = %d (0x%hhx)\n", x3, x3);
  printf("x4 = %d (0x%hhx)\n", x4, x4);
}

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) %d = %d\n", x1, y1);
  show_bytes(&x1,4);
  show_bytes(&y1,2);

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

  printf("\n\t(short) %d = %d\n",x3, 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) %d = %d\n", x1, y1);
  show_bytes(&x1,2);
  show_bytes(&y1,4);

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


void casting_demo_signed_unsigned(){
  printf("\nCasting 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) %d = %u\n", x1, y1);
  show_bytes(&x1,4);
  show_bytes(&y1,4);

  printf("\n\t(unsigned int) %d = %u\n", x2, 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) %d = %d\n", x1, y1);
  show_bytes(&x1,4);
  show_bytes(&y1,4);

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

void casting_demo(){

  casting_demo_shorter();
  casting_demo_longer();

  casting_demo_signed_unsigned();
  casting_demo_unsigned_signed();


}


void why_unsigned_is_dangerous(){

  int a[8] = {0,1,2,3,4,5,6,7};

  for(unsigned int i = 6; 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 = 23;
  char x;

  printf("%d = 0x%hhx\n", a, a);
  printf("%d = 0x%hhx\n", b, b);

  x = ~a;
  printf("~(-30) = %d (0x%hhx)\n", x, x);

  x = a & b;
  printf("-30 & 23 = %d (0x%hhx)\n", x, x);
  x = a && b;
  printf("-30 && 23 = %d (0x%hhx)\n", x, x);

  x = a >> 2;
  printf("-30 >> 2 = %d (0x%hhx)\n", x, x);

}

int main(int argc, char ** argv){
  //exercise1();

  //casting_demo();
  
  //why_unsigned_is_dangerous();

  exercise3();
  return 0;
}