blob: e3746ec14b8a58ba04c1ffd344536f50aa0da2aa (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
|
#ifndef QPID_HANDLERCHAIN_H
#define QPID_HANDLERCHAIN_H
/*
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*
*/
#include <qpid/Plugin.h>
#include <boost/ptr_container/ptr_vector.hpp>
#include <memory>
namespace qpid {
/**
* Chain-of-responsibility design pattern.
*
* Construct a chain of objects deriving from Base. Each implements
* Base::f by doing its own logic and then calling Base::f on the next
* handler (or not if it chooses not to.)
*
* HandlerChain acts as a smart pointer to the first object in the chain.
*/
template <class Base>
class HandlerChain {
public:
/** Base class for chainable handlers */
class Handler : public Base {
public:
Handler() : next() {}
virtual ~Handler() {}
virtual void setNext(Base* next_) { next = next_; }
protected:
Base* next;
};
typedef std::auto_ptr<Handler> HandlerAutoPtr;
/**@param target is the object at the end of the chain. */
HandlerChain(Base& target) : first(&target) {}
/** HandlerChain owns the ChainableHandler. */
void push(HandlerAutoPtr h) {
handlers.push_back(h.release());
h->setNext(first);
first = h.get();
}
// Smart pointer functions
Base* operator*() { return first; }
const Base* operator*() const { return first; }
Base* operator->() { return first; }
const Base* operator->() const { return first; }
operator bool() const { return first; }
private:
boost::ptr_vector<Base> handlers;
Base* first;
};
/**
* A PluginHandlerChain calls Plugin::initAll(*this) on construction,
* allowing plugins to add handlers.
*
* @param Tag can be any class, use to distinguish different plugin
* chains with the same Base type.
*/
template <class Base, class Tag=void>
struct PluginHandlerChain : public HandlerChain<Base>,
public Plugin::Target
{
PluginHandlerChain(Base& target) : HandlerChain<Base>(target) {
Plugin::initAll(*this);
}
};
} // namespace qpid
#endif /*!QPID_HANDLERCHAIN_H*/
|
