Category : C++ Source Code
Archive : IDIOMS.ZIP
Filename : 5-11.C
Output of file : 5-11.C contained in archive : IDIOMS.ZIP
/* Advanced C++ Programming Styles and Idioms */
/* James O. Coplien */
/* All rights reserved. */
#include
#include
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;
}
Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!
This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.
But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/