C++ MemoryPool::allocate方法代码示例

Address PoolAllocator::allocate(Size *size)
{
    Size index, nPools = 1;
    MemoryPool *pool = ZERO;
    
    /* Find the correct pool size. */
    for (index = POOL_MIN_POWER; index < POOL_MAX_POWER; index++)
        if (*size <= (Size) 1 << (index + 1)) break;

    /* Do we need to allocate an initial pool? */
    if (!pools[index] && parent)
        pool = pools[index] = newPool(index, POOL_MIN_COUNT(*size));

    /* Search for pool with enough memory. */
    else {
        /* Loop current pools. */
        for (pool = pools[index]; pool; pool = pool->next, nPools++) {
            /* At least one block still free? */
            if (pool->free)
                break;

            /* If no pool has free space anymore, allocate another. */
            if (!pool->next) {
                pool = newPool(index, POOL_MIN_COUNT(*size) * nPools);
                break;
            }
        }
    }
    
    /* Attempt to allocate. */
    return pool ? pool->allocate() : ZERO;
}

int main() {
    MemoryPool<A, 32> m;
    cout << endl;

    for (int i = 0; i < 5; ++i) {
        cout << "***** " << i << " *****" << endl << endl;
        A *temp = m.allocate();
        cout << "return pointer = " << static_cast<const void *>(temp) << endl;
        m.deallocate(temp);
        cout << endl;
    }

    return 0;
}

	explicit SecurityAttributes(MemoryPool& pool)
		: m_pool(pool)
	{
		// Ensure that our process has the SYNCHRONIZE privilege granted to everyone
		PSECURITY_DESCRIPTOR pOldSD = NULL;
		PACL pOldACL = NULL;

		// Pseudo-handles do not work on WinNT. Need real process handle.
		HANDLE hCurrentProcess = OpenProcess(READ_CONTROL | WRITE_DAC, FALSE, GetCurrentProcessId());
		if (hCurrentProcess == NULL) {
			Firebird::system_call_failed::raise("OpenProcess");
		}

		DWORD result = GetSecurityInfo(hCurrentProcess, SE_KERNEL_OBJECT, DACL_SECURITY_INFORMATION,
							NULL, NULL, &pOldACL, NULL, &pOldSD);

		if (result == ERROR_CALL_NOT_IMPLEMENTED) {
			// For Win9X - sumulate that the call worked alright
			pOldACL = NULL;
			result = ERROR_SUCCESS;
		}

		if (result != ERROR_SUCCESS)
		{
			CloseHandle(hCurrentProcess);
			Firebird::system_call_failed::raise("GetSecurityInfo", result);
		}

		// NULL pOldACL means all privileges. If we assign pNewACL in this case
		// we'll lost all privileges except assigned SYNCHRONIZE
		if (pOldACL)
		{
			SID_IDENTIFIER_AUTHORITY sidAuth = SECURITY_WORLD_SID_AUTHORITY;
			PSID pSID = NULL;
			AllocateAndInitializeSid(&sidAuth, 1, SECURITY_WORLD_RID,
									 0, 0, 0, 0, 0, 0, 0, &pSID);

			EXPLICIT_ACCESS ea;
			memset(&ea, 0, sizeof(EXPLICIT_ACCESS));
			ea.grfAccessPermissions = SYNCHRONIZE;
			ea.grfAccessMode = GRANT_ACCESS;
			ea.grfInheritance = NO_INHERITANCE;
			ea.Trustee.TrusteeForm = TRUSTEE_IS_SID;
			ea.Trustee.TrusteeType = TRUSTEE_IS_WELL_KNOWN_GROUP;
			ea.Trustee.ptstrName  = (LPTSTR) pSID;

			PACL pNewACL = NULL;
			SetEntriesInAcl(1, &ea, pOldACL, &pNewACL);

			SetSecurityInfo(hCurrentProcess, SE_KERNEL_OBJECT, DACL_SECURITY_INFORMATION,
							NULL, NULL, pNewACL, NULL);

			if (pSID) {
				FreeSid(pSID);
			}
			if (pNewACL) {
				LocalFree(pNewACL);
			}
		}

		CloseHandle(hCurrentProcess);

		if (pOldSD) {
			LocalFree(pOldSD);
		}

		// Create and initialize the default security descriptor
		// to be assigned to various IPC objects.
		//
		// WARNING!!! The absent DACL means full access granted
		// to everyone, this is a huge security risk!

