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-rw-r--r--REORG.TODO/sysdeps/posix/preadv_common.c83
1 files changed, 83 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/posix/preadv_common.c b/REORG.TODO/sysdeps/posix/preadv_common.c
new file mode 100644
index 0000000000..37efdc0ec0
--- /dev/null
+++ b/REORG.TODO/sysdeps/posix/preadv_common.c
@@ -0,0 +1,83 @@
+/* Read data into multiple buffers. Base implementation for preadv
+ and preadv64.
+ Copyright (C) 2017 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>
+
+/* Read data from file descriptor FD at the given position OFFSET
+ without change the file pointer, and put the result in the buffers
+ described by VECTOR, which is a vector of COUNT 'struct iovec's.
+ The buffers are filled in the order specified. Operates just like
+ 'pread' (see <unistd.h>) except that data are put in VECTOR instead
+ of a contiguous buffer. */
+ssize_t
+PREADV (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 = NULL;
+ if (__posix_memalign (&buffer, GLRO(dl_pagesize), bytes) != 0)
+ return -1;
+
+ ssize_t bytes_read = PREAD (fd, buffer, bytes, offset);
+ if (bytes_read < 0)
+ goto end;
+
+ /* Copy the data from BUFFER into the memory specified by VECTOR. */
+ bytes = bytes_read;
+ void *buf = buffer;
+ for (int i = 0; i < count; ++i)
+ {
+ size_t copy = MIN (vector[i].iov_len, bytes);
+
+ memcpy (vector[i].iov_base, buf, copy);
+
+ buf += copy;
+ bytes -= copy;
+ if (bytes == 0)
+ break;
+ }
+
+end:
+ free (buffer);
+ return bytes_read;
+}