MemStream.pas

   1 unit MemStream;
   2
   3 INTERFACE
   4 uses SysUtils;
   5 type tMemoryStream=object
   6  length: LongWord;
   7  size: LongWord;
   8  data: pointer;
   9  position: pointer;
  10  procedure Seek(absolute:LongWord);
  11  procedure Skip(cnt:Word);
  12  procedure Read(var buf; cnt:Word);
  13  function  ReadByte:byte;
  14  function  ReadWord(cnt:byte): LongWord; experimental;
  15  procedure Rewind;
  16  procedure Append;
  17  function  Tell:LongWord;
  18  procedure Write(var buf; cnt:word);
  19  procedure WriteByte(v:byte);
  20  procedure WriteWord(v:LongWord; cnt:byte); experimental;
  21  procedure Init(ibuf:pointer; ilen,isize:LongWord);
  22  end;
  23
  24 type eInvalidMemStreamAccess=class(Exception)
  25  {no details jet}
  26 end;
  27
  28 IMPLEMENTATION
  29
  30 procedure tMemoryStream.Seek(absolute:LongWord);
  31  begin
  32  if absolute>=size then raise eInvalidMemStreamAccess.Create('Seek out of bounds');
  33  position:=data+absolute;
  34 end;
  35
  36 procedure tMemoryStream.Skip(cnt:Word);
  37  begin
  38  if cnt>=size then raise eInvalidMemStreamAccess.Create('Seek out of bounds');
  39  position:=position+cnt;
  40 end;
  41
  42 procedure tMemoryStream.Read(var buf; cnt:Word);
  43  begin
  44  if (position+cnt)>=(data+length) then raise eInvalidMemStreamAccess.Create('Read out of bounds');
  45  Move(position^,buf,cnt);
  46  position:=position+cnt;
  47 end;
  48
  49 function  tMemoryStream.ReadByte:byte;
  50  begin Read(result, 1); end;
  51
  52 function  tMemoryStream.ReadWord(cnt:byte): LongWord;
  53  {$IFDEF ENDIAN_LITTLE}
  54  var tm:packed array [0..3] of byte;
  55  var i:byte;
  56  begin
  57  if (position+cnt)>=(data+length) then raise eInvalidMemStreamAccess.Create('Read out of bounds');
  58  for i:=cnt-1 downto 0 do begin
  59   tm[i]:=byte((position)^);
  60   inc(position);
  61  end;
  62  {$ELSE}
  63  begin
  64  Read(tm[4-cnt],cnt);
  65  {$ENDIF}
  66  ReadWord:=LongWord(pointer(@tm)^);
  67 end;
  68
  69 procedure tMemoryStream.Rewind;
  70  begin position:=data; end;
  71 procedure tMemoryStream.Append;
  72  begin position:=data+length; end;
  73 function  tMemoryStream.Tell:LongWord;
  74  begin Tell:=position-data; end;
  75 procedure tMemoryStream.Write(var buf; cnt:word);
  76  begin
  77  if (position+cnt)>=(data+size) then raise eInvalidMemStreamAccess.Create('Write out of bounds');
  78  Move(buf,position^,cnt);
  79  length:=position-data;
  80 end;
  81 procedure tMemoryStream.WriteByte(v:byte);
  82  begin Write(v,1); end;
  83
  84 procedure tMemoryStream.WriteWord(v:LongWord; cnt:byte);
  85  var tm:packed array [0..3] of byte absolute v;
  86  var i:byte;
  87  begin
  88  {$IFDEF ENDIAN_LITTLE}
  89  if (position+cnt)>=(data+size) then raise eInvalidMemStreamAccess.Create('Write out of bounds');
  90  for i:=cnt-1 to 0 do begin
  91   byte(position^):=tm[i];
  92   inc(position);
  93  end;
  94  {$ELSE}
  95  Write(tm[4-cnt],cnt);
  96  {$ENDIF}
  97  length:=position-data;
  98 end;
  99
 100 procedure tMemoryStream.Init(ibuf:pointer; ilen,isize:LongWord);
 101  begin
 102  data:=ibuf;
 103  length:=ilen;
 104  size:=isize;
 105 end;
 106
 107 END.
 108