#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>

#include <fcntl.h>
#include <unistd.h>

#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/uio.h>

#define PATH        "c-mmap-testfile"
#define PAGESIZE    4096

static void sighdl(int);

static void
sighdl(int signo)
{
    const char errmsg[] = "\nSignal occurred, cleaning up\n";
    (void)signo;
    (void)signal(SIGSEGV, SIG_DFL);
    (void)signal(SIGBUS, SIG_DFL);
    write(2, errmsg, sizeof(errmsg)-1);
    (void)unlink(PATH);
    return;
}

int
main(void) {
    int fd, estat = 0;
    void *addr;
    auto struct stat s;
    /* *Final* sizes (string written after lseek(2): "abcd") */
    const size_t *ct, tests[] = {
        /* Tested good */
        //0x100000000 - PAGESIZE - 5,
        //0x100000000 - 4,
        //0x100000000 - 3,
        //0x100000000 - 1,
        0x100000000 + PAGESIZE + 4,
        //0x100000000 + PAGESIZE + 5,
        /* Tested bad */
        //0x100000000,
        //0x100000000 + PAGESIZE,
        //0x100000000 + PAGESIZE + 1,
        //0x100000000 + PAGESIZE + 3,
        0
    };

    if (signal(SIGSEGV, &sighdl) == SIG_ERR)
        goto jerror;
    if (signal(SIGBUS, &sighdl) == SIG_ERR)
        goto jerror;

    for (ct = tests; *ct != 0; ++ct) {
        fprintf(stderr, "Size %lu/0x%lX: open", *ct, *ct);
        fd = open(PATH, O_RDWR|O_TRUNC|O_CREAT, 0666);
        if (fd < 0)
            goto jerror;
        fprintf(stderr, ". ");

        fprintf(stderr, "lseek");
        if (lseek(fd, *ct-4, SEEK_END) < 0)
            goto jerror;
        fprintf(stderr, ". ");

        fprintf(stderr, "write");
        if (write(fd, "abcd", 4) != 4)
            goto jerror;
        fprintf(stderr, ". ");

        fprintf(stderr, "fsync");
        if (fsync(fd) != 0)
            goto jerror;
        fprintf(stderr, ". ");

        fprintf(stderr, "fstat");
        if (fstat(fd, &s) != 0)
            goto jerror;
        fprintf(stderr, ". ");

        if (*ct != (size_t)s.st_size) {
            fprintf(stderr, "fstat size mismatch: %lu is not %lu\n",
                    (size_t)s.st_size, *ct);
            continue;
        }

        fprintf(stderr, "mmap");
        addr = mmap(NULL, s.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
        if (addr == NULL)
            goto jerror;
        fprintf(stderr, ". ");

        (void)close(fd);

        fprintf(stderr, "[0]");
        if (((char*)addr)[0] != '\0')
            goto jerror;
        fprintf(stderr, ". ");

        fprintf(stderr, "[s.st_size-4]");
        if (((char*)addr)[s.st_size-4] != 'a')
            goto jerror;
        fprintf(stderr, ". ");

        fprintf(stderr, "munmap");
        if (munmap(addr, s.st_size) != 0)
            goto jerror;
        fprintf(stderr, ".");

        fprintf(stderr, "\n");
    }

jleave:
    (void)unlink(PATH);
    return estat;

jerror:
    fprintf(stderr, "\n%s\n", strerror(errno));
    estat = 1;
    goto jleave;
}