cpython/Modules/_io/iobase.c

/*
    An implementation of the I/O abstract base classes hierarchy
    as defined by PEP 3116 - "New I/O"
    
    Classes defined here: IOBase, RawIOBase.
    
    Written by Amaury Forgeot d'Arc and Antoine Pitrou
*/


#define PY_SSIZE_T_CLEAN
#include "Python.h"
#include "structmember.h"
#include "_iomodule.h"

/*
 * IOBase class, an abstract class
 */

typedef struct {
    PyObject_HEAD
    
    PyObject *dict;
    PyObject *weakreflist;
} iobase;

PyDoc_STRVAR(iobase_doc,
    "The abstract base class for all I/O classes, acting on streams of\n"
    "bytes. There is no public constructor.\n"
    "\n"
    "This class provides dummy implementations for many methods that\n"
    "derived classes can override selectively; the default implementations\n"
    "represent a file that cannot be read, written or seeked.\n"
    "\n"
    "Even though IOBase does not declare read, readinto, or write because\n"
    "their signatures will vary, implementations and clients should\n"
    "consider those methods part of the interface. Also, implementations\n"
    "may raise UnsupportedOperation when operations they do not support are\n"
    "called.\n"
    "\n"
    "The basic type used for binary data read from or written to a file is\n"
    "bytes. bytearrays are accepted too, and in some cases (such as\n"
    "readinto) needed. Text I/O classes work with str data.\n"
    "\n"
    "Note that calling any method (even inquiries) on a closed stream is\n"
    "undefined. Implementations may raise IOError in this case.\n"
    "\n"
    "IOBase (and its subclasses) support the iterator protocol, meaning\n"
    "that an IOBase object can be iterated over yielding the lines in a\n"
    "stream.\n"
    "\n"
    "IOBase also supports the :keyword:`with` statement. In this example,\n"
    "fp is closed after the suite of the with statement is complete:\n"
    "\n"
    "with open('spam.txt', 'r') as fp:\n"
    "    fp.write('Spam and eggs!')\n");

/* Use this macro whenever you want to check the internal `closed` status
   of the IOBase object rather than the virtual `closed` attribute as returned
   by whatever subclass. */

_Py_IDENTIFIER(__IOBase_closed);
#define IS_CLOSED(self) \
    _PyObject_HasAttrId(self, &PyId___IOBase_closed)

/* Internal methods */
static PyObject *
iobase_unsupported(const char *message)
{
    PyErr_SetString(IO_STATE->unsupported_operation, message);
    return NULL;
}

/* Positionning */

PyDoc_STRVAR(iobase_seek_doc,
    "Change stream position.\n"
    "\n"
    "Change the stream position to the given byte offset. The offset is\n"
    "interpreted relative to the position indicated by whence.  Values\n"
    "for whence are:\n"
    "\n"
    "* 0 -- start of stream (the default); offset should be zero or positive\n"
    "* 1 -- current stream position; offset may be negative\n"
    "* 2 -- end of stream; offset is usually negative\n"
    "\n"
    "Return the new absolute position.");

static PyObject *
iobase_seek(PyObject *self, PyObject *args)
{
    return iobase_unsupported("seek");
}

PyDoc_STRVAR(iobase_tell_doc,
             "Return current stream position.");

static PyObject *
iobase_tell(PyObject *self, PyObject *args)
{
    _Py_IDENTIFIER(seek);

    return _PyObject_CallMethodId(self, &PyId_seek, "ii", 0, 1);
}

PyDoc_STRVAR(iobase_truncate_doc,
    "Truncate file to size bytes.\n"
    "\n"
    "File pointer is left unchanged.  Size defaults to the current IO\n"
    "position as reported by tell().  Returns the new size.");

static PyObject *
iobase_truncate(PyObject *self, PyObject *args)
{
    return iobase_unsupported("truncate");
}

