diff options
Diffstat (limited to 'src/core/bitmath_func.cpp')
| -rw-r--r-- | src/core/bitmath_func.cpp | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/src/core/bitmath_func.cpp b/src/core/bitmath_func.cpp index 9f36ed9a8..53139308a 100644 --- a/src/core/bitmath_func.cpp +++ b/src/core/bitmath_func.cpp @@ -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; +} |