Samples of LIBFFI usage in pypy/rpython

pyffi.py

# Simple sample of LIBFFI usage in pypy/rpython

import sys
from rpython.rtyper.lltypesystem import rffi, lltype
from rpython.rlib import jit_libffi, rdynload, clibffi

def entry_point(argv):
    lib = rdynload.dlopen('libSDL.so')
    SDL_Init = rdynload.dlsym(lib, "SDL_Init")

    argc = 1

    # The cif is initialized with the stuff needed to call the function
    # In pixie the cif was built during the first call to the function.
    exchange_size = 0
    exchange_arg0 = argc * rffi.sizeof(rffi.CCHARP)
    exchange_result = exchange_arg0
    # ARG[0]
    exchange_result = exchange_size
    exchange_size  += rffi.sizeof(rffi.LONG)
    # RETVAL
    exchange_result = exchange_size
    exchange_size  += rffi.sizeof(rffi.LONG)

    cif = lltype.malloc(jit_libffi.CIF_DESCRIPTION, 1, flavor='raw')
    cif.abi = clibffi.FFI_DEFAULT_ABI
    cif.nargs = argc
    cif.rtype = clibffi.cast_type_to_ffitype(rffi.LONG)

    atypes = lltype.malloc(clibffi.FFI_TYPE_PP.TO, argc, flavor='raw')
    atypes[0] = clibffi.cast_type_to_ffitype(rffi.LONG)

    cif.atypes = atypes
    cif.exchange_size = exchange_size
    cif.exchange_result = exchange_result
    cif.exchange_result_libffi = exchange_result
    cif.exchange_args[0] = exchange_arg0
    jit_libffi.jit_ffi_prep_cif(cif)


    # Exchange buffer is built for every call. Filled with arguments that are passed to the function.
    exc = lltype.malloc(rffi.CCHARP.TO, cif.exchange_size, flavor='raw')
    offset_p = rffi.ptradd(exc, cif.exchange_args[0])

    pnt = rffi.cast(rffi.LONGP, offset_p)
    pnt[0] = rffi.cast(rffi.LONG, 0x00000020) # SDL_INIT_VIDEO
    offset_p = rffi.cast(rffi.CCHARP, rffi.ptradd(pnt, rffi.sizeof(rffi.LONG)))


    jit_libffi.jit_ffi_call(cif, SDL_Init, exc)

    offset_p = rffi.ptradd(exc, cif.exchange_result)
    retval = rffi.cast(rffi.LONGP, offset_p)[0]

    print "SDL_Init returned", retval

    lltype.free(exc, flavor='raw')

    return 0

def target(*args):
    return entry_point, None

if __name__=='__main__':
    sys.exit(entry_point(sys.argv))