text: // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
  // Copyright (c) 2010 The Chromium Authors. All rights reserved.
  //
  // Redistribution and use in source and binary forms, with or without
  // modification, are permitted provided that the following conditions are
  // met:
  //
  //    * Redistributions of source code must retain the above copyright
  // notice, this list of conditions and the following disclaimer.
  //    * Redistributions in binary form must reproduce the above
  // copyright notice, this list of conditions and the following disclaimer
  // in the documentation and/or other materials provided with the
  // distribution.
  //    * Neither the name of Google Inc. nor the names of its
  // contributors may be used to endorse or promote products derived from
  // this software without specific prior written permission.
  //
  // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  //
  // Utility for using SideStep with unit tests.
  
  #ifndef CEEE_TESTING_SIDESTEP_AUTO_TESTING_HOOK_H_
  #define CEEE_TESTING_SIDESTEP_AUTO_TESTING_HOOK_H_
  
  #include "base/basictypes.h"
  #include "base/logging.h"
  #include "preamble_patcher.h"
  
  #define SIDESTEP_CHK(x)  CHECK(x)
  #define SIDESTEP_EXPECT_TRUE(x)  SIDESTEP_CHK(x)
  
  namespace sidestep {
  
  // Same trick as common/scope_cleanup.h ScopeGuardImplBase
  class AutoTestingHookBase {
   public:
    virtual ~AutoTestingHookBase() {}
  };
  
  // This is the typedef you normally use for the class, e.g.
  //
  // AutoTestingHook hook = MakeTestingHook(TargetFunc, HookTargetFunc);
  //
  // The 'hook' variable will then be destroyed when it goes out of scope.
  //
  // NOTE: You must not hold this type as a member of another class.  Its
  // destructor will not get called.
  typedef const AutoTestingHookBase& AutoTestingHook;
  
  // This is the class you must use when holding a hook as a member of another
  // class, e.g.
  //
  // public:
  //  AutoTestingHookHolder holder_;
  //  MyClass() : my_hook_holder(MakeTestingHookHolder(Target, Hook)) {}
  class AutoTestingHookHolder {
   public:
    explicit AutoTestingHookHolder(AutoTestingHookBase* hook) : hook_(hook) {}
    ~AutoTestingHookHolder() { delete hook_; }
   private:
    AutoTestingHookHolder() {}  // disallow
    AutoTestingHookBase* hook_;
  };
  
  // This class helps patch a function, then unpatch it when the object exits
  // scope, and also maintains the pointer to the original function stub.
  //
  // To enable use of the class without having to explicitly provide the
  // type of the function pointers (and instead only providing it
  // implicitly) we use the same trick as ScopeGuard (see
  // common/scope_cleanup.h) uses, so to create a hook you use the MakeHook
  // function rather than a constructor.
  //
  // NOTE:  This function is only safe for e.g. unit tests and _not_ for
  // production code.  See PreamblePatcher class for details.
  template <typename T>
  class AutoTestingHookImpl : public AutoTestingHookBase {
   public:
    static AutoTestingHookImpl<T> MakeTestingHook(T target_function,
                                                  T replacement_function,
                                                  bool do_it) {
      return AutoTestingHookImpl<T>(target_function, replacement_function, do_it);
    }
  
    static AutoTestingHookImpl<T>* MakeTestingHookHolder(T target_function,
                                                         T replacement_function,
                                                         bool do_it) {
      return new AutoTestingHookImpl<T>(target_function,
                                        replacement_function, do_it);
    }
  
    ~AutoTestingHookImpl() {
      if (did_it_) {
        SIDESTEP_CHK(SIDESTEP_SUCCESS == PreamblePatcher::Unpatch(
            (void*)target_function_, (void*)replacement_function_,
            (void*)original_function_));
      }
    }
  
    // Returns a pointer to the original function.  To use this method you will
    // have to explicitly create an AutoTestingHookImpl of the specific
    // function pointer type (i.e. not use the AutoTestingHook typedef).
    T original_function() {
      return original_function_;
    }
  
   private:
    AutoTestingHookImpl(T target_function, T replacement_function, bool do_it)
        : target_function_(target_function),
          original_function_(NULL),
          replacement_function_(replacement_function),
          did_it_(do_it) {
      if (do_it) {
        SIDESTEP_CHK(SIDESTEP_SUCCESS == PreamblePatcher::Patch(target_function,
                                                       replacement_function,
                                                       &original_function_));
      }
    }
  
    T target_function_;  // always valid
    T original_function_;  // always valid
    T replacement_function_;  // always valid
    bool did_it_;  // Remember if we did it or not...
  };
  
  template <typename T>
  inline AutoTestingHookImpl<T> MakeTestingHook(T target,
                                                T replacement,
                                                bool do_it) {
    return AutoTestingHookImpl<T>::MakeTestingHook(target, replacement, do_it);
  }
  
  template <typename T>
  inline AutoTestingHookImpl<T> MakeTestingHook(T target, T replacement) {
    return AutoTestingHookImpl<T>::MakeTestingHook(target, replacement, true);
  }
  
  template <typename T>
  inline AutoTestingHookImpl<T>* MakeTestingHookHolder(T target, T replacement) {
    return AutoTestingHookImpl<T>::MakeTestingHookHolder(target, replacement,
                                                         true);
  }
  
  };  // namespace sidestep
  
  #endif  // CEEE_TESTING_SIDESTEP_AUTO_TESTING_HOOK_H_
  