#include "csapp.h"

/* Read in all data from stdin and write it out in a reverse
   order --- using only system APIs, so no malloc() for fread()
   or fwrite() */

int main()
{
  char *in, *out;
  int got = 0, done = 0, n, i,curr_sz = 4096;
  char *tmp;

  in = mmap(NULL,curr_sz,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANON,-1,0);
  
  n = 0;
  do {
    if(curr_sz == n)
      {
	curr_sz *= 2;
	tmp = mmap(NULL,curr_sz,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANON,-1,0);
	memcpy(tmp,in,n);
	in = tmp;
      }
    got = Read(0, in+n, curr_sz-n);
    n += got;
  } while(got != 0);

  out = mmap(NULL,n,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANON,-1,0);

  for (i = 0; i < n; i++)
    out[n-1-i] = in[i];

  while(done < n) {
    done += Write(1, out+done, n-done);
  }

  return 0;
}