libbb: move is_in_supplementary_groups() from test to libbb

function                                             old     new   delta
is_in_supplementary_groups                             -      54     +54
nexpr                                                766     721     -45
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/1 up/down: 54/-45)              Total: 9 bytes

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

1 files changed, 20 insertions, 0 deletions

diff --git a/libbb/bb_getgroups.c b/libbb/bb_getgroups.c
index 5d83c729a..f030d5eac 100644
--- a/libbb/bb_getgroups.c
+++ b/libbb/bb_getgroups.c
@@ -45,3 +45,23 @@ gid_t* FAST_FUNC bb_getgroups(int *ngroups, gid_t *group_array)
                 *ngroups = n;
         return group_array;
 }
+
+/* Return non-zero if GID is in our supplementary group list. */
+int FAST_FUNC is_in_supplementary_groups(int *pngroups, gid_t **pgroup_array, gid_t gid)
+{
+        int i;
+        int ngroups;
+        gid_t *group_array;
+
+        if (*pngroups == 0)
+                *pgroup_array = bb_getgroups(pngroups, NULL);
+        ngroups = *pngroups;
+        group_array = *pgroup_array;
+
+        /* Search through the list looking for GID. */
+        for (i = 0; i < ngroups; i++)
+                if (gid == group_array[i])
+                        return 1;
+
+        return 0;
+}