/**
 * Looking Glass
 * Copyright © 2017-2024 The Looking Glass Authors
 * https://looking-glass.io
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation; either version 2 of the License, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc., 59
 * Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include "platform.h"
#include "service.h"
#include "windows/mousehook.h"
#include "ods.h"

#include <windows.h>
#include <shellapi.h>
#include <shlwapi.h>
#include <fcntl.h>
#include <powrprof.h>
#include <ntstatus.h>
#include <wtsapi32.h>
#include <userenv.h>
#include <winternl.h>
#include <dwmapi.h>
#include <avrt.h>
#include <sys/stat.h>

#include "interface/platform.h"
#include "common/debug.h"
#include "common/windebug.h"
#include "common/option.h"
#include "common/locking.h"
#include "common/thread.h"
#include "common/time.h"
#include "common/stringutils.h"

#define ID_MENU_SHOW_LOG 3000
#define ID_MENU_EXIT     3001
#define LOG_NAME         "looking-glass-host"

struct AppState
{
  LARGE_INTEGER perfFreq;
  HINSTANCE hInst;

  int     argc;
  char ** argv;

  char           executable[MAX_PATH + 1];
  char           systemLogDir[MAX_PATH];
  char           systemTempDir[MAX_PATH];
  char         * osVersion;
  HWND           messageWnd;
  UINT           shellHookMsg;
  NOTIFYICONDATA iconData;
  UINT           trayRestartMsg;
  HMENU          trayMenu;
  HANDLE         exitWait;
  HANDLE         taskHandle;

  FILE * stdErrFile;
  FILE * stdOutFile;

  _Atomic(bool)  hasPendingActivationRequest;
};

static struct AppState app = {0};
HWND MessageHWND;

CreateProcessAsUserA_t f_CreateProcessAsUserA = NULL;

bool windowsSetupAPI(void)
{
  /* first look in kernel32.dll */
  HMODULE mod;

  mod = GetModuleHandleA("kernel32.dll");
  if (mod)
  {
    f_CreateProcessAsUserA = (CreateProcessAsUserA_t)
      GetProcAddress(mod, "CreateProcessAsUserA");
    if (f_CreateProcessAsUserA)
      return true;
  }

  mod = GetModuleHandleA("advapi32.dll");
  if (mod)
  {
    f_CreateProcessAsUserA = (CreateProcessAsUserA_t)
      GetProcAddress(mod, "CreateProcessAsUserA");
    if (f_CreateProcessAsUserA)
      return true;
  }

  return false;
}

static void RegisterTrayIcon(void)
{
  // register our TrayIcon
  if (!app.iconData.cbSize)
  {
    app.iconData.cbSize           = sizeof(NOTIFYICONDATA);
    app.iconData.hWnd             = app.messageWnd;
    app.iconData.uFlags           = NIF_ICON | NIF_MESSAGE | NIF_TIP;
    app.iconData.uCallbackMessage = WM_TRAYICON;
    strncpy(app.iconData.szTip, "Looking Glass (host)", sizeof(app.iconData.szTip));
    app.iconData.hIcon            = LoadIcon(app.hInst, IDI_APPLICATION);
  }
  Shell_NotifyIcon(NIM_ADD, &app.iconData);
}

// This function executes notepad as the logged in user, and therefore is secure to use.
static bool OpenLogFile(const char * logFile)
{
  bool result = false;

  DWORD console = WTSGetActiveConsoleSessionId();
  if (console == 0xFFFFFFFF)
  {
    DEBUG_WINERROR("Failed to get active console session ID", GetLastError());
    return false;
  }

