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(svn r11559) -Fix [FS#1505]: overflow when drawing graphics with high company values.

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rubidium
2007-12-02 19:21:56 +00:00
parent b5a902703e
commit faf096f506
3 changed files with 53 additions and 7 deletions
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28
src/core/bitmath_func.cpp
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@@ -25,7 +25,7 @@ const uint8 _ffb_64[64] = {
* way further. If no bit is set return 0.
*
* @param x The value to search
* @param The position of the first bit set
* @return The position of the first bit set
*/
uint8 FindFirstBit(uint32 x)
{
@@ -43,3 +43,29 @@ uint8 FindFirstBit(uint32 x)
return pos;
}
/**
* Search the last set bit in a 32 bit variable.
*
* This algorithm is a static implementation of a log
* conguence search algorithm. It checks the first half
* if there is a bit set search there further. And this
* way further. If no bit is set return 0.
*
* @param x The value to search
* @return The position of the last bit set
*/
uint8 FindLastBit(uint32 x)
{
if (x == 0) return 0;
uint8 pos = 0;
if ((x & 0xffff0000) != 0) { x >>= 16; pos += 16; }
if ((x & 0x0000ff00) != 0) { x >>= 8; pos += 8; }
if ((x & 0x000000f0) != 0) { x >>= 4; pos += 4; }
if ((x & 0x0000000c) != 0) { x >>= 2; pos += 2; }
if ((x & 0x00000002) != 0) { pos += 1; }
return pos;
}