src/main/tools/build-runfiles-windows.cc - bazel - Git at Google

 // Copyright 2017 The Bazel Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //    http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.

 #ifndef WIN32_LEAN_AND_MEAN
 #define WIN32_LEAN_AND_MEAN
 #endif
 #include <windows.h>

 #include <string.h>

 #include <fstream>
 #include <iostream>
 #include <sstream>
 #include <string>
 #include <unordered_map>

 #include "src/main/cpp/util/file_platform.h"
 #include "src/main/cpp/util/path_platform.h"
 #include "src/main/cpp/util/strings.h"
 #include "src/main/native/windows/file.h"

 using std::ifstream;
 using std::string;
 using std::stringstream;
 using std::unordered_map;
 using std::wstring;

 #ifndef SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
 #define SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE 0x2
 #endif

 #ifndef SYMBOLIC_LINK_FLAG_DIRECTORY
 #define SYMBOLIC_LINK_FLAG_DIRECTORY 0x1
 #endif

 namespace {

 const wchar_t* manifest_filename;
 const wchar_t* runfiles_base_dir;

 string GetLastErrorString() {
   DWORD last_error = GetLastError();
   if (last_error == 0) {
     return string();
   }

   char* message_buffer;
   size_t size = FormatMessageA(
       FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM |
           FORMAT_MESSAGE_IGNORE_INSERTS,
       NULL, last_error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
       (LPSTR)&message_buffer, 0, NULL);

   stringstream result;
   result << "(error: " << last_error << "): " << message_buffer;
   LocalFree(message_buffer);
   return result.str();
 }

 void die(const wchar_t* format, ...) {
   va_list ap;
   va_start(ap, format);
   fputws(L"build-runfiles error: ", stderr);
   vfwprintf(stderr, format, ap);
   va_end(ap);
   fputwc(L'\n', stderr);
   fputws(L"manifest file name: ", stderr);
   fputws(manifest_filename, stderr);
   fputwc(L'\n', stderr);
   fputws(L"runfiles base directory: ", stderr);
   fputws(runfiles_base_dir, stderr);
   fputwc(L'\n', stderr);
   exit(1);
 }

 wstring AsAbsoluteWindowsPath(const wchar_t* path) {
   wstring wpath;
   string error;
   if (!blaze_util::AsAbsoluteWindowsPath(path, &wpath, &error)) {
     die(L"Couldn't convert %s to absolute Windows path: %hs", path,
         error.c_str());
   }
   return wpath;
 }

 bool DoesDirectoryPathExist(const wchar_t* path) {
   DWORD dwAttrib = GetFileAttributesW(AsAbsoluteWindowsPath(path).c_str());

   return (dwAttrib != INVALID_FILE_ATTRIBUTES &&
           (dwAttrib & FILE_ATTRIBUTE_DIRECTORY));
 }

 wstring GetParentDirFromPath(const wstring& path) {
   return path.substr(0, path.find_last_of(L"\\/"));
 }

 inline void Trim(wstring& str) {
   str.erase(0, str.find_first_not_of(' '));
   str.erase(str.find_last_not_of(' ') + 1);
 }

 bool ReadSymlink(const wstring& abs_path, wstring* target, wstring* error) {
   switch (bazel::windows::ReadSymlinkOrJunction(abs_path, target, error)) {
     case bazel::windows::ReadSymlinkOrJunctionResult::kSuccess:
       return true;
     case bazel::windows::ReadSymlinkOrJunctionResult::kAccessDenied:
       *error = L"access is denied";
       break;
     case bazel::windows::ReadSymlinkOrJunctionResult::kDoesNotExist:
       *error = L"path does not exist";
       break;
     case bazel::windows::ReadSymlinkOrJunctionResult::kNotALink:
       *error = L"path is not a link";
       break;
     case bazel::windows::ReadSymlinkOrJunctionResult::kUnknownLinkType:
       *error = L"unknown link type";
       break;
     default:
       // This is bazel::windows::ReadSymlinkOrJunctionResult::kError (1).
       // The JNI code puts a custom message in 'error'.
       break;
   }
   return false;
 }

