adb_object_handle.h revision acc6f826433e639b1ba00c021ab5f9161eb56e59 
1/*
2 * Copyright (C) 2006 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_USB_API_ADB_OBJECT_HANDLE_H__
18#define ANDROID_USB_API_ADB_OBJECT_HANDLE_H__
19/** \file
20  This file consists of declaration of a class AdbObjectHandle that
21  encapsulates an internal API object that is visible to the outside
22  of the API through a handle.
23*/
24
25#include "adb_api.h"
26#include "adb_api_private_defines.h"
27
28/** \brief Defines types of internal API objects
29*/
30enum AdbObjectType {
31  /// Object is AdbInterfaceEnumObject.
32  AdbObjectTypeInterfaceEnumerator,
33
34  /// Object is AdbInterfaceObject.
35  AdbObjectTypeInterface,
36
37  /// Object is AdbEndpointObject.
38  AdbObjectTypeEndpoint,
39
40  /// Object is AdbIOCompletion.
41  AdbObjectTypeIoCompletion,
42
43  AdbObjectTypeMax
44};
45
46/** \brief Encapsulates an internal API basic object that is visible to the
47  outside of the API through a handle.
48
49  In order to prevent crashes when API client tries to access an object through
50  an invalid or already closed handle, we keep track of all opened handles in
51  AdbObjectHandleMap that maps association between valid ADBAPIHANDLE and
52  an object that this handle represents. All objects that are exposed to the
53  outside of API via ADBAPIHANDLE are self-destructing referenced objects.
54  The reference model for these objects is as such:
55  1. When CreateHandle() method is called on an object, a handle (ADBAPIHANDLE
56     that is) is assigned to it, a pair <handle, object> is added to the global
57     AdbObjectHandleMap instance, object is referenced and then handle is
58     returned to the API client.
59  2. Every time API is called with a handle, a lookup is performed in
60     AdbObjectHandleMap to find an object that is associated with the handle.
61     If object is not found then ERROR_INVALID_HANDLE is immediatelly returned
62     (via SetLastError() call). If object is found then it is referenced and
63     API call is dispatched to appropriate method of the found object. Upon
64     return from this method, just before returning from the API call, object
65     is dereferenced back to match lookup reference.
66  3. When object handle gets closed, assuming object is found in the map, that
67     <handle, object> pair is deleted from the map and object's refcount is
68     decremented to match refcount increment performed when object has been
69     added to the map.
70  4. When object's refcount drops to zero, the object commits suicide by
71     calling "delete this".
72  All API objects that have handles that are sent back to API client must be
73  derived from this class.
74*/
75class ADBWIN_API_CLASS AdbObjectHandle {
76 public:
77  /** \brief Constructs the object
78
79    Refernce counter is set to 1 in the constructor.
80    @param[in] obj_type Object type from AdbObjectType enum
81  */
82  explicit AdbObjectHandle(AdbObjectType obj_type);
83
84 protected:
85  /** \brief Destructs the object.
86
87   We hide destructor in order to prevent ourseves from accidentaly allocating
88   instances on the stack. If such attempt occurs, compiler will error.
89  */
90  virtual ~AdbObjectHandle();
91
92 public:
93  /** \brief References the object.
94
95    @return Value of the reference counter after object is referenced in this
96            method.
97  */
98  virtual LONG AddRef();
99
100  /** \brief Releases the object.
101
102    If refcount drops to zero as the result of this release, the object is
103    destroyed in this method. As a general rule, objects must not be touched
104    after this method returns even if returned value is not zero.
105    @return Value of the reference counter after object is released in this
106            method.
107  */
108  virtual LONG Release();
109
110  /** \brief Creates handle to this object.
111
112    In this call a handle for this object is generated and object is added
113    to the AdbObjectHandleMap.
114    @return A handle to this object on success or NULL on an error.
115            If NULL is returned GetLastError() provides extended error
116            information. ERROR_GEN_FAILURE is set if an attempt was
117            made to create already opened object.
118  */
119  virtual ADBAPIHANDLE CreateHandle();
120
121  /** \brief This method is called when handle to this object gets closed.
122
123    In this call object is deleted from the AdbObjectHandleMap.
124    @return true on success or false if object is already closed. If
125            false is returned GetLastError() provides extended error
126            information.
127  */
128  virtual bool CloseHandle();
129
130  /** \brief Checks if this object is of the given type.
131
132    @param[in] obj_type One of the AdbObjectType types to check
133    @return true is this object type matches obj_type, or false otherwise.
134  */
135  virtual bool IsObjectOfType(AdbObjectType obj_type) const;
136
137  /** \brief Looks up AdbObjectHandle instance associated with the given handle
138    in the AdbObjectHandleMap.
139
140    This method increments reference counter for the returned found object.
141    @param[in] adb_handle ADB handle to the object
142    @return API object associated with the handle or NULL if object is not
143            found. If NULL is returned GetLastError() provides extended error
144            information.
145  */
146  static AdbObjectHandle* Lookup(ADBAPIHANDLE adb_handle);
147
148 protected:
149  /** \brief Called when last reference to this object is released.
150
151    Derived object should override this method to perform cleanup that is not
152    suitable for destructors.
153  */
154  virtual void LastReferenceReleased();
155
156 public:
157  /// Gets ADB handle associated with this object
158  ADBAPIHANDLE adb_handle() const {
159    return adb_handle_;
160  }
161
162  /// Gets type of this object
163  AdbObjectType object_type() const {
164    return object_type_;
165  }
166
167  /// Checks if object is still opened. Note that it is not guaranteed that
168  /// object remains opened when this method returns.
169  bool IsOpened() const {
170    return (NULL != adb_handle());
171  }
172
173 protected:
174  /// API handle associated with this object
175  ADBAPIHANDLE  adb_handle_;
176
177  /// Type of this object
178  AdbObjectType object_type_;
179
180  /// This object's reference counter
181  LONG          ref_count_;
182};
183
184/// Maps ADBAPIHANDLE to associated AdbObjectHandle object
185typedef std::map< ADBAPIHANDLE, AdbObjectHandle* > AdbObjectHandleMap;
186
187/** \brief Template routine that unifies extracting of objects of different
188  types from the AdbObjectHandleMap
189
190  @param[in] adb_handle API handle for the object
191  @return Object associated with the handle or NULL on error. If NULL is
192          returned GetLastError() provides extended error information.
193*/
194template<class obj_class>
195obj_class* LookupObject(ADBAPIHANDLE adb_handle) {
196  // Lookup object for the handle in the map
197  AdbObjectHandle* adb_object = AdbObjectHandle::Lookup(adb_handle);
198  if (NULL != adb_object) {
199    // Make sure it's of the correct type
200    if (!adb_object->IsObjectOfType(obj_class::Type())) {
201      adb_object->Release();
202      adb_object = NULL;
203      SetLastError(ERROR_INVALID_HANDLE);
204    }
205  } else {
206    SetLastError(ERROR_INVALID_HANDLE);
207  }
208  return (adb_object != NULL) ? reinterpret_cast<obj_class*>(adb_object) :
209                                NULL;
210}
211
212#endif  // ANDROID_USB_API_ADB_OBJECT_HANDLE_H__
213