/* Flush and close methods */

PyDoc_STRVAR(iobase_flush_doc,
    "Flush write buffers, if applicable.\n"
    "\n"
    "This is not implemented for read-only and non-blocking streams.\n");

static PyObject *
iobase_flush(PyObject *self, PyObject *args)
{
    /* XXX Should this return the number of bytes written??? */
    if (IS_CLOSED(self)) {
        PyErr_SetString(PyExc_ValueError, "I/O operation on closed file.");
        return NULL;
    }
    Py_RETURN_NONE;
}

PyDoc_STRVAR(iobase_close_doc,
    "Flush and close the IO object.\n"
    "\n"
    "This method has no effect if the file is already closed.\n");

static int
iobase_closed(PyObject *self)
{
    PyObject *res;
    int closed;
    /* This gets the derived attribute, which is *not* __IOBase_closed
       in most cases! */
    res = PyObject_GetAttr(self, _PyIO_str_closed);
    if (res == NULL)
        return 0;
    closed = PyObject_IsTrue(res);
    Py_DECREF(res);
    return closed;
}

static PyObject *
iobase_closed_get(PyObject *self, void *context)
{
    return PyBool_FromLong(IS_CLOSED(self));
}

PyObject *
_PyIOBase_check_closed(PyObject *self, PyObject *args)
{
    if (iobase_closed(self)) {
        PyErr_SetString(PyExc_ValueError, "I/O operation on closed file.");
        return NULL;
    }
    if (args == Py_True)
        return Py_None;
    else
        Py_RETURN_NONE;
}

/* XXX: IOBase thinks it has to maintain its own internal state in
   `__IOBase_closed` and call flush() by itself, but it is redundant with
   whatever behaviour a non-trivial derived class will implement. */

static PyObject *
iobase_close(PyObject *self, PyObject *args)
{
    PyObject *res;
    _Py_IDENTIFIER(__IOBase_closed);

    if (IS_CLOSED(self))
        Py_RETURN_NONE;

    res = PyObject_CallMethodObjArgs(self, _PyIO_str_flush, NULL);
    _PyObject_SetAttrId(self, &PyId___IOBase_closed, Py_True);
    if (res == NULL) {
        return NULL;
    }
    Py_XDECREF(res);
    Py_RETURN_NONE;
}

/* Finalization and garbage collection support */

int
_PyIOBase_finalize(PyObject *self)
{
    PyObject *res;
    PyObject *tp, *v, *tb;
    int closed = 1;
    int is_zombie;

    /* If _PyIOBase_finalize() is called from a destructor, we need to
       resurrect the object as calling close() can invoke arbitrary code. */
    is_zombie = (Py_REFCNT(self) == 0);
    if (is_zombie) {
        ++Py_REFCNT(self);
    }
    PyErr_Fetch(&tp, &v, &tb);
    /* If `closed` doesn't exist or can't be evaluated as bool, then the
       object is probably in an unusable state, so ignore. */
    res = PyObject_GetAttr(self, _PyIO_str_closed);
    if (res == NULL)
        PyErr_Clear();
    else {
        closed = PyObject_IsTrue(res);
        Py_DECREF(res);
        if (closed == -1)
            PyErr_Clear();
    }
    if (closed == 0) {
        res = PyObject_CallMethodObjArgs((PyObject *) self, _PyIO_str_close,
                                          NULL);
        /* Silencing I/O errors is bad, but printing spurious tracebacks is
           equally as bad, and potentially more frequent (because of
           shutdown issues). */
        if (res == NULL)
            PyErr_Clear();
        else
            Py_DECREF(res);
    }
    PyErr_Restore(tp, v, tb);
    if (is_zombie) {
        if (--Py_REFCNT(self) != 0) {
            /* The object lives again. The following code is taken from
               slot_tp_del in typeobject.c. */
            Py_ssize_t refcnt = Py_REFCNT(self);
            _Py_NewReference(self);
            Py_REFCNT(self) = refcnt;
            /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
             * we need to undo that. */
            _Py_DEC_REFTOTAL;
            /* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
             * chain, so no more to do there.
             * If COUNT_ALLOCS, the original decref bumped tp_frees, and
             * _Py_NewReference bumped tp_allocs:  both of those need to be
             * undone.
             */
#ifdef COUNT_ALLOCS
            --Py_TYPE(self)->tp_frees;
            --Py_TYPE(self)->tp_allocs;
#endif
            return -1;
        }
    }
    return 0;
}

