c How can i return a parity of char read from binary file

int parity (char msg[1400]) {

  int parity = 0;
  int i,j;
  char c;

  for(i=0;i<strlen(msg);i++) {
    for(j=0;j<8;j++) {
      c = msg[i];
      int bit = (c>>j)&1;
      parity ^= bit;
    }
  }

  return parity;
}

This function return a good result, for the next example:

char* msg = malloc(sizeof(char*)*1400);
strcpy(msg,"some string");
int parity = parity(msg);

For next example the result isn't good:

    char* msg = malloc(sizeof(char*)*1400);
    FILE *fp;
    fp = fopen(filename,"r");  //filename is a binary file
    while( !feof(fp) ){
      fread(msg,1399,sizeof(char),fp);
      int parity = parity(msg); //--> the result isn't well
      //.......
    }

I saw strlen(msg) is variable at each step (192,80,200...etc) when i read from file in while. I have to change the "parity" function for second example. Any suggestions?