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+{******************************************************************************}
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+{* Simple 32-bits checksum class integrated in existing **********}
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+{* DCPcrypt v2.0 written by David Barton ([email protected]) **********}
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+{******************************************************************************}
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+{* A binary compatible implementation of simple 32-bits checksum *}
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+{******************************************************************************}
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+{* Copyright (C) 2021 Alexander Koblov ([email protected]) *}
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+{* Permission is hereby granted, free of charge, to any person obtaining a *}
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+{* copy of this software and associated documentation files (the "Software"), *}
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+{* to deal in the Software without restriction, including without limitation *}
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+{* the rights to use, copy, modify, merge, publish, distribute, sublicense, *}
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+{* and/or sell copies of the Software, and to permit persons to whom the *}
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+{* Software is furnished to do so, subject to the following conditions: *}
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+{* *}
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+{* The above copyright notice and this permission notice shall be included in *}
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+{* all copies or substantial portions of the Software. *}
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+{* *}
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+{* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR *}
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+{* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, *}
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+{* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL *}
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+{* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER *}
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+{* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING *}
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+{* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER *}
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+{* DEALINGS IN THE SOFTWARE. *}
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+{******************************************************************************}
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+unit dcpchecksum32;
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+
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+{$mode objfpc}{$H+}
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+
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+interface
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+
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+uses
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+ Classes, Sysutils, DCPcrypt2, DCPconst;
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+
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+type
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+
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+ { TDCP_checksum32 }
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+
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+ TDCP_checksum32 = class(TDCP_hash)
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+ protected
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+ CurrentHash: DWORD;
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+ public
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+ class function GetId: integer; override;
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+ class function GetAlgorithm: string; override;
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+ class function GetHashSize: integer; override;
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+ class function SelfTest: boolean; override;
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+ constructor Create(AOwner: TComponent); override;
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+ procedure Init; override;
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+ procedure Burn; override;
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+ procedure Update(const Buffer; Size: longword); override;
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+ procedure Final(var Digest); override;
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+ end;
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+
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+implementation
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+{$R-}{$Q-}
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+
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+{ TDCP_checksum32 }
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+
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+{ TDCP_checksum32.GetHashSize }
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+class function TDCP_checksum32.GetHashSize: integer;
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+begin
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+ Result:= 32;
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+end;
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+
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+{ TDCP_checksum32.GetId }
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+class function TDCP_checksum32.GetId: integer;
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+begin
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+ Result:= DCP_checksum32;
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+end;
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+
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+{ TDCP_checksum32.GetAlgorithm }
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+class function TDCP_checksum32.GetAlgorithm: string;
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+begin
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+ Result:= 'CHECKSUM32';
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+end;
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+
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+{ TDCP_checksum32.SelfTest }
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+class function TDCP_checksum32.SelfTest: boolean;
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+const
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+ Test1Out: array[0..3] of byte=($00, $00, $01, $26); //Verified on 2021-08-24
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+ Test2Out: array[0..3] of byte=($00, $00, $0B, $1F);
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+var
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+ TestHash: TDCP_checksum32;
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+ TestOut: array[0..3] of byte;
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+begin
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+ dcpFillChar(TestOut, SizeOf(TestOut), 0);
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+ TestHash:= TDCP_checksum32.Create(nil);
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+ TestHash.Init;
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+ TestHash.UpdateStr('abc');
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+ TestHash.Final(TestOut);
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+ Result:= CompareMem(@TestOut,@Test1Out,Sizeof(Test1Out));
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+ TestHash.Init;
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+ TestHash.UpdateStr('abcdefghijklmnopqrstuvwxyz');
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+ TestHash.Final(TestOut);
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+ Result:= CompareMem(@TestOut,@Test2Out,Sizeof(Test2Out)) and Result;
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+ TestHash.Free;
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+end;
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+
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+{ TDCP_checksum32.Create }
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+constructor TDCP_checksum32.Create(AOwner: TComponent);
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+begin
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+ inherited Create(AOwner);
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+end;
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+
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+{ TDCP_checksum32.Init }
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+procedure TDCP_checksum32.Init;
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+begin
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+ Burn;
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+ CurrentHash:= 0;
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+ fInitialized:= true;
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+end;
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+
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+{ TDCP_checksum32 }
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+procedure TDCP_checksum32.Burn;
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+begin
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+ CurrentHash:= 0;
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+ fInitialized:= false;
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+end;
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+
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+{ TDCP_checksum32.Update }
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+{$PUSH}{$R-}{$Q-}{$OPTIMIZATION LEVEL4} // no range, no overflow checks, optimize for speed (not size)
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+procedure TDCP_checksum32.Update(const Buffer; Size: longword);
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+var
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+ data: PByte;
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+ iIndex: longword;
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+ iChecksumLocal: DWORD;
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+begin
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+ iChecksumLocal := CurrentHash; //Manipulating the copy "iChecksumLocal" in the loop is overall faster then working directly with property "CurrentHash".
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+ data := @Buffer;
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+ for iIndex := 1 to Size do
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+ begin
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+ iChecksumLocal := iChecksumLocal + data^;
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+ inc(data);
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+ end;
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+ CurrentHash := iChecksumLocal;
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+end;
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+{$POP}
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+
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+{ TDCP_checksum32.Final }
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+procedure TDCP_checksum32.Final(var Digest);
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+begin
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+ if not fInitialized then
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+ raise EDCP_hash.Create('Hash not initialized');
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+ CurrentHash:= SwapEndian(CurrentHash);
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+ Move(CurrentHash, Digest, Sizeof(CurrentHash));
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+ Burn;
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+end;
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+
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+end.
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+
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Denis Bisson