static int
iobase_traverse(iobase *self, visitproc visit, void *arg)
{
    Py_VISIT(self->dict);
    return 0;
}

static int
iobase_clear(iobase *self)
{
    if (_PyIOBase_finalize((PyObject *) self) < 0)
        return -1;
    Py_CLEAR(self->dict);
    return 0;
}

/* Destructor */

static void
iobase_dealloc(iobase *self)
{
    /* NOTE: since IOBaseObject has its own dict, Python-defined attributes
       are still available here for close() to use.
       However, if the derived class declares a __slots__, those slots are
       already gone.
    */
    if (_PyIOBase_finalize((PyObject *) self) < 0) {
        /* When called from a heap type's dealloc, the type will be
           decref'ed on return (see e.g. subtype_dealloc in typeobject.c). */
        if (PyType_HasFeature(Py_TYPE(self), Py_TPFLAGS_HEAPTYPE))
            Py_INCREF(Py_TYPE(self));
        return;
    }
    _PyObject_GC_UNTRACK(self);
    if (self->weakreflist != NULL)
        PyObject_ClearWeakRefs((PyObject *) self);
    Py_CLEAR(self->dict);
    Py_TYPE(self)->tp_free((PyObject *) self);
}

/* Inquiry methods */

PyDoc_STRVAR(iobase_seekable_doc,
    "Return whether object supports random access.\n"
    "\n"
    "If False, seek(), tell() and truncate() will raise UnsupportedOperation.\n"
    "This method may need to do a test seek().");

static PyObject *
iobase_seekable(PyObject *self, PyObject *args)
{
    Py_RETURN_FALSE;
}

PyObject *
_PyIOBase_check_seekable(PyObject *self, PyObject *args)
{
    PyObject *res  = PyObject_CallMethodObjArgs(self, _PyIO_str_seekable, NULL);
    if (res == NULL)
        return NULL;
    if (res != Py_True) {
        Py_CLEAR(res);
        iobase_unsupported("File or stream is not seekable.");
        return NULL;
    }
    if (args == Py_True) {
        Py_DECREF(res);
    }
    return res;
}

PyDoc_STRVAR(iobase_readable_doc,
    "Return whether object was opened for reading.\n"
    "\n"
    "If False, read() will raise UnsupportedOperation.");

static PyObject *
iobase_readable(PyObject *self, PyObject *args)
{
    Py_RETURN_FALSE;
}

/* May be called with any object */
PyObject *
_PyIOBase_check_readable(PyObject *self, PyObject *args)
{
    PyObject *res  = PyObject_CallMethodObjArgs(self, _PyIO_str_readable, NULL);
    if (res == NULL)
        return NULL;
    if (res != Py_True) {
        Py_CLEAR(res);
        iobase_unsupported("File or stream is not readable.");
        return NULL;
    }
    if (args == Py_True) {
        Py_DECREF(res);
    }
    return res;
}

PyDoc_STRVAR(iobase_writable_doc,
    "Return whether object was opened for writing.\n"
    "\n"
    "If False, write() will raise UnsupportedOperation.");

static PyObject *
iobase_writable(PyObject *self, PyObject *args)
{
    Py_RETURN_FALSE;
}

