Changes between Version 43 and Version 44 of HashSourceCodes

Timestamp:

Mar 17, 2013, 6:14:07 PM (11 years ago)

Author:

os

Comment:

--

HashSourceCodes

@@ -459 +459 @@
 }}}
 
+alternate version by TRP
+
+{{{
+unction CalcGabestHash(const Stream: TStream): Int64; overload;
+const HashPartSize = 1 shl 16; // 64 KiB
+
+  procedure UpdateHashFromStream(const Stream: TStream; var Hash:
+Int64); inline;
+  var buffer: Array[0..HashPartSize div SizeOf(Int64) - 1] of Int64;
+      i     : integer;
+  begin
+    Stream.ReadBuffer(buffer[0], SizeOf(buffer));
+    for i := Low(buffer) to High(buffer) do
+      Inc(Hash, buffer[i]);
+  end;
+
+begin
+  result:= Stream.Size;
+
+  if result < HashPartSize then
+  begin
+    // stream too small return invalid hash
+    result:= 0;
+    exit;
+  end;
+
+  // first 64 KiB
+  Stream.Position:= 0;
+  UpdateHashFromStream(Stream, result);
+
+  // last 64 KiB
+  Stream.Seek(-HashPartSize, soEnd);
+  UpdateHashFromStream(Stream, result);
+
+  // use "IntToHex(result, 16);" to get a string and "StrToInt64('$' +
+hash);" to get your Int64 back
+end;
+
+function CalcGabestHash(const FileName: TFileName): Int64; overload;
+var stream: TStream;
+begin
+  stream:= TFileStream.Create(FileName, fmOpenRead or fmShareDenyWrite);
+  try
+    result:= CalcGabestHash(stream);
+  finally
+    stream.Free;
+  end;
+end;
+}}}
+
 
 == Lua ==