Prepare for radical source tree reorganization. zack/build-layout-experiment

All top-level files and directories are moved into a temporary storage
directory, REORG.TODO, except for files that will certainly still
exist in their current form at top level when we're done (COPYING,
COPYING.LIB, LICENSES, NEWS, README), all old ChangeLog files (which
are moved to the new directory OldChangeLogs, instead), and the
generated file INSTALL (which is just deleted; in the new order, there
will be no generated files checked into version control).

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;
+}