  WTS_CONNECTSTATE_CLASS * state;
  DWORD size;
  if (!WTSQuerySessionInformationA(WTS_CURRENT_SERVER_HANDLE, console, WTSConnectState,
      (LPSTR *) &state, &size))
  {
    DEBUG_WINERROR("Failed to get session information", GetLastError());
    return false;
  }

  if (*state != WTSActive)
  {
    DEBUG_WINERROR("Will not open log file because user is not logged in", GetLastError());
    WTSFreeMemory(state);
    return false;
  }
  WTSFreeMemory(state);

  char system32[MAX_PATH];
  if (!GetSystemDirectoryA(system32, MAX_PATH))
  {
    DEBUG_WINERROR("Failed to get system directory", GetLastError());
    return false;
  }

  if (!f_CreateProcessAsUserA && !windowsSetupAPI())
  {
    DEBUG_WINERROR("Failed to get CreateProcessAsUserA", GetLastError());
    return false;
  }

  HANDLE hToken;
  if (!WTSQueryUserToken(console, &hToken))
  {
    DEBUG_WINERROR("Failed to get active console session user token", GetLastError());
    return false;
  }

  LPVOID env;
  if (!CreateEnvironmentBlock(&env, hToken, FALSE))
  {
    DEBUG_WINERROR("Failed to create environment", GetLastError());
    goto fail_token;
  }

  char notepad[MAX_PATH];
  PathCombineA(notepad, system32, "notepad.exe");

  char cmdline[MAX_PATH + 10];
  snprintf(cmdline, sizeof(cmdline), "notepad \"%s\"", logFile);

  STARTUPINFO si = { .cb = sizeof(STARTUPINFO) };
  PROCESS_INFORMATION pi = {0};
  if (!f_CreateProcessAsUserA(
      hToken,
      notepad,
      cmdline,
      NULL,
      NULL,
      FALSE,
      CREATE_UNICODE_ENVIRONMENT,
      env,
      os_getDataPath(),
      &si,
      &pi
    ))
  {
    DEBUG_WINERROR("Failed to open log file", GetLastError());
    goto fail_env;
  }

  result = true;
  CloseHandle(pi.hThread);
  CloseHandle(pi.hProcess);

fail_env:
  DestroyEnvironmentBlock(env);
fail_token:
  CloseHandle(hToken);
  return result;
}

LRESULT CALLBACK DummyWndProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
  switch(msg)
  {
    case WM_DESTROY:
      Shell_NotifyIcon(NIM_DELETE, &app.iconData);
      MessageHWND = NULL;
      PostQuitMessage(0);
      break;

    case WM_CALL_FUNCTION:
    {
      struct MSG_CALL_FUNCTION * cf = (struct MSG_CALL_FUNCTION *)lParam;
      return cf->fn(cf->wParam, cf->lParam);
    }

    case WM_TRAYICON:
    {
      if (lParam == WM_RBUTTONDOWN)
      {
        POINT curPoint;
        GetCursorPos(&curPoint);
        SetForegroundWindow(hwnd);
        UINT clicked = TrackPopupMenu(
          app.trayMenu,
          TPM_RETURNCMD | TPM_NONOTIFY,
          curPoint.x,
          curPoint.y,
          0,
          hwnd,
          NULL
        );

             if (clicked == ID_MENU_EXIT    ) app_quit(LG_HOST_EXIT_USER);
        else if (clicked == ID_MENU_SHOW_LOG)
        {
          const char * logFile = option_get_string("os", "logFile");
          if (strcmp(logFile, "stderr") == 0)
            DEBUG_INFO("Ignoring request to open the logFile, logging to stderr");
          else if (!OpenLogFile(logFile))
            MessageBoxA(hwnd, logFile, "Log File Location", MB_OK | MB_ICONINFORMATION);
        }
      }
      break;
    }

    case WM_WTSSESSION_CHANGE:
      if (wParam == WTS_CONSOLE_DISCONNECT)
      {
        DEBUG_INFO("Console disconnected, shutting down");
        app_quit(LG_HOST_EXIT_CAPTURE);
      }
      break;

    default:
      if (msg == app.trayRestartMsg)
        RegisterTrayIcon();
      else if (msg == app.shellHookMsg)
      {
        switch (LOWORD(wParam))
        {
          case HSHELL_FLASH:
            atomic_store(&app.hasPendingActivationRequest, true);
        }
      }
      break;
  }

  return DefWindowProc(hwnd, msg, wParam, lParam);
}

static int appThread(void * opaque)
{
  RegisterTrayIcon();
  int result = app_main(app.argc, app.argv);
  SendMessage(app.messageWnd, WM_CLOSE, 0, 0);
  return result;
}

