Re: Question for Diego Park and oc you

From:
"Alex Blekhman" <tkfx.REMOVE@yahoo.com>
Newsgroups:
microsoft.public.vc.language
Date:
Sat, 9 Feb 2008 11:03:14 +0200
Message-ID:
<eQ3HbqvaIHA.5164@TK2MSFTNGP03.phx.gbl>
"Jack" wrote:

memcpy(iktransf,keyframes+animations[animation].index,numbones*sizeof(spatial_t<real>));


More info:
spatial_t<real> iktransf[MAX_BONES];
////////////////////////////////
template <class real>
class spatial_t
{
public:
spatial_t();

vector3_t<real> operator*(const vector3_t<real>& vec) const;

matrix3_t<real> rotation;
vector3_t<real> position;
};

Animation is spatial_t<real>, but its member "index" is an
"int".
numbones is an int as well. How can a class be added to an
integer and then memcpy'ed to a spatial<real>
Any thoughts?


Jack, the information you provided doesn't make sense. What is
`keyframes'? According to the declaration of `spatial_t' template
there is no `index' member, too. Also, `matrix3_t' and `vector3_t'
types are undefined, so it's impossible to tell definitely what's
going on there.

It seems that one or more instances of `spatial_t' are copied to
an array with `memcpy' call. Usually copying objects with `memcpy'
is wrong because `memcpy' just copies memory bits and completely
ignores class' copy semantics. Only POD (plain old data)
structures can be copied with defined result.

Unless `matrix3_t' and `vector3_t' classes (and other members of
`spatial_t' template) are specifically designed to be copied with
`memcpy' such copy will break them. Why don't you just assign it:

spatial_t<real>* src =
    keyframes + animations[animation].index;

for(size_t i = 0; i < numbones && i < MAX_BONES; ++i)
{
    iktransf[i] = src[i];
}

HTH
Alex

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