/* May be called with any object */
PyObject *
_PyIOBase_check_writable(PyObject *self, PyObject *args)
{
    PyObject *res  = PyObject_CallMethodObjArgs(self, _PyIO_str_writable, NULL);
    if (res == NULL)
        return NULL;
    if (res != Py_True) {
        Py_CLEAR(res);
        iobase_unsupported("File or stream is not writable.");
        return NULL;
    }
    if (args == Py_True) {
        Py_DECREF(res);
    }
    return res;
}

/* Context manager */

static PyObject *
iobase_enter(PyObject *self, PyObject *args)
{
    if (_PyIOBase_check_closed(self, Py_True) == NULL)
        return NULL;

    Py_INCREF(self);
    return self;
}

static PyObject *
iobase_exit(PyObject *self, PyObject *args)
{
    return PyObject_CallMethodObjArgs(self, _PyIO_str_close, NULL);
}

/* Lower-level APIs */

/* XXX Should these be present even if unimplemented? */

PyDoc_STRVAR(iobase_fileno_doc,
    "Returns underlying file descriptor if one exists.\n"
    "\n"
    "An IOError is raised if the IO object does not use a file descriptor.\n");

static PyObject *
iobase_fileno(PyObject *self, PyObject *args)
{
    return iobase_unsupported("fileno");
}

PyDoc_STRVAR(iobase_isatty_doc,
    "Return whether this is an 'interactive' stream.\n"
    "\n"
    "Return False if it can't be determined.\n");

static PyObject *
iobase_isatty(PyObject *self, PyObject *args)
{
    if (_PyIOBase_check_closed(self, Py_True) == NULL)
        return NULL;
    Py_RETURN_FALSE;
}

/* Readline(s) and writelines */

PyDoc_STRVAR(iobase_readline_doc,
    "Read and return a line from the stream.\n"
    "\n"
    "If limit is specified, at most limit bytes will be read.\n"
    "\n"
    "The line terminator is always b'\\n' for binary files; for text\n"
    "files, the newlines argument to open can be used to select the line\n"
    "terminator(s) recognized.\n");

static PyObject *
iobase_readline(PyObject *self, PyObject *args)
{
    /* For backwards compatibility, a (slowish) readline(). */

    Py_ssize_t limit = -1;
    int has_peek = 0;
    PyObject *buffer, *result;
    Py_ssize_t old_size = -1;
    _Py_IDENTIFIER(read);
    _Py_IDENTIFIER(peek);

    if (!PyArg_ParseTuple(args, "|O&:readline", &_PyIO_ConvertSsize_t, &limit)) {
        return NULL;
    }

    if (_PyObject_HasAttrId(self, &PyId_peek))
        has_peek = 1;

    buffer = PyByteArray_FromStringAndSize(NULL, 0);
    if (buffer == NULL)
        return NULL;

    while (limit < 0 || Py_SIZE(buffer) < limit) {
        Py_ssize_t nreadahead = 1;
        PyObject *b;

        if (has_peek) {
            PyObject *readahead = _PyObject_CallMethodId(self, &PyId_peek, "i", 1);
            if (readahead == NULL) {
                /* NOTE: PyErr_SetFromErrno() calls PyErr_CheckSignals()
                   when EINTR occurs so we needn't do it ourselves. */
                if (_PyIO_trap_eintr()) {
                    continue;
                }
                goto fail;
            }
            if (!PyBytes_Check(readahead)) {
                PyErr_Format(PyExc_IOError,
                             "peek() should have returned a bytes object, "
                             "not '%.200s'", Py_TYPE(readahead)->tp_name);
                Py_DECREF(readahead);
                goto fail;
            }
            if (PyBytes_GET_SIZE(readahead) > 0) {
                Py_ssize_t n = 0;
                const char *buf = PyBytes_AS_STRING(readahead);
                if (limit >= 0) {
                    do {
                        if (n >= PyBytes_GET_SIZE(readahead) || n >= limit)
                            break;
                        if (buf[n++] == '\n')
                            break;
                    } while (1);
                }
                else {
                    do {
                        if (n >= PyBytes_GET_SIZE(readahead))
                            break;
                        if (buf[n++] == '\n')
                            break;
                    } while (1);
                }
                nreadahead = n;
            }
            Py_DECREF(readahead);
        }

