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

#include "protocol.h"
#include "utility.h"

int main(int argc, char ** argv)
{
   char errorstr[100];
   
   // Check command line
   
   if (argc <= 1) {
      fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
      exit(1);
   }
   
   // Open the file given on the command line, exiting on error
   
   int fd = open(argv[1], O_RDONLY);
   if (fd < 0) {
      sprintf(errorstr, "open() failed on file: %s", argv[1]);   
      perror(errorstr);
      exit(1);
   }
   
   // Create a buffer large enough for the pcap header and read from file into
   // buffer.  Then use a pointer to a struct to be able to "interpret" the bytes.
   
   int hdr_size = sizeof(struct pcap_hdr);
   char * buffer = malloc(hdr_size);
   int nread;
   
   nread = read(fd, buffer, hdr_size);
   if (nread < 0) {
      perror("Failed read() on file");
      exit(1);
   } else if (nread == 0) {
      fprintf(stderr, "Unexpected end-of-file on read()\n");
      exit(1);
   } else if (nread < hdr_size) {
      fprintf(stderr, "Unable to get entire header on read()\n");
      exit(1);
   }
   
   dumpBytes(stdout, buffer, hdr_size);
   pcap_hdr_t * pcapHdr = (pcap_hdr_t *)buffer;
   
   fprintf(stdout, "Magic: %8.8lx\n", (unsigned long)pcapHdr->magic);
   
   // Be careful about aliasing and then freeing the underlying buffer!
   free(buffer);
   buffer = NULL;
   
   // Repeat above, but for first pcap record in the file
   
   int rec_size = sizeof(struct pcap_rec);
   buffer = malloc(rec_size);
   
   nread = read(fd, buffer, rec_size);
   if (nread < 0) {
      perror("Failed read() on file");
      exit(1);
   } else if (nread == 0) {
      fprintf(stderr, "Unexpected end-of-file on read()\n");
      exit(1);
   } else if (nread < rec_size) {
      fprintf(stderr, "Unable to get entire header on read()\n");
      exit(1);
   }
   
   dumpBytes(stdout, buffer, rec_size);
   return 0;
}