LRESULT sendAppMessage(UINT Msg, WPARAM wParam, LPARAM lParam)
{
  return SendMessage(app.messageWnd, Msg, wParam, lParam);
}

static BOOL WINAPI CtrlHandler(DWORD dwCtrlType)
{
  if (dwCtrlType == CTRL_C_EVENT)
  {
    SendMessage(app.messageWnd, WM_CLOSE, 0, 0);
    return TRUE;
  }

  return FALSE;
}

const char * getSystemTempDirectory(void)
{
  return app.systemTempDir;
}

const char *getSystemLogDirectory(void)
{
  return app.systemLogDir;
}

static void populateSystemLogDirectory(void)
{
  char programData[MAX_PATH];
  if (GetEnvironmentVariableA("ProgramData", programData, sizeof(programData)) &&
      PathIsDirectoryA(programData))
  {
    if (!PathCombineA(app.systemLogDir, programData, "Looking Glass (host)"))
      goto fail;

    if (!PathIsDirectoryA(app.systemLogDir) && !CreateDirectoryA(app.systemLogDir, NULL))
      goto fail;

    return;
  }
fail:
  strcpy(app.systemLogDir, "");
}

int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nCmdShow)
{
  // initialize for DEBUG_* macros
  debug_init();

  // convert the command line to the standard argc and argv
  LPWSTR * wargv = CommandLineToArgvW(GetCommandLineW(), &app.argc);
  app.argv = malloc(sizeof(char *) * app.argc);
  for(int i = 0; i < app.argc; ++i)
  {
    const size_t s = (wcslen(wargv[i])+1) * 2;
    app.argv[i] = malloc(s);
    wcstombs(app.argv[i], wargv[i], s);
  }
  LocalFree(wargv);

  GetModuleFileName(NULL, app.executable, sizeof(app.executable));
  populateSystemLogDirectory();
  GetTempPathA(sizeof(app.systemTempDir), app.systemTempDir);

  if (HandleService(app.argc, app.argv))
    return LG_HOST_EXIT_FAILED;

  /* this is a bit of a hack but without this --help will produce no output in a windows command prompt */
  if (!IsDebuggerPresent() && AttachConsole(ATTACH_PARENT_PROCESS))
  {
    HANDLE std_err = GetStdHandle(STD_ERROR_HANDLE);
    HANDLE std_out = GetStdHandle(STD_OUTPUT_HANDLE);
    int std_err_fd = _open_osfhandle((intptr_t)std_err, _O_TEXT);
    int std_out_fd = _open_osfhandle((intptr_t)std_out, _O_TEXT);

    if (std_err_fd > 0)
    {
      app.stdErrFile = _fdopen(std_err_fd, "w");
      *stderr = *app.stdErrFile;
    }

    if  (std_out_fd > 0)
    {
      app.stdOutFile = _fdopen(std_out_fd, "w");
      *stdout = *app.stdOutFile;
    }
  }

  int result = 0;
  app.hInst = hInstance;

  char logFilePath[MAX_PATH];
  if (!PathCombineA(logFilePath, app.systemLogDir, LOG_NAME))
    strcpy(logFilePath, LOG_NAME);

  struct Option options[] =
  {
    {
      .module         = "os",
      .name           = "logFile",
      .description    = "The log file to write to",
      .type           = OPTION_TYPE_STRING,
      .value.x_string = logFilePath
    },
    {
      .module         = "os",
      .name           = "exitEvent",
      .description    = "Exit when the specified event is signaled",
      .type           = OPTION_TYPE_STRING,
      .value.x_string = ""
    },
    {
      .module         = "os",
      .name           = "ods",
      .description    = "Capture and log OutputDebugString messages",
      .type           = OPTION_TYPE_BOOL,
      .value.x_bool   = false
    },
    {0}
  };

  option_register(options);