 }  // namespace

 class RunfilesCreator {
   typedef std::unordered_map<std::wstring, std::wstring> ManifestFileMap;

  public:
   RunfilesCreator(const wstring& manifest_path,
                   const wstring& runfiles_output_base)
       : manifest_path_(manifest_path),
         runfiles_output_base_(runfiles_output_base) {
     SetupOutputBase();
     if (!SetCurrentDirectoryW(runfiles_output_base_.c_str())) {
       die(L"SetCurrentDirectoryW failed (%s): %hs",
           runfiles_output_base_.c_str(), GetLastErrorString().c_str());
     }
   }

   void ReadManifest(bool allow_relative, bool ignore_metadata) {
     ifstream manifest_file(
         AsAbsoluteWindowsPath(manifest_path_.c_str()).c_str());

     if (!manifest_file) {
       die(L"Couldn't open MANIFEST file: %s", manifest_path_.c_str());
     }

     string line;
     int lineno = 0;
     while (getline(manifest_file, line)) {
       lineno++;
       // Skip metadata lines. They are used solely for
       // dependency checking.
       if (ignore_metadata && lineno % 2 == 0) {
         continue;
       }

       size_t space_pos = line.find_first_of(' ');
       wstring wline = blaze_util::CstringToWstring(line);
       wstring link, target;
       if (space_pos == string::npos) {
         link = wline;
         target = wstring();
       } else {
         link = wline.substr(0, space_pos);
         target = wline.substr(space_pos + 1);
       }

       // Removing leading and trailing spaces
       Trim(link);
       Trim(target);

       // We sometimes need to create empty files under the runfiles tree.
       // For example, for python binary, __init__.py is needed under every
       // directory. Storing an entry with an empty target indicates we need to
       // create such a file when creating the runfiles tree.
       if (!allow_relative && !target.empty() &&
           !blaze_util::IsAbsolute(target)) {
         die(L"Target cannot be relative path: %hs", line.c_str());
       }

       link = AsAbsoluteWindowsPath(link.c_str());
       if (!target.empty()) {
         target = AsAbsoluteWindowsPath(target.c_str());
       }

       manifest_file_map.insert(make_pair(link, target));
     }
   }

   void CreateRunfiles() {
     bool symlink_needs_privilege =
         DoesCreatingSymlinkNeedAdminPrivilege(runfiles_output_base_);
     ScanTreeAndPrune(runfiles_output_base_);
     CreateFiles(symlink_needs_privilege);
     CopyManifestFile();
   }

  private:
   void SetupOutputBase() {
     if (!DoesDirectoryPathExist(runfiles_output_base_.c_str())) {
       MakeDirectoriesOrDie(runfiles_output_base_);
     }
   }

   void MakeDirectoriesOrDie(const wstring& path) {
     if (!blaze_util::MakeDirectoriesW(path, 0755)) {
       die(L"MakeDirectoriesW failed (%s): %hs", path.c_str(),
           GetLastErrorString().c_str());
     }
   }

   void RemoveDirectoryOrDie(const wstring& path) {
     if (!RemoveDirectoryW(path.c_str())) {
       die(L"RemoveDirectoryW failed (%s): %hs", GetLastErrorString().c_str());
     }
   }

   void DeleteFileOrDie(const wstring& path) {
     SetFileAttributesW(path.c_str(), GetFileAttributesW(path.c_str()) &
                                          ~FILE_ATTRIBUTE_READONLY);
     if (!DeleteFileW(path.c_str())) {
       die(L"DeleteFileW failed (%s): %hs", path.c_str(),
           GetLastErrorString().c_str());
     }
   }

   bool DoesCreatingSymlinkNeedAdminPrivilege(const wstring& runfiles_base_dir) {
     wstring dummy_link = runfiles_base_dir + L"\\dummy_link";
     wstring dummy_target = runfiles_base_dir + L"\\dummy_target";

