I want to get the low 32 bit of a int64 as int32

Question

I have an Int64 value, but I only need the lower 32 bits. Thus I want a quick way to get the Int32 value from the lower 32 bits of the Int64 value.

Thanks

Answer 1

You didn't specify the language, but in many, all you need to do is cast it to an Int32. The top bits will be discarded.

Answer 2

Basically you will want to shift the lower 4 bytes into a 32-bit int.

The discussion in this forum may be of use: http://forums.sun.com/thread.jspa?threadID=764603

Answer 3

Do something like this:

long tempLong = ((yourLong >> 32) << 32); //shift it right then left 32 bits, which zeroes the lower half of the long
int yourInt = (int)(yourLong - tempLong);

This may not be the most compact way to do it, but it seems to be the most readable to me. The following code will extract the high half of the long:

long tempLong = (int)(yourLong >> 32);

Answer 4

If you assign a int64 value into a int32 value, the compiler will automatically do that for you
(as Steven Sudit mentioned):

int64 val64 = ...;
int32 val32 = ...;
...

val32 = val64; // get the low 32 bits
// or
val32 = (val64 >> 32); // get the high 32 bits

and because the compiler may display warnings you can specify the cast

val32 = (int32)val64;