  // setup a handler for ctrl+c
  SetConsoleCtrlHandler(CtrlHandler, TRUE);

  // create a message window so that our message pump works
  WNDCLASSEX wx    = {};
  wx.cbSize        = sizeof(WNDCLASSEX);
  wx.lpfnWndProc   = DummyWndProc;
  wx.hInstance     = hInstance;
  wx.lpszClassName = "DUMMY_CLASS";
  wx.hIcon         = LoadIcon(NULL, IDI_APPLICATION);
  wx.hIconSm       = LoadIcon(NULL, IDI_APPLICATION);
  wx.hCursor       = LoadCursor(NULL, IDC_ARROW);
  wx.hbrBackground = (HBRUSH)COLOR_APPWORKSPACE;
  ATOM class;
  if (!(class = RegisterClassEx(&wx)))
  {
    DEBUG_ERROR("Failed to register message window class");
    result = LG_HOST_EXIT_FAILED;
    goto finish;
  }

  app.trayRestartMsg = RegisterWindowMessage("TaskbarCreated");

  app.messageWnd = CreateWindowEx(0, MAKEINTATOM(class), NULL, 0, 0, 0, 0, 0, NULL, NULL, hInstance, NULL);

  // this is needed so that unprivileged processes can send us this message
  ChangeWindowMessageFilterEx(app.messageWnd, app.trayRestartMsg, MSGFLT_ALLOW, NULL);

  // set the global
  MessageHWND = app.messageWnd;

  // get shell events (e.g., for activation requests)
  app.shellHookMsg = RegisterWindowMessage(TEXT("SHELLHOOK"));
  RegisterShellHookWindow(app.messageWnd);

  app.trayMenu = CreatePopupMenu();
  AppendMenu(app.trayMenu, MF_STRING   , ID_MENU_SHOW_LOG, "Open Log File");
  AppendMenu(app.trayMenu, MF_SEPARATOR, 0               , NULL           );
  AppendMenu(app.trayMenu, MF_STRING   , ID_MENU_EXIT    , "Exit"         );

  if (!WTSRegisterSessionNotification(app.messageWnd, NOTIFY_FOR_THIS_SESSION))
    DEBUG_WINERROR("WTSRegisterSessionNotification failed", GetLastError());

  // create the application thread
  LGThread * thread;
  if (!lgCreateThread("appThread", appThread, NULL, &thread))
  {
    DEBUG_ERROR("Failed to create the main application thread");
    result = LG_HOST_EXIT_FAILED;
    goto finish;
  }

  while(true)
  {
    MSG  msg;
    BOOL bRet = GetMessage(&msg, NULL, 0, 0);
    if (bRet > 0)
    {
      TranslateMessage(&msg);
      DispatchMessage(&msg);
      continue;
    }
    else if (bRet < 0)
    {
      DEBUG_ERROR("Unknown error from GetMessage");
      result = LG_HOST_EXIT_FAILED;
      goto shutdown;
    }

    break;
  }

shutdown:
  WTSUnRegisterSessionNotification(app.messageWnd);

