src/main/cpp/blaze_util_windows.cc

// Copyright 2014 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.

#include <errno.h>  // errno, ENAMETOOLONG
#include <limits.h>
#include <string.h>  // strerror

#ifndef COMPILER_MSVC
#include <sys/cygwin.h>
#include <sys/socket.h>
#include <sys/statfs.h>
#include <unistd.h>
#endif  // COMPILER_MSVC

#include <windows.h>

#include <cstdlib>
#include <cstdio>
#include <thread>  // NOLINT (to slience Google-internal linter)

#include "src/main/cpp/blaze_util.h"
#include "src/main/cpp/blaze_util_platform.h"
#include "src/main/cpp/util/errors.h"
#include "src/main/cpp/util/exit_code.h"
#include "src/main/cpp/util/file.h"
#include "src/main/cpp/util/strings.h"

namespace blaze {

using blaze_util::die;
using blaze_util::pdie;
using std::string;
using std::vector;

class WindowsClock {
 public:
  uint64_t GetMilliseconds() const;
  uint64_t GetProcessMilliseconds() const;

  static const WindowsClock INSTANCE;

 private:
  // Clock frequency per seconds.
  // It's safe to cache this because (from QueryPerformanceFrequency on MSDN):
  // "The frequency of the performance counter is fixed at system boot and is
  // consistent across all processors. Therefore, the frequency need only be
  // queried upon application initialization, and the result can be cached."
  const LARGE_INTEGER kFrequency;

  // Time (in milliseconds) at process start.
  const LARGE_INTEGER kStart;

  WindowsClock();

  static LARGE_INTEGER GetFrequency();
  static LARGE_INTEGER GetMillisecondsAsLargeInt(const LARGE_INTEGER& freq);
};

static void PrintError(const string& op) {
    DWORD last_error = ::GetLastError();
    if (last_error == 0) {
        return;
    }

    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);

    fprintf(stderr, "ERROR: %s: %s (%d)\n",
            op.c_str(), message_buffer, last_error);
    LocalFree(message_buffer);
}

void WarnFilesystemType(const string& output_base) {
}

string GetSelfPath() {
  char buffer[PATH_MAX] = {};
  if (!GetModuleFileName(0, buffer, sizeof(buffer))) {
    pdie(255, "Error %u getting executable file name\n", GetLastError());
  }

  // TODO(bazel-team): Implement proper handling for UNC paths
  // (e.g. "\\?\C:\foo\bar") instead of erroring out when we see them.
  if (strlen(buffer) == 0 || buffer[0] == '\\') {
    PrintError("GetModuleFileName");
    buffer[PATH_MAX - 1] = '\0';
    pdie(255, "Error in GetSelfPath, buffer=(%s)", buffer);
  }
  return string(buffer);
}

string GetOutputRoot() {
#ifdef COMPILER_MSVC
  // GetTempPathA and GetEnvironmentVariableA only work properly when Bazel
  // runs under cmd.exe, not when it's run from msys.
  // We don't know the reason for this; what's sure is GetEnvironmentVariableA
  // returns nothing for TEMP under msys, though it can retrieve WINDIR.

  char buf[MAX_PATH + 1];
  if (!GetTempPathA(sizeof(buf), buf)) {
    PrintError("GetTempPath");
    pdie(255, "Could not retrieve the temp directory path");
  }
  return buf;
#else  // not COMPILER_MSVC
  for (const char* i : {"TMPDIR", "TEMPDIR", "TMP", "TEMP"}) {
    char* tmpdir = getenv(i);
    if (tmpdir != NULL && strlen(tmpdir) > 0) {
      return tmpdir;
    }
  }

  return "/var/tmp";
#endif  // COMPILER_MSVC
}

uint64_t GetMillisecondsMonotonic() {
  return WindowsClock::INSTANCE.GetMilliseconds();
}

uint64_t GetMillisecondsSinceProcessStart() {
  return WindowsClock::INSTANCE.GetProcessMilliseconds();
}

void SetScheduling(bool batch_cpu_scheduling, int io_nice_level) {
  // TODO(bazel-team): There should be a similar function on Windows.
}

string GetProcessCWD(int pid) {
  char server_cwd[PATH_MAX] = {};
  if (readlink(
          ("/proc/" + ToString(pid) + "/cwd").c_str(),
          server_cwd, sizeof(server_cwd)) < 0) {
    return "";
  }

