libq/move_file: code to move a file or copy+remove it

This code originated from qmerge.c, it was adapted to be more generic in
a function.

Signed-off-by: Fabian Groffen <grobian@gentoo.org>

3 files changed, 127 insertions, 0 deletions

diff --git a/libq/Makefile.am b/libq/Makefile.am
index da100b6..c0402a4 100644
--- a/libq/Makefile.am
+++ b/libq/Makefile.am
@@ -11,6 +11,7 @@ QFILES = \
 	hash.c hash.h \
 	human_readable.c human_readable.h \
 	i18n.h \
+	move_file.c move_file.h \
 	prelink.c prelink.h \
 	profile.c profile.h \
 	rmspace.c rmspace.h \
diff --git a/libq/move_file.c b/libq/move_file.c
new file mode 100644
index 0000000..07cf69f
--- /dev/null
+++ b/libq/move_file.c
@@ -0,0 +1,105 @@
+/*
+ * Copyright 2005-2021 Gentoo Authors
+ * Distributed under the terms of the GNU General Public License v2
+ *
+ * Copyright 2005-2010 Ned Ludd        - <solar@gentoo.org>
+ * Copyright 2005-2014 Mike Frysinger  - <vapier@gentoo.org>
+ * Copyright 2018-     Fabian Groffen  - <grobian@gentoo.org>
+ */
+
+#include "main.h"
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include "stat-time.h"
+
+#include "copy_file.h"
+#include "move_file.h"
+
+int
+move_file(int rootfd_src, const char *name_src,
+		  int rootfd_dst, const char *name_dst,
+		  struct stat *stat_src)
+{
+	/* first try fast path -- src/dst are same device, else
+	 * fall back to slow path -- manual read/write */
+	if (renameat(rootfd_src, name_src, rootfd_dst, name_dst) != 0) {
+		int             fd_src;
+		int             fd_dst;
+		char            tmpname_dst[_Q_PATH_MAX];
+		struct stat     st;
+		struct timespec times[2];
+
+		fd_src = openat(rootfd_src, name_src, O_RDONLY|O_CLOEXEC);
+		if (fd_src < 0) {
+			warnp("could not read source file %s", name_src);
+			return fd_src;
+		}
+
+		if (stat_src == NULL) {
+			if (fstat(fd_src, &st) != 0) {
+				warnp("could not stat source file %s", name_src);
+				return -1;
+			}
+
+			stat_src = &st;
+		}
+
+		/* do not write the file in place ...
+	 	 * will fail with files that are in use
+	 	 * plus it isn't atomic, so we could leave a mess */
+	 	snprintf(tmpname_dst, sizeof(tmpname_dst), ".%u.%s",
+	 			 getpid(), name_dst);
+		fd_dst = openat(rootfd_dst, tmpname_dst,
+					 	O_WRONLY|O_CLOEXEC|O_CREAT|O_TRUNC,
+					 	stat_src->st_mode);
+		if (fd_dst < 0) {
+			warnp("could not open destination file %s (for %s)",
+				  tmpname_dst, name_dst);
+			close(fd_src);
+			return fd_dst;
+		}
+
+		/* make sure owner/mode is sane before we write out data */
+		if (fchown(fd_dst, stat_src->st_uid, stat_src->st_gid) != 0) {
+			warnp("could not set ownership (%zu/%zu) for %s",
+			  	  (size_t)stat_src->st_uid, (size_t)stat_src->st_gid, name_dst);
+			return -1;
+		}
+		if (fchmod(fd_dst, stat_src->st_mode) != 0) {
+			warnp("could not set permission (%u) for %s",
+			  	  (int)stat_src->st_mode, name_dst);
+			return -1;
+		}
+
+		/* do the actual data copy */
+		if (copy_file_fd(fd_src, fd_dst)) {
+			warnp("could not write to file %s", name_dst);
+			if (unlinkat(rootfd_dst, tmpname_dst, 0) != 0) {
+				/* don't care */;
+			}
+			close(fd_src);
+			close(fd_dst);
+			return -1;
+		}
+
+		/* Preserve the file times */
+		times[0] = get_stat_atime(&st);
+		times[1] = get_stat_mtime(&st);
+		futimens(fd_dst, times);
+
+		close(fd_src);
+		close(fd_dst);
+
+		/* finally move the new tmp dst file to the right place, which
+		 * should be on the same FS/device now */
+		if (renameat(rootfd_dst, tmpname_dst, rootfd_dst, name_dst)) {
+			warnp("could not rename %s to %s", tmpname_dst, name_dst);
+			return -1;
+		}
+	}
+
+	return 0;
+}
diff --git a/libq/move_file.h b/libq/move_file.h
new file mode 100644
index 0000000..a454165
--- /dev/null
+++ b/libq/move_file.h
@@ -0,0 +1,21 @@
+/*
+ * Copyright 2005-2021 Gentoo Authors
+ * Distributed under the terms of the GNU General Public License v2
+ *
+ * Copyright 2005-2010 Ned Ludd        - <solar@gentoo.org>
+ * Copyright 2005-2014 Mike Frysinger  - <vapier@gentoo.org>
+ * Copyright 2018-     Fabian Groffen  - <grobian@gentoo.org>
+ */
+
+#ifndef _MOVE_FILE_H
+
+#define _MOVE_FILE_H 1
+
+#include <sys/types.h>
+#include <sys/stat.h>
+
+int move_file(int rootfd_src, const char *name_src,
+			  int rootfd_dst, const char *name_dst,
+		  	  struct stat *stat_src);
+
+#endif