  DestroyMenu(app.trayMenu);
  app_shutdown();
  UnregisterWait(app.exitWait);

  if (!lgJoinThread(thread, &result))
  {
    DEBUG_ERROR("Failed to join the main application thread");
    result = LG_HOST_EXIT_FAILED;
  }

finish:

  free(app.osVersion);

  for(int i = 0; i < app.argc; ++i)
    free(app.argv[i]);
  free(app.argv);

  if (app.taskHandle)
    AvRevertMmThreadCharacteristics(app.taskHandle);

  ods_stop();

  if (app.stdErrFile)
    fclose(app.stdErrFile);

  if (app.stdOutFile)
    fclose(app.stdOutFile);

  return result;
}

typedef enum _D3DKMT_SCHEDULINGPRIORITYCLASS
{
  D3DKMT_SCHEDULINGPRIORITYCLASS_IDLE         = 0,
  D3DKMT_SCHEDULINGPRIORITYCLASS_BELOW_NORMAL = 1,
  D3DKMT_SCHEDULINGPRIORITYCLASS_NORMAL       = 2,
  D3DKMT_SCHEDULINGPRIORITYCLASS_ABOVE_NORMAL = 3,
  D3DKMT_SCHEDULINGPRIORITYCLASS_HIGH         = 4,
  D3DKMT_SCHEDULINGPRIORITYCLASS_REALTIME     = 5,
}
D3DKMT_SCHEDULINGPRIORITYCLASS;

NTSTATUS APIENTRY D3DKMTSetProcessSchedulingPriorityClass(
  _In_ HANDLE, _In_ D3DKMT_SCHEDULINGPRIORITYCLASS
);

void boostPriority(void)
{
  if (FAILED(D3DKMTSetProcessSchedulingPriorityClass(GetCurrentProcess(),
        D3DKMT_SCHEDULINGPRIORITYCLASS_REALTIME)))
  {
    DEBUG_WARN("Failed to set realtime GPU priority.");
    DEBUG_INFO("This is not a failure, please do not report this as an issue.");
    DEBUG_INFO("To fix this, install and run the Looking Glass host as a service.");
    DEBUG_INFO("looking-glass-host.exe InstallService");
  }

  DWORD taskIndex = 0;
  app.taskHandle =
    AvSetMmThreadCharacteristicsA("Capture", &taskIndex);

  if (!app.taskHandle)
    DEBUG_WINERROR("AvSetMmThreadCharacteristicsA failed", GetLastError());

  if (!AvSetMmThreadPriority(app.taskHandle, AVRT_PRIORITY_CRITICAL))
    DEBUG_WINERROR("Failed to set thread priority", GetLastError());
}

void CALLBACK exitEventCallback(PVOID opaque, BOOLEAN timedOut)
{
  DEBUG_INFO("Received exit event");
  SendMessage(app.messageWnd, WM_CLOSE, 0, 0);
}

bool app_init(void)
{
  const char * logFile = option_get_string("os", "logFile");
  const bool   ods     = option_get_bool  ("os", "ods"    );

  // redirect stderr to a file
  if (logFile && strcmp(logFile, "stderr") != 0)
  {
    // if the log file already exists, rotate it out
    char finalName[strlen(logFile)+5];
    char name1[strlen(logFile)+7];
    char name2[strlen(logFile)+7];

    sprintf(finalName, "%s.txt", logFile);

    struct stat st;
    if (stat(finalName, &st) == 0)
    {
      sprintf(name2, "%s.%d.txt", logFile, 3);
      if (stat(name2, &st) == 0)
        unlink(name2);

      for(int i = 2; i > 0; --i)
      {
        sprintf(name1, "%s.%d.txt", logFile, i);
        if (stat(name1, &st) == 0)
          rename(name1, name2);
        strcpy(name2, name1);
      }

      rename(finalName, name2);
    }

    DEBUG_INFO("Logs will be written to: %s", finalName);
    DEBUG_INFO("Please see there for any further information");

    if (!freopen(finalName, "a", stderr))
      DEBUG_WARN("Failed to open log file, will log to stderr");
  }

  // always flush stderr
  setbuf(stderr, NULL);

  if (ods && !ods_start())
    DEBUG_WARN("Failed to setup capture of debug messages");

  windowsSetTimerResolution();

  // get the performance frequency for spinlocks
  QueryPerformanceFrequency(&app.perfFreq);

  // try to boost the scheduler priority
  boostPriority();

