/*
* set both the signatures for a chunk to a particular value
* 'chunk' must be the index of the bottom signature for a chunk
* NOTE: if you change the size of this chunk with this function
* then we'll set the end signature for the NEW SIZE!
*/
void setBothSignatures(unsigned chunk, int value) {
unsigned top;
memory_pool[chunk] = value;
top = topSignature(chunk);
memory_pool[top] = value;
}
void displayChunks(void) {
int size;
int num_chunks = 0;
unsigned chunk = 0;
int top_signature;
while (chunk < pool_size) {
num_chunks += 1;
size = memory_pool[chunk];
printf("chunk %d ", num_chunks);
top_signature = memory_pool[topSignature(chunk)];
if (size != top_signature) {
printf(" has a signature mismatch problem! oh fudge\n");
exit(-1);
}
if (size > 0) {
printf(" is available");
}
else {
printf(" is in use");
}
if (size < 0) { size = -size; }
printf(" and has %d words of available storage\n", size);
chunk = successorChunk(chunk);
}
}
void deallocateMemory(void *p)
{
/* since the available memory is one position above the signature
* the signature can be found at one position below the first
* byte of available memory
*/
int *chunk_address = ((int *)p) - 1;
unsigned chunk;
int top_signature;
int bottom_signature;
int size;
if ((chunk_address < memory_pool)
|| (chunk_address >= &memory_pool[pool_size]))
{
/* due to silliness in the MetroWerks compiler, it is possible
* for new to be called before the memory heap is on-line. In that
* case the system default heap is used, and not this one.
* this generally only happens for global constructors, such as
* the stuff associated with cout and cin.
* When these objects are destroyed (after main ends) the
* runtime system calls delete on all these things but
* since our heap is now online, we get all the other heap's memory
* back. We're just going to ignore it. The OS will clean up
* that memory anyway when the application quits, so its
* no big deal.
*/
/* if you want to see this in action, de-comment the following line */
// cout << "hey! that ain't mine, don't throw that junk at me\n";
return;
}
chunk = chunk_address - memory_pool;
bottom_signature = memory_pool[chunk];
top_signature = memory_pool[topSignature(chunk)];
/* another sanity check, not really insane at all. */
assert(bottom_signature == top_signature
&& bottom_signature < 0);
size = -bottom_signature;
setBothSignatures(chunk, size);
mergeChunkIfOK(chunk);
if (chunk > 0)
{ // this is not quite silly, chunk could be equal to zero
unsigned previous_chunk = predecessorChunk(chunk);
mergeChunkIfOK(previous_chunk);
}
if (mem_leak_check && isEmptyHeap())
{
std::cout << "Yay, you do not have a memory leak!" << std::endl;
}
}
/*
* sanity check the heap and return true if it looks OK,
* return false if something is messed up
*/
bool isSaneHeap(void) {
unsigned chunk = 0;
/* check each chunk to see if top and bottom sigs match */
while (chunk < pool_size) {
if (memory_pool[chunk] != memory_pool[topSignature(chunk)]) {
return false;
}
chunk = successorChunk(chunk);
}
return true;
}