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POImplementation of FNV
 

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  1. POImplementation of FNV
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    <p>I am trying to implement FNV hash from <a href="http://isthe.com/chongo/tech/comp/fnv/" rel="nofollow">http://isthe.com/chongo/tech/comp/fnv/</a></p> <p>I converted the PowerBasic's inline asm on that page into Delphi.</p> <pre><code> function ReadFileToMem(sPath:string):Pointer; var hFile: THandle; pBuffer: Pointer; dSize: DWORD; dRead: DWORD; begin hFile := CreateFile(PChar(sPath), GENERIC_READ, FILE_SHARE_READ, nil, OPEN_EXISTING, 0, 0); if hFile &lt;&gt; 0 then dSize := GetFileSize(hFile, nil); if dSize &lt;&gt; 0 then begin SetFilePointer(hFile, 0, nil, FILE_BEGIN); GetMem(Result, dSize); ReadFile(hFile, Result^, dSize, dRead, nil); if dRead = 0 then MessageBox(0, PChar('Error reading file.'), PChar('Read Error'), MB_ICONEXCLAMATION) end; CloseHandle(hFile); end; function GetPointerSize(lpBuffer: Pointer): Cardinal; // Function by ErazerZ begin if lpBuffer = nil then Result := Cardinal(-1) else Result := Cardinal(Pointer(Cardinal(lpBuffer) -4)^) and $7FFFFFFC -4; end; FUNCTION FNV32( dwOffset : Pointer; dwLen : DWORD; offset_basis : DWORD) : DWORD ; asm mov esi, dwOffset //;esi = ptr to buffer mov ecx, dwLen //;ecx = length of buffer (counter) mov eax, offset_basis //;set to 2166136261 for FNV-1 mov edi, 16777619//&amp;h01000193 //;FNV_32_PRIME = 16777619 xor ebx, ebx //;ebx = 0 @nextbyte: mul edi //;eax = eax * FNV_32_PRIME mov bl, [esi] //;bl = byte from esi xor eax, ebx //;al = al xor bl inc esi //;esi = esi + 1 (buffer pos) dec ecx //;ecx = ecx - 1 (counter) jnz @nextbyte //;if ecx is 0, jmp to NextByte mov @result, eax //;else, function = eax end; procedure TForm1.Button1Click(Sender: TObject); var pFile : Pointer; hFile : Cardinal; begin //Profiler1['Test'].Start; pFile := ReadFileToMem(fn); hFile := FNV32(pFile,GetPointerSize(pFile),2166136261); //Profiler1['Test'].Stop; //OutputDebugString(pchar(Profiler1['Test'].AsText[tiAll])); OutputDebugString(pchar(inttostr(hFile))); end; </code></pre> <p>If a size of given file is more that 200KB, the output is random (hash) number. Am I missing something?</p>
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