1/* Flush wrapper for struct __*printf_buffer. Generic version.
2 Copyright (C) 2022-2023 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <printf_buffer.h>
20
21#include <assert.h>
22#include <stdint.h>
23
24/* Xprintf (buffer_do_flush) (BUF) performs the flush operation. The
25 actual implementation is specific to the multibyte and wide
26 variants.
27
28 If the flush fails, Xprintf_buffer_mark_failed (BUF) must be
29 called, and BUF->write_ptr and BUF->write_end can be left
30 unchanged.
31
32 The function must not do anything if failure has already occurred,
33 that is, if BUF->mode == Xprintf (buffer_mode_failed).
34
35 The framework implicitly invokes flush with BUF->write_ptr ==
36 BUF->write_end only. (This is particularly relevant to the
37 __sprintf_chk flush, which just calls __chk_fail.) But in some
38 cases, Xprintf_buffer_flush may be called explicitly (when
39 BUF->mode/the backing function is known). In that case, it is
40 possible that BUF->write_ptr < BUF->write_end is true.
41
42 If the flush succeeds, the pointers are changed so that
43 BUF->write_ptr < BUF->write_end. It is possible to switch to a
44 completely different buffer here. If the buffer is moved, it may
45 be necessary to updated BUF->write_base and BUF->written from the
46 flush function as well.
47
48 Note that when chaining buffers, in the flush function for the
49 outer buffer (to which data is written first), it is necessary to
50 check for BUF->next->failed (for the inner buffer) and set
51 BUF->base.failed to true (for the outer buffer). This should come
52 towards the end of the outer flush function. Usually, there is
53 also some unwrapping step afterwards; it has to check the outer
54 buffer (BUF->base.failed) and propagate any error to the inner
55 buffer (BUF->next->failed), so essentially in the other
56 direction. */
57static void Xprintf (buffer_do_flush) (struct Xprintf_buffer *buf);
58
59bool
60Xprintf_buffer_flush (struct Xprintf_buffer *buf)
61{
62 if (__glibc_unlikely (Xprintf_buffer_has_failed (buf)))
63 return false;
64
65 Xprintf (buffer_do_flush) (buf);
66 if (Xprintf_buffer_has_failed (buf))
67 return false;
68
69 /* Ensure that the flush has made available some bytes. */
70 assert (buf->write_ptr != buf->write_end);
71 return true;
72}
73