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Added integer log2 implementation with compute_log2 class

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This commit is contained in:
Christophe Riccio 2011-10-13 19:07:54 +01:00
parent c004d95bdf
commit 742013f6d3
2 changed files with 13 additions and 14 deletions
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3
glm/gtx/integer.hpp
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@ -60,7 +60,8 @@ namespace glm
//! Returns the log2 of x. Can be reliably using to compute mipmap count from the texture size.
//! From GLM_GTX_integer extension.
unsigned int log2(unsigned int x);
template <typename genType>
genType log2(genType const & x);
//! Returns the floor log2 of x.
//! From GLM_GTX_integer extension.

24
glm/gtx/integer.inl
View file

@ -53,23 +53,21 @@ namespace detail
x += (x >> 16);
return(x & 0x0000003f);
}
}//namespace detail
template <>
struct compute_log2<float_or_int_value::INT>
{
template <typename T>
T operator() (T const & Value) const
{
#if(GLM_COMPILER & (GLM_COMPILER_VC | GLM_COMPILER_GCC))
GLM_FUNC_QUALIFIER unsigned int log2(unsigned int x)
{
return x <= 1 ? 0 : unsigned(32) - nlz(x - 1u);
}
return Value <= T(1) ? T(0) : T(32) - nlz(Value - T(1));
#else
GLM_FUNC_QUALIFIER unsigned int log2(unsigned int x)
{
return unsigned(32) - nlz(x - 1u);
}
return T(32) - nlz(Value - T(1));
#endif
}
};
}//namespace detail
// Henry Gordon Dietz: http://aggregate.org/MAGIC/
unsigned int floor_log2(unsigned int x)