| /* Write data into multiple buffers. Base implementation for pwritev |
| and pwritev64. |
| Copyright (C) 2017-2018 Free Software Foundation, Inc. |
| This file is part of the GNU C Library. |
| |
| The GNU C Library is free software; you can redistribute it and/or |
| modify it under the terms of the GNU Lesser General Public |
| License as published by the Free Software Foundation; either |
| version 2.1 of the License, or (at your option) any later version. |
| |
| The GNU C Library is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| Lesser General Public License for more details. |
| |
| You should have received a copy of the GNU Lesser General Public |
| License along with the GNU C Library; if not, see |
| <http://www.gnu.org/licenses/>. */ |
| |
| #include <unistd.h> |
| #include <sys/uio.h> |
| #include <sys/param.h> |
| #include <errno.h> |
| #include <malloc.h> |
| |
| #include <ldsodefs.h> |
| #include <libc-pointer-arith.h> |
| |
| /* Write data pointed by the buffers described by IOVEC, which is a |
| vector of COUNT 'struct iovec's, to file descriptor FD at the given |
| position OFFSET without change the file pointer. The data is |
| written in the order specified. Operates just like 'write' (see |
| <unistd.h>) except that the data are taken from IOVEC instead of a |
| contiguous buffer. */ |
| ssize_t |
| PWRITEV (int fd, const struct iovec *vector, int count, OFF_T offset) |
| { |
| /* Find the total number of bytes to be read. */ |
| size_t bytes = 0; |
| for (int i = 0; i < count; ++i) |
| { |
| /* Check for ssize_t overflow. */ |
| if (SSIZE_MAX - bytes < vector[i].iov_len) |
| { |
| __set_errno (EINVAL); |
| return -1; |
| } |
| bytes += vector[i].iov_len; |
| } |
| |
| /* Allocate a temporary buffer to hold the data. It could be done with a |
| stack allocation, but due limitations on some system (Linux with |
| O_DIRECT) it aligns the buffer to pagesize. A possible optimization |
| would be querying if the syscall would impose any alignment constraint, |
| but 1. it is system specific (not meant in generic implementation), and |
| 2. it would make the implementation more complex, and 3. it will require |
| another syscall (fcntl). */ |
| void *buffer = __mmap (NULL, bytes, PROT_READ | PROT_WRITE, |
| MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); |
| if (__glibc_unlikely (buffer == MAP_FAILED)) |
| return -1; |
| |
| /* Copy the data from BUFFER into the memory specified by VECTOR. */ |
| char *ptr = buffer; |
| for (int i = 0; i < count; ++i) |
| ptr = __mempcpy ((void *) ptr, (void *) vector[i].iov_base, |
| vector[i].iov_len); |
| |
| ssize_t ret = PWRITE (fd, buffer, bytes, offset); |
| |
| __munmap (buffer, bytes); |
| |
| return ret; |
| } |