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Diffstat (limited to 'sysdeps/posix/pwritev_common.c')
-rw-r--r-- | sysdeps/posix/pwritev_common.c | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/sysdeps/posix/pwritev_common.c b/sysdeps/posix/pwritev_common.c new file mode 100644 index 0000000000..344ab4d61b --- /dev/null +++ b/sysdeps/posix/pwritev_common.c @@ -0,0 +1,74 @@ +/* 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; +} |