1#include "stdio_impl.h"
2#include <fcntl.h>
3
4/* The basic idea of this implementation is to open a new FILE,
5 * hack the necessary parts of the new FILE into the old one, then
6 * close the new FILE. */
7
8/* Locking IS necessary because another thread may provably hold the
9 * lock, via flockfile or otherwise, when freopen is called, and in that
10 * case, freopen cannot act until the lock is released. */
11
12int __dup3(int, int, int);
13
14FILE *freopen(const char *restrict filename, const char *restrict mode, FILE *restrict f)
15{
16	int fl = __fmodeflags(mode);
17	FILE *f2;
18
19	FLOCK(f);
20
21	fflush(f);
22
23	if (!filename) {
24		if (fl&O_CLOEXEC)
25			__syscall(SYS_fcntl, f->fd, F_SETFD, FD_CLOEXEC);
26		fl &= ~(O_CREAT|O_EXCL|O_CLOEXEC);
27		if (syscall(SYS_fcntl, f->fd, F_SETFL, fl) < 0)
28			goto fail;
29	} else {
30		f2 = fopen(filename, mode);
31		if (!f2) goto fail;
32		if (f2->fd == f->fd) f2->fd = -1; /* avoid closing in fclose */
33		else if (__dup3(f2->fd, f->fd, fl&O_CLOEXEC)<0) goto fail2;
34
35		f->flags = (f->flags & F_PERM) | f2->flags;
36		f->read = f2->read;
37		f->write = f2->write;
38		f->seek = f2->seek;
39		f->close = f2->close;
40
41		fclose(f2);
42	}
43
44	FUNLOCK(f);
45	return f;
46
47fail2:
48	fclose(f2);
49fail:
50	fclose(f);
51	return NULL;
52}
53
54LFS64(freopen);
55