     // Try creating symlink without admin privilege.
     if (CreateSymbolicLinkW(dummy_link.c_str(), dummy_target.c_str(),
                             SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE)) {
       DeleteFileOrDie(dummy_link);
       return false;
     }

     // Try creating symlink with admin privilege
     if (CreateSymbolicLinkW(dummy_link.c_str(), dummy_target.c_str(), 0)) {
       DeleteFileOrDie(dummy_link);
       return true;
     }

     // If we couldn't create symlink, print out an error message and exit.
     if (GetLastError() == ERROR_PRIVILEGE_NOT_HELD) {
       die(L"CreateSymbolicLinkW failed:\n%hs\n",
           "Bazel needs to create symlink for building runfiles tree.\n"
           "Creating symlink on Windows requires either of the following:\n"
           "    1. Program is running with elevated privileges (Admin rights).\n"
           "    2. The system version is Windows 10 Creators Update (1703) or "
           "later and "
           "developer mode is enabled.",
           GetLastErrorString().c_str());
     } else {
       die(L"CreateSymbolicLinkW failed: %hs", GetLastErrorString().c_str());
     }

     return true;
   }

   // This function scan the current directory, remove all
   // files/symlinks/directories that are not presented in manifest file. If a
   // symlink already exists and points to the correct target, this function
   // erases its entry from manifest_file_map, so that we won't recreate it.
   void ScanTreeAndPrune(const wstring& path) {
     static const wstring kDot(L".");
     static const wstring kDotDot(L"..");

     WIN32_FIND_DATAW metadata;
     HANDLE handle = ::FindFirstFileW((path + L"\\*").c_str(), &metadata);
     if (handle == INVALID_HANDLE_VALUE) {
       return;  // directory does not exist or is empty
     }

     do {
       if (kDot != metadata.cFileName && kDotDot != metadata.cFileName) {
         wstring subpath = path + L"\\" + metadata.cFileName;
         subpath = AsAbsoluteWindowsPath(subpath.c_str());
         bool is_dir =
             (metadata.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0;
         bool is_symlink =
             (metadata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) != 0;
         if (is_symlink) {
           wstring target, werror;
           if (!ReadSymlink(subpath, &target, &werror)) {
             die(L"ReadSymlinkW failed (%s): %hs", subpath.c_str(),
                 werror.c_str());
           }

           target = AsAbsoluteWindowsPath(target.c_str());
           ManifestFileMap::iterator expected_target =
               manifest_file_map.find(subpath);

           if (expected_target == manifest_file_map.end() ||
               expected_target->second.empty()
               // Both paths are normalized paths in lower case, we can compare
               // them directly.
               || target != expected_target->second.c_str() ||
               blaze_util::IsDirectoryW(target) != is_dir) {
             if (is_dir) {
               RemoveDirectoryOrDie(subpath);
             } else {
               DeleteFileOrDie(subpath);
             }
           } else {
             manifest_file_map.erase(expected_target);
           }
         } else {
           if (is_dir) {
             ScanTreeAndPrune(subpath);
             // If the directory is empty, then we remove the directory.
             // Otherwise RemoveDirectory will fail with ERROR_DIR_NOT_EMPTY,
             // which we can just ignore.
             // Because if the directory is not empty, it means it contains some
             // symlinks already pointing to the correct targets (we just called
             // ScanTreeAndPrune). Then this directory shouldn't be removed in
             // the first place.
             if (!RemoveDirectoryW(subpath.c_str()) &&
                 GetLastError() != ERROR_DIR_NOT_EMPTY) {
               die(L"RemoveDirectoryW failed (%s): %hs", subpath.c_str(),
                   GetLastErrorString().c_str());
             }
           } else {
             DeleteFileOrDie(subpath);
           }
         }
       }
     } while (::FindNextFileW(handle, &metadata));
     ::FindClose(handle);
   }

