#include	<stdio.h>
#include	<fcntl.h>
#include	<unistd.h>
#include	<sys/types.h>
#include	<sys/stat.h>
#include	<sys/mman.h>
#include	<stdlib.h>

/*
 * mmcat.c -  cat a file using mmap
 *
 * idea: no read or lseek, just mmap and *p
 *
 * system calls used:
 *	open - to get a fd for a file
 *	mmap - to map file to memory
 */

#define oops(m,x) { perror(m); exit(x); }

main(int ac, char *av[])
{
	int	fd;
	char	*region;
	char	*p;
	off_t	filesize;
	struct	stat	info;
	int	rv;
	off_t	pos = 0;
	int	not_printed;
	long	pagesize;

	if ( ac != 2 ){
		fprintf(stderr, "usage: mmcat filename\n");
		exit(1);
	}

	if ( stat(av[1], &info) == -1 )
		oops(av[1], 2);
	filesize = info.st_size;

	pagesize = sysconf(_SC_PAGESIZE);

	if ( (fd = open(av[1],O_RDONLY)) == -1 )
		oops(av[1], 3);

	region = (char*)mmap(NULL,pagesize,PROT_READ,MAP_SHARED,fd,pos);
	p = region;
	not_printed = pagesize;

	if ( region == (char *)MAP_FAILED )
		oops("mmap",4);

	for(pos=0; pos<filesize; pos++){
		if ( not_printed == 0 ){
			region=(char*)mmap(NULL,pagesize,PROT_READ,
						MAP_SHARED,fd,pos);
			if ( region == (char *)MAP_FAILED )
				oops("mmap",5);
			p = region;
			not_printed = pagesize;
		}
		putchar(*p++);
		not_printed--;
	}
	rv = munmap(region, pagesize);
	/* printf("\nmunmap returned %d\n", rv); */
}