tar: code shrink

function                                             old     new   delta
writeLongname                                        226     228      +2
static.prefilled                                      48       -     -48
------------------------------------------------------------------------------
(add/remove: 0/1 grow/shrink: 1/0 up/down: 2/-48)             Total: -46 bytes

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

1 files changed, 13 insertions, 12 deletions

diff --git a/archival/tar.c b/archival/tar.c
index ca802f73c..f10781a58 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -232,7 +232,7 @@ static HardLinkInfo *findHardLinkInfo(HardLinkInfo *hlInfo, struct stat *statbuf
 }
 
 /* Put an octal string into the specified buffer.
- * The number is zero padded and possibly null terminated.
+ * The number is zero padded and possibly NUL terminated.
  * Stores low-order bits only if whole value does not fit. */
 static void putOctal(char *cp, int len, off_t value)
 {
@@ -283,31 +283,32 @@ static void chksum_and_xwrite(int fd, struct tar_header_t* hp)
 # if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
 static void writeLongname(int fd, int type, const char *name, int dir)
 {
-        static const struct {
+        struct prefilled {
                 char mode[8];             /* 100-107 */
                 char uid[8];              /* 108-115 */
                 char gid[8];              /* 116-123 */
                 char size[12];            /* 124-135 */
                 char mtime[12];           /* 136-147 */
-        } prefilled = {
-                "0000000",
-                "0000000",
-                "0000000",
-                "00000000000",
-                "00000000000",
         };
         struct tar_header_t header;
         int size;
 
+        memset(&header, 0, sizeof(header));
+        header.typeflag = type;
+        strcpy(header.name, "././@LongLink");
+        /* This sets mode/uid/gid/mtime to "00...00<NUL>" strings */
+        memset(header.mode, '0', sizeof(struct prefilled));
+        header.mode [sizeof(header.mode ) - 1] = '\0';
+        header.uid  [sizeof(header.uid  ) - 1] = '\0';
+        header.gid  [sizeof(header.gid  ) - 1] = '\0';
+        /* header.size is filled by '0' now, will be corrected below */
+        header.mtime[sizeof(header.mtime) - 1] = '\0';
+
         dir = !!dir; /* normalize: 0/1 */
         size = strlen(name) + 1 + dir; /* GNU tar uses strlen+1 */
         /* + dir: account for possible '/' */
 
-        memset(&header, 0, sizeof(header));
-        strcpy(header.name, "././@LongLink");
-        memcpy(header.mode, prefilled.mode, sizeof(prefilled));
         PUT_OCTAL(header.size, size);
-        header.typeflag = type;
         chksum_and_xwrite(fd, &header);
 
         /* Write filename[/] and pad the block. */