libbb: auto_string() for efficient handling of temporary malloced stirngs

Use it in libiproute: get rid of one static string buffer.

function                                             old     new   delta
auto_string                                            -      51     +51
ll_index_to_name                                      10      49     +39
buffer_fill_and_print                                169     178      +9
scan_recursive                                       378     380      +2
decode_one_format                                    732     734      +2
cmdputs                                              334     332      -2
static.cur_saved                                       4       1      -3
static.nbuf                                           16       -     -16
printable_string                                      94      57     -37
ll_idx_n2a                                            53       -     -53
------------------------------------------------------------------------------
(add/remove: 2/2 grow/shrink: 4/3 up/down: 103/-111)           Total: -8 bytes
   text	   data	    bss	    dec	    hex	filename
 939880	    992	  17496	 958368	  e9fa0	busybox_old
 939880	    992	  17480	 958352	  e9f90	busybox_unstripped

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

2 files changed, 24 insertions, 9 deletions

diff --git a/libbb/auto_string.c b/libbb/auto_string.c
new file mode 100644
index 000000000..ae940069a
--- /dev/null
+++ b/libbb/auto_string.c
@@ -0,0 +1,23 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Utility routines.
+ *
+ * Copyright (C) 2015 Denys Vlasenko
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+//kbuild:lib-y += auto_string.o
+
+#include "libbb.h"
+
+char* FAST_FUNC auto_string(char *str)
+{
+        static char *saved[4];
+        static uint8_t cur_saved; /* = 0 */
+
+        free(saved[cur_saved]);
+        saved[cur_saved] = str;
+        cur_saved = (cur_saved + 1) & (ARRAY_SIZE(saved)-1);
+
+        return str;
+}
diff --git a/libbb/printable_string.c b/libbb/printable_string.c
index a316f60de..077d58d32 100644
--- a/libbb/printable_string.c
+++ b/libbb/printable_string.c
@@ -11,9 +11,6 @@
 
 const char* FAST_FUNC printable_string(uni_stat_t *stats, const char *str)
 {
-        static char *saved[4];
-        static unsigned cur_saved; /* = 0 */
-
         char *dst;
         const char *s;
 
@@ -56,10 +53,5 @@ const char* FAST_FUNC printable_string(uni_stat_t *stats, const char *str)
                 }
         }
 #endif
-
-        free(saved[cur_saved]);
-        saved[cur_saved] = dst;
-        cur_saved = (cur_saved + 1) & (ARRAY_SIZE(saved)-1);
-
-        return dst;
+        return auto_string(dst);
 }