Fix ftw/nftw to only report unreadable directories once.

Also remove all the copy & paste.

Bug: http://b/28197840
Change-Id: Ia43e9ffd838dabb511a6e54403d6f62066383e4d
diff --git a/libc/bionic/ftw.cpp b/libc/bionic/ftw.cpp
new file mode 100644
index 0000000..2123619
--- /dev/null
+++ b/libc/bionic/ftw.cpp
@@ -0,0 +1,124 @@
+/*
+ * Copyright (c) 2003, 2004 Todd C. Miller <Todd.Miller@courtesan.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ * Sponsored in part by the Defense Advanced Research Projects
+ * Agency (DARPA) and Air Force Research Laboratory, Air Force
+ * Materiel Command, USAF, under agreement number F39502-99-1-0512.
+ */
+
+#include <errno.h>
+#include <fts.h>
+#include <ftw.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+static int do_nftw(const char *path,
+                   int (*ftw_fn)(const char*, const struct stat*, int),
+                   int (*nftw_fn)(const char*, const struct stat*, int, FTW*),
+                   int nfds,
+                   int nftw_flags) {
+  // TODO: nfds is currently unused.
+  if (nfds < 1) {
+    errno = EINVAL;
+    return -1;
+  }
+
+  // Translate to fts_open options.
+  int fts_options = FTS_LOGICAL | FTS_COMFOLLOW | FTS_NOCHDIR;
+  if (nftw_fn) {
+    fts_options = FTS_COMFOLLOW | ((nftw_flags & FTW_PHYS) ? FTS_PHYSICAL : FTS_LOGICAL);
+    if (!(nftw_flags & FTW_CHDIR)) fts_options |= FTS_NOCHDIR;
+    if (nftw_flags & FTW_MOUNT) fts_options |= FTS_XDEV;
+  }
+  bool postorder = (nftw_flags & FTW_DEPTH) != 0;
+
+  // Call fts_open.
+  char* const paths[2] = { const_cast<char*>(path), nullptr };
+  FTS* fts = fts_open(paths, fts_options, nullptr);
+  if (fts == nullptr) {
+    return -1;
+  }
+
+  // Translate fts_read results into ftw/nftw callbacks.
+  int error = 0;
+  FTSENT* cur;
+  while (error == 0 && (cur = fts_read(fts)) != nullptr) {
+    int fn_flag;
+    switch (cur->fts_info) {
+      case FTS_D:
+        // In the postorder case, we'll translate FTS_DP to FTW_DP later.
+        // In the can't-access case, we'll translate FTS_DNR to FTW_DNR later.
+        if (postorder || access(cur->fts_path, R_OK) == -1) continue;
+        fn_flag = FTW_D;
+        break;
+      case FTS_DNR:
+        fn_flag = FTW_DNR;
+        break;
+      case FTS_DP:
+        if (!postorder) continue;
+        fn_flag = FTW_DP;
+        break;
+      case FTS_F:
+      case FTS_DEFAULT:
+        fn_flag = FTW_F;
+        break;
+      case FTS_NS:
+      case FTS_NSOK:
+        fn_flag = FTW_NS;
+        break;
+      case FTS_SL:
+        fn_flag = FTW_SL;
+        break;
+      case FTS_SLNONE:
+        fn_flag = (nftw_fn != nullptr) ? FTW_SLN : FTW_NS;
+        break;
+      case FTS_DC:
+        errno = ELOOP;
+        error = -1;
+        continue;
+      default:
+        error = -1;
+        continue;
+    }
+
+    // Call the appropriate function.
+    if (nftw_fn != nullptr) {
+      FTW ftw;
+      ftw.base = cur->fts_pathlen - cur->fts_namelen;
+      ftw.level = cur->fts_level;
+      error = nftw_fn(cur->fts_path, cur->fts_statp, fn_flag, &ftw);
+    } else {
+      error = ftw_fn(cur->fts_path, cur->fts_statp, fn_flag);
+    }
+  }
+
+  int saved_errno = errno;
+  if (fts_close(fts) != 0 && error == 0) {
+    error = -1;
+  } else {
+    errno = saved_errno;
+  }
+  return error;
+}
+
+int ftw(const char* path, int (*ftw_fn)(const char*, const struct stat*, int), int nfds) {
+  return do_nftw(path, ftw_fn, nullptr, nfds, 0);
+}
+
+int nftw(const char* path, int (*nftw_fn)(const char*, const struct stat*, int, FTW*),
+         int nfds, int nftw_flags) {
+  return do_nftw(path, nullptr, nftw_fn, nfds, nftw_flags);
+}