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//
//
// The Nimrod Compiler
// (c) Copyright 2008 Andreas Rumpf
//
// See the file "copying.txt", included in this
// distribution, for details about the copyright.
//
unit nmath;
interface
{$include 'config.inc'}
{@ignore}
uses
nsystem;
{@emit}
function countBits(n: cardinal): int;
function IsPowerOfTwo(x: int): Boolean;
function nextPowerOfTwo(x: int): int;
implementation
function countBits(n: cardinal): int;
const
lookup: array [0..255] of Byte = (
0, 1, 1, 2, 1, 2, 2, 3, 1, 2, 2, 3, 2, 3, 3, 4, 1, 2, 2, 3,
2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5, 1, 2, 2, 3, 2, 3, 3, 4,
2, 3, 3, 4, 3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5,
4, 5, 5, 6, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4, 3, 4, 4, 5,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 2, 3, 3, 4,
3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6,
4, 5, 5, 6, 5, 6, 6, 7, 1, 2, 2, 3, 2, 3, 3, 4, 2, 3, 3, 4,
3, 4, 4, 5, 2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6,
2, 3, 3, 4, 3, 4, 4, 5, 3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5,
4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7, 2, 3, 3, 4, 3, 4, 4, 5,
3, 4, 4, 5, 4, 5, 5, 6, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6,
5, 6, 6, 7, 3, 4, 4, 5, 4, 5, 5, 6, 4, 5, 5, 6, 5, 6, 6, 7,
4, 5, 5, 6, 5, 6, 6, 7, 5, 6, 6, 7, 6, 7, 7, 8
);
var
i: int;
begin
result := 0;
for i := 0 to sizeof(n)-1 do
Inc(result, lookup[ (n shr (i * 8)) and 255 ])
end;
function IsPowerOfTwo(x: int): Boolean;
begin
result := x and -x = x
end;
function nextPowerOfTwo(x: int): int;
begin
result := x - 1;
result := result or (result shr 16);
result := result or (result shr 8);
result := result or (result shr 4);
result := result or (result shr 2);
result := result or (result shr 1);
Inc(result)
end;
end.
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