1#include "stdio_impl.h"
 2#include <fcntl.h>
 3#include <unistd.h>
 4
 5/* The basic idea of this implementation is to open a new FILE,
 6 * hack the necessary parts of the new FILE into the old one, then
 7 * close the new FILE. */
 8
 9/* Locking IS necessary because another thread may provably hold the
10 * lock, via flockfile or otherwise, when freopen is called, and in that
11 * case, freopen cannot act until the lock is released. */
12
13FILE *freopen(const char *restrict filename, const char *restrict mode, FILE *restrict f)
14{
15	int fl = __fmodeflags(mode);
16	FILE *f2;
17
18	FLOCK(f);
19
20	fflush(f);
21
22	if (!filename) {
23		if (fl&O_CLOEXEC)
24			__syscall(SYS_fcntl, f->fd, F_SETFD, FD_CLOEXEC);
25		fl &= ~(O_CREAT|O_EXCL|O_CLOEXEC);
26		if (syscall(SYS_fcntl, f->fd, F_SETFL, fl) < 0)
27			goto fail;
28	} else {
29		f2 = fopen(filename, mode);
30		if (!f2) goto fail;
31		if (f2->fd == f->fd) f2->fd = -1; /* avoid closing in fclose */
32		else if (__dup3(f2->fd, f->fd, fl&O_CLOEXEC)<0) goto fail2;
33
34		f->flags = (f->flags & F_PERM) | f2->flags;
35		f->read = f2->read;
36		f->write = f2->write;
37		f->seek = f2->seek;
38		f->close = f2->close;
39
40		fclose(f2);
41	}
42
43	f->mode = 0;
44	f->locale = 0;
45	FUNLOCK(f);
46	return f;
47
48fail2:
49	fclose(f2);
50fail:
51	fclose(f);
52	return NULL;
53}