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delphiconstantsdelphi-7delphi-5int64

How to declare an Int64 constant?

i'm trying to define a constant in Delphi:

const
   FNV_offset_basis = 14695981039346656037;

And i get the error: Integer constant too large

Note: 14,695,981,039,346,656,037 decimal is equal to 0x14650FB0739D0383 hex.

How can i declare this Int64 constant?

Some other things i've tried:

const
   FNV_offset_basis: Int64 = 14695981039346656037;
   FNV_offset_basis = Int64(14695981039346656037);
   FNV_offset_basis: Int64 = Int64(14695981039346656037);


var
   offset: LARGE_INTEGER;
begin
   //recalculate constant every function call
   offset.LowPart = $739D0383;
   offset.HighPart = $14650FB0;

Correction

My fundamental assumption was wrong.

Pasting 14695981039346656037 into Windows 7 Calculator, and converting to hex, led me to believe that the hex equivalent of 14695981039346656037 is 0x14650FB0739D0383:

enter image description here

That is incorrect.

So when i saw a 16-digit hex value, with the high bit not set, i presumed it could fit in a 64-bit signed integer.

In reality the hex equivalent of 14695981039346656037 is...something else. Rob, you were right! (probably)

Solution

  • Your hex conversion in the question is incorrect. That number is actually $cbf29ce484222000 and does not fit into a signed 64 bit integer. You would need an unsigned 64 bit integer to represent it. There is no unsigned UInt64 in Delphi 5 and so you are out of luck. There is no integral data type that can represent that number in your version of Delphi.

    You could perhaps interpret the bit pattern as a signed value if that does what you need. In that case you would have a negative number.