  // open exit signaling event
  HANDLE exitEvent = NULL;
  const char * exitEventName = option_get_string("os", "exitEvent");
  if (exitEventName && exitEventName[0])
  {
    exitEvent = OpenEvent(SYNCHRONIZE, FALSE, exitEventName);
    if (!exitEvent)
    {
      DEBUG_WINERROR("Failed to open exitEvent", GetLastError());
      DEBUG_INFO("Exit event name: %s", exitEventName);
    }
  }

  if (exitEvent)
  {
    if (!RegisterWaitForSingleObject(
          &app.exitWait, exitEvent, exitEventCallback, NULL,
          INFINITE, WT_EXECUTEONLYONCE))
      DEBUG_WINERROR("Failed to register wait for exit event", GetLastError());
    CloseHandle(exitEvent);
  }

  return true;
}

const char * os_getExecutable(void)
{
  return app.executable;
}

const char * os_getDataPath(void)
{
  static char path[MAX_PATH] = { 0 };
  if (!path[0])
  {
    if (!GetModuleFileName(NULL, path, MAX_PATH))
      return NULL;

    char *p = strrchr(path, '\\');
    if (!p)
      return NULL;

    ++p;
    *p = '\0';
  }
  return path;
}

HWND os_getMessageWnd(void)
{
  return app.messageWnd;
}

bool os_getAndClearPendingActivationRequest(void)
{
  return atomic_exchange(&app.hasPendingActivationRequest, false);
}

bool os_blockScreensaver(void)
{
  static bool      lastResult = false;
  static ULONGLONG lastCheck  = 0;

  ULONGLONG now = GetTickCount64();
  if (now - lastCheck >= 1000)
  {
    ULONG executionState;
    NTSTATUS status = CallNtPowerInformation(SystemExecutionState, NULL, 0,
      &executionState, sizeof executionState);

    if (status == STATUS_SUCCESS)
      lastResult = executionState & ES_DISPLAY_REQUIRED;
    else
      DEBUG_WINERROR("Failed to call CallNtPowerInformation(SystemExecutionState)",
        RtlNtStatusToDosError(status));
    lastCheck = now;
  }
  return lastResult;
}

void os_showMessage(const char * caption, const char * msg)
{
  MessageBoxA(NULL, msg, caption, MB_OK | MB_ICONINFORMATION);
}

bool os_hasSetCursorPos(void)
{
  return true;
}

void os_setCursorPos(int x, int y)
{
  SetCursorPos(x, y);
}

KVMFROS os_getKVMFRType(void)
{
  return KVMFR_OS_WINDOWS;
}

static bool getProductName(char * buffer, DWORD bufferSize)
{
  LSTATUS status = RegGetValueA(HKEY_LOCAL_MACHINE,
    "Software\\Microsoft\\Windows NT\\CurrentVersion", "ProductName",
    RRF_RT_REG_SZ, NULL, buffer, &bufferSize);

  if (status != ERROR_SUCCESS)
  {
    DEBUG_WINERROR("Failed to read ProductName from registry", status);
    return false;
  }

  return true;
}

const char * os_getOSName(void)
{
  if (app.osVersion)
    return app.osVersion;

  OSVERSIONINFOA osvi = { 0 };
  osvi.dwOSVersionInfoSize = sizeof(osvi);
  GetVersionExA(&osvi);

  char productName[1024];
  if (getProductName(productName, sizeof(productName)))
  {
    alloc_sprintf(
      &app.osVersion,
      "%s (Build: %lu) %s",
      productName,
      osvi.dwBuildNumber,
      osvi.szCSDVersion
    );
  }
  else
  {
    alloc_sprintf(
      &app.osVersion,
      "Windows %lu.%lu (Build: %lu) %s",
      osvi.dwMajorVersion,
      osvi.dwMinorVersion,
      osvi.dwBuildNumber,
      osvi.szCSDVersion
    );
  }

  return app.osVersion;
}

#define TABLE_SIG(x) (\
    ((uint32_t)(x[0]) << 24) | \
    ((uint32_t)(x[1]) << 16) | \
    ((uint32_t)(x[2]) << 8 ) | \
    ((uint32_t)(x[3]) << 0 ))

