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[brdnet.git] / MemStream.pas
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1 unit MemStream;
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;
32 type eInvalidMemStreamAccess=class(Exception)
33 {no details jet}
34 end;
36 IMPLEMENTATION
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;
44 procedure tMemoryStream.Skip(cnt:Word);
45 begin
46 Seek(position+cnt);
47 end;
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;
56 function tMemoryStream.ReadPtr(cnt:Word):pointer;
57 begin
58 result:=base+position;
59 skip(cnt);
60 end;
62 function tMemoryStream.ReadByte:byte;
63 begin Read(result, 1); end;
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 {$ENDIF}
80 ReadWord:=LongWord(pointer(@tm)^);
81 end;
83 procedure tMemoryStream.Trunc;
84 begin length:=position; end;
85 procedure tMemoryStream.Append;
86 begin position:=length; end;
87 function tMemoryStream.Tell:LongWord;
88 begin Tell:=position; end;
90 procedure tMemoryStream.Write(const buf; cnt:word);
91 begin
92 if (position+cnt)>size then raise eInvalidMemStreamAccess.Create('Write out of bounds');
93 Move(buf,(base+position)^,cnt);
94 position:=position+cnt;
95 if position>length then length:=position;
96 end;
97 procedure tMemoryStream.WriteByte(v:byte);
98 begin Write(v,1); end;
100 procedure tMemoryStream.WriteWord(v:LongWord; cnt:byte);
101 var tm:packed array [0..3] of byte absolute v;
102 var i:byte;
103 begin
104 {$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;
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;
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;
141 END.