   void CreateFiles(bool creating_symlink_needs_admin_privilege) {
     DWORD privilege_flag = creating_symlink_needs_admin_privilege
                                ? 0
                                : SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;

     for (const auto& it : manifest_file_map) {
       // Ensure the parent directory exists
       wstring parent_dir = GetParentDirFromPath(it.first);
       if (!DoesDirectoryPathExist(parent_dir.c_str())) {
         MakeDirectoriesOrDie(parent_dir);
       }

       if (it.second.empty()) {
         // Create an empty file
         HANDLE h = CreateFileW(it.first.c_str(),  // name of the file
                                GENERIC_WRITE,     // open for writing
                                // Must share for reading, otherwise
                                // symlink-following file existence checks (e.g.
                                // java.nio.file.Files.exists()) fail.
                                FILE_SHARE_READ,
                                0,  // use default security descriptor
                                CREATE_ALWAYS,  // overwrite if exists
                                FILE_ATTRIBUTE_NORMAL, 0);
         if (h != INVALID_HANDLE_VALUE) {
           CloseHandle(h);
         } else {
           die(L"CreateFileW failed (%s): %hs", it.first.c_str(),
               GetLastErrorString().c_str());
         }
       } else {
         DWORD create_dir = 0;
         if (blaze_util::IsDirectoryW(it.second.c_str())) {
           create_dir = SYMBOLIC_LINK_FLAG_DIRECTORY;
         }
         if (!CreateSymbolicLinkW(it.first.c_str(), it.second.c_str(),
                                  privilege_flag | create_dir)) {
           die(L"CreateSymbolicLinkW failed (%s -> %s): %hs", it.first.c_str(),
               it.second.c_str(), GetLastErrorString().c_str());
         }
       }
     }
   }

   void CopyManifestFile() {
     wstring new_manifest_file = runfiles_output_base_ + L"\\MANIFEST";
     if (!CopyFileW(manifest_path_.c_str(), new_manifest_file.c_str(),
                    /*bFailIfExists=*/FALSE)) {
       die(L"CopyFileW failed (%s -> %s): %hs", manifest_path_.c_str(),
           new_manifest_file.c_str(), GetLastErrorString().c_str());
     }
   }

  private:
   wstring manifest_path_;
   wstring runfiles_output_base_;
   ManifestFileMap manifest_file_map;
 };

 int wmain(int argc, wchar_t** argv) {
   argc--;
   argv++;
   bool allow_relative = false;
   bool ignore_metadata = false;

   while (argc >= 1) {
     if (wcscmp(argv[0], L"--allow_relative") == 0) {
       allow_relative = true;
       argc--;
       argv++;
     } else if (wcscmp(argv[0], L"--use_metadata") == 0) {
       // If --use_metadata is passed, it means manifest file contains metadata
       // lines, which we should ignore when reading manifest file.
       ignore_metadata = true;
       argc--;
       argv++;
     } else {
       break;
     }
   }

   if (argc != 2) {
     fprintf(stderr,
             "usage: [--allow_relative] [--use_metadata] "
             "<manifest_file> <runfiles_base_dir>\n");
     return 1;
   }

   manifest_filename = argv[0];
   runfiles_base_dir = argv[1];

   wstring manifest_absolute_path = AsAbsoluteWindowsPath(manifest_filename);
   wstring output_base_absolute_path = AsAbsoluteWindowsPath(runfiles_base_dir);

   RunfilesCreator runfiles_creator(manifest_absolute_path,
                                    output_base_absolute_path);
   runfiles_creator.ReadManifest(allow_relative, ignore_metadata);
   runfiles_creator.CreateRunfiles();

   return 0;
 }
	// Copyright 2017 The Bazel Authors. All rights reserved.
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.

