[MacRuby-devel] Bitfields and arrays in structures
Steven Canfield
stevencanfield.macruby at gmail.com
Mon Jan 4 06:58:34 PST 2010
Hello all,
I'm new to MacRuby so please bear with me. Yesterday I was going
through the buglist and happened upon bug #280 (https://www.macruby.org/trac/ticket/280
) "NSNumber#decimalValue cant convert to ruby object". I created an
objective c file to print out the method signature and I got this:
{?=b8b4b1b1b18[8S]}16 at 0:8
(The ? would be replaced by NSDecimal_ when in MacRuby)
The initial problem is happening inside of RoxorCompiler::convert_type
(compiler.cpp) which doesn't handle the _C_BFLD type. Upon some
further testing, it also doesn't handle the [8S] part (array of 8
short), which is also bug #178 (https://www.macruby.org/trac/ticket/
178). So it seems like I need to add bitfield and structure array
support.
My question is, how is all of this supposed to be represented. I
assume the arrays part can just be ArrayType, while we probably want
to treat a bitfield declaration as just a regular structure, i.e.
typedef struct {
signed int _exponent:8;
unsigned int _length:4; // length == 0 && isNegative -> NaN
unsigned int _isNegative:1;
unsigned int _isCompact:1;
unsigned int _reserved:18;
unsigned short _mantissa[NSDecimalMaxSize];
} NSDecimal;
would be interpreted as
typedef struct {
signed int _exponent;
unsigned int _length; // length == 0 && isNegative -> NaN
unsigned int _isNegative;
unsigned int _isCompact;
unsigned int _reserved;
unsigned short _mantissa[NSDecimalMaxSize];
} NSDecimal;
The only problem I see with this is that we have to convert back to
NSDecimal packing on return. Maybe it would be better to have a ruby
class that provides accessors to the NSDecimal similar to Boxed (or
modify Boxed to handle this situation).
Just looking for a little bit of guidance,
-Steve
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