Category : C Source Code
Archive   : GCOBJECT.ZIP
Filename : GCOBJECT.CPP
These C++ classes are copyright 1989, 1990 by William Herrera.
All those who put this code or its derivatives in a commercial product MUST
mention this copyright in their documentation for users of the products in
which this code or its derivative classes are used. Otherwise, this code
may be freely distributed and used for any purpose.
William Herrera
contacts:
GENIE
FidoNet c_plusplus
**************************************************************************/
// file gcobject.cpp class definition for functions in gcobject class.
#include "gcobject.hpp"
//#define __TURBOC__
char heap_alloc_err[] = "Error: Out of heap space";
char gcobject_alloc_err[] = "Error: Out of gcobject space";
char cr[] = "\n";
void gcobject::Initialize(unsigned int buf_size, int gci)
{
buffer_size = buf_size;
buffer_start = ::new char[buffer_size];
if(buffer_start == NULL)
FatalError(heap_alloc_err);
allocated_size = 0;
delete_count = 0;
garbage_collection_interval = gci;
}
int gcobject::CollectGarbage()
{
#ifdef DEBUG
cerr << "\nCollecting Garbage ...\n";
#endif
int num_collected = 0; // number of data_records collected out.
unsigned int garbage_bottom = 0;
data_record * dptr;
while(garbage_bottom < allocated_size)
{
dptr = (data_record *) &buffer_start[garbage_bottom];
if(dptr->ref_count == 0) // dptr points to garbage
break; // so exit
garbage_bottom += dptr->alloc_length; // skip past area in use
} // now we have found an area of garbage (ref_count == 0).
unsigned int garbage_top = garbage_bottom;
while(garbage_top < allocated_size)
{
dptr = (data_record *) &buffer_start[garbage_top];
if(dptr->ref_count != 0) // dptr points to non-garbage
break; // so exit
garbage_top += dptr->alloc_length; // skip past garbage record
++num_collected; // we've got one to collect.
}
if(garbage_bottom < allocated_size && num_collected > 0)
// there is stuff to collect!
{
unsigned int bytes_above_garbage = allocated_size - garbage_top;
if(bytes_above_garbage > 0)
memmove(&buffer_start[garbage_bottom],
&buffer_start[garbage_top], bytes_above_garbage);
// move stuff to cover garbage.
allocated_size -= garbage_top - garbage_bottom;
// reset amount of buffer currently used.
// Now update the allocated pointers to the buffer records.
// Each record in the buffer keeps track of what pointer is pointing
// to it and can change its value when we reshuffle the buffer.
unsigned int i = 0;
while(i < allocated_size)
{
dptr = (data_record *) &buffer_start[i];
data_record ** owner = dptr->owner_record;
*owner = dptr;
i += dptr->alloc_length;
}
}
delete_count = 0; // reset the counter, since we've done garbage.
return num_collected; // this is zero if there was none to collect.
}
data_record * gcobject::Allocate(size_t sz, data_record ** owner)
{
// this function allocates memory to pointer "owner" but keeps
// track of owner's address so it can update owner if the
// allocation changes position.
size_t len = sizeof(data_record) - 1 + sz;
// this is the size of the variable length records in the buffer.
if(len & 1) // odd # of bytes
++len; // so make even for alignment.
while(allocated_size + len > buffer_size) // oops, out of room
{
if(CollectGarbage() == 0) // try to get some space!
return NULL; // if can't, return NULL as failure flag.
}
data_record * dptr = (data_record *) &buffer_start[allocated_size];
allocated_size += len;
dptr->alloc_length = len;
dptr->ref_count = 1; // base reference count is always 1.
dptr->owner_record = owner;
return dptr;
}
void gcobject::IncDeleteCount()
{
++delete_count;
if(delete_count > garbage_collection_interval)
CollectGarbage();
}
#ifdef DEBUG
void gcobject::DumpBuffer()
{
for(unsigned int i = 0; i < buffer_size; ++i)
cerr.put(buffer_start[i]);
cerr.put('\n');
}
#endif
// end of file gcobject.cpp
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