| Preliminary notes/documentation for the calldll module, version 0.2. |
| ==================================================================== |
| |
| Calldll allows you to call random C functions from python without writing any |
| C code. It is mainly meant to call MacOS toolbox routines for which no Python |
| wrapper module is available. It is also incomplete, in that only a few argument |
| types are currently supported. Please let me know which other argument types |
| you need, and/or whether you have any ideas on a general "escape" allowing people |
| to pass anything. |
| |
| The module exports three functions: |
| - symtable = getlibrary(libraryname) |
| Get a reference to import library libraryname. "InterfaceLib" is the most commonly |
| used one, containing most toolbox routines. The symbol table can be used |
| to lookup routines to be passed to newcall: "symtable.WaitNextEvent" will |
| return the address of routine WaitNextEvent. and so will "symtable['WaitNextEvent']". |
| The symtable is a mapping, so you can use keys() and len(...) to inspect it. |
| - symtable = getdiskfragment(file) |
| Load the specified file (given by fsspec or filename) and return a reference to |
| its symboltable. |
| - callable = newcall(routine, returntype, [argtype, ...]) |
| Return a callable object. You specify the C routine to be called (as explained above), |
| the type of the return value and the argument types. The resulting object can |
| be called from Python code in the normal way, and typechecking on arguments is |
| performed (but, of course, if you specify incorrect argument types in this call |
| you may well crash your machine). Printing a callable will give you a description |
| of the (C-) calling sequence. |
| |
| The C return value can be one of 'None', 'Byte', 'Short', 'Long', 'Pstring' (a pascal |
| string returned by address, copied to a Python string), 'Cobject' (a wrapper around a void |
| pointer), 'Handle' (a new handle, returned as a Res.Resource object) or 'OSErr' (which raises |
| MacOS.Error if non-zero). |
| |
| Arguments can be any of 'InByte', 'InShort', 'InLong', 'InString' (a python string, with the |
| address of the data passed to the C routine, so be careful!), 'InPstring' (a python string copied |
| to a Str255 and passed by address), 'InCobject', 'InHandle', 'OutByte' (storage is allocated for |
| a single byte, the address passed to C and the resulting value returned to Python), 'OutShort', |
| 'OutLong', 'OutPstring' (again: storage pre-allocated and the address passed to C), 'OutCobject' |
| (storage for a void * is allocated, this void ** is passed to C and the resulting void * is |
| encapsulated in the Cobject returned) or 'OutHandle' (ditto, which means that this is usually *not* |
| what you use, you normally use 'InHandle' because most toolbox calls expect you to preallocate |
| the handle). |
| |
| All values to be returned (from the return value and the Out arguments) are collected. If there |
| aren't any None is returned, if there is one value this value is returned, if there are multiple |
| values a tuple is returned. |
| |
| There is test code in testcalldll.py, and a minimal example in samplecalldll.py. |