  return string(server_cwd);
}

bool IsSharedLibrary(const string &filename) {
  return blaze_util::ends_with(filename, ".dll");
}

string GetDefaultHostJavabase() {
  const char *javahome = getenv("JAVA_HOME");
  if (javahome == NULL) {
    die(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR,
        "Error: JAVA_HOME not set.");
  }
  return javahome;
}

namespace {
void ReplaceAll(
        std::string* s, const std::string& pattern, const std::string with) {
  size_t pos = 0;
  while (true) {
    size_t pos = s->find(pattern, pos);
    if (pos == std::string::npos) return;
    *s = s->replace(pos, pattern.length(), with);
    pos += with.length();
  }
}

// Max command line length is per CreateProcess documentation
// (https://msdn.microsoft.com/en-us/library/ms682425(VS.85).aspx)
//
// Quoting rules are described here:
// https://blogs.msdn.microsoft.com/twistylittlepassagesallalike/2011/04/23/everyone-quotes-command-line-arguments-the-wrong-way/

static const int MAX_CMDLINE_LENGTH = 32768;

struct CmdLine {
  char cmdline[MAX_CMDLINE_LENGTH];
};
static void CreateCommandLine(CmdLine* result, const string& exe,
                              const vector<string>& args_vector) {
  string cmdline;
  bool first = true;
  for (const auto& s : args_vector) {
    if (first) {
      first = false;
      // Skip first argument, instead use quoted executable name with ".exe"
      // suffix.
      cmdline.append("\"");
      cmdline.append(exe);
      cmdline.append(".exe");
      cmdline.append("\"");
      continue;
    } else {
      cmdline.append(" ");
    }

    bool has_space = s.find(" ") != string::npos;

    if (has_space) {
      cmdline.append("\"");
    }

    std::string::const_iterator it = s.begin();
    while (it != s.end()) {
      char ch = *it++;
      switch (ch) {
        case '"':
          // Escape double quotes
          cmdline.append("\\\"");
          break;

        case '\\':
          if (it == s.end()) {
            // Backslashes at the end of the string are quoted if we add quotes
            cmdline.append(has_space ? "\\\\" : "\\");
          } else {
            // Backslashes everywhere else are quoted if they are followed by a
            // quote or a backslash
            cmdline.append(*it == '"' || *it == '\\' ? "\\\\" : "\\");
          }
          break;

         default:
           cmdline.append(1, ch);
      }
    }

    if (has_space) {
      cmdline.append("\"");
    }
  }

  if (cmdline.size() >= MAX_CMDLINE_LENGTH) {
    pdie(blaze_exit_code::INTERNAL_ERROR,
         "Command line too long: %s", cmdline.c_str());
  }

  // Copy command line into a mutable buffer.
  // CreateProcess is allowed to mutate its command line argument.
  strncpy(result->cmdline, cmdline.c_str(), MAX_CMDLINE_LENGTH - 1);
  result->cmdline[MAX_CMDLINE_LENGTH - 1] = 0;
}

}  // namespace

string RunProgram(
    const string& exe, const vector<string>& args_vector) {
  SECURITY_ATTRIBUTES sa = {0};

  sa.nLength = sizeof(SECURITY_ATTRIBUTES);
  sa.bInheritHandle = TRUE;
  sa.lpSecurityDescriptor = NULL;

  HANDLE pipe_read, pipe_write;
  if (!CreatePipe(&pipe_read, &pipe_write, &sa, 0)) {
    pdie(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR, "CreatePipe");
  }

  if (!SetHandleInformation(pipe_read, HANDLE_FLAG_INHERIT, 0)) {
    pdie(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR, "SetHandleInformation");
  }

  PROCESS_INFORMATION processInfo = {0};
  STARTUPINFO startupInfo = {0};

  startupInfo.hStdError = pipe_write;
  startupInfo.hStdOutput = pipe_write;
  startupInfo.dwFlags |= STARTF_USESTDHANDLES;
  CmdLine cmdline;
  CreateCommandLine(&cmdline, exe, args_vector);