	#ifndef WIN32_LEAN_AND_MEAN
	#define WIN32_LEAN_AND_MEAN
	#endif
	#include <windows.h>

	#include <string.h>

	#include <fstream>
	#include <iostream>
	#include <sstream>
	#include <string>
	#include <unordered_map>

	#include "src/main/cpp/util/file_platform.h"
	#include "src/main/cpp/util/path_platform.h"
	#include "src/main/cpp/util/strings.h"
	#include "src/main/native/windows/file.h"

	using std::ifstream;
	using std::string;
	using std::stringstream;
	using std::unordered_map;
	using std::wstring;

	#ifndef SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE
	#define SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE 0x2
	#endif

	#ifndef SYMBOLIC_LINK_FLAG_DIRECTORY
	#define SYMBOLIC_LINK_FLAG_DIRECTORY 0x1
	#endif

	namespace {

	const wchar_t* manifest_filename;
	const wchar_t* runfiles_base_dir;

	string GetLastErrorString() {
	DWORD last_error = GetLastError();
	if (last_error == 0) {
	return string();
	}

	char* message_buffer;
	size_t size = FormatMessageA(
	FORMAT_MESSAGE_ALLOCATE_BUFFER \| FORMAT_MESSAGE_FROM_SYSTEM \|
	FORMAT_MESSAGE_IGNORE_INSERTS,
	NULL, last_error, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
	(LPSTR)&message_buffer, 0, NULL);

	stringstream result;
	result << "(error: " << last_error << "): " << message_buffer;
	LocalFree(message_buffer);
	return result.str();
	}

	void die(const wchar_t* format, ...) {
	va_list ap;
	va_start(ap, format);
	fputws(L"build-runfiles error: ", stderr);
	vfwprintf(stderr, format, ap);
	va_end(ap);
	fputwc(L'\n', stderr);
	fputws(L"manifest file name: ", stderr);
	fputws(manifest_filename, stderr);
	fputwc(L'\n', stderr);
	fputws(L"runfiles base directory: ", stderr);
	fputws(runfiles_base_dir, stderr);
	fputwc(L'\n', stderr);
	exit(1);
	}

	wstring AsAbsoluteWindowsPath(const wchar_t* path) {
	wstring wpath;
	string error;
	if (!blaze_util::AsAbsoluteWindowsPath(path, &wpath, &error)) {
	die(L"Couldn't convert %s to absolute Windows path: %hs", path,
	error.c_str());
	}
	return wpath;
	}

	bool DoesDirectoryPathExist(const wchar_t* path) {
	DWORD dwAttrib = GetFileAttributesW(AsAbsoluteWindowsPath(path).c_str());

	return (dwAttrib != INVALID_FILE_ATTRIBUTES &&
	(dwAttrib & FILE_ATTRIBUTE_DIRECTORY));
	}

	wstring GetParentDirFromPath(const wstring& path) {
	return path.substr(0, path.find_last_of(L"\\/"));
	}

	inline void Trim(wstring& str) {
	str.erase(0, str.find_first_not_of(' '));
	str.erase(str.find_last_not_of(' ') + 1);
	}

	bool ReadSymlink(const wstring& abs_path, wstring* target, wstring* error) {
	switch (bazel::windows::ReadSymlinkOrJunction(abs_path, target, error)) {
	case bazel::windows::ReadSymlinkOrJunctionResult::kSuccess:
	return true;
	case bazel::windows::ReadSymlinkOrJunctionResult::kAccessDenied:
	*error = L"access is denied";
	break;
	case bazel::windows::ReadSymlinkOrJunctionResult::kDoesNotExist:
	*error = L"path does not exist";
	break;
	case bazel::windows::ReadSymlinkOrJunctionResult::kNotALink:
	*error = L"path is not a link";
	break;
	case bazel::windows::ReadSymlinkOrJunctionResult::kUnknownLinkType:
	*error = L"unknown link type";
	break;
	default:
	// This is bazel::windows::ReadSymlinkOrJunctionResult::kError (1).
	// The JNI code puts a custom message in 'error'.
	break;
	}
	return false;
	}

