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source: vbox/trunk/src/libs/xpcom18a4/xpcom/io/nsFastLoadPtr.h@ 6542

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1/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
2/* ***** BEGIN LICENSE BLOCK *****
3 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
4 *
5 * The contents of this file are subject to the Mozilla Public License Version
6 * 1.1 (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 * http://www.mozilla.org/MPL/
9 *
10 * Software distributed under the License is distributed on an "AS IS" basis,
11 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
12 * for the specific language governing rights and limitations under the
13 * License.
14 *
15 * The Original Code is Mozilla FastLoad code.
16 *
17 * The Initial Developer of the Original Code is
18 * Netscape Communications Corporation.
19 * Portions created by the Initial Developer are Copyright (C) 2001
20 * the Initial Developer. All Rights Reserved.
21 *
22 * Contributor(s):
23 * Brendan Eich <[email protected]> (original author)
24 *
25 * Alternatively, the contents of this file may be used under the terms of
26 * either of the GNU General Public License Version 2 or later (the "GPL"),
27 * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
28 * in which case the provisions of the GPL or the LGPL are applicable instead
29 * of those above. If you wish to allow use of your version of this file only
30 * under the terms of either the GPL or the LGPL, and not to allow others to
31 * use your version of this file under the terms of the MPL, indicate your
32 * decision by deleting the provisions above and replace them with the notice
33 * and other provisions required by the GPL or the LGPL. If you do not delete
34 * the provisions above, a recipient may use your version of this file under
35 * the terms of any one of the MPL, the GPL or the LGPL.
36 *
37 * ***** END LICENSE BLOCK ***** */
38
39#ifndef nsFastLoadPtr_h___
40#define nsFastLoadPtr_h___
41
42/**
43 * Mozilla FastLoad file object pointer template type.
44 *
45 * Use nsFastLoadPtr<T> rather than nsCOMPtr<T> when declaring a strong XPCOM
46 * ref member of a data structure that's conditionally loaded at application
47 * startup. You must be willing to tolerate the null mRawPtr test on every
48 * dereference of this member pointer, or else copy it to a local to optimize
49 * away the cost.
50 */
51
52#ifndef nsCOMPtr_h___
53#include "nsCOMPtr.h"
54#endif
55
56#ifndef nsIFastLoadService_h___
57#include "nsIFastLoadService.h"
58#endif
59
60/**
61 * nsFastLoadPtr is a template class, so we don't want a class static service
62 * pointer member declared in nsFastLoadPtr, above. Plus, we need special
63 * declaration magic to export data across DLL/DSO boundaries. So we use an
64 * old-fashioned global variable that refers weakly to the one true FastLoad
65 * service. This pointer is maintained by that singleton's ctor and dtor.
66 */
67PR_EXPORT_DATA(nsIFastLoadService*) gFastLoadService_;
68
69template <class T>
70class nsFastLoadPtr : public nsCOMPtr<T> {
71 public:
72 nsDerivedSafe<T>* get() const {
73 if (!this->mRawPtr) {
74 gFastLoadService_->GetFastLoadReferent(
75 NS_REINTERPRET_CAST(nsISupports**,
76 &this->mRawPtr));
77 }
78 return NS_REINTERPRET_CAST(nsDerivedSafe<T>*, this->mRawPtr);
79 }
80
81 /**
82 * Deserialize an nsFastLoadPtr from aInputStream, skipping the referent
83 * object, but saving the object's offset for later deserialization.
84 *
85 * Lowercase name _a la_ get, because it's called the same way -- not via
86 * operator->().
87 */
88 nsresult read(nsIObjectInputStream* aInputStream) {
89 return gFastLoadService_->ReadFastLoadPtr(aInputStream,
90 NS_REINTERPRET_CAST(nsISupports**,
91 &this->mRawPtr));
92 }
93
94 /**
95 * Serialize an nsFastLoadPtr reference and possibly the referent object,
96 * if that object has not yet been serialized.
97 *
98 * Lowercase name _a la_ get, because it's called the same way -- not via
99 * operator->().
100 */
101 nsresult write(nsIObjectOutputStream* aOutputStream) {
102 return gFastLoadService_->WriteFastLoadPtr(aOutputStream,
103 NS_REINTERPRET_CAST(nsISupports*,
104 this->mRawPtr));
105 }
106};
107
108#endif // nsFastLoadPtr_h___
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