  bool ok = CreateProcess(
      NULL,           // _In_opt_    LPCTSTR               lpApplicationName,
      //                 _Inout_opt_ LPTSTR                lpCommandLine,
      cmdline.cmdline,
      NULL,           // _In_opt_    LPSECURITY_ATTRIBUTES lpProcessAttributes,
      NULL,           // _In_opt_    LPSECURITY_ATTRIBUTES lpThreadAttributes,
      true,           // _In_        BOOL                  bInheritHandles,
      0,              // _In_        DWORD                 dwCreationFlags,
      NULL,           // _In_opt_    LPVOID                lpEnvironment,
      NULL,           // _In_opt_    LPCTSTR               lpCurrentDirectory,
      &startupInfo,   // _In_        LPSTARTUPINFO         lpStartupInfo,
      &processInfo);  // _Out_       LPPROCESS_INFORMATION lpProcessInformation

  if (!ok) {
    pdie(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR,
         "RunProgram/CreateProcess: Error %d while executing %s",
         GetLastError(), cmdline.cmdline);
  }

  CloseHandle(pipe_write);
  std::string result = "";
  DWORD bytes_read;
  CHAR buf[1024];

  for (;;) {
    ok = ::ReadFile(pipe_read, buf, 1023, &bytes_read, NULL);
    if (!ok || bytes_read == 0) {
      break;
    }
    buf[bytes_read] = 0;
    result = result + buf;
  }

  CloseHandle(pipe_read);
  CloseHandle(processInfo.hProcess);
  CloseHandle(processInfo.hThread);

  return result;
}

// If we pass DETACHED_PROCESS to CreateProcess(), cmd.exe appropriately
// returns the command prompt when the client terminates. msys2, however, in
// its infinite wisdom, waits until the *server* terminates and cannot be
// convinced otherwise.
//
// So, we first pretend to be a POSIX daemon so that msys2 knows about our
// intentions and *then* we call CreateProcess(). Life ain't easy.
static bool DaemonizeOnWindows() {
  if (fork() > 0) {
    // We are the original client process.
    return true;
  }

  if (fork() > 0) {
    // We are the child of the original client process. Terminate so that the
    // actual server is not a child process of the client.
    exit(0);
  }

  setsid();
  // Contrary to the POSIX version, we are not closing the three standard file
  // descriptors here. CreateProcess() will take care of that and it's useful
  // to see the error messages in ExecuteDaemon() on the console of the client.
  return false;
}

// Keeping an eye on the server process on Windows is not implemented yet.
// TODO(lberki): Implement this, because otherwise if we can't start up a server
// process, the client will hang until it times out.
class DummyBlazeServerStartup : public BlazeServerStartup {
 public:
  DummyBlazeServerStartup() {}
  virtual ~DummyBlazeServerStartup() {}
  virtual bool IsStillAlive() { return true; }
};

void ExecuteDaemon(const string& exe, const std::vector<string>& args_vector,
                   const string& daemon_output, const string& server_dir,
                   BlazeServerStartup** server_startup) {
  if (DaemonizeOnWindows()) {
    // We are the client process
    *server_startup = new DummyBlazeServerStartup();
    return;
  }

  SECURITY_ATTRIBUTES sa;
  sa.nLength = sizeof(SECURITY_ATTRIBUTES);
  // We redirect stdout and stderr by telling CreateProcess to use a file handle
  // we open below and these handles must be inheriatable
  sa.bInheritHandle = TRUE;
  sa.lpSecurityDescriptor = NULL;

  HANDLE output_file = CreateFile(
      ConvertPath(daemon_output).c_str(),  // lpFileName
      GENERIC_READ | GENERIC_WRITE,        // dwDesiredAccess
      // So that the file can be read while the server is running
      FILE_SHARE_READ,                     // dwShareMode
      &sa,                                 // lpSecurityAttributes
      CREATE_ALWAYS,                       // dwCreationDisposition
      FILE_ATTRIBUTE_NORMAL,               // dwFlagsAndAttributes
      NULL);                               // hTemplateFile

  if (output_file == INVALID_HANDLE_VALUE) {
    pdie(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR, "CreateFile");
  }

  HANDLE pipe_read, pipe_write;
  if (!CreatePipe(&pipe_read, &pipe_write, &sa, 0)) {
    pdie(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR, "CreatePipe");
  }

  if (!SetHandleInformation(pipe_write, HANDLE_FLAG_INHERIT, 0)) {
    pdie(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR, "SetHandleInformation");
  }

  PROCESS_INFORMATION processInfo = {0};
  STARTUPINFO startupInfo = {0};

  startupInfo.hStdInput = pipe_read;
  startupInfo.hStdError = output_file;
  startupInfo.hStdOutput = output_file;
  startupInfo.dwFlags |= STARTF_USESTDHANDLES;
  CmdLine cmdline;
  CreateCommandLine(&cmdline, exe, args_vector);

