copy_file_range: New function to copy file data

The semantics are based on the Linux system call, but a very close
emulation in user space is provided.

5 files changed, 90 insertions, 0 deletions

diff --git a/support/Makefile b/support/Makefile
index bfde79333e..8458840cd8 100644
--- a/support/Makefile
+++ b/support/Makefile
@@ -36,6 +36,7 @@ libsupport-routines = \
   oom_error \
   resolv_test \
   set_fortify_handler \
+  support-xfstat \
   support-xstat \
   support_become_root \
   support_can_chroot \
@@ -73,8 +74,10 @@ libsupport-routines = \
   xfclose \
   xfopen \
   xfork \
+  xftruncate \
   xgetsockname \
   xlisten \
+  xlseek \
   xmalloc \
   xmemstream \
   xmkdir \
diff --git a/support/support-xfstat.c b/support/support-xfstat.c
new file mode 100644
index 0000000000..4c8ee9142b
--- /dev/null
+++ b/support/support-xfstat.c
@@ -0,0 +1,28 @@
+/* fstat64 with error checking.
+   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 <support/check.h>
+#include <support/xunistd.h>
+#include <sys/stat.h>
+
+void
+xfstat (int fd, struct stat64 *result)
+{
+  if (fstat64 (fd, result) != 0)
+    FAIL_EXIT1 ("fstat64 (%d): %m", fd);
+}
diff --git a/support/xftruncate.c b/support/xftruncate.c
new file mode 100644
index 0000000000..9c4e9e3050
--- /dev/null
+++ b/support/xftruncate.c
@@ -0,0 +1,27 @@
+/* ftruncate with error checking.
+   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 <support/check.h>
+#include <support/xunistd.h>
+
+void
+xftruncate (int fd, long long length)
+{
+  if (ftruncate64 (fd, length) != 0)
+    FAIL_EXIT1 ("ftruncate64 (%d, %lld): %m", fd, length);
+}
diff --git a/support/xlseek.c b/support/xlseek.c
new file mode 100644
index 0000000000..0a75a9f2e6
--- /dev/null
+++ b/support/xlseek.c
@@ -0,0 +1,29 @@
+/* lseek with error checking.
+   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 <support/check.h>
+#include <support/xunistd.h>
+
+long long
+xlseek (int fd, long long offset, int whence)
+{
+  long long result = lseek64 (fd, offset, whence);
+  if (result < 0)
+    FAIL_EXIT1 ("lseek64 (%d, %lld, %d): %m", fd, offset, whence);
+  return result;
+}
diff --git a/support/xunistd.h b/support/xunistd.h
index 00376f7aae..29da063c15 100644
--- a/support/xunistd.h
+++ b/support/xunistd.h
@@ -36,10 +36,13 @@ void xpipe (int[2]);
 void xdup2 (int, int);
 int xopen (const char *path, int flags, mode_t);
 void xstat (const char *path, struct stat64 *);
+void xfstat (int fd, struct stat64 *);
 void xmkdir (const char *path, mode_t);
 void xchroot (const char *path);
 void xunlink (const char *path);
 long xsysconf (int name);
+long long xlseek (int fd, long long offset, int whence);
+void xftruncate (int fd, long long length);
 
 /* Read the link at PATH.  The caller should free the returned string
    with free.  */