        b = _PyObject_CallMethodId(self, &PyId_read, "n", nreadahead);
        if (b == NULL) {
            /* NOTE: PyErr_SetFromErrno() calls PyErr_CheckSignals()
               when EINTR occurs so we needn't do it ourselves. */
            if (_PyIO_trap_eintr()) {
                continue;
            }
            goto fail;
        }
        if (!PyBytes_Check(b)) {
            PyErr_Format(PyExc_IOError,
                         "read() should have returned a bytes object, "
                         "not '%.200s'", Py_TYPE(b)->tp_name);
            Py_DECREF(b);
            goto fail;
        }
        if (PyBytes_GET_SIZE(b) == 0) {
            Py_DECREF(b);
            break;
        }

        old_size = PyByteArray_GET_SIZE(buffer);
        PyByteArray_Resize(buffer, old_size + PyBytes_GET_SIZE(b));
        memcpy(PyByteArray_AS_STRING(buffer) + old_size,
               PyBytes_AS_STRING(b), PyBytes_GET_SIZE(b));

        Py_DECREF(b);

        if (PyByteArray_AS_STRING(buffer)[PyByteArray_GET_SIZE(buffer) - 1] == '\n')
            break;
    }

    result = PyBytes_FromStringAndSize(PyByteArray_AS_STRING(buffer),
                                       PyByteArray_GET_SIZE(buffer));
    Py_DECREF(buffer);
    return result;
  fail:
    Py_DECREF(buffer);
    return NULL;
}

static PyObject *
iobase_iter(PyObject *self)
{
    if (_PyIOBase_check_closed(self, Py_True) == NULL)
        return NULL;

    Py_INCREF(self);
    return self;
}

static PyObject *
iobase_iternext(PyObject *self)
{
    PyObject *line = PyObject_CallMethodObjArgs(self, _PyIO_str_readline, NULL);

    if (line == NULL)
        return NULL;

    if (PyObject_Size(line) == 0) {
        Py_DECREF(line);
        return NULL;
    }

    return line;
}

PyDoc_STRVAR(iobase_readlines_doc,
    "Return a list of lines from the stream.\n"
    "\n"
    "hint can be specified to control the number of lines read: no more\n"
    "lines will be read if the total size (in bytes/characters) of all\n"
    "lines so far exceeds hint.");

static PyObject *
iobase_readlines(PyObject *self, PyObject *args)
{
    Py_ssize_t hint = -1, length = 0;
    PyObject *result;

    if (!PyArg_ParseTuple(args, "|O&:readlines", &_PyIO_ConvertSsize_t, &hint)) {
        return NULL;
    }

    result = PyList_New(0);
    if (result == NULL)
        return NULL;

    if (hint <= 0) {
        /* XXX special-casing this made sense in the Python version in order
           to remove the bytecode interpretation overhead, but it could
           probably be removed here. */
        _Py_IDENTIFIER(extend);
        PyObject *ret = _PyObject_CallMethodId(result, &PyId_extend, "O", self);

        if (ret == NULL) {
            Py_DECREF(result);
            return NULL;
        }
        Py_DECREF(ret);
        return result;
    }

    while (1) {
        PyObject *line = PyIter_Next(self);
        if (line == NULL) {
            if (PyErr_Occurred()) {
                Py_DECREF(result);
                return NULL;
            }
            else
                break; /* StopIteration raised */
        }

        if (PyList_Append(result, line) < 0) {
            Py_DECREF(line);
            Py_DECREF(result);
            return NULL;
        }
        length += PyObject_Size(line);
        Py_DECREF(line);

        if (length > hint)
            break;
    }
    return result;
}

static PyObject *
iobase_writelines(PyObject *self, PyObject *args)
{
    PyObject *lines, *iter, *res;

