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/* $OpenBSD: mmap_4g.c,v 1.3 2010/06/20 17:56:07 phessler Exp $ */
/*
* Public domain. 2005, Otto Moerbeek <otto@drijf.net>
*/
#include <sys/types.h>
#include <sys/mman.h>
#include <err.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
/*
* Write near the 4g boundary using a mmaped file and check if the
* bytes do not wrap to offset 0.
*/
int
main()
{
int fd, i;
off_t offset;
size_t sz;
char *p, buf[100];
const char * file = "foo";
fd = open(file, O_WRONLY | O_CREAT | O_TRUNC, 0666);
if (fd == -1)
err(1, "open");
sz = sizeof(buf);
offset = 4LL * 1024LL * 1024LL * 1024LL - sz/2;
if (lseek(fd, offset, SEEK_SET) != offset)
err(1, "lseek");
memset(buf, 0, sz);
if (write(fd, buf, sz) != sz)
err(1, "write");
close(fd);
fd = open(file, O_RDWR, 0);
if (fd == -1)
err(1, "open");
p = mmap(NULL, 100, PROT_READ | PROT_WRITE, MAP_FILE | MAP_SHARED,
fd, offset);
if (p == MAP_FAILED)
err(1, "mmap");
for (i = 0; i < sz; i++)
p[i] = i + 1;
if (munmap(p, sz) == -1)
err(1, "munmap");
close(fd);
fd = open(file, O_RDONLY, 0);
if (fd == -1)
err(1, "open");
if (read(fd, buf, sz) != sz)
err(1, "read");
for (i = 0; i < sz; i++)
if (buf[i])
errx(1, "nonzero byte 0x%02x found at offset %zu",
buf[i], i);
if (lseek(fd, offset, SEEK_SET) != offset)
err(1, "lseek");
if (read(fd, buf, sz) != sz)
err(1, "read");
for (i = 0; i < sz; i++)
if (buf[i] != i + 1)
err(1, "incorrect value 0x%02x at offset %llx",
p[i], offset + i);
close(fd);
unlink(file);
return 0;
}
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