/
5-11.C
194 lines (180 loc) · 4.98 KB
/
5-11.C
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
183
184
185
186
187
188
189
190
191
192
193
194
/* Copyright (c) 1992 by AT&T Bell Laboratories. */
/* Advanced C++ Programming Styles and Idioms */
/* James O. Coplien */
/* All rights reserved. */
#include <stddef.h>
#include <memory.h>
class LAPD {
friend class LAPDMemoryManager;
public:
virtual int size() { return 0; }
void *operator new(size_t);
void operator delete(void *);
LAPD(char *const);
protected:
LAPD() { /* no-op */ }
private:
int:8;
union {
struct {
unsigned char flag;
unsigned int sapi:6;
unsigned int commandResponse:1;
unsigned int zero:1;
unsigned int tei:7;
unsigned int ext:1;
unsigned char control;
} header;
struct {
LAPD *linkf, *linkb;
unsigned short size;
} minfo;
};
unsigned char tag; // minfo system allocated tag
int performCRCCheck() { /* . . . */ }
};
#define round(a,b) (((a+b-1)/b)*b)
class LAPDMemoryManager {
friend LAPD;
private:
enum { MessageBufSize=4096, Log2MessageBufSize=13 };
unsigned char availBuf[
(1+Log2MessageBufSize)*round(sizeof(LAPD),4)];
LAPD *avail;
unsigned char buf[MessageBufSize];
LAPD *buddy(int k, LAPD *l) {
char *cp = (char *) l;
return (LAPD*)(long(cp) ^ (1<<(k+1)));
}
public:
LAPDMemoryManager() {
LAPD* buf = (LAPD*)this->buf;
avail = (LAPD*)availBuf;
avail[Log2MessageBufSize].minfo.linkf = 0;
avail[Log2MessageBufSize].minfo.linkb = 0;
buf[0].minfo.linkf = buf[0].minfo.linkb =
&avail[Log2MessageBufSize];
buf[0].tag = 1;
buf[0].minfo.size = Log2MessageBufSize;
for (int k = 0; k < Log2MessageBufSize; k++) {
avail[k].minfo.linkf = avail[k].minfo.linkb =
(LAPD*)&avail[k];
}
}
int savej;
LAPD *largestBlock() {
for (int k = Log2MessageBufSize; k >= 0; --k) {
if (avail[k].minfo.linkf != &avail[k]) {
savej = k;
return avail[k].minfo.linkf;
}
}
return 0;
}
void allocateResizeBlock(int ktemp) {
int k, j = savej;
// Round up to next 2**n
for (int i = 1; i < Log2MessageBufSize; i++) {
k = 1 << i;
if (k > ktemp) break;
}
LAPD *l = avail[j].minfo.linkf;
avail[j].minfo.linkf = l->minfo.linkf;
l->minfo.linkf->minfo.linkb = &avail[j];
for(l->tag = 0; j - k; ) {
--j;
LAPD *p = (LAPD*)(((char *)l) + (1 << j));
p->tag = 1;
p->minfo.size = j;
p->minfo.linkf = &avail[j];
p->minfo.linkb = &avail[j];
avail[j].minfo.linkf = p;
avail[j].minfo.linkb = p;
}
}
void deallocateBlock(LAPD *l, int k) {
for(;;) {
LAPD *p = buddy(k,l);
if (k==Log2MessageBufSize || p->tag == 0 ||
p->minfo.size != k) {
break;
}
p->minfo.linkb->minfo.linkf = p->minfo.linkf;
p->minfo.linkf->minfo.linkb = p->minfo.linkb;
++k;
if (p < l) l = p;
}
l->tag = 1;
l->minfo.linkf = avail[k].minfo.linkf;
avail[k].minfo.linkb = l;
l->minfo.size = k;
l->minfo.linkb = &avail[k];
avail[k].minfo.linkf = l;
}
};
static LAPDMemoryManager manager;
// this operator allows one object in the LAPD
// hierarchy to overlay itself with an instance
// of one of its derived classes
inline void *operator new(size_t, LAPD* l) { return l; }
class X25: public LAPD {
friend LAPD;
private:
struct X25PacketBody {
unsigned char rep[4096];
};
int size() { return sizeof(X25); }
X25(char *const m): LAPD() {
manager.allocateResizeBlock( size() );
::memcpy(&body, m, sizeof(body));
}
X25PacketBody body;
};
class EIN: public LAPD {
friend LAPD;
private:
struct EINPacketBody {
unsigned char rep[4096];
};
int size() { return sizeof(EIN); }
EIN(char *const m): LAPD() {
manager.allocateResizeBlock( size() );
::memcpy(&body, m, sizeof(body));
}
EINPacketBody body;
};
void *
LAPD::operator new(size_t /* unused */) {
return manager.largestBlock();
}
void
LAPD::operator delete(void *l) {
manager.deallocateBlock((LAPD*)l, ((LAPD*)l)->size());
}
LAPD::LAPD(char *const bits) {
::memcpy(&header, bits, sizeof(header));
performCRCCheck();
// Determine type of message based on address
switch(bits[0]) {
case 'a':
(void) ::new(this) X25(bits); break;
case 'b':
(void) ::new(this) EIN(bits); break;
default:
// error("invalid message"); break;
;
}
}
int main() {
LAPD *m, *n, *o, *p;
m = new LAPD("abcdefg");
n = new LAPD("badfljk;adsflkj;asldf");
delete n;
n = new LAPD("aadflkj;sadf");
o = new LAPD("aad;sflkj;lsdf");
p = new LAPD("bb");
delete p;
delete m;
delete n;
delete o;
}