	} // namespace

	class RunfilesCreator {
	typedef std::unordered_map<std::wstring, std::wstring> ManifestFileMap;

	public:
	RunfilesCreator(const wstring& manifest_path,
	const wstring& runfiles_output_base)
	: manifest_path_(manifest_path),
	runfiles_output_base_(runfiles_output_base) {
	SetupOutputBase();
	if (!SetCurrentDirectoryW(runfiles_output_base_.c_str())) {
	die(L"SetCurrentDirectoryW failed (%s): %hs",
	runfiles_output_base_.c_str(), GetLastErrorString().c_str());
	}
	}

	void ReadManifest(bool allow_relative, bool ignore_metadata) {
	ifstream manifest_file(
	AsAbsoluteWindowsPath(manifest_path_.c_str()).c_str());

	if (!manifest_file) {
	die(L"Couldn't open MANIFEST file: %s", manifest_path_.c_str());
	}

	string line;
	int lineno = 0;
	while (getline(manifest_file, line)) {
	lineno++;
	// Skip metadata lines. They are used solely for
	// dependency checking.
	if (ignore_metadata && lineno % 2 == 0) {
	continue;
	}

	size_t space_pos = line.find_first_of(' ');
	wstring wline = blaze_util::CstringToWstring(line);
	wstring link, target;
	if (space_pos == string::npos) {
	link = wline;
	target = wstring();
	} else {
	link = wline.substr(0, space_pos);
	target = wline.substr(space_pos + 1);
	}

	// Removing leading and trailing spaces
	Trim(link);
	Trim(target);

	// We sometimes need to create empty files under the runfiles tree.
	// For example, for python binary, __init__.py is needed under every
	// directory. Storing an entry with an empty target indicates we need to
	// create such a file when creating the runfiles tree.
	if (!allow_relative && !target.empty() &&
	!blaze_util::IsAbsolute(target)) {
	die(L"Target cannot be relative path: %hs", line.c_str());
	}

	link = AsAbsoluteWindowsPath(link.c_str());
	if (!target.empty()) {
	target = AsAbsoluteWindowsPath(target.c_str());
	}

	manifest_file_map.insert(make_pair(link, target));
	}
	}

	void CreateRunfiles() {
	bool symlink_needs_privilege =
	DoesCreatingSymlinkNeedAdminPrivilege(runfiles_output_base_);
	ScanTreeAndPrune(runfiles_output_base_);
	CreateFiles(symlink_needs_privilege);
	CopyManifestFile();
	}

	private:
	void SetupOutputBase() {
	if (!DoesDirectoryPathExist(runfiles_output_base_.c_str())) {
	MakeDirectoriesOrDie(runfiles_output_base_);
	}
	}

	void MakeDirectoriesOrDie(const wstring& path) {
	if (!blaze_util::MakeDirectoriesW(path, 0755)) {
	die(L"MakeDirectoriesW failed (%s): %hs", path.c_str(),
	GetLastErrorString().c_str());
	}
	}

	void RemoveDirectoryOrDie(const wstring& path) {
	if (!RemoveDirectoryW(path.c_str())) {
	die(L"RemoveDirectoryW failed (%s): %hs", GetLastErrorString().c_str());
	}
	}

	void DeleteFileOrDie(const wstring& path) {
	SetFileAttributesW(path.c_str(), GetFileAttributesW(path.c_str()) &
	~FILE_ATTRIBUTE_READONLY);
	if (!DeleteFileW(path.c_str())) {
	die(L"DeleteFileW failed (%s): %hs", path.c_str(),
	GetLastErrorString().c_str());
	}
	}

	bool DoesCreatingSymlinkNeedAdminPrivilege(const wstring& runfiles_base_dir) {
	wstring dummy_link = runfiles_base_dir + L"\\dummy_link";
	wstring dummy_target = runfiles_base_dir + L"\\dummy_target";

