Squashed 'third_party/elfutils/' content from commit 555e15e

Change-Id: I61cde98949e47e5c8c09c33260de17f30921be79
git-subtree-dir: third_party/elfutils
git-subtree-split: 555e15ebe8bf1eb33d00747173cfc80cc65648a4
diff --git a/libelf/elf_getarhdr.c b/libelf/elf_getarhdr.c
new file mode 100644
index 0000000..509f1da
--- /dev/null
+++ b/libelf/elf_getarhdr.c
@@ -0,0 +1,73 @@
+/* Read header of next archive member.
+   Copyright (C) 1998, 1999, 2000, 2002, 2008, 2015 Red Hat, Inc.
+   This file is part of elfutils.
+   Written by Ulrich Drepper <drepper@redhat.com>, 1998.
+
+   This file is free software; you can redistribute it and/or modify
+   it under the terms of either
+
+     * the GNU Lesser General Public License as published by the Free
+       Software Foundation; either version 3 of the License, or (at
+       your option) any later version
+
+   or
+
+     * the GNU General Public License as published by the Free
+       Software Foundation; either version 2 of the License, or (at
+       your option) any later version
+
+   or both in parallel, as here.
+
+   elfutils is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received copies of the GNU General Public License and
+   the GNU Lesser General Public License along with this program.  If
+   not, see <http://www.gnu.org/licenses/>.  */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <assert.h>
+#include <libelf.h>
+#include <stddef.h>
+
+#include "libelfP.h"
+
+
+Elf_Arhdr *
+elf_getarhdr (Elf *elf)
+{
+  if (elf == NULL)
+    return NULL;
+
+  Elf *parent = elf->parent;
+
+  /* Calling this function is not ok for any file type but archives.  */
+  if (parent == NULL)
+    {
+      __libelf_seterrno (ELF_E_INVALID_OP);
+      return NULL;
+    }
+
+  /* Make sure we have read the archive header.  */
+  if (parent->state.ar.elf_ar_hdr.ar_name == NULL
+      && __libelf_next_arhdr_wrlock (parent) != 0)
+    {
+      rwlock_wrlock (parent->lock);
+      int st = __libelf_next_arhdr_wrlock (parent);
+      rwlock_unlock (parent->lock);
+
+      if (st != 0)
+	/* Something went wrong.  Maybe there is no member left.  */
+	return NULL;
+    }
+
+  /* We can be sure the parent is an archive.  */
+  assert (parent->kind == ELF_K_AR);
+
+  return &parent->state.ar.elf_ar_hdr;
+}