Possible improvements of the rpython language¶
Improve the interpreter API¶
Rationalize the modules, and the names, of the different functions needed to implement a pypy module. A typical rpython file is likely to contain many import statements:
from pypy.interpreter.baseobjspace import W_Root from pypy.interpreter.gateway import ObjSpace, W_Root from pypy.interpreter.argument import Arguments from pypy.interpreter.typedef import TypeDef, GetSetProperty from pypy.interpreter.typedef import interp_attrproperty, interp_attrproperty_w from pypy.interpreter.gateway import interp2app from pypy.interpreter.error import OperationError from rpython.rtyper.lltypesystem import rffi, lltype
A more direct declarative way to write Typedef:
class W_Socket(W_Root): _typedef_name_ = 'socket' _typedef_base_ = W_EventualBaseClass @interp2app_method("connect", ['self', ObjSpace, W_Root]) def connect_w(self, space, w_addr): ...
Support for metaclasses written in rpython. For a sample, see the skipped test pypy.objspace.std.test.TestTypeObject.test_metaclass_typedef
- Arithmetic with unsigned integer, and between integer of different signedness, when this is not ambiguous. At least, comparison and assignment with constants should be allowed.
- Allocate variables on the stack, and pass their address (“by reference”) to llexternal functions. For a typical usage, see rpython.rlib.rsocket.RSocket.getsockopt_int.
Extensible type system for llexternal¶
llexternal allows the description of a C function, and conveys the same information about the arguments as a C header. But this is often not enough. For example, a parameter of type int* is converted to rffi.CArrayPtr(rffi.INT), but this information is not enough to use the function. The parameter could be an array of int, a reference to a single value, for input or output…
A “type system” could hold this additional information, and automatically generate some conversion code to ease the usage of the function from rpython. For example:
# double frexp(double x, int *exp); frexp = llexternal("frexp", [rffi.DOUBLE, OutPtr(rffi.int)], rffi.DOUBLE)
OutPtr indicates that the parameter is output-only, which need not to be initialized, and which value is returned to the caller. In rpython the call becomes:
fraction, exponent = frexp(value)
Also, we could imagine that one item in the llexternal argument list corresponds to two parameters in C. Here, OutCharBufferN indicates that the caller will pass a rpython string; the framework will pass buffer and length to the function:
# ssize_t write(int fd, const void *buf, size_t count); write = llexternal("write", [rffi.INT, CharBufferAndSize], rffi.SSIZE_T)
The rpython code that calls this function is very simple:
written = write(fd, data)
compared with the present:
count = len(data) buf = rffi.get_nonmovingbuffer(data) try: written = rffi.cast(lltype.Signed, os_write( rffi.cast(rffi.INT, fd), buf, rffi.cast(rffi.SIZE_T, count))) finally: rffi.free_nonmovingbuffer(data, buf)
Typemaps are very useful for large APIs where the same conversions are needed in many places. XXX example