	// Try creating symlink without admin privilege.
	if (CreateSymbolicLinkW(dummy_link.c_str(), dummy_target.c_str(),
	SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE)) {
	DeleteFileOrDie(dummy_link);
	return false;
	}

	// Try creating symlink with admin privilege
	if (CreateSymbolicLinkW(dummy_link.c_str(), dummy_target.c_str(), 0)) {
	DeleteFileOrDie(dummy_link);
	return true;
	}

	// If we couldn't create symlink, print out an error message and exit.
	if (GetLastError() == ERROR_PRIVILEGE_NOT_HELD) {
	die(L"CreateSymbolicLinkW failed:\n%hs\n",
	"Bazel needs to create symlink for building runfiles tree.\n"
	"Creating symlink on Windows requires either of the following:\n"
	" 1. Program is running with elevated privileges (Admin rights).\n"
	" 2. The system version is Windows 10 Creators Update (1703) or "
	"later and "
	"developer mode is enabled.",
	GetLastErrorString().c_str());
	} else {
	die(L"CreateSymbolicLinkW failed: %hs", GetLastErrorString().c_str());
	}

	return true;
	}

	// This function scan the current directory, remove all
	// files/symlinks/directories that are not presented in manifest file. If a
	// symlink already exists and points to the correct target, this function
	// erases its entry from manifest_file_map, so that we won't recreate it.
	void ScanTreeAndPrune(const wstring& path) {
	static const wstring kDot(L".");
	static const wstring kDotDot(L"..");

	WIN32_FIND_DATAW metadata;
	HANDLE handle = ::FindFirstFileW((path + L"\\*").c_str(), &metadata);
	if (handle == INVALID_HANDLE_VALUE) {
	return; // directory does not exist or is empty
	}

	do {
	if (kDot != metadata.cFileName && kDotDot != metadata.cFileName) {
	wstring subpath = path + L"\\" + metadata.cFileName;
	subpath = AsAbsoluteWindowsPath(subpath.c_str());
	bool is_dir =
	(metadata.dwFileAttributes & FILE_ATTRIBUTE_DIRECTORY) != 0;
	bool is_symlink =
	(metadata.dwFileAttributes & FILE_ATTRIBUTE_REPARSE_POINT) != 0;
	if (is_symlink) {
	wstring target, werror;
	if (!ReadSymlink(subpath, &target, &werror)) {
	die(L"ReadSymlinkW failed (%s): %hs", subpath.c_str(),
	werror.c_str());
	}

	target = AsAbsoluteWindowsPath(target.c_str());
	ManifestFileMap::iterator expected_target =
	manifest_file_map.find(subpath);

	if (expected_target == manifest_file_map.end() \|\|
	expected_target->second.empty()
	// Both paths are normalized paths in lower case, we can compare
	// them directly.
	\|\| target != expected_target->second.c_str() \|\|
	blaze_util::IsDirectoryW(target) != is_dir) {
	if (is_dir) {
	RemoveDirectoryOrDie(subpath);
	} else {
	DeleteFileOrDie(subpath);
	}
	} else {
	manifest_file_map.erase(expected_target);
	}
	} else {
	if (is_dir) {
	ScanTreeAndPrune(subpath);
	// If the directory is empty, then we remove the directory.
	// Otherwise RemoveDirectory will fail with ERROR_DIR_NOT_EMPTY,
	// which we can just ignore.
	// Because if the directory is not empty, it means it contains some
	// symlinks already pointing to the correct targets (we just called
	// ScanTreeAndPrune). Then this directory shouldn't be removed in
	// the first place.
	if (!RemoveDirectoryW(subpath.c_str()) &&
	GetLastError() != ERROR_DIR_NOT_EMPTY) {
	die(L"RemoveDirectoryW failed (%s): %hs", subpath.c_str(),
	GetLastErrorString().c_str());
	}
	} else {
	DeleteFileOrDie(subpath);
	}
	}
	}
	} while (::FindNextFileW(handle, &metadata));
	::FindClose(handle);
	}

