/*
 * mmap-test.c
 */

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

int main(int argc, char *argv[])
{
    char *file_data;
    struct stat sb;
    int fd;
    char buf[1];

    /* open the file */
    if((fd = open("test-file", O_RDONLY)) < 0) {
        perror("open");
        exit(1);
    }

    /* get file metadata including, most especially, its size */
    if(fstat(fd, &sb) < 0) {
        perror("fstat");
        exit(2);
    }

    /* pause */
    write(1, "hit enter to mmap\n", 18);
    read(0, buf, 1);

    /* set up the mapping */
    file_data = mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
    if(file_data == MAP_FAILED) {
        perror("mmap");
        exit(3);
    }

    printf("file is mapped at address %p\n", file_data);

    /* write the data to stdout */
    if(write(1, file_data, sb.st_size) < 0) {
        perror("write");
        exit(4);
    }

    /* write the data to stdout, this time with more pointer arithmetic */
    if(write(1, file_data + 13, sb.st_size - 13) < 0) {
        perror("write");
        exit(5);
    }

    /* pause */
    write(1, "hit enter to munmap\n", 20);
    read(0, buf, 1);

    /* clean up after ourselves */
    if(munmap(file_data, sb.st_size) < 0) {
        perror("munmap");
        exit(6);
    }

    if(close(fd) < 0) {
        perror("close");
        exit(7);
    }
}