  // Propagate BAZEL_SH environment variable to a sub-process.
  // todo(dslomov): More principled approach to propagating
  // environment variables.
  SetEnvironmentVariable("BAZEL_SH", getenv("BAZEL_SH"));

  bool ok = CreateProcess(
      NULL,  // _In_opt_    LPCTSTR               lpApplicationName,
      //                 _Inout_opt_ LPTSTR                lpCommandLine,
      cmdline.cmdline,
      NULL,  // _In_opt_    LPSECURITY_ATTRIBUTES lpProcessAttributes,
      NULL,  // _In_opt_    LPSECURITY_ATTRIBUTES lpThreadAttributes,
      TRUE,  // _In_        BOOL                  bInheritHandles,
      //                 _In_        DWORD                 dwCreationFlags,
      DETACHED_PROCESS | CREATE_NEW_PROCESS_GROUP,
      NULL,           // _In_opt_    LPVOID                lpEnvironment,
      NULL,           // _In_opt_    LPCTSTR               lpCurrentDirectory,
      &startupInfo,   // _In_        LPSTARTUPINFO         lpStartupInfo,
      &processInfo);  // _Out_       LPPROCESS_INFORMATION lpProcessInformation

  if (!ok) {
    pdie(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR,
         "ExecuteDaemon/CreateProcess: error %u executing: %s\n",
         GetLastError(), cmdline.cmdline);
  }

  CloseHandle(output_file);
  CloseHandle(pipe_write);
  CloseHandle(pipe_read);

  string pid_string = ToString(processInfo.dwProcessId);
  string pid_file = blaze_util::JoinPath(server_dir, kServerPidFile);
  if (!WriteFile(pid_string, pid_file)) {
    // Not a lot we can do if this fails
    fprintf(stderr, "Cannot write PID file %s\n", pid_file.c_str());
  }

  CloseHandle(processInfo.hProcess);
  CloseHandle(processInfo.hThread);

  exit(0);
}

void BatchWaiterThread(HANDLE java_handle) {
  WaitForSingleObject(java_handle, INFINITE);
}

static void MingwSignalHandler(int signum) {
  // Java process will be terminated because we set the job to terminate if its
  // handle is closed.
  //
  // Note that this is different how interruption is handled on Unix, where the
  // Java process sets up a signal handler for SIGINT itself. That cannot be
  // done on Windows without using native code, and it's better to have as
  // little JNI as possible. The most important part of the cleanup after
  // termination (killing all child processes) happens automatically on Windows
  // anyway, since we put the batch Java process in its own job which does not
  // allow breakaway processes.
  exit(blaze_exit_code::ExitCode::INTERRUPTED);
}

// Returns whether assigning the given process to a job failed because nested
// jobs are not available on the current system.
static bool IsFailureDueToNestedJobsNotSupported(HANDLE process) {
  BOOL is_in_job;
  if (!IsProcessInJob(process, NULL, &is_in_job)) {
    PrintError("IsProcessInJob()");
    return false;
  }

  if (!is_in_job) {
    // Not in a job.
    return false;
  }

  OSVERSIONINFOEX version_info;
  version_info.dwOSVersionInfoSize = sizeof(version_info);
  if (!GetVersionEx(reinterpret_cast<OSVERSIONINFO*>(&version_info))) {
    PrintError("GetVersionEx()");
    return false;
  }

  return version_info.dwMajorVersion < 6
      || version_info.dwMajorVersion == 6 && version_info.dwMinorVersion <= 1;
}

// Run the given program in the current working directory,
// using the given argument vector.
void ExecuteProgram(
    const string& exe, const vector<string>& args_vector) {
  CmdLine cmdline;
  CreateCommandLine(&cmdline, exe, args_vector);

  STARTUPINFO startupInfo = {0};
  PROCESS_INFORMATION processInfo = {0};

  // Propagate BAZEL_SH environment variable to a sub-process.
  // todo(dslomov): More principled approach to propagating
  // environment variables.
  SetEnvironmentVariable("BAZEL_SH", getenv("BAZEL_SH"));

  HANDLE job = CreateJobObject(NULL, NULL);
  if (job == NULL) {
    pdie(255, "Error %u while creating job\n", GetLastError());
  }

