src/win32/base/input_dll.cc

// Copyright 2010-2014, Google Inc.
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//
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#include "win32/base/input_dll.h"

#include "base/logging.h"
#include "base/util.h"
#include "base/win_util.h"

namespace mozc {
namespace win32 {

const wchar_t kInputDllName[] = L"input.dll";

const char kEnumEnabledLayoutOrTipName[]    = "EnumEnabledLayoutOrTip";
const char kEnumLayoutOrTipForSetup[]       = "EnumLayoutOrTipForSetup";
const char kInstallLayoutOrTipName[]        = "InstallLayoutOrTip";
const char kInstallLayoutOrTipUserRegName[] = "InstallLayoutOrTipUserReg";
const char kSetDefaultLayoutOrTipName[]     = "SetDefaultLayoutOrTip";

bool InputDll::EnsureInitialized() {
  if (not_found_) {
    // Previous trial was not successful.  give up.
    return false;
  }

  if (module_ != nullptr) {
    // Already initialized.
    return true;
  }

  bool lock_held = false;
  if (!WinUtil::IsDLLSynchronizationHeld(&lock_held)) {
    LOG(ERROR) << "IsDLLSynchronizationHeld failed.";
    return false;
  }
  if (lock_held) {
    LOG(INFO) << "This thread has loader lock. "
              << "LoadLibrary should not be called.";
    return false;
  }

  const HMODULE input_dll = WinUtil::LoadSystemLibrary(kInputDllName);
  if (input_dll == nullptr) {
    const int last_error = ::GetLastError();
    DLOG(INFO) << "LoadSystemLibrary(\"" << kInputDllName << "\") failed. "
               << "error = " << last_error;
    if (last_error == ERROR_MOD_NOT_FOUND) {
      not_found_ = true;
    }
    return false;
  }

  enum_enabled_layout_or_tip_ =
      reinterpret_cast<FPEnumEnabledLayoutOrTip>(
          ::GetProcAddress(input_dll, kEnumEnabledLayoutOrTipName));

  enum_layout_or_tip_for_setup_ =
      reinterpret_cast<FPEnumLayoutOrTipForSetup>(
          ::GetProcAddress(input_dll, kEnumLayoutOrTipForSetup));

  install_layout_or_tip_ =
      reinterpret_cast<FPInstallLayoutOrTip>(
          ::GetProcAddress(input_dll, kInstallLayoutOrTipName));

  install_layout_or_tip_user_reg_ =
      reinterpret_cast<FPInstallLayoutOrTipUserReg>(
          ::GetProcAddress(input_dll, kInstallLayoutOrTipUserRegName));

  set_default_layout_or_tip_ =
      reinterpret_cast<FPSetDefaultLayoutOrTip>(
          ::GetProcAddress(input_dll, kSetDefaultLayoutOrTipName));

  // Other threads may load the same DLL concurrently.
  // Check if this thread is the first thread which updated the |module_|.
  const HMODULE original = static_cast<HMODULE>(
    ::InterlockedCompareExchangePointer(
          reinterpret_cast<volatile PVOID *>(&module_), input_dll, nullptr));
  if (original == nullptr) {
    // This is the first thread which updated the |module_| with valid handle.
    // Do not call FreeLibrary to keep the reference count positive.
  } else {
    // |module_| has already been updated by another thread.  Call FreeLibrary
    // to decrement the reference count which this thread owns.
    ::FreeLibrary(input_dll);
  }

  return true;
}

InputDll::FPEnumEnabledLayoutOrTip InputDll::enum_enabled_layout_or_tip() {
  return enum_enabled_layout_or_tip_;
}

InputDll::FPEnumLayoutOrTipForSetup InputDll::enum_layout_or_tip_for_setup() {
  return enum_layout_or_tip_for_setup_;
}

InputDll::FPInstallLayoutOrTip InputDll::install_layout_or_tip() {
  return install_layout_or_tip_;
}

InputDll::FPInstallLayoutOrTipUserReg
    InputDll::install_layout_or_tip_user_reg() {
  return install_layout_or_tip_user_reg_;
}

InputDll::FPSetDefaultLayoutOrTip InputDll::set_default_layout_or_tip() {
  return set_default_layout_or_tip_;
}

bool InputDll::not_found_;

volatile HMODULE InputDll::module_;
InputDll::FPEnumEnabledLayoutOrTip InputDll::enum_enabled_layout_or_tip_;
InputDll::FPEnumLayoutOrTipForSetup InputDll::enum_layout_or_tip_for_setup_;
InputDll::FPInstallLayoutOrTip InputDll::install_layout_or_tip_;
InputDll::FPInstallLayoutOrTipUserReg
InputDll::install_layout_or_tip_user_reg_;
InputDll::FPSetDefaultLayoutOrTip InputDll::set_default_layout_or_tip_;

}  // namespace win32
}  // namespace mozc