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author | Bruno de Oliveira Abinader <bruno@mapbox.com> | 2016-10-29 18:13:12 +0300 |
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committer | Bruno de Oliveira Abinader <bruno@mapbox.com> | 2016-10-31 16:53:07 +0200 |
commit | 38f536049a8ed8f4bdf7706f4afcbbaf06c974c9 (patch) | |
tree | f65bb6ad0ebde1840e523b18d539f122548194ab /src/mbgl/math | |
parent | a70bfd89108cf1aef75181819ae43e550a69255e (diff) | |
download | qtlocation-mapboxgl-38f536049a8ed8f4bdf7706f4afcbbaf06c974c9.tar.gz |
[core] Moved util::log2 to its own header
- Added util::{MIN,MAX}_ZOOM_F to avoid consecutive conversions from
double to float
- Move util::log2 to its own header (part of mbgl/math)
Diffstat (limited to 'src/mbgl/math')
-rw-r--r-- | src/mbgl/math/log2.cpp | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/src/mbgl/math/log2.cpp b/src/mbgl/math/log2.cpp new file mode 100644 index 0000000000..222e67dbd7 --- /dev/null +++ b/src/mbgl/math/log2.cpp @@ -0,0 +1,25 @@ +#include <mbgl/math/log2.hpp> + +namespace mbgl { +namespace util { + +// From http://stackoverflow.com/questions/3272424/compute-fast-log-base-2-ceiling +uint32_t ceil_log2(uint64_t x) { + static const uint64_t t[6] = {0xFFFFFFFF00000000, 0x00000000FFFF0000, + 0x000000000000FF00, 0x00000000000000F0, + 0x000000000000000C, 0x0000000000000002}; + uint32_t y = (((x & (x - 1)) == 0) ? 0 : 1); + uint32_t j = 32; + + for (const auto& i : t) { + const uint32_t k = (((x & i) == 0) ? 0 : j); + y += k; + x >>= k; + j >>= 1; + } + + return y; +} + +} // namespace util +} // namespace mbgl |