  JOBOBJECT_EXTENDED_LIMIT_INFORMATION job_info = { 0 };
  job_info.BasicLimitInformation.LimitFlags =
      JOB_OBJECT_LIMIT_KILL_ON_JOB_CLOSE;
  if (!SetInformationJobObject(
      job,
      JobObjectExtendedLimitInformation,
      &job_info,
      sizeof(job_info))) {
    pdie(255, "Error %u while setting up job\n", GetLastError());
  }

  bool success = CreateProcess(
      NULL,           // _In_opt_    LPCTSTR               lpApplicationName,
      //                 _Inout_opt_ LPTSTR                lpCommandLine,
      cmdline.cmdline,
      NULL,           // _In_opt_    LPSECURITY_ATTRIBUTES lpProcessAttributes,
      NULL,           // _In_opt_    LPSECURITY_ATTRIBUTES lpThreadAttributes,
      true,           // _In_        BOOL                  bInheritHandles,
      //                 _In_        DWORD                 dwCreationFlags,
      CREATE_NEW_PROCESS_GROUP  // So that Ctrl-Break does not affect it
          | CREATE_BREAKAWAY_FROM_JOB  // We'll put it in a new job
          | CREATE_SUSPENDED,  // So that it doesn't start a new job itself
      NULL,           // _In_opt_    LPVOID                lpEnvironment,
      NULL,           // _In_opt_    LPCTSTR               lpCurrentDirectory,
      &startupInfo,   // _In_        LPSTARTUPINFO         lpStartupInfo,
      &processInfo);  // _Out_       LPPROCESS_INFORMATION lpProcessInformation

  if (!success) {
    pdie(255, "ExecuteProgram/CreateProcess: error %u executing: %s\n",
         GetLastError(), cmdline.cmdline);
  }

  if (!AssignProcessToJobObject(job, processInfo.hProcess)) {
    if (!IsFailureDueToNestedJobsNotSupported(processInfo.hProcess)) {
      pdie(255, "Error %u while assigning process to job\n", GetLastError());
    }

    // Otherwise, the OS doesn't support nested jobs so we'll just have to
    // make do without.
  }

  // Now that we put the process in a new job object, we can start executing it
  if (ResumeThread(processInfo.hThread) == -1) {
    pdie(255, "Error %u while starting Java process\n", GetLastError());
  }

  // msys doesn't deliver signals while a Win32 call is pending so we need to
  // do the blocking call in another thread
  signal(SIGINT, MingwSignalHandler);
  std::thread batch_waiter_thread([=]() {
    BatchWaiterThread(processInfo.hProcess);
  });

  // The output base lock is held while waiting
  batch_waiter_thread.join();
  DWORD exit_code;
  GetExitCodeProcess(processInfo.hProcess, &exit_code);
  CloseHandle(processInfo.hProcess);
  CloseHandle(processInfo.hThread);
  exit(exit_code);
}

string ListSeparator() { return ";"; }

string ConvertPath(const string& path) {
  // If the path looks like %USERPROFILE%/foo/bar, don't convert.
  if (path.empty() || path[0] == '%') {
    return path;
  }
  char* wpath = static_cast<char*>(cygwin_create_path(
      CCP_POSIX_TO_WIN_A, static_cast<const void*>(path.c_str())));
  string result(wpath);
  free(wpath);
  return result;
}

// Convert a Unix path list to Windows path list
string ConvertPathList(const string& path_list) {
  string w_list = "";
  int start = 0;
  int pos;
  while ((pos = path_list.find(":", start)) != string::npos) {
    w_list += ConvertPath(path_list.substr(start, pos - start)) + ";";
    start = pos + 1;
  }
  if (start < path_list.size()) {
    w_list += ConvertPath(path_list.substr(start));
  }
  return w_list;
}

string ConvertPathToPosix(const string& win_path) {
  char* posix_path = static_cast<char*>(cygwin_create_path(
      CCP_WIN_A_TO_POSIX, static_cast<const void*>(win_path.c_str())));
  string result(posix_path);
  free(posix_path);
  return result;
}

// Cribbed from ntifs.h, not present in windows.h

#define REPARSE_MOUNTPOINT_HEADER_SIZE   8

typedef struct {
  DWORD ReparseTag;
  WORD ReparseDataLength;
  WORD Reserved;
  WORD SubstituteNameOffset;
  WORD SubstituteNameLength;
  WORD PrintNameOffset;
  WORD PrintNameLength;
  WCHAR PathBuffer[ANYSIZE_ARRAY];
} REPARSE_MOUNTPOINT_DATA_BUFFER, *PREPARSE_MOUNTPOINT_DATA_BUFFER;

