MemStream.pas

   1 unit MemStream;
   2
   3 INTERFACE
   4 uses SysUtils;
   5 type tMemoryStream=object
   6  length: LongWord;
   7  size: LongWord;
   8  base: pointer;
   9  position: LongWord;
  10  procedure Seek(absolute:LongWord);
  11  procedure Skip(cnt:Word);
  12  procedure Read(var buf; cnt:Word);
  13  function  ReadPtr(cnt:Word):pointer;
  14  function  ReadByte:byte;
  15  function  ReadWord(cnt:byte): LongWord;
  16  procedure Trunc;
  17  procedure Append;
  18  function  Tell:LongWord;
  19  procedure Write(const buf; cnt:word);
  20  procedure WriteByte(v:byte);
  21  procedure WriteWord(v:LongWord; cnt:byte);
  22  procedure Init(ibuf:pointer; ilen,isize:LongWord);
  23  procedure Init(isize:LongWord);
  24  function WRBuf:pointer;
  25  function WRBufLen:LongWord;
  26  procedure WREnd(used:LongWord);
  27  function RDBuf:pointer;
  28  function RDBufLen:LongWord;
  29  procedure RDEnd(used:LongWord);
  30  end;
  31
  32 type eInvalidMemStreamAccess=class(Exception)
  33  {no details jet}
  34 end;
  35
  36 IMPLEMENTATION
  37
  38 procedure tMemoryStream.Seek(absolute:LongWord);
  39  begin
  40  if absolute>size then raise eInvalidMemStreamAccess.Create('Seek out of bounds');
  41  position:=absolute;
  42 end;
  43
  44 procedure tMemoryStream.Skip(cnt:Word);
  45  begin
  46  Seek(position+cnt);
  47 end;
  48
  49 procedure tMemoryStream.Read(var buf; cnt:Word);
  50  begin
  51  if (position+cnt)>length then raise eInvalidMemStreamAccess.Create('Read out of bounds');
  52  Move((base+position)^,buf,cnt);
  53  position:=position+cnt;
  54 end;
  55
  56 function tMemoryStream.ReadPtr(cnt:Word):pointer;
  57  begin
  58  result:=base+position;
  59  skip(cnt);
  60 end;
  61
  62 function  tMemoryStream.ReadByte:byte;
  63  begin Read(result, 1); end;
  64
  65 function  tMemoryStream.ReadWord(cnt:byte): LongWord;
  66  {$IFDEF ENDIAN_LITTLE}
  67  var tm:packed array [0..3] of byte;
  68  var i:byte;
  69  begin
  70  FillChar(tm,4,0);
  71  if (position+cnt)>length then raise eInvalidMemStreamAccess.Create('Read out of bounds');
  72  for i:=cnt-1 downto 0 do begin
  73   tm[i]:=byte((base+position)^);
  74   inc(position);
  75  end;
  76  {$ELSE}
  77  begin
  78  Read(tm[4-cnt],cnt);
  79  {$ENDIF}
  80  ReadWord:=LongWord(pointer(@tm)^);
  81 end;
  82
  83 procedure tMemoryStream.Trunc;
  84  begin length:=position; end;
  85 procedure tMemoryStream.Append;
  86  begin position:=length; end;
  87 function tMemoryStream.Tell:LongWord;
  88  begin Tell:=position; end;
  89
  90 procedure tMemoryStream.Write(const buf; cnt:word);
  91  begin
  92  if (position+cnt)>size then raise eInvalidMemStreamAccess.Create('Write out of bounds');
  93  Move(buf,(base+position)^,cnt);
  94  position:=position+cnt;
  95  if position>length then length:=position;
  96 end;
  97 procedure tMemoryStream.WriteByte(v:byte);
  98  begin Write(v,1); end;
  99
 100 procedure tMemoryStream.WriteWord(v:LongWord; cnt:byte);
 101  var tm:packed array [0..3] of byte absolute v;
 102  var i:byte;
 103  begin
 104  {$IFDEF ENDIAN_LITTLE}
 105  if (position+cnt)>size then raise eInvalidMemStreamAccess.Create('Write out of bounds');
 106  for i:=cnt-1 downto 0 do begin
 107   byte((base+position)^):=tm[i];
 108   inc(position);
 109  end;
 110  if position>length then length:=position;
 111  {$ELSE}
 112  Write(tm[4-cnt],cnt);
 113  {$ENDIF}
 114 end;
 115
 116 procedure tMemoryStream.Init(ibuf:pointer; ilen,isize:LongWord);
 117  begin
 118  base:=ibuf;
 119  length:=ilen;
 120  size:=isize;
 121  seek(0);
 122 end;
 123 procedure tMemoryStream.Init(isize:LongWord);
 124  begin
 125  Init(GetMem(isize),0,isize);
 126 end;
 127
 128 function tMemoryStream.WRBuf:pointer;
 129  begin result:=base+position end;
 130 function tMemoryStream.WRBufLen:LongWord;
 131  begin result:=size-position end;
 132 procedure tMemoryStream.WREnd(used:LongWord);
 133  begin RDEnd(used); if position>length then length:=position end;
 134 function tMemoryStream.RDBuf:pointer;
 135  begin result:=base+position end;
 136 function tMemoryStream.RDBufLen:LongWord;
 137  begin result:=length-position end;
 138 procedure tMemoryStream.RDEnd(used:LongWord);
 139  begin skip(used) end;
 140
 141 END.
 142