Delphi in a Nutshell

Name

SysReallocMem Function

Syntax

function SysReallocMem(P: Pointer; NewSize: Integer): Pointer;

Description

The SysReallocMem function calls Delphi’s built-in memory manager to reallocate a block of memory with a new size. The new block might be at the same address as the old block, or it might be copied to a new address. In either case, SysReallocMem returns a pointer to the start of the block.

If the new size is larger than the old size, the extra memory is uninitialized. If the request cannot be fulfilled, SysReallocMem leaves the old block alone and returns nil. SysReallocMem is a real function.

Example

// See SetMemoryManager for an explanation of this memory manager.
// See SysFreeMem for the GuardsAreOkay function.
// See SetMemoryManager for the RoundUpSize function.

// Reallocate the block to the new size. Return a pointer to the
// new memory block or nil for failure.
function DebugRealloc(Mem: Pointer; Size: Integer): Pointer;
var
  PArray: PIntegerArray;
begin
  // Get the pointer to the true start of the memory block.
  PArray := PIntegerArray(PChar(Mem) - GuardSize);

  if not GuardsAreOkay(PArray, False) then
    ReportError(2); // invalid pointer

  // Round up Size to a multiple of the guard word size
  Size := RoundUpSize(Size);

  PArray := SysReallocMem (PArray, Size); if PArray = nil then Result := nil else begin // Store the guard words. PArray[0] := AllocatedGuard; PArray[Size div GuardSize + 1] := AllocatedGuard; // Return a pointer to the memory just past the first guard. Result ...