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authorDenys Vlasenko2017-07-04 18:49:24 +0200
committerDenys Vlasenko2017-07-04 18:56:45 +0200
commita8cf9c5a3ffd1601872d1ab14c5be00fde29209c (patch)
tree20d9accf1cfeeea31a7252f6d12889160cf3aab0 /libbb
parent6a3bcf340aa9d7defc86f21d75fd9412c5b9f427 (diff)
downloadbusybox-a8cf9c5a3ffd1601872d1ab14c5be00fde29209c.zip
busybox-a8cf9c5a3ffd1601872d1ab14c5be00fde29209c.tar.gz
libbb: new function bb_getgroups() - allocating wrapper around getgroups()
function old new delta bb_getgroups - 111 +111 nexpr 843 757 -86 ------------------------------------------------------------------------------ (add/remove: 2/0 grow/shrink: 0/1 up/down: 111/-86) Total: 25 bytes Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Diffstat (limited to 'libbb')
-rw-r--r--libbb/bb_getgroups.c47
1 files changed, 47 insertions, 0 deletions
diff --git a/libbb/bb_getgroups.c b/libbb/bb_getgroups.c
new file mode 100644
index 0000000..59ae537
--- /dev/null
+++ b/libbb/bb_getgroups.c
@@ -0,0 +1,47 @@
+/*
+ * Utility routines.
+ *
+ * Copyright (C) 2017 Denys Vlasenko
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+
+//kbuild:lib-y += bb_getgroups.o
+
+#include "libbb.h"
+
+gid_t* FAST_FUNC bb_getgroups(int *ngroups, gid_t *group_array)
+{
+ int n = ngroups ? *ngroups : 0;
+
+ /* getgroups may be a bit expensive, try to use it only once */
+ if (n < 32)
+ n = 32;
+
+ for (;;) {
+// FIXME: ash tries so hard to not die on OOM (when we are called from test),
+// and we spoil it with just one xrealloc here
+ group_array = xrealloc(group_array, (n+1) * sizeof(group_array[0]));
+ n = getgroups(n, group_array);
+ /*
+ * If buffer is too small, kernel does not return new_n > n.
+ * It returns -1 and EINVAL:
+ */
+ if (n >= 0) {
+ /* Terminator for bb_getgroups(NULL, NULL) usage */
+ group_array[n] = (gid_t) -1;
+ break;
+ }
+ if (errno == EINVAL) { /* too small? */
+ /* This is the way to ask kernel how big the array is */
+ n = getgroups(0, group_array);
+ continue;
+ }
+ /* Some other error (should never happen on Linux) */
+ bb_perror_msg_and_die("getgroups");
+ }
+
+ if (ngroups)
+ *ngroups = n;
+ return group_array;
+}