[boost] [endian] Comments on Endian 0.5

From: Dave Dribin (dave-ml_at_[hidden])
Date: 2006-07-20 16:49:23

Hello,

I started a thread on Boost-users about the proposed endian library,  
but it's probably more suitable on the dev list.  Here's a link to  
the thread in the archives:

   <http://lists.boost.org/boost-users/2006/07/20887.php>

I see two issues with the library as  of 0.5.  First, the endian  
classes cannot be used in unions.  And, second the classes cannot be  
used in variable argument lists.  I'm attaching a patch to help  
resolve both of these issues.

In order to be used in a union, a class must not have any  
constructors.  However, removing constructors breaks the following code:

   big4_t x = 42;

My solution was to provide a static init() method to help in these  
situations:

   big4_t x = big_t::init(42);

The second problem shows up using varargs.  For example, this will  
not compile:

   printf("x = %d\n", x);

The solution I came up with is to use operator() to get the native  
value:

   printf("x = %d\n", x());

In my patch, I've also added a check_unions() function to  
endian_test.cpp that tests the sizes of unions.

Thanks,

-Dave