float bytes = whatever;
//Filter out the bytes with a binary mask
char byteLowest = static_cast<char> (bytes & 255);
char byteSecondLowest = static_cast<char> ((bytes & 65280) >> 8);
char byteSecondHighest = static_cast<char> ((bytes & 16711680) >> 16);
char byteHighest = static_cast<char> ((bytes & 4278190080) >> 24);Bitmasking with floats and doubles
Author
What I want to do is to take a float and bitmask out each of the for bytes in the float and save each byte in a char.
This is how I tried to do it:
float myfloat = whatever;unsigned int myuint = reinterpret_cast<unsigned int&>(myfloat);
Author
Is the point of reinterpret_cast to maintain the bits in the float the exact same way in the int?
quote:Original post by Mr CucumberYeah; it''s one way to reinterpret the underlying bits. Such reinterpretation can also be done with a union, or with a C-style cast, as billybob pointed out.
Is the point of reinterpret_cast to maintain the bits in the float the exact same way in the int?
Author
Im trying to step away from the C ways of doing things. I realised recently that I do a lot of things in deprecated ways. Thanks all anyway.
Author
When you cast it to int you use a reference int, why is that necessary?
[edited by - Mr Cucumber on July 26, 2003 8:26:47 AM]
[edited by - Mr Cucumber on July 26, 2003 8:26:47 AM]
if & isn''t between a type and a name, it is used to get the adress of the variable right to it...
to take the bits out of a float/double , you cant cast it to something else , because cast tries to change the varible to the new type , like if you cast a float like 12.42 to an int , you will get 12 !.
they showed you how to do it and i will explain :
take the float "f" , now the its address "&f" , now you have pointer to the place where the float is in memory , now you tell the compiler that the pointer is not pointing to a float but to and int (the same number of bits) "(*int)&if" .
ok now we want the actuall bits and not a pointer so we tell the compiler we want whats in that address
"int i=*((int*)&f)" , this is little ugly so you can do this in nicer way like this
union
{
float f;
char c[4];
} floatchar;
floatchar.f=1.3242;
printf(floatchar.c[0]);
printf(floatchar.c[1]);
...
you get the idea , enjoy
they showed you how to do it and i will explain :
take the float "f" , now the its address "&f" , now you have pointer to the place where the float is in memory , now you tell the compiler that the pointer is not pointing to a float but to and int (the same number of bits) "(*int)&if" .
ok now we want the actuall bits and not a pointer so we tell the compiler we want whats in that address
"int i=*((int*)&f)" , this is little ugly so you can do this in nicer way like this
union
{
float f;
char c[4];
} floatchar;
floatchar.f=1.3242;
printf(floatchar.c[0]);
printf(floatchar.c[1]);
...
you get the idea , enjoy
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