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bugfix/clean up in MP_Float to split an int into 

high and low bits using a mask rather than a union (the initialization
of union changed in cpp0x and the former implementation was "dangerous")
This commit is contained in:
Sébastien Loriot 2011-10-31 11:33:42 +00:00
parent fde8fd1c5a
commit c271379d25
1 changed files with 8 additions and 12 deletions
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20
Number_types/include/CGAL/MP_Float.h
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@ -132,15 +132,6 @@ private:
v.erase(v.begin(), i);
}
// This union is used to convert an unsigned short to a short with
// the same binary representation, without invoking implementation-defined
// behavior (standard 4.7.3).
// It is needed by PGCC, which behaves differently from the others.
union to_signed {
unsigned short us;
short s;
};
// The constructors from float/double/long_double are factorized in the
// following template :
template < typename T >
@ -155,9 +146,14 @@ public:
static
void split(limb2 l, limb & high, limb & low)
{
to_signed l2 = {static_cast<limb>(l)};
low = l2.s;
high = (l - low) >> (8*sizeof(limb));
const unsigned int sizeof_limb=8*sizeof(limb);
const limb2 mask= ~( static_cast<limb2>(-1) << sizeof_limb ); //0000ffff
//Note: For Integer type, if the destination type is signed, the value is unchanged
//if it can be represented in the destination type)
low=static_cast<limb>(l & mask); //extract low bits from l
high = (l - low) >> sizeof_limb; //extract high bits from l
CGAL_postcondition ( l == low + ( static_cast<limb2>(high) << sizeof_limb ) );
}
// Given a limb2, returns the higher limb.