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123 lines
2.7 KiB
ObjectPascal
123 lines
2.7 KiB
ObjectPascal
{
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$Id$
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Copyright (c) 2000 by Free Pascal Development Team
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Routines to compute CRC values
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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****************************************************************************
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}
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Unit CRC;
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{$i defines.inc}
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Interface
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Function Crc32(Const HStr:String):longint;
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Function UpdateCrc32(InitCrc:longint;var InBuf;InLen:Longint):longint;
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Function UpdCrc32(InitCrc:longint;b:byte):longint;
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Implementation
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{*****************************************************************************
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Crc 32
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*****************************************************************************}
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var
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Crc32Tbl : array[0..255] of longint;
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procedure MakeCRC32Tbl;
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var
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crc : longint;
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i,n : byte;
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begin
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for i:=0 to 255 do
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begin
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crc:=i;
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for n:=1 to 8 do
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if odd(crc) then
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crc:=(crc shr 1) xor longint($edb88320)
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else
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crc:=crc shr 1;
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Crc32Tbl[i]:=crc;
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end;
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end;
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{$ifopt R+}
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{$define Range_check_on}
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{$endif opt R+}
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{$R- needed here }
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{CRC 32}
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Function Crc32(Const HStr:String):longint;
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var
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i,InitCrc : longint;
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begin
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if Crc32Tbl[1]=0 then
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MakeCrc32Tbl;
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InitCrc:=longint($ffffffff);
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for i:=1 to Length(Hstr) do
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InitCrc:=Crc32Tbl[byte(InitCrc) xor ord(Hstr[i])] xor (InitCrc shr 8);
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Crc32:=InitCrc;
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end;
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Function UpdateCrc32(InitCrc:longint;var InBuf;InLen:Longint):longint;
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var
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i : word;
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p : pchar;
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begin
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if Crc32Tbl[1]=0 then
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MakeCrc32Tbl;
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p:=@InBuf;
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for i:=1 to InLen do
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begin
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InitCrc:=Crc32Tbl[byte(InitCrc) xor byte(p^)] xor (InitCrc shr 8);
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inc(longint(p));
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end;
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UpdateCrc32:=InitCrc;
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end;
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Function UpdCrc32(InitCrc:longint;b:byte):longint;
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begin
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if Crc32Tbl[1]=0 then
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MakeCrc32Tbl;
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UpdCrc32:=Crc32Tbl[byte(InitCrc) xor b] xor (InitCrc shr 8);
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end;
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{$ifdef Range_check_on}
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{$R+}
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{$undef Range_check_on}
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{$endif Range_check_on}
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end.
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{
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$Log$
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Revision 1.4 2000-09-24 15:06:14 peter
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* use defines.inc
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Revision 1.3 2000/08/13 13:04:38 peter
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* new ppu version
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Revision 1.2 2000/07/13 11:32:39 michael
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+ removed logs
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}
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