		PSECURITY_DESCRIPTOR p_security_desc = static_cast<PSECURITY_DESCRIPTOR>(
			pool.allocate(SECURITY_DESCRIPTOR_MIN_LENGTH));

		attributes.nLength = sizeof(attributes);
		attributes.lpSecurityDescriptor = p_security_desc;
		attributes.bInheritHandle = TRUE;

		if (!InitializeSecurityDescriptor(p_security_desc, SECURITY_DESCRIPTOR_REVISION) ||
			!SetSecurityDescriptorDacl(p_security_desc, TRUE, NULL, FALSE))
		{
			pool.deallocate(p_security_desc);
			attributes.lpSecurityDescriptor = NULL;
		}
	}

void testAllocator()
{
	printf("Test Firebird::MemoryPool\n");
	MemoryPool* parent = getDefaultMemoryPool();
	MemoryPool* pool = MemoryPool::createPool(parent);

	MallocAllocator allocator;
	BePlusTree<AllocItem, AllocItem, MallocAllocator, DefaultKeyValue<AllocItem>, AllocItem> items(&allocator),
		bigItems(&allocator);

	Vector<void*, LARGE_ITEMS> la;
	printf("Allocate %d large items: ", LARGE_ITEMS);
	int i;
	for (i = 0; i<LARGE_ITEMS; i++) {
		la.add(pool->allocate(LARGE_ITEM_SIZE));
		VERIFY_POOL(pool);
	}
	VERIFY_POOL(pool);
	printf(" DONE\n");

	printf("Allocate %d items: ", ALLOC_ITEMS);
	int n = 0;
	VERIFY_POOL(pool);
	for (i = 0; i < ALLOC_ITEMS; i++) {
		n = n * 47163 - 57412;
		// n = n * 45578 - 17651;
		AllocItem temp = {n, pool->allocate((n % MAX_ITEM_SIZE + MAX_ITEM_SIZE) / 2 + 1)};
		items.add(temp);
	}
	printf(" DONE\n");
	VERIFY_POOL(pool);
	VERIFY_POOL(parent);

	printf("Deallocate half of items in quasi-random order: ");
	n = 0;
	if (items.getFirst()) do {
		pool->deallocate(items.current().item);
		n++;
	} while (n < ALLOC_ITEMS / 2 && items.getNext());
	printf(" DONE\n");
	VERIFY_POOL(pool);
	VERIFY_POOL(parent);

	printf("Allocate %d big items: ", BIG_ITEMS);
	n = 0;
	VERIFY_POOL(pool);
	for (i = 0; i < BIG_ITEMS; i++) {
		n = n * 47163 - 57412;
		// n = n * 45578 - 17651;
		AllocItem temp = {n, pool->allocate((n % BIG_SIZE + BIG_SIZE) / 2 + 1)};
		bigItems.add(temp);
	}
	printf(" DONE\n");
	VERIFY_POOL(pool);
	VERIFY_POOL(parent);

	printf("Deallocate the rest of small items in quasi-random order: ");
	while (items.getNext()) {
		pool->deallocate(items.current().item);
	}
	printf(" DONE\n");
	VERIFY_POOL(pool);
	VERIFY_POOL(parent);

	printf("Deallocate big items in quasi-random order: ");
	if (bigItems.getFirst()) do {
		pool->deallocate(bigItems.current().item);
	} while (bigItems.getNext());
	printf(" DONE\n");

	printf("Deallocate %d large items: ", LARGE_ITEMS/2);
	for (i = 0; i<LARGE_ITEMS/2; i++)
		pool->deallocate(la[i]);
	VERIFY_POOL(pool);
	printf(" DONE\n");


//	pool->verify_pool();
//	parent->verify_pool();
	pool->print_contents(stdout, false);
	parent->print_contents(stdout, false);
	MemoryPool::deletePool(pool);
//	parent->verify_pool();
//  TODO:
//	Test critically low memory conditions
//  Test that tree correctly recovers in low-memory conditions
}