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unit memmgr;



interface



function dGetMem(size: integer): pointer;

function dFreeMem(p: pointer): integer;

function dReallocMem(p: pointer; size: integer): pointer;



implementation



uses Libc;



const hashSize = 32;



var heap, base, bbase, bend, current: pointer;

  memSize, heapCount: cardinal;



type

  block = ^rblock;

  rblock = record

    size: cardinal;

    ptr: pointer;

    prev: block;

    next: block;

    free: word;

  end;



var 

  table: array[0..hashSize-1] of block;



function hash(p: pointer): byte;

var o: cardinal;

begin

  o := cardinal(p) shr 1;

  o := (o AND $00FF00 shr 8) + (o AND $FF0000 shr 16) + (o AND $0000FF);

  result := o MOD hashSize;

end;



function getBlockSlot(hint: block): pointer;

var found: boolean;

  c: block;

begin

  result := nil;

  found := false;

  c := hint;

  while found <> true do

  begin

    if c = bend then

      c := bbase;

    if c.ptr = nil then

    begin

      result := c;

      found := true;

      continue;

    end;

    //c := pointer(cardinal(c)+sizeof(rblock));

    inc(c);

    if c = hint then

      exit;

  end;

end;



function dGetMem(size: integer): pointer;

var c, n: block;

  o: cardinal;

  found: boolean;

  s: pointer;

begin

  result := nil;

  if size MOD 4 <> 0 then

    size := size + (4 - (size mod 4));

  // First, find an empty block

  c := block(current);

  found := false;

  while found <> true do

  begin

    if c = nil then exit;

    if c.size >= size then

      found := true

    else

      c := c.next;

  end;

  { Find a new block to put the new free infomation }

  n := getBlockSlot(c);

  n.ptr := pointer(cardinal(c.ptr)+size);

  n.size := c.size-size;

  n.next := c.next;

  if current = c then

    current := n;

  // Allocate the block

  result := c.ptr;

  c.free := 1;

  c.size := size;

  c.prev := nil;

  o := hash(c.ptr);

  c.next := table[o];

  if table[o] <> nil then

    table[o].prev := c;

  table[o] := c;

end;



function dFreeMem(p: pointer): integer;

var found: boolean;

  c: block;

begin

  result := 1;

  c := table[hash(p)];

  { Find the block pointed to by p }

  while (c.ptr <> p) and (c <> nil) do

  begin

    c := c.next;

  end;

  if c = nil then

    exit;

  c.free := 0;

  result := 0;

end;



function dReallocMem(p: pointer; size: integer): pointer;

begin



end;



const

  dMemMgr: TMemoryManager = (

    GetMem: dGetMem;

    FreeMem: dFreeMem;

    ReallocMem: dReallocMem);



var i: cardinal;



begin

  memSize := 8*1024*1024;

  heapCount := 1024;

  heap := malloc(memSize);

  base := heap; 

  bbase := malloc(sizeof(rblock)*heapCount);

  bend := pointer(cardinal(bbase)+sizeof(rblock)*heapCount);

  current := bbase;

  for i := 0 to hashSize-1 do

    table[i] := nil;

  with block(current)^ do

  begin

    size := memSize;

    ptr := base;

    next := nil;

    free := 0;

  end;

//  SetMemoryManager(dMemMgr);

end.