Title: ed2k hash
Question: how calculate ed2k hash (for eMule, edonkey,...)?
ie: 965c013e991ee246d63d45ea71954c4d
ed2k://|file|The_Two_Towers-The_Purist_Edit-Trailer.avi|14997504|965c013e991ee246d63d45ea71954c4d|/
Answer:
http://en.wikipedia.org/wiki/Ed2k_link
The ed2k hash function is based on MD4 but differs for files in excess of approximately 9.5 MB. The file is divided into 9.28Mb (the exact value is 9,728,000 byte) chunks and the hash is calculated for each one. The resulting hash table is hashed once again, and the final value is used as a part of the ed2k link.
code:
// require delphi component DCPcrypt v2 Beta 3 - http://www.cityinthesky.co.uk/files/dcpcrypt2.zip
uses
..., DCPmd4;
Function GetEd2kHash(FN:string):string;
const
chunks=9728000;
var
Hash: TDCP_md4;
Digest: array[0..15] of byte; //16 bajtni hash
Source: TFileStream;
ed2k:TMemoryStream;
sizedc,i,k: integer;
s: string;
begin
Result:='';
Source:= nil;
try
Source:= TFileStream.Create(FN,fmOpenRead);
except
MessageDlg('Unable to open file',mtError,[mbOK],0);
end;
if Source nil then
begin
Hash:= TDCP_md4.Create(NIL); // create the hash
ed2k :=TMemoryStream.Create;
sizedc:=(Source.Size div chunks)+1;
if Source.Size mod chunks =0 then dec(sizedc);
for i:=1 to sizedc do
begin
Hash.Init; // initialize it
if i=sizedc then
Hash.UpdateStream(Source,(Source.Size mod chunks))
else
Hash.UpdateStream(Source,chunks); // hash the stream contents
Hash.Final(Digest);
for k:=0 to 15 do
begin ed2k.WriteBuffer(Digest[k],1); end;
//possible usage ProgressBar1.Position:=100*i div sizedc;
end;
ed2k.Seek(0,soFromBeginning);
Hash.Init;
Hash.UpdateStream(ed2k, ed2k.Size); // hash the stream contents
Hash.Final(Digest);
ed2k.Free;
Hash.Free;
s:= '';
for i:= 0 to 15 do
s:= s +IntToHex(Digest[i],2);
Result:=s;
end;
Source.Free;
end;