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
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
|
#ifndef QPID_FRAMING_BLOB_H
#define QPID_FRAMING_BLOB_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 <boost/static_assert.hpp>
#include <boost/aligned_storage.hpp>
#include <boost/checked_delete.hpp>
#include <boost/utility/typed_in_place_factory.hpp>
#include <new>
#include <assert.h>
namespace boost {
/**
* 0-arg typed_in_place_factory constructor and in_place() override.
*
* Boost doesn't provide the 0 arg version since it assumes
* in_place_factory will be used when there is no default ctor.
*/
template <class T>
class typed_in_place_factory0 : public typed_in_place_factory_base {
public:
typedef T value_type ;
void apply ( void* address ) const { new (address) T(); }
};
template<class T>
typed_in_place_factory0<T> in_place() { return typed_in_place_factory0<T>(); }
} // namespace boost
namespace qpid {
namespace framing {
using boost::in_place;
template <class T> struct BlobHelper {
static void destroy(void* ptr) { static_cast<T*>(ptr)->~T(); }
static void copy(void* dest, const void* src) {
new (dest) T(*static_cast<const T*>(src));
}
};
template <> struct BlobHelper<void> {
static void destroy(void*);
static void copy(void* to, const void* from);
};
/**
* A "blob" is a chunk of memory which can contain a single object at
* a time arbitrary type, provided sizeof(T)<=blob.size(). Blob
* ensures proper construction and destruction of its contents,
* and proper copying between Blobs, but nothing else.
*
* In particular the user must ensure the blob is big enough for its
* contents and must know the type of object in the blob to cast get().
*
* Objects can be allocated directly in place using
* construct(in_place<T>(...)) or copied using operator=.
* Constructing a new object in the blob destroys the old one.
*
* If BaseType is specified then only object that can be
* safely static_cast to BaseType may be stored in the Blob.
*/
template <size_t Size, class BaseType=void>
class Blob
{
boost::aligned_storage<Size> store;
BaseType* basePtr;
void (*destroy)(void*);
void (*copy)(void*, const void*);
template <class T>void setType() {
BOOST_STATIC_ASSERT(sizeof(T) <= Size);
destroy=&BlobHelper<T>::destroy;
copy=&BlobHelper<T>::copy;
// Base pointer may be offeset from store.address()
basePtr = reinterpret_cast<T*>(store.address());
}
void initialize() {
destroy=&BlobHelper<void>::destroy;
copy=&BlobHelper<void>::copy;
basePtr=0;
}
template<class TypedInPlaceFactory>
void construct (const TypedInPlaceFactory& factory,
const boost::typed_in_place_factory_base* )
{
typedef typename TypedInPlaceFactory::value_type T;
assert(empty());
factory.apply(store.address());
setType<T>();
}
void assign(const Blob& b) {
assert(empty());
b.copy(this->store.address(), b.store.address());
copy = b.copy;
destroy = b.destroy;
basePtr = reinterpret_cast<BaseType*>(
((char*)this)+ ((char*)(b.basePtr) - (char*)(&b)));
}
public:
/** Construct an empty blob. */
Blob() { initialize(); }
/** Copy a blob. */
Blob(const Blob& b) { initialize(); assign(b); }
/** @see construct() */
template<class Expr>
Blob( const Expr & expr ) { initialize(); construct(expr,&expr); }
~Blob() { clear(); }
/** Assign a blob */
Blob& operator=(const Blob& b) {
clear();
assign(b);
return *this;
}
/** Construcct an object in the blob. Destroyes the previous object.
*@param expr an expresion of the form: in_place<T>(x,y,z)
* will construct an object using the constructor T(x,y,z)
*/
template<class Expr> void
construct(const Expr& expr) { clear(); construct(expr,&expr); }
/** Copy construct an instance of T into the Blob. */
template <class T>
Blob& operator=(const T& x) { clear(); construct(in_place<T>(x)); return *this; }
/** Get pointer to blob contents, returns 0 if empty. */
BaseType* get() { return basePtr; }
/** Get pointer to blob contents, returns 0 if empty. */
const BaseType* get() const { return basePtr; }
/** Destroy the object in the blob making it empty. */
void clear() {
void (*oldDestroy)(void*) = destroy;
initialize();
oldDestroy(store.address());
}
bool empty() const { return destroy==BlobHelper<void>::destroy; }
static size_t size() { return Size; }
};
}} // namespace qpid::framing
#endif /*!QPID_FRAMING_BLOB_H*/
|
