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import sys
from pypy.rpython.lltypesystem import lltype, rffi
from pypy.rlib import clibffi, jit

FFI_ABI = clibffi.FFI_ABI
SIZE_OF_FFI_ARG = rffi.sizeof(clibffi.ffi_arg)

# Usage: for each C function, make one CIF_DESCRIPTION block of raw
# memory.  Initialize it by filling all its fields apart from 'cif'.
# The 'atypes' points to an array of ffi_type pointers; a reasonable
# place to locate this array's memory is in the same block of raw
# memory, by allocating more than sizeof(CIF_DESCRIPTION).
# The four fields 'abi', 'nargs', 'rtype', 'atypes' are the same as
# the arguments to ffi_prep_cif().
# Following this, we find jit_libffi-specific information:
#  - 'exchange_size': an integer that tells how big a buffer we must
#    allocate to do the call; this buffer should have enough room at the
#    beginning for an array of NARGS pointers which is initialized
#    internally by jit_ffi_call().
#  - 'exchange_result': the offset in that buffer for the result of the call.
#    (this and the other offsets must be at least NARGS * sizeof(void*).)
#  - 'exchange_result_libffi': the actual offset passed to ffi_call().
#    Differs on big-endian machines if the result is an integer type smaller
#    than SIZE_OF_FFI_ARG (blame libffi).
#  - 'exchange_args[nargs]': the offset in that buffer for each argument.

CIF_DESCRIPTION = lltype.Struct(
    ('cif', FFI_CIF),
    ('abi', lltype.Signed),    # these 4 fields could also be read directly
    ('nargs', lltype.Signed),  # from 'cif', but doing so adds a dependency
    ('rtype', FFI_TYPE_P),     # on the exact fields available from ffi_cif.
    ('atypes', FFI_TYPE_PP),   #
    ('exchange_size', lltype.Signed),
    ('exchange_result', lltype.Signed),
    ('exchange_result_libffi', lltype.Signed),
    ('exchange_args', lltype.Array(lltype.Signed,
                          hints={'nolength': True, 'immutable': True})),
    hints={'immutable': True})


def jit_ffi_prep_cif(cif_description):
    """Minimal wrapper around ffi_prep_cif().  Call this after
    cif_description is initialized, in order to fill the last field: 'cif'.
    res = clibffi.c_ffi_prep_cif(cif_description.cif,
    return rffi.cast(lltype.Signed, res)

@jit.oopspec("libffi_call(cif_description, func_addr, exchange_buffer)")
def jit_ffi_call(cif_description, func_addr, exchange_buffer):
    """Wrapper around ffi_call().  Must receive a CIF_DESCRIPTION_P that
    describes the layout of the 'exchange_buffer'.
    buffer_array = rffi.cast(rffi.VOIDPP, exchange_buffer)
    for i in range(cif_description.nargs):
        data = rffi.ptradd(exchange_buffer, cif_description.exchange_args[i])
        buffer_array[i] = data
    resultdata = rffi.ptradd(exchange_buffer,
    clibffi.c_ffi_call(cif_description.cif, func_addr,
                       rffi.cast(rffi.VOIDP, resultdata),

# ____________________________________________________________

class types(object):
    This namespace contains the mapping the JIT needs from ffi types to
    a less strict "kind" character.

    def _import(cls):
        prefix = 'ffi_type_'
        for key, value in clibffi.__dict__.iteritems():
            if key.startswith(prefix):
                name = key[len(prefix):]
                setattr(cls, name, value)
        cls.slong = clibffi.cast_type_to_ffitype(rffi.LONG)
        cls.ulong = clibffi.cast_type_to_ffitype(rffi.ULONG)
        cls.slonglong = clibffi.cast_type_to_ffitype(rffi.LONGLONG)
        cls.ulonglong = clibffi.cast_type_to_ffitype(rffi.ULONGLONG)
        cls.signed = clibffi.cast_type_to_ffitype(rffi.SIGNED)
        cls.wchar_t = clibffi.cast_type_to_ffitype(lltype.UniChar)
        del cls._import

    def getkind(ffi_type):
        """Returns 'v' for void, 'f' for float, 'i' for signed integer,
        'u' for unsigned integer, 'S' for singlefloat, 'L' for long long
        integer (signed or unsigned), '*' for struct, or '?' for others
        (e.g. long double).
        if   ffi_type == types.void:    return 'v'
        elif ffi_type == types.double:  return 'f'
        elif ffi_type == types.float:   return 'S'
        elif ffi_type == types.pointer: return 'i'
        elif ffi_type == types.schar:   return 'i'
        elif ffi_type == types.uchar:   return 'u'
        elif ffi_type == types.sshort:  return 'i'
        elif ffi_type == types.ushort:  return 'u'
        elif ffi_type == types.sint:    return 'i'
        elif ffi_type == types.uint:    return 'u'
        elif ffi_type == types.slong:   return 'i'
        elif ffi_type == types.ulong:   return 'u'
        elif ffi_type == types.sint8:   return 'i'
        elif ffi_type == types.uint8:   return 'u'
        elif ffi_type == types.sint16:  return 'i'
        elif ffi_type == types.uint16:  return 'u'
        elif ffi_type == types.sint32:  return 'i'
        elif ffi_type == types.uint32:  return 'u'
        ## (note that on 64-bit platforms, types.sint64 == types.slong and the
        ## case == caught above)
        elif ffi_type == types.sint64:  return 'L'
        elif ffi_type == types.uint64:  return 'L'
        elif types.is_struct(ffi_type): return '*'
        return '?'

    def is_struct(ffi_type):
        return rffi.getintfield(ffi_type, 'c_type') == FFI_TYPE_STRUCT