    if (!PyArg_ParseTuple(args, "O:writelines", &lines)) {
        return NULL;
    }

    if (_PyIOBase_check_closed(self, Py_True) == NULL)
        return NULL;

    iter = PyObject_GetIter(lines);
    if (iter == NULL)
        return NULL;

    while (1) {
        PyObject *line = PyIter_Next(iter);
        if (line == NULL) {
            if (PyErr_Occurred()) {
                Py_DECREF(iter);
                return NULL;
            }
            else
                break; /* Stop Iteration */
        }

        res = NULL;
        do {
            res = PyObject_CallMethodObjArgs(self, _PyIO_str_write, line, NULL);
        } while (res == NULL && _PyIO_trap_eintr());
        Py_DECREF(line);
        if (res == NULL) {
            Py_DECREF(iter);
            return NULL;
        }
        Py_DECREF(res);
    }
    Py_DECREF(iter);
    Py_RETURN_NONE;
}

static PyMethodDef iobase_methods[] = {
    {"seek", iobase_seek, METH_VARARGS, iobase_seek_doc},
    {"tell", iobase_tell, METH_NOARGS, iobase_tell_doc},
    {"truncate", iobase_truncate, METH_VARARGS, iobase_truncate_doc},
    {"flush", iobase_flush, METH_NOARGS, iobase_flush_doc},
    {"close", iobase_close, METH_NOARGS, iobase_close_doc},

    {"seekable", iobase_seekable, METH_NOARGS, iobase_seekable_doc},
    {"readable", iobase_readable, METH_NOARGS, iobase_readable_doc},
    {"writable", iobase_writable, METH_NOARGS, iobase_writable_doc},

    {"_checkClosed",   _PyIOBase_check_closed, METH_NOARGS},
    {"_checkSeekable", _PyIOBase_check_seekable, METH_NOARGS},
    {"_checkReadable", _PyIOBase_check_readable, METH_NOARGS},
    {"_checkWritable", _PyIOBase_check_writable, METH_NOARGS},

    {"fileno", iobase_fileno, METH_NOARGS, iobase_fileno_doc},
    {"isatty", iobase_isatty, METH_NOARGS, iobase_isatty_doc},

    {"__enter__", iobase_enter, METH_NOARGS},
    {"__exit__", iobase_exit, METH_VARARGS},

    {"readline", iobase_readline, METH_VARARGS, iobase_readline_doc},
    {"readlines", iobase_readlines, METH_VARARGS, iobase_readlines_doc},
    {"writelines", iobase_writelines, METH_VARARGS},

    {NULL, NULL}
};

static PyGetSetDef iobase_getset[] = {
    {"__dict__", PyObject_GenericGetDict, NULL, NULL},
    {"closed", (getter)iobase_closed_get, NULL, NULL},
    {NULL}
};


PyTypeObject PyIOBase_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_io._IOBase",              /*tp_name*/
    sizeof(iobase),             /*tp_basicsize*/
    0,                          /*tp_itemsize*/
    (destructor)iobase_dealloc, /*tp_dealloc*/
    0,                          /*tp_print*/
    0,                          /*tp_getattr*/
    0,                          /*tp_setattr*/
    0,                          /*tp_compare */
    0,                          /*tp_repr*/
    0,                          /*tp_as_number*/
    0,                          /*tp_as_sequence*/
    0,                          /*tp_as_mapping*/
    0,                          /*tp_hash */
    0,                          /*tp_call*/
    0,                          /*tp_str*/
    0,                          /*tp_getattro*/
    0,                          /*tp_setattro*/
    0,                          /*tp_as_buffer*/
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
        | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
    iobase_doc,                 /* tp_doc */
    (traverseproc)iobase_traverse, /* tp_traverse */
    (inquiry)iobase_clear,      /* tp_clear */
    0,                          /* tp_richcompare */
    offsetof(iobase, weakreflist), /* tp_weaklistoffset */
    iobase_iter,                /* tp_iter */
    iobase_iternext,            /* tp_iternext */
    iobase_methods,             /* tp_methods */
    0,                          /* tp_members */
    iobase_getset,              /* tp_getset */
    0,                          /* tp_base */
    0,                          /* tp_dict */
    0,                          /* tp_descr_get */
    0,                          /* tp_descr_set */
    offsetof(iobase, dict),     /* tp_dictoffset */
    0,                          /* tp_init */
    0,                          /* tp_alloc */
    PyType_GenericNew,          /* tp_new */
};


