#include <stdio.h>
#include <stdlib.h>

// scan values, swap, and write each as 1 or 2 bytes along with bit map

#define SetBit(A,k)     ( A[(k/32)] |= (1 << (k%32)) )
#define ClearBit(A,k)   ( A[(k/32)] &= ~(1 << (k%32)) )            

#define DoByteSwap(x) ByteSwap((unsigned char *) &x, sizeof(x))

void ByteSwap(unsigned char * b, int n){
   register int i = 0;
   register int j = n-1;
   unsigned char temp;

   while (i<j){
      /* swap(b[i], b[j]) */
	  temp = b[i];
	  b[i] = b[j];
	  b[j] = temp;
      i++, j--;
   }
}

char *decimal_to_binary(int n){
   int c, d, count = 0;
   char *pointer = (char*)malloc(16+1);

   if (pointer == NULL)
      exit(1);
     
   for (c = 15 ; c >= 0 ; c--){
      d = n >> c;
      if (d & 1)
         *(pointer+count) = 1 + '0';
      else
         *(pointer+count) = 0 + '0';
      count++;
   }
   *(pointer+count) = '\0';
   
   return pointer;
}


int main(){
printf("reading Y,U,V data\n");
char * file1 = "yuv_data/V.dat"; 
char * file2 = "yuv_data_shifted/V2.dat"; 
char * file3 = "yuv_data_shifted/V2_map.dat"; 
unsigned short val, bsval;
unsigned char cval; 
int *map;
int i, nvals = 1920*1080; 
FILE *fp, *fp2, *fp3;
map = (int*)malloc(nvals/(4*8)*sizeof(int)); // bit array

printf("swapping bytes in %s\n", file1);
fp = fopen(file1,"r");
fp2 = fopen(file2,"w");
fp3 = fopen(file3,"w");
for(i=0; i<nvals; i++){ 
fread(&val, sizeof(val), 1, fp);
bsval = val;
//printf("before val[%d] = %d (%s)\n", i, bsval, decimal_to_binary(bsval));
DoByteSwap(bsval); 
//cval = (bsval >> (0)) & 0xff;
//printf("after val[%d] = %d (%s) and cval = %d\n", i, bsval, decimal_to_binary(bsval), cval);
if(val > 255){
SetBit(map,i);
fwrite(&bsval, sizeof(bsval), 1, fp2);
} else {
cval = val;
fwrite(&cval, sizeof(cval), 1, fp2);
}
}
fwrite(map,sizeof(int),nvals/32,fp3); 
fclose(fp);
fclose(fp2);
fclose(fp3);

return 0;
}