#define SMBVER(major, minor) \
  ((smbData->SMBIOSMajorVersion == major && \
    smbData->SMBIOSMinorVersion >= minor) || \
    (smbData->SMBIOSMajorVersion > major))

#define SMB_SST_SystemInformation 1

#define REVERSE32(x) \
  *(uint32_t*)(x) = ((*(uint32_t*)(x) & 0xFFFF0000) >> 16) | \
                    ((*(uint32_t*)(x) & 0x0000FFFF) << 16)

#define REVERSE16(x) \
  *(uint16_t*)(x) = ((*(uint16_t*)(x) & 0xFF00) >> 8) | \
                    ((*(uint16_t*)(x) & 0x00FF) << 8)


static void * smbParseData(uint8_t ** data, char * strings[])
{
  typedef struct
  {
    uint8_t type;
    uint8_t length;
  }
  __attribute__((packed)) SMBHeader;

  SMBHeader *h = (SMBHeader *)*data;

  *data += h->length;
  if (**data)
    for(int i = 1; i < 256 && **data; ++i)
    {
      strings[i] = (char *)*data;
      *data += strlen((char *)*data) + 1;
    }
  else
    ++*data;

  ++*data;
  return h;
}

const uint8_t * os_getUUID(void)
{
  static uint8_t uuid[16] = {0};
  static bool uuidValid = false;

  if (uuidValid)
    return uuid;

  typedef struct
  {
    BYTE  Used20CallingMethod;
    BYTE  SMBIOSMajorVersion;
    BYTE  SMBIOSMinorVersion;
    BYTE  DmiRevision;
    DWORD Length;
    BYTE  SMBIOSTableData[];
  }
  RawSMBIOSData;

  typedef struct
  {
    uint8_t  type;
    uint8_t  length;
    uint16_t handle;
    uint8_t  manufacturerStr;
    uint8_t  productStr;
    uint8_t  versionStr;
    uint8_t  serialStr;
    uint8_t  uuid[16];
    uint8_t  wakeupType;
    uint8_t  skuNumberStr;
    uint8_t  familyStr;
  }
  __attribute__((packed)) SMBSystemInformation;

  DWORD           smbDataSize;
  RawSMBIOSData * smbData;

  smbDataSize = GetSystemFirmwareTable(TABLE_SIG("RSMB"), 0, NULL, 0);
  smbData     = (RawSMBIOSData *)malloc(smbDataSize);
  if (!smbData)
  {
    DEBUG_ERROR("out of memory");
    return NULL;
  }

  if (GetSystemFirmwareTable(TABLE_SIG("RSMB"), 0, smbData, smbDataSize)
      != smbDataSize)
  {
    DEBUG_ERROR("Failed to read the RSMB table");
    goto err;
  }

  uint8_t * data         = (uint8_t *)smbData->SMBIOSTableData;
  uint8_t * end          = (uint8_t *)smbData->SMBIOSTableData + smbData->Length;
  char    * strings[256] = {0};

  while(data != end)
  {
    if (data[0] == SMB_SST_SystemInformation)
    {
      SMBSystemInformation * info = smbParseData(&data, strings);
      memcpy(uuid, &info->uuid, 16);

      // convert to the same format that SPICE is using
      REVERSE32(&uuid[0]);
      REVERSE16(&uuid[0]);
      REVERSE16(&uuid[2]);
      REVERSE16(&uuid[4]);
      REVERSE16(&uuid[6]);
      uuidValid = true;
      break;
    }

    smbParseData(&data, strings);
  }

  free(smbData);
  return uuid;

err:
  free(smbData);
  return NULL;
}