HANDLE OpenDirectory(const string& path, bool readWrite) {
  HANDLE result = ::CreateFile(
      path.c_str(),
      readWrite ? (GENERIC_READ | GENERIC_WRITE) : GENERIC_READ,
      0,
      NULL,
      OPEN_EXISTING,
      FILE_FLAG_OPEN_REPARSE_POINT | FILE_FLAG_BACKUP_SEMANTICS,
      NULL);
  if (result == INVALID_HANDLE_VALUE) {
    PrintError("CreateFile(" + path + ")");
  }

  return result;
}

bool SymlinkDirectories(const string &posix_target, const string &posix_name) {
  string target = ConvertPath(posix_target);
  string name = ConvertPath(posix_name);

  // Junctions are directories, so create one
  if (!::CreateDirectory(name.c_str(), NULL)) {
    PrintError("CreateDirectory(" + name + ")");
    return false;
  }

  HANDLE directory = OpenDirectory(name, true);
  if (directory == INVALID_HANDLE_VALUE) {
    return false;
  }

  char reparse_buffer_bytes[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
  REPARSE_MOUNTPOINT_DATA_BUFFER* reparse_buffer =
      reinterpret_cast<REPARSE_MOUNTPOINT_DATA_BUFFER *>(reparse_buffer_bytes);
  memset(reparse_buffer_bytes, 0, MAXIMUM_REPARSE_DATA_BUFFER_SIZE);

  // non-parsed path prefix. Required for junction targets.
  string prefixed_target = "\\??\\" + target;
  int prefixed_target_length = ::MultiByteToWideChar(
      CP_ACP,
      0,
      prefixed_target.c_str(),
      -1,
      reparse_buffer->PathBuffer,
      MAX_PATH);
  if (prefixed_target_length == 0) {
    PrintError("MultiByteToWideChar(" + prefixed_target + ")");
    CloseHandle(directory);
    return false;
  }

  // In addition to their target, junctions also have another string which
  // tells which target to show to the user. mklink cuts of the \??\ part, so
  // that's what we do, too.
  int target_length = ::MultiByteToWideChar(
      CP_UTF8,
      0,
      target.c_str(),
      -1,
      reparse_buffer->PathBuffer + prefixed_target_length,
      MAX_PATH);
  if (target_length == 0) {
    PrintError("MultiByteToWideChar(" + target + ")");
    CloseHandle(directory);
    return false;
  }

  reparse_buffer->ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
  reparse_buffer->PrintNameOffset = prefixed_target_length * sizeof(WCHAR);
  reparse_buffer->PrintNameLength = (target_length - 1) * sizeof(WCHAR);
  reparse_buffer->SubstituteNameLength =
      (prefixed_target_length - 1) * sizeof(WCHAR);
  reparse_buffer->SubstituteNameOffset = 0;
  reparse_buffer->Reserved = 0;
  reparse_buffer->ReparseDataLength =
       reparse_buffer->SubstituteNameLength +
       reparse_buffer->PrintNameLength + 12;

  DWORD bytes_returned;
  bool result = ::DeviceIoControl(
      directory,
      FSCTL_SET_REPARSE_POINT,
      reparse_buffer,
      reparse_buffer->ReparseDataLength + REPARSE_MOUNTPOINT_HEADER_SIZE,
      NULL,
      0,
      &bytes_returned,
      NULL);
  if (!result) {
    PrintError("DeviceIoControl(FSCTL_SET_REPARSE_POINT, " + name + ")");
  }
  CloseHandle(directory);
  return result;
}

bool ReadDirectorySymlink(const string &posix_name, string* result) {
  string name = ConvertPath(posix_name);
  HANDLE directory = OpenDirectory(name, false);
  if (directory == INVALID_HANDLE_VALUE) {
    return false;
  }

  char reparse_buffer_bytes[MAXIMUM_REPARSE_DATA_BUFFER_SIZE];
  REPARSE_MOUNTPOINT_DATA_BUFFER* reparse_buffer =
      reinterpret_cast<REPARSE_MOUNTPOINT_DATA_BUFFER *>(reparse_buffer_bytes);
  memset(reparse_buffer_bytes, 0, MAXIMUM_REPARSE_DATA_BUFFER_SIZE);

  reparse_buffer->ReparseTag = IO_REPARSE_TAG_MOUNT_POINT;
  DWORD bytes_returned;
  bool ok = ::DeviceIoControl(
      directory,
      FSCTL_GET_REPARSE_POINT,
      NULL,
      0,
      reparse_buffer,
      MAXIMUM_REPARSE_DATA_BUFFER_SIZE,
      &bytes_returned,
      NULL);
  if (!ok) {
    PrintError("DeviceIoControl(FSCTL_GET_REPARSE_POINT, " + name + ")");
  }

