Category : Pascal Source Code
Archive   : HEAPSW.ZIP
Filename : _HEAPSWP.INT

{unit _HeapSwp;}

{----------------------------------------------------------------------------}
{ _HEAPSWP }
{ }
{ This unit allows a program that uses all available memory for Heap }
{ to still be able to EXEC a program such as COMMAND.COM and return }
{ to the original program. It does this by saving the Heap to disk }
{ and freeing the Heap memory for the EXEC program. After the program }
{ is terminated, the Heap is retrieved from the disk. }
{ }
{ For example: }
{ if PutHeap('.',0) then }
{ begin }
{ SwapVectors; }
{ exec(GetEnv('COMSPEC'),''); }
{ SwapVectors; }
{ GetHeap; }
{ end }
{ else }
{ (*Error Handling*) }
{ }
{----------------------------------------------------------------------------}

interface

uses crt,
dos;

{----------------------------------------------------------------------------}
{ FUNCTION HEAPSIZE : WORD; }
{ Return the size of the complete HEAP in paragraphs. }
{ For the number of bytes multiply by 16. }
{----------------------------------------------------------------------------}

function HeapSize : word; {Returns size of the Heap in Paragraphs}

{----------------------------------------------------------------------------}
{ FUNCTION PUTHEAP( HeapFilePath : PathStr; }
{ UserID : BYTE): BOOLEAN; }
{ }
{ }
{ This function attempts to create a Heap swap file in the HeapFilePath }
{ directory, save the entire Heap to the file, and then deallocate the }
{ the memory used by the Heap for the program to be executed. }
{ }
{ If all is successful the function returns TRUE }
{ The function will return FALSE if -> }
{ 1 - There is not enough room in the HeapFilePath to store the Heap. }
{ 2 - There was a problem in creating or writing the file. }
{ 3 - There was a problem in DeAllocating the Heap Memory }
{ }
{ HeapFilePath is the PATH ONLY. No file name. For example. }
{ '' = Put it in the Root of the Current Drive. }
{ '.' = Put it in the Current Directory of the Current Drive. }
{ 'D:' = Put it in the Root of the D: Drive. }
{ 'D:.' = Put it in the Current Directory of the D: Drive. }
{ 'D:\TEMP' = Put it in the \TEMP Directory on the D: Drive. }
{ }
{ You should not put a '\' on the end of the HeapFilePath. }
{ }
{ The UserID is for NetWork usage. In order to make sure the Swap file }
{ name is Unique for each User on the network. it is up to the Programmer }
{ to determine a unique ID number for each user. On Novell the Physical }
{ Station Number is a perfect choice. On single user systems just use 0. }
{ }
{ The Swap File created will have a name of the form HEAP3.$5 }
{ The 3 indicates the UserID=3. The 5 is a Process ID to keep track of }
{ Multiple programs using _HEAPSWP at the same time. For example a }
{ program could call another copy of itself and a separate Heap Swap file }
{ would be created for each invocation. }
{ }
{ The Heap Swap file will be marked Read Only to discourage crashing the }
{ program by erasing the Swap file. }
{ }
{----------------------------------------------------------------------------}

function PutHeap(HeapFilePath : PathStr;
UserID : byte) : boolean;

{----------------------------------------------------------------------------}
{ PROCEDURE GETHEAP; }
{ }
{ This procedure ReAllocates the memory for the Heap and Loads in the }
{ Heap Swap file and erases the swap file. }
{ }
{ Failure to reallocate the memory or correctly read the Swap file is }
{ Bad News ! The program will halt with an error level 1. }
{ }
{ Be Aware that executing a program that permanently allocates memory }
{ such as a TSR while the heap is swapped is going to Crash. }
{ }
{ Be aware the Exit procedures that use variables on the Heap may not }
{ function properly. }
{ }
{ Also be aware that failure to call GetHeap after a PutHeap or }
{ crashing the system before calling a GetHeap will result in }
{ Orphaned Swap files laying around. Re-running the program will }
{ normally clean them up if the program runs in the same environment. }
{ }
{----------------------------------------------------------------------------}

procedure GetHeap;