[libc-commits] [libc] [libc] Implement basename and dirname in libgen.h (PR #204554)

[Pavel Labath via libc-commits]

================
@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// Implementation of dirname.
+///
+//===----------------------------------------------------------------------===//
+
+#include "src/libgen/dirname.h"
+#include "src/__support/CPP/string_view.h"
+#include "src/__support/common.h"
+#include "src/__support/macros/config.h"
+
+namespace LIBC_NAMESPACE_DECL {
+
+LLVM_LIBC_FUNCTION(char *, dirname, (char *path)) {
+  if (path == nullptr || path[0] == '\0') {
+    static char dot[] = ".";
+    return dot;
+  }
+
+  cpp::string_view sv(path);
+  size_t last_non_slash = sv.find_last_not_of('/');
+
+  if (last_non_slash == cpp::string_view::npos) {
+    static char slash[] = "/";
+    return slash;
+  }
+
+  size_t last_slash = sv.substr(0, last_non_slash).find_last_of('/');
+
+  if (last_slash == cpp::string_view::npos) {
+    static char dot[] = ".";
+    return dot;
----------------
labath wrote:

Or maybe even better. `return const_cast<char *>(".")`, and let the compiler merge all "." strings ?

https://github.com/llvm/llvm-project/pull/204554