Revert "Delete rtc::Pathname"

This reverts commit 6b9dec0d16f2df59fa2820c5ec1341be52fb9f32.

Reason for revert: speculative revert for breaking internal projects

Original change's description:
> Delete rtc::Pathname
> 
> Bug: webrtc:6424
> Change-Id: Iec01dc5dd1426d4558983b828b67af872107d723
> Reviewed-on: https://webrtc-review.googlesource.com/c/108400
> Commit-Queue: Niels Moller <nisse@webrtc.org>
> Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#25479}

TBR=kwiberg@webrtc.org,nisse@webrtc.org

Change-Id: I3129a81a1d8e36b3e6c67572410bdc478ec4d5e9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:6424
Reviewed-on: https://webrtc-review.googlesource.com/c/109201
Reviewed-by: Qingsi Wang <qingsi@webrtc.org>
Commit-Queue: Qingsi Wang <qingsi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25490}
diff --git a/rtc_base/pathutils.cc b/rtc_base/pathutils.cc
new file mode 100644
index 0000000..0764671
--- /dev/null
+++ b/rtc_base/pathutils.cc
@@ -0,0 +1,154 @@
+/*
+ *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#if defined(WEBRTC_WIN)
+#include <windows.h>
+#include <shellapi.h>
+#include <shlobj.h>
+#include <tchar.h>
+#endif  // WEBRTC_WIN
+
+#include <string.h>  // for strchr
+
+#include "rtc_base/pathutils.h"
+
+namespace rtc {
+
+static const char EMPTY_STR[] = "";
+
+// EXT_DELIM separates a file basename from extension
+const char EXT_DELIM = '.';
+
+// FOLDER_DELIMS separate folder segments and the filename
+const char* const FOLDER_DELIMS = "/\\";
+
+// DEFAULT_FOLDER_DELIM is the preferred delimiter for this platform
+#ifdef WEBRTC_WIN
+const char DEFAULT_FOLDER_DELIM = '\\';
+#else  // !WEBRTC_WIN
+const char DEFAULT_FOLDER_DELIM = '/';
+#endif  // !WEBRTC_WIN
+
+///////////////////////////////////////////////////////////////////////////////
+// Pathname - parsing of pathnames into components, and vice versa
+///////////////////////////////////////////////////////////////////////////////
+
+bool Pathname::IsFolderDelimiter(char ch) {
+  return (nullptr != ::strchr(FOLDER_DELIMS, ch));
+}
+
+char Pathname::DefaultFolderDelimiter() {
+  return DEFAULT_FOLDER_DELIM;
+}
+
+Pathname::Pathname()
+    : folder_delimiter_(DEFAULT_FOLDER_DELIM) {
+}
+
+Pathname::Pathname(const Pathname&) = default;
+Pathname::Pathname(Pathname&&) = default;
+
+Pathname::Pathname(const std::string& pathname)
+    : folder_delimiter_(DEFAULT_FOLDER_DELIM) {
+  SetPathname(pathname);
+}
+
+Pathname::Pathname(const std::string& folder, const std::string& filename)
+    : folder_delimiter_(DEFAULT_FOLDER_DELIM) {
+  SetPathname(folder, filename);
+}
+
+Pathname& Pathname::operator=(const Pathname&) = default;
+Pathname& Pathname::operator=(Pathname&&) = default;
+
+std::string Pathname::pathname() const {
+  std::string pathname(folder_);
+  pathname.append(basename_);
+  pathname.append(extension_);
+  if (pathname.empty()) {
+    // Instead of the empty pathname, return the current working directory.
+    pathname.push_back('.');
+    pathname.push_back(folder_delimiter_);
+  }
+  return pathname;
+}
+
+void Pathname::SetPathname(const std::string& pathname) {
+  std::string::size_type pos = pathname.find_last_of(FOLDER_DELIMS);
+  if (pos != std::string::npos) {
+    SetFolder(pathname.substr(0, pos + 1));
+    SetFilename(pathname.substr(pos + 1));
+  } else {
+    SetFolder(EMPTY_STR);
+    SetFilename(pathname);
+  }
+}
+
+void Pathname::SetPathname(const std::string& folder,
+                           const std::string& filename) {
+  SetFolder(folder);
+  SetFilename(filename);
+}
+
+void Pathname::SetFolder(const std::string& folder) {
+  folder_.assign(folder);
+  // Ensure folder ends in a path delimiter
+  if (!folder_.empty() && !IsFolderDelimiter(folder_[folder_.length()-1])) {
+    folder_.push_back(folder_delimiter_);
+  }
+}
+
+void Pathname::AppendFolder(const std::string& folder) {
+  folder_.append(folder);
+  // Ensure folder ends in a path delimiter
+  if (!folder_.empty() && !IsFolderDelimiter(folder_[folder_.length()-1])) {
+    folder_.push_back(folder_delimiter_);
+  }
+}
+
+bool Pathname::SetBasename(const std::string& basename) {
+  if(basename.find_first_of(FOLDER_DELIMS) != std::string::npos) {
+    return false;
+  }
+  basename_.assign(basename);
+  return true;
+}
+
+bool Pathname::SetExtension(const std::string& extension) {
+  if (extension.find_first_of(FOLDER_DELIMS) != std::string::npos ||
+    extension.find_first_of(EXT_DELIM, 1) != std::string::npos) {
+      return false;
+  }
+  extension_.assign(extension);
+  // Ensure extension begins with the extension delimiter
+  if (!extension_.empty() && (extension_[0] != EXT_DELIM)) {
+    extension_.insert(extension_.begin(), EXT_DELIM);
+  }
+  return true;
+}
+
+std::string Pathname::filename() const {
+  std::string filename(basename_);
+  filename.append(extension_);
+  return filename;
+}
+
+bool Pathname::SetFilename(const std::string& filename) {
+  std::string::size_type pos = filename.rfind(EXT_DELIM);
+  if ((pos == std::string::npos) || (pos == 0)) {
+    return SetExtension(EMPTY_STR) && SetBasename(filename);
+  } else {
+    return SetExtension(filename.substr(pos)) && SetBasename(filename.substr(0, pos));
+  }
+}
+
+///////////////////////////////////////////////////////////////////////////////
+
+} // namespace rtc