In order to bind more easily to SDL I have added
a bit of new grammar.
1. In a struct or cstruct you can now write
name : type;
as usual or
type name;
for elements. For example:
struct X {
x: int;
int y;
};
is valid. Note the type must be a valid Felix type. So type names
like "char *" or "void *" in the C form will not (currently) work.
2. Felix now recognizes this hackery:
typedef struct { ... } typename;
typedef struct typename1 { ... } typename2;
In the second form, typename1 and typename2 must be identical.
This syntax makes a cstruct NOT a struct, that is, it doesn't
define any struct, just binds to an existing C one.
As a result of this, I have been able to lift many type definitions
straight from SDL header files with only trivial modifications.
This is much easier than laboriously changing int x to x: int
for every field!
For example this C:
/**
* \brief A user-defined event type (event.user.*)
*/
typedef struct SDL_UserEvent
{
Uint32 type; /**< ::SDL_USEREVENT through ::SDL_LASTEVENT-1 */
Uint32 timestamp;
Uint32 windowID; /**< The associated window if any */
Sint32 code; /**< User defined event code */
void *data1; /**< User defined data pointer */
void *data2; /**< User defined data pointer */
} SDL_UserEvent;
translates to this Felix:
/**
* \brief A user-defined event type (event.user.*)
*/
typedef struct SDL_UserEvent
{
uint32 type; /**< ::SDL_USEREVENT through ::SDL_LASTEVENT-1 */
uint32 timestamp;
uint32 windowID; /**< The associated window if any */
int32 n"code"; /**< User defined event code */
address data1; /**< User defined data pointer */
address data2; /**< User defined data pointer */
} SDL_UserEvent;
A quick global change on the integer types was done.
A void* is changed to address. And the field name
"code" caused Felix to barf, so I used this:
n"code"
In case you haven't seen this one before: this is a string form that
represents an identifier with ANY sequence of characters.
It is necessary here because cstructs bind field names from felix
to C and there's no way other simple way to lift a C identifier which
is a Felix "keyword" thing in a particular context. Note "type" didn't
barf, the parser knew it wasn't the statement "type ...".
Note that cstruct can be used for unions too. However there's
a caveat (BUG!) for all cstructs: if they're not full models of the
C struct being bound to, then constructors based on tuples will
silently fail (i.e. write garbage all over the place). This is because
Felix reinterpret casts a tuple to the relevant struct, and the cast
will only put things in the right place if the struct for the tuple and
the specified C struct are layout compatible.
in case you haven't seen them, check out
cenum
cflags
as well. The map **named** C enumerations (you have to use "const"
for an unnamed enumeration or the type binding fails). cenum supports
equality operator. cflags also supports bitwise operators.
I will look to see if C function prototypes can also be handled
a bit more easily too (something like
cfunc type name (type arg, ...);
might work. Note cfun is unrelated! cfun defines a Felix function
which must be translated to a C function with the exact same
signature as a C function type, and can thus be used as a callback,
whereas cfunc (bad name I know) would just be a binding.
--
john skaller
[email protected]
http://felix-lang.org
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