auto import from //depot/cupcake/@135843
diff --git a/libc/bionic/dirname_r.c b/libc/bionic/dirname_r.c
new file mode 100644
index 0000000..df2e9bf
--- /dev/null
+++ b/libc/bionic/dirname_r.c
@@ -0,0 +1,88 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in
+ * the documentation and/or other materials provided with the
+ * distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <libgen.h>
+#include <errno.h>
+#include <string.h>
+#include <sys/param.h>
+
+int
+dirname_r(const char* path, char* buffer, size_t bufflen)
+{
+ const char *endp;
+ int result, len;
+
+ /* Empty or NULL string gets treated as "." */
+ if (path == NULL || *path == '\0') {
+ path = ".";
+ len = 1;
+ goto Exit;
+ }
+
+ /* Strip trailing slashes */
+ endp = path + strlen(path) - 1;
+ while (endp > path && *endp == '/')
+ endp--;
+
+ /* Find the start of the dir */
+ while (endp > path && *endp != '/')
+ endp--;
+
+ /* Either the dir is "/" or there are no slashes */
+ if (endp == path) {
+ path = (*endp == '/') ? "/" : ".";
+ len = 1;
+ goto Exit;
+ }
+
+ do {
+ endp--;
+ } while (endp > path && *endp == '/');
+
+ len = endp - path +1;
+
+Exit:
+ result = len;
+ if (len+1 > MAXPATHLEN) {
+ errno = ENAMETOOLONG;
+ return -1;
+ }
+ if (buffer == NULL)
+ return result;
+
+ if (len > (int)bufflen-1) {
+ len = (int)bufflen-1;
+ result = -1;
+ errno = ERANGE;
+ }
+
+ if (len >= 0) {
+ memcpy( buffer, path, len );
+ buffer[len] = 0;
+ }
+ return result;
+}