  CloseHandle(directory);
  if (!ok) {
    return false;
  }

  vector<char> print_name(reparse_buffer->PrintNameLength * sizeof(WCHAR) + 1);
  int count = ::WideCharToMultiByte(
      CP_UTF8,
      0,
      reparse_buffer->PathBuffer +
         (reparse_buffer->PrintNameOffset / sizeof(WCHAR)),
      reparse_buffer->PrintNameLength,
      &print_name[0],
      print_name.size(),
      NULL,
      NULL);
  if (count == 0) {
    PrintError("WideCharToMultiByte()");
    *result = "";
    return false;
  } else {
    *result = ConvertPathToPosix(&print_name[0]);
    return true;
  }
}

static bool IsAbsoluteWindowsPath(const string& p) {
  if (p.size() < 3) {
    return false;
  }

  if (p.substr(1, 2) == ":/") {
    return true;
  }

  if (p.substr(1, 2) == ":\\") {
    return true;
  }

  return false;
}

bool CompareAbsolutePaths(const string& a, const string& b) {
  string a_real = IsAbsoluteWindowsPath(a) ? ConvertPathToPosix(a) : a;
  string b_real = IsAbsoluteWindowsPath(b) ? ConvertPathToPosix(b) : b;
  return a_real == b_real;
}

bool VerifyServerProcess(
    int pid, const string& output_base, const string& install_base) {
  // TODO(lberki): This might accidentally kill an unrelated process if the
  // server died and the PID got reused.
  return true;
}

bool KillServerProcess(int pid) {
  HANDLE process = OpenProcess(PROCESS_TERMINATE, FALSE, pid);
  if (process == NULL) {
    // Cannot find the server process. Can happen if the PID file is stale.
    return false;
  }

  bool result = TerminateProcess(process, /*uExitCode*/0);
  if (!result) {
    fprintf(stderr, "Cannot terminate server process with PID %d\n", pid);
  }

  CloseHandle(process);
  return result;
}

// Not supported.
void ExcludePathFromBackup(const string &path) {
}

LARGE_INTEGER WindowsClock::GetFrequency() {
  LARGE_INTEGER result;
  if (!QueryPerformanceFrequency(&result)) {
    PrintError("QueryPerformanceFrequency");
    pdie(255, "Error getting time resolution\n");
  }

  // On ancient Windows versions (pre-XP) and specific hardware the result may
  // be 0. Since this is pre-XP, we don't handle that, just error out.
  if (result.QuadPart <= 0) {
    pdie(255, "QueryPerformanceFrequency returned invalid result (%llu)\n",
         result.QuadPart);
  }

  return result;
}

LARGE_INTEGER WindowsClock::GetMillisecondsAsLargeInt(
    const LARGE_INTEGER& freq) {
  LARGE_INTEGER counter;
  if (!QueryPerformanceCounter(&counter)) {
    PrintError("QueryPerformanceCounter");
    pdie(255, "Error getting performance counter\n");
  }

  LARGE_INTEGER result;
  result.QuadPart =
      // seconds
      (counter.QuadPart / freq.QuadPart) * 1000LL +
      // milliseconds
      (((counter.QuadPart % freq.QuadPart) * 1000LL) / freq.QuadPart);

  return result;
}

const WindowsClock WindowsClock::INSTANCE;

WindowsClock::WindowsClock()
    : kFrequency(GetFrequency()),
      kStart(GetMillisecondsAsLargeInt(kFrequency)) {}

uint64_t WindowsClock::GetMilliseconds() const {
  return GetMillisecondsAsLargeInt(kFrequency).QuadPart;
}

uint64_t WindowsClock::GetProcessMilliseconds() const {
  return GetMilliseconds() - kStart.QuadPart;
}

}  // namespace blaze