{
* UCheckSum.pas
*
* Static class that gets and checks checksums of data. Uses the MD5 algorithm.
*
* Uses MD5.pas by Matthias Fichtner (modified by Peter Johnson 12 Jan 2006).
*
* $Rev$
* $Date$
*
* ***** BEGIN LICENSE BLOCK *****
*
* Version: MPL 1.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
* the specific language governing rights and limitations under the License.
*
* The Original Code is UCheckSum.pas
*
* The Initial Developer of the Original Code is Peter Johnson
* (http://www.delphidabbler.com/).
*
* Portions created by the Initial Developer are Copyright (C) 2006-2009 Peter
* Johnson. All Rights Reserved.
*
* Contributor(s)
* NONE
*
* ***** END LICENSE BLOCK *****
}
unit UCheckSum;
interface
uses
// Delphi
Classes,
// Project
UBaseObjects;
type
{
TCheckSum:
Static class that gets and checks checksums of data. Uses the MD5 algorithm.
}
TCheckSum = class(TNoConstructObject)
public
class function Calculate(const Stm: TStream): string; overload;
{Calculates MD5 checksum of whole contents of a stream. Position in stream
is preserved.
@param Stm [in] Stream to check.
@return Checksum as string.
}
class function Calculate(const S: string): string; overload;
{Calculates MD5 checksum of a string.
@param S [in] String to check.
@return Checksum as string.
}
class function Compare(const Stm: TStream; const CheckSum: string): Boolean;
overload;
{Compares MD5 checksum of content of a stream against a known checksum.
@param Stm [in] Stream whose checksum is to be compared.
@param CheckSum [in] Known checksum string to compare to stream's
checksum.
@return True if stream's checksum is same as CheckSum, False otherwise.
}
class function Compare(const S, CheckSum: string): Boolean; overload;
{Compares MD5 checksum of a string against a known checksum.
@param S [in] String whose checksum is to be compared.
@param CheckSum [in] Known checksum string to compare to string's
checksum.
@return True if string's checksum is same as CheckSum, False otherwise.
}
end;
implementation
uses
// Delphi
SysUtils,
// 3rd Party
MD5; // must be on search path
{ TCheckSum }
class function TCheckSum.Calculate(const Stm: TStream): string;
{Calculates MD5 checksum of whole contents of a stream. Position in stream is
preserved.
@param Stm [in] Stream to check.
@return Checksum as string.
}
var
StmCopy: TMemoryStream; // copy of stream in memory
StmPos: Int64; // preserves stream position
Context: MD5Context; // MD5 context used in calculating checksum
Digest: MD5Digest; // MD5 digest stores checksum
begin
StmCopy := TMemoryStream.Create;
try
// Copy stream to memory stream preserving position
StmPos := Stm.Position;
Stm.Position := 0;
StmCopy.CopyFrom(Stm, 0);
Stm.Position := StmPos;
// Calculate MD5 checksum of copied stream as string
MD5Init(Context);
MD5Update(Context, StmCopy.Memory, StmCopy.Size);
MD5Final(Context, Digest);
Result := MD5Print(Digest);
finally
FreeAndNil(StmCopy);
end;
end;
class function TCheckSum.Calculate(const S: string): string;
{Calculates MD5 checksum of a string.
@param S [in] String to check.
@return Checksum as string.
}
begin
Result := MD5Print(MD5String(S));
end;
class function TCheckSum.Compare(const S, CheckSum: string): Boolean;
{Compares MD5 checksum of a string against a known checksum.
@param S [in] String whose checksum is to be compared.
@param CheckSum [in] Known checksum string to compare to string's checksum.
@return True if string's checksum is same as CheckSum, False otherwise.
}
begin
Result := Calculate(S) = CheckSum;
end;
class function TCheckSum.Compare(const Stm: TStream;
const CheckSum: string): Boolean;
{Compares MD5 checksum of content of a stream against a known checksum.
@param Stm [in] Stream whose checksum is to be compared.
@param CheckSum [in] Known checksum string to compare to stream's checksum.
@return True if stream's checksum is same as CheckSum, False otherwise.
}
begin
Result := Calculate(Stm) = CheckSum;
end;
end.
