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  1. PO
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    <p>Well here's a option that would do the conversion as fast as I can think of.</p> <p>Features of the code:</p> <ul> <li>Only one allocation for the string (so no realloc and no move or copy)</li> <li>Fast read from the file.</li> </ul> <p>Since we know that one byte translates to exactly two hexadecimal chars, we know our result string needs to be exactly twice the size of the file. We allocate an string of the required size and then we read from the file in large-enough blocks so the OS can optimize it for us (reading byte-by-byte is evil). We use an actual string but we write into the string using an pointer:</p> <pre><code>function TEditorDeschidereDeCredite.FileToHex(FileName: string): AnsiString; var FS:TFileStream; PS:PAnsiChar; Block:array[0..1023] of byte; // 1Kb len,i,pos:Integer; B:Byte; const Nibbs: array[0..15] of AnsiChar = ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'); begin FS := TFileStream.Create(FileName, fmOpenRead); try Result := ''; SetLength(Result, FS.Size * 2); PS := PAnsiChar(Result); pos := 0; // position into the result string len := FS.Read(Block, SizeOf(Block)); while len &lt;&gt; 0 do begin for i:=0 to len-1 do begin B := Block[i]; PS[pos] := Nibbs[B div $F]; Inc(pos); PS[pos] := Nibbs[B mod $F]; Inc(pos); end; len := FS.Read(Block, SizeOf(Block)); end; finally FS.Free; end; end; </code></pre> <p>P.S: I'm using AnsiString, and PAnsiChar so the code works also works with Unicode Delphi. If you happen to be on Delphi 2010 find a way to use this in it's current form (AnsiString) so you can skip the conversions.</p>
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    1. PODelphi: how to efficently read a big binary file, converting it to hexadecimal for passing it as a varbinary(max) parameter?
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    1. USCosmin Prund
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    1. PODelphi: how to efficently read a big binary file, converting it to hexadecimal for passing it as a varbinary(max) parameter?
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    1. COThanks for this that does the conversion work as I desired, I modified it for D2009 as you suggested. Anyway this still doesn't make me certain that this is the most efficient way for doing FileToHex in delphi, but it could be.
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    2. COThis is going to take two comments, one comment is too short. Sorry. I wasn't suggesting any changes, I said I used AnsiString and not String so it also works effectively on Delphi 2009 and Delphi 2010. On those platforms the default String type is actually UTF16 encoded Unicode, so it uses 2 bytes per char! Ansi string is the ancient 1 byte char, so there's no overhead. In Unicode Delphi's notation, one byte converts to two chars when translated to hex, and that ocupies 4 bytes! So your 100Mb file takes up 400Mb in RAM.
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    3. CO... what I was suggesting was to find a way to keep it as AnsiString ALL THE WAY to the stored procedure in the DB! If at any point you do a conversion to UTF16 then you pay the penalty for the 2 bytes chars. This is why using text to represent non-text data is such a problem: Just imagine your 100Mb file converted to a 400Mb UTF16 string, then converted to UTF8 (200Mb) on the way to the SQL server and converted back to UTF16 (400Mb) if the stored procedure wants unicode text. I don't actually know how text is passed to SQL on the wire, this just an scare-scenario.
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