Re: copy_file_preserving variant that doesn't exit on error?

[Reuben Thomas]

On 24 July 2011 21:05, Reuben Thomas <r...@sc3d.org> wrote:
> I just came across the copy-file module, which does exactly what I
> want (it is even geared to making backup files), but (unfortunately
> for use in an interactive program) exits on error.

Just to move this along a bit, I attach a patch which changes
copy_file_preserving to return error codes instead of calling error.

Obviously, I don't expect this to be applied to gnulib, but as per my
original message, I'd like to know if a version of
copy_file_preserving along these lines is thought to be a good idea
for interactive use (I need it for creating backup files in GNU Zile),
and how I might produce a patch that provides an error-returning
variant without duplicating all the code.

diff --git a/lib/copy-file.h b/lib/copy-file.h
index cb8b1f7..b0c29e0 100644
--- a/lib/copy-file.h
+++ b/lib/copy-file.h
@@ -26,7 +26,7 @@ extern "C" {
    Modification times, owner, group and access permissions are preserved as
    far as possible.
    Exit upon failure.  */
-extern void copy_file_preserving (const char *src_filename, const
char *dest_filename);
+extern int copy_file_preserving (const char *src_filename, const char
*dest_filename);


 #ifdef __cplusplus
diff --git a/lib/copy-file.c b/lib/copy-file.c
index f9cd9c0..b5b8447 100644
--- a/lib/copy-file.c
+++ b/lib/copy-file.c
@@ -53,7 +53,7 @@

 enum { IO_SIZE = 32 * 1024 };

-void
+int
 copy_file_preserving (const char *src_filename, const char *dest_filename)
 {
   int src_fd;
@@ -63,37 +63,37 @@ copy_file_preserving (const char *src_filename,
const char *dest_filename)
   char *buf = xmalloc (IO_SIZE);

   src_fd = open (src_filename, O_RDONLY | O_BINARY);
-  if (src_fd < 0 || fstat (src_fd, &statbuf) < 0)
-    error (EXIT_FAILURE, errno, _("error while opening \"%s\" for reading"),
-           src_filename);
+  if (src_fd < 0)
+    return -1;
+  if (fstat (src_fd, &statbuf) < 0)
+    goto error_exit_2;

   mode = statbuf.st_mode & 07777;

   dest_fd = open (dest_filename, O_WRONLY | O_CREAT | O_TRUNC |
O_BINARY, 0600);
   if (dest_fd < 0)
-    error (EXIT_FAILURE, errno, _("cannot open backup file \"%s\" for
writing"),
-           dest_filename);
+    return -1;

   /* Copy the file contents.  */
   for (;;)
     {
       size_t n_read = safe_read (src_fd, buf, IO_SIZE);
       if (n_read == SAFE_READ_ERROR)
-        error (EXIT_FAILURE, errno, _("error reading \"%s\""), src_filename);
+        goto error_exit;
       if (n_read == 0)
         break;

       if (full_write (dest_fd, buf, n_read) < n_read)
-        error (EXIT_FAILURE, errno, _("error writing \"%s\""), dest_filename);
+        goto error_exit;
     }

   free (buf);

 #if !USE_ACL
   if (close (dest_fd) < 0)
-    error (EXIT_FAILURE, errno, _("error writing \"%s\""), dest_filename);
+    goto error_exit_2;
   if (close (src_fd) < 0)
-    error (EXIT_FAILURE, errno, _("error after reading \"%s\""), src_filename);
+    return -1;
 #endif

   /* Preserve the access and modification times.  */
@@ -123,15 +123,23 @@ copy_file_preserving (const char *src_filename,
const char *dest_filename)
   /* Preserve the access permissions.  */
 #if USE_ACL
   if (copy_acl (src_filename, src_fd, dest_filename, dest_fd, mode))
-    exit (EXIT_FAILURE);
+    goto error_exit;
 #else
   chmod (dest_filename, mode);
 #endif

 #if USE_ACL
   if (close (dest_fd) < 0)
-    error (EXIT_FAILURE, errno, _("error writing \"%s\""), dest_filename);
+    goto error_exit_2;
   if (close (src_fd) < 0)
-    error (EXIT_FAILURE, errno, _("error after reading \"%s\""), src_filename);
+    return -1;
 #endif
+
+  return 0;
+
+ error_exit:
+  close (dest_fd);
+ error_exit_2:
+  close (src_fd);
+  return -1;
 }