tar: add support for --overwrite. +70 bytes.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

4 files changed, 30 insertions, 4 deletions

diff --git a/archival/libunarchive/data_extract_all.c b/archival/libunarchive/data_extract_all.c
index ae242df..874d37d 100644
--- a/archival/libunarchive/data_extract_all.c
+++ b/archival/libunarchive/data_extract_all.c
@@ -72,8 +72,11 @@ void FAST_FUNC data_extract_all(archive_handle_t *archive_handle)
 		switch (file_header->mode & S_IFMT) {
 		case S_IFREG: {
 			/* Regular file */
+			int flags = O_WRONLY | O_CREAT | O_EXCL;
+			if (archive_handle->ah_flags & ARCHIVE_O_TRUNC)
+				flags = O_WRONLY | O_CREAT | O_TRUNC;
 			dst_fd = xopen3(file_header->name,
-				O_WRONLY | O_CREAT | O_EXCL,
+				flags,
 				file_header->mode
 				);
 			bb_copyfd_exact_size(archive_handle->src_fd, dst_fd, file_header->size);
diff --git a/archival/tar.c b/archival/tar.c
index 7ec101d..5994d89 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -751,6 +751,7 @@ enum {
 #if ENABLE_FEATURE_TAR_LONG_OPTIONS
 	OPTBIT_NUMERIC_OWNER,
 	OPTBIT_NOPRESERVE_PERM,
+	OPTBIT_OVERWRITE,
 #endif
 	OPT_TEST         = 1 << 0, // t
 	OPT_EXTRACT      = 1 << 1, // x
@@ -771,6 +772,7 @@ enum {
 	OPT_COMPRESS     = IF_FEATURE_SEAMLESS_Z(   (1 << OPTBIT_COMPRESS    )) + 0, // Z
 	OPT_NUMERIC_OWNER   = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_NUMERIC_OWNER  )) + 0, // numeric-owner
 	OPT_NOPRESERVE_PERM = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_NOPRESERVE_PERM)) + 0, // no-same-permissions
+	OPT_OVERWRITE       = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_OVERWRITE      )) + 0, // overwrite
 };
 #if ENABLE_FEATURE_TAR_LONG_OPTIONS
 static const char tar_longopts[] ALIGN1 =
@@ -807,9 +809,11 @@ static const char tar_longopts[] ALIGN1 =
 	"compress\0"            No_argument       "Z"
 # endif
 	/* use numeric uid/gid from tar header, not textual */
-	"numeric-owner\0"       No_argument       "\xfd"
+	"numeric-owner\0"       No_argument       "\xfc"
 	/* do not restore mode */
-	"no-same-permissions\0" No_argument       "\xfe"
+	"no-same-permissions\0" No_argument       "\xfd"
+	/* on unpack, open with O_TRUNC and !O_EXCL */
+	"overwrite\0"           No_argument       "\xfe"
 	/* --exclude takes next bit position in option mask, */
 	/* therefore we have to put it _after_ --no-same-permissions */
 # if ENABLE_FEATURE_TAR_FROM
@@ -924,6 +928,11 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
 	if (opt & OPT_NOPRESERVE_PERM)
 		tar_handle->ah_flags |= ARCHIVE_DONT_RESTORE_PERM;
 
+	if (opt & OPT_OVERWRITE) {
+		tar_handle->ah_flags &= ~ARCHIVE_UNLINK_OLD;
+		tar_handle->ah_flags |= ARCHIVE_O_TRUNC;
+	}
+
 	if (opt & OPT_GZIP)
 		get_header_ptr = get_header_tar_gz;
 
diff --git a/include/unarchive.h b/include/unarchive.h
index 35ce521..68e83f0 100644
--- a/include/unarchive.h
+++ b/include/unarchive.h
@@ -58,7 +58,7 @@ typedef struct archive_handle_t {
 	char *ah_buffer;
 
 	/* Flags and misc. stuff */
-	unsigned char ah_flags;
+	unsigned ah_flags;
 
 	/* "Private" storage for archivers */
 //	unsigned char ah_priv_inited;
@@ -74,6 +74,7 @@ typedef struct archive_handle_t {
 #define ARCHIVE_DONT_RESTORE_OWNER  (1 << 5)
 #define ARCHIVE_DONT_RESTORE_PERM   (1 << 6)
 #define ARCHIVE_NUMERIC_OWNER       (1 << 7)
+#define ARCHIVE_O_TRUNC             (1 << 8)
 
 
 /* Info struct unpackers can fill out to inform users of thing like
diff --git a/testsuite/tar.tests b/testsuite/tar.tests
index 35f96b7..6c136a6 100755
--- a/testsuite/tar.tests
+++ b/testsuite/tar.tests
@@ -31,6 +31,19 @@ Ok
 " \
 "" ""
 
+testing "tar --overwrite" "\
+rm -rf input_* test.tar 2>/dev/null
+ln input input_hard
+tar cf test.tar input_hard
+echo WRONG >input
+# --overwrite opens 'input_hard' without unlinking,
+# thus 'input_hard' still linked to 'input' and we write 'Ok' into it
+tar xf test.tar --overwrite 2>&1 && cat input
+" "\
+Ok
+" \
+"Ok\n" ""
+
 cd .. && rm -rf tempdir || exit 1
 
 exit $FAILCOUNT