	void CreateFiles(bool creating_symlink_needs_admin_privilege) {
	DWORD privilege_flag = creating_symlink_needs_admin_privilege
	? 0
	: SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE;

	for (const auto& it : manifest_file_map) {
	// Ensure the parent directory exists
	wstring parent_dir = GetParentDirFromPath(it.first);
	if (!DoesDirectoryPathExist(parent_dir.c_str())) {
	MakeDirectoriesOrDie(parent_dir);
	}

	if (it.second.empty()) {
	// Create an empty file
	HANDLE h = CreateFileW(it.first.c_str(), // name of the file
	GENERIC_WRITE, // open for writing
	// Must share for reading, otherwise
	// symlink-following file existence checks (e.g.
	// java.nio.file.Files.exists()) fail.
	FILE_SHARE_READ,
	0, // use default security descriptor
	CREATE_ALWAYS, // overwrite if exists
	FILE_ATTRIBUTE_NORMAL, 0);
	if (h != INVALID_HANDLE_VALUE) {
	CloseHandle(h);
	} else {
	die(L"CreateFileW failed (%s): %hs", it.first.c_str(),
	GetLastErrorString().c_str());
	}
	} else {
	DWORD create_dir = 0;
	if (blaze_util::IsDirectoryW(it.second.c_str())) {
	create_dir = SYMBOLIC_LINK_FLAG_DIRECTORY;
	}
	if (!CreateSymbolicLinkW(it.first.c_str(), it.second.c_str(),
	privilege_flag \| create_dir)) {
	die(L"CreateSymbolicLinkW failed (%s -> %s): %hs", it.first.c_str(),
	it.second.c_str(), GetLastErrorString().c_str());
	}
	}
	}
	}

	void CopyManifestFile() {
	wstring new_manifest_file = runfiles_output_base_ + L"\\MANIFEST";
	if (!CopyFileW(manifest_path_.c_str(), new_manifest_file.c_str(),
	/bFailIfExists=/FALSE)) {
	die(L"CopyFileW failed (%s -> %s): %hs", manifest_path_.c_str(),
	new_manifest_file.c_str(), GetLastErrorString().c_str());
	}
	}

	private:
	wstring manifest_path_;
	wstring runfiles_output_base_;
	ManifestFileMap manifest_file_map;
	};

	int wmain(int argc, wchar_t** argv) {
	argc--;
	argv++;
	bool allow_relative = false;
	bool ignore_metadata = false;

	while (argc >= 1) {
	if (wcscmp(argv[0], L"--allow_relative") == 0) {
	allow_relative = true;
	argc--;
	argv++;
	} else if (wcscmp(argv[0], L"--use_metadata") == 0) {
	// If --use_metadata is passed, it means manifest file contains metadata
	// lines, which we should ignore when reading manifest file.
	ignore_metadata = true;
	argc--;
	argv++;
	} else {
	break;
	}
	}

	if (argc != 2) {
	fprintf(stderr,
	"usage: [--allow_relative] [--use_metadata] "
	"<manifest_file> <runfiles_base_dir>\n");
	return 1;
	}

	manifest_filename = argv[0];
	runfiles_base_dir = argv[1];

	wstring manifest_absolute_path = AsAbsoluteWindowsPath(manifest_filename);
	wstring output_base_absolute_path = AsAbsoluteWindowsPath(runfiles_base_dir);

	RunfilesCreator runfiles_creator(manifest_absolute_path,
	output_base_absolute_path);
	runfiles_creator.ReadManifest(allow_relative, ignore_metadata);
	runfiles_creator.CreateRunfiles();

	return 0;
	}