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 | /* Read data from file descriptor FD, and put the result in the |
35 | buffers described by VECTOR, which is a vector of COUNT 'struct iovec's. |
36 | The buffers are filled in the order specified. |
37 | Operates just like 'read' (see <unistd.h>) except that data are |
38 | put in VECTOR instead of a contiguous buffer. */ |
39 | ssize_t |
40 | __readv (int fd, const struct iovec *vector, int count) |
41 | { |
42 | /* Find the total number of bytes to be read. */ |
43 | size_t bytes = 0; |
44 | for (int i = 0; i < count; ++i) |
45 | { |
46 | /* Check for ssize_t overflow. */ |
47 | if (SSIZE_MAX - bytes < vector[i].iov_len) |
48 | { |
49 | __set_errno (EINVAL); |
50 | return -1; |
51 | } |
52 | bytes += vector[i].iov_len; |
53 | } |
54 | |
55 | /* Allocate a temporary buffer to hold the data. We should normally |
56 | use alloca since it's faster and does not require synchronization |
57 | with other threads. But we cannot if the amount of memory |
58 | required is too large. */ |
59 | char *buffer; |
60 | char *malloced_buffer __attribute__ ((__cleanup__ (ifree))) = NULL; |
61 | if (__libc_use_alloca (size: bytes)) |
62 | buffer = (char *) __alloca (bytes); |
63 | else |
64 | { |
65 | malloced_buffer = buffer = (char *) malloc (size: bytes); |
66 | if (buffer == NULL) |
67 | return -1; |
68 | } |
69 | |
70 | /* Read the data. */ |
71 | ssize_t bytes_read = __read (fd, buffer, bytes); |
72 | if (bytes_read < 0) |
73 | return -1; |
74 | |
75 | /* Copy the data from BUFFER into the memory specified by VECTOR. */ |
76 | bytes = bytes_read; |
77 | for (int i = 0; i < count; ++i) |
78 | { |
79 | size_t copy = MIN (vector[i].iov_len, bytes); |
80 | |
81 | (void) memcpy ((void *) vector[i].iov_base, (void *) buffer, copy); |
82 | |
83 | buffer += copy; |
84 | bytes -= copy; |
85 | if (bytes == 0) |
86 | break; |
87 | } |
88 | |
89 | return bytes_read; |
90 | } |
91 | libc_hidden_def (__readv) |
92 | weak_alias (__readv, readv) |
93 | |