1/* Copyright (C) 1991-2024 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 <scratch_buffer.h>
23#include <stdbool.h>
24#include <sys/param.h>
25#include <sys/uio.h>
26#include <errno.h>
27
28
29static void
30ifree (struct scratch_buffer *sbuf)
31{
32 scratch_buffer_free (buffer: sbuf);
33}
34
35/* Read data from file descriptor FD, and put the result in the
36 buffers described by VECTOR, which is a vector of COUNT 'struct iovec's.
37 The buffers are filled in the order specified.
38 Operates just like 'read' (see <unistd.h>) except that data are
39 put in VECTOR instead of a contiguous buffer. */
40ssize_t
41__readv (int fd, const struct iovec *vector, int count)
42{
43 /* Find the total number of bytes to be read. */
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. Use a scratch_buffer
57 since it's faster for small buffer sizes but can handle larger
58 allocations as well. */
59
60 struct scratch_buffer __attribute__ ((__cleanup__ (ifree))) buf;
61 scratch_buffer_init (buffer: &buf);
62 if (!scratch_buffer_set_array_size (buffer: &buf, nelem: 1, size: bytes))
63 return -1;
64 char *buffer = buf.data;
65
66 /* Read the data. */
67 ssize_t bytes_read = __read (fd, buffer, bytes);
68 if (bytes_read < 0)
69 return -1;
70
71 /* Copy the data from BUFFER into the memory specified by VECTOR. */
72 bytes = bytes_read;
73 for (int i = 0; i < count; ++i)
74 {
75 size_t copy = MIN (vector[i].iov_len, bytes);
76
77 (void) memcpy ((void *) vector[i].iov_base, (void *) buffer, copy);
78
79 buffer += copy;
80 bytes -= copy;
81 if (bytes == 0)
82 break;
83 }
84
85 return bytes_read;
86}
87libc_hidden_def (__readv)
88weak_alias (__readv, readv)
89

source code of glibc/sysdeps/posix/readv.c