/*
 * RawIOBase class, Inherits from IOBase.
 */
PyDoc_STRVAR(rawiobase_doc,
             "Base class for raw binary I/O.");

/*
 * The read() method is implemented by calling readinto(); derived classes
 * that want to support read() only need to implement readinto() as a
 * primitive operation.  In general, readinto() can be more efficient than
 * read().
 *
 * (It would be tempting to also provide an implementation of readinto() in
 * terms of read(), in case the latter is a more suitable primitive operation,
 * but that would lead to nasty recursion in case a subclass doesn't implement
 * either.)
*/

static PyObject *
rawiobase_read(PyObject *self, PyObject *args)
{
    Py_ssize_t n = -1;
    PyObject *b, *res;

    if (!PyArg_ParseTuple(args, "|n:read", &n)) {
        return NULL;
    }

    if (n < 0) {
        _Py_IDENTIFIER(readall);

        return _PyObject_CallMethodId(self, &PyId_readall, NULL);
    }

    /* TODO: allocate a bytes object directly instead and manually construct
       a writable memoryview pointing to it. */
    b = PyByteArray_FromStringAndSize(NULL, n);
    if (b == NULL)
        return NULL;

    res = PyObject_CallMethodObjArgs(self, _PyIO_str_readinto, b, NULL);
    if (res == NULL || res == Py_None) {
        Py_DECREF(b);
        return res;
    }

    n = PyNumber_AsSsize_t(res, PyExc_ValueError);
    Py_DECREF(res);
    if (n == -1 && PyErr_Occurred()) {
        Py_DECREF(b);
        return NULL;
    }

    res = PyBytes_FromStringAndSize(PyByteArray_AsString(b), n);
    Py_DECREF(b);
    return res;
}


PyDoc_STRVAR(rawiobase_readall_doc,
             "Read until EOF, using multiple read() call.");

static PyObject *
rawiobase_readall(PyObject *self, PyObject *args)
{
    int r;
    PyObject *chunks = PyList_New(0);
    PyObject *result;
    
    if (chunks == NULL)
        return NULL;

    while (1) {
        _Py_IDENTIFIER(read);
        PyObject *data = _PyObject_CallMethodId(self, &PyId_read,
                                                "i", DEFAULT_BUFFER_SIZE);
        if (!data) {
            /* NOTE: PyErr_SetFromErrno() calls PyErr_CheckSignals()
               when EINTR occurs so we needn't do it ourselves. */
            if (_PyIO_trap_eintr()) {
                continue;
            }
            Py_DECREF(chunks);
            return NULL;
        }
        if (data == Py_None) {
            if (PyList_GET_SIZE(chunks) == 0) {
                Py_DECREF(chunks);
                return data;
            }
            Py_DECREF(data);
            break;
        }
        if (!PyBytes_Check(data)) {
            Py_DECREF(chunks);
            Py_DECREF(data);
            PyErr_SetString(PyExc_TypeError, "read() should return bytes");
            return NULL;
        }
        if (PyBytes_GET_SIZE(data) == 0) {
            /* EOF */
            Py_DECREF(data);
            break;
        }
        r = PyList_Append(chunks, data);
        Py_DECREF(data);
        if (r < 0) {
            Py_DECREF(chunks);
            return NULL;
        }
    }
    result = _PyBytes_Join(_PyIO_empty_bytes, chunks);
    Py_