1 | /* Copyright (C) 1991-2022 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the License, or (at your option) any later version. |
8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <https://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <stdlib.h> |
19 | #include <unistd.h> |
20 | #include <string.h> |
21 | #include <limits.h> |
22 | #include <stdbool.h> |
23 | #include <sys/param.h> |
24 | #include <sys/uio.h> |
25 | #include <errno.h> |
26 | |
27 | |
28 | static void |
29 | ifree (char **ptrp) |
30 | { |
31 | free (ptr: *ptrp); |
32 | } |
33 | |
34 | |
35 | /* Write data pointed by the buffers described by VECTOR, which |
36 | is a vector of COUNT 'struct iovec's, to file descriptor FD. |
37 | The data is written in the order specified. |
38 | Operates just like 'write' (see <unistd.h>) except that the data |
39 | are taken from VECTOR instead of a contiguous buffer. */ |
40 | ssize_t |
41 | __writev (int fd, const struct iovec *vector, int count) |
42 | { |
43 | /* Find the total number of bytes to be written. */ |
44 | size_t bytes = 0; |
45 | for (int i = 0; i < count; ++i) |
46 | { |
47 | /* Check for ssize_t overflow. */ |
48 | if (SSIZE_MAX - bytes < vector[i].iov_len) |
49 | { |
50 | __set_errno (EINVAL); |
51 | return -1; |
52 | } |
53 | bytes += vector[i].iov_len; |
54 | } |
55 | |
56 | /* Allocate a temporary buffer to hold the data. We should normally |
57 | use alloca since it's faster and does not require synchronization |
58 | with other threads. But we cannot if the amount of memory |
59 | required is too large. */ |
60 | char *buffer; |
61 | char *malloced_buffer __attribute__ ((__cleanup__ (ifree))) = NULL; |
62 | if (__libc_use_alloca (size: bytes)) |
63 | buffer = (char *) __alloca (bytes); |
64 | else |
65 | { |
66 | malloced_buffer = buffer = (char *) malloc (size: bytes); |
67 | if (buffer == NULL) |
68 | /* XXX I don't know whether it is acceptable to try writing |
69 | the data in chunks. Probably not so we just fail here. */ |
70 | return -1; |
71 | } |
72 | |
73 | /* Copy the data into BUFFER. */ |
74 | size_t to_copy = bytes; |
75 | char *bp = buffer; |
76 | for (int i = 0; i < count; ++i) |
77 | { |
78 | size_t copy = MIN (vector[i].iov_len, to_copy); |
79 | |
80 | bp = __mempcpy ((void *) bp, (void *) vector[i].iov_base, copy); |
81 | |
82 | to_copy -= copy; |
83 | if (to_copy == 0) |
84 | break; |
85 | } |
86 | |
87 | ssize_t bytes_written = __write (fd, buffer, bytes); |
88 | |
89 | return bytes_written; |
90 | } |
91 | libc_hidden_def (__writev) |
92 | #ifndef __writev |
93 | weak_alias (__writev, writev) |
94 | #endif |
95 | |