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copy-file now uses GNU/Linux file cloning

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From a suggestion by Kieran Colford (see Bug#23904).
* configure.ac: Check for linux/fs.h.
* src/fileio.c [HAVE_LINUX_FS_H]: Include sys/ioctl.h and linux/fs.h.
(clone_file): New function.
(Fcopy_file): Use it.
This commit is contained in:
Paul Eggert 2016-09-10 12:51:27 -07:00
parent 0fca290ddf
commit 9b21d9f911
2 changed files with 26 additions and 8 deletions
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1
configure.ac
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@ -1638,6 +1638,7 @@ fi
dnl checks for header files
AC_CHECK_HEADERS_ONCE(
linux/fs.h
malloc.h
sys/systeminfo.h
sys/sysinfo.h

33
src/fileio.c
View file

@ -52,6 +52,11 @@ along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */
#include "region-cache.h"
#include "frame.h"
#ifdef HAVE_LINUX_FS_H
# include <sys/ioctl.h>
# include <linux/fs.h>
#endif
#ifdef WINDOWSNT
#define NOMINMAX 1
#include <windows.h>
@ -1829,6 +1834,16 @@ barf_or_query_if_file_exists (Lisp_Object absname, bool known_to_exist,
}
}
/* Copy data to DEST from SOURCE if possible. Return true if OK. */
static bool
clone_file (int dest, int source)
{
#ifdef FICLONE
return ioctl (dest, FICLONE, source) == 0;
#endif
return false;
}
DEFUN ("copy-file", Fcopy_file, Scopy_file, 2, 6,
"fCopy file: \nGCopy %s to file: \np\nP",
doc: /* Copy FILE to NEWNAME. Both args must be strings.
@ -1975,7 +1990,7 @@ permissions. */)
record_unwind_protect_int (close_file_unwind, ofd);
off_t oldsize = 0, newsize = 0;
off_t oldsize = 0, newsize;
if (already_exists)
{
@ -1991,17 +2006,19 @@ permissions. */)
immediate_quit = 1;
QUIT;
while (true)
if (clone_file (ofd, ifd))
newsize = st.st_size;
else
{
char buf[MAX_ALLOCA];
ptrdiff_t n = emacs_read (ifd, buf, sizeof buf);
ptrdiff_t n;
for (newsize = 0; 0 < (n = emacs_read (ifd, buf, sizeof buf));
newsize += n)
if (emacs_write_sig (ofd, buf, n) != n)
report_file_error ("Write error", newname);
if (n < 0)
report_file_error ("Read error", file);
if (n == 0)
break;
if (emacs_write_sig (ofd, buf, n) != n)
report_file_error ("Write error", newname);
newsize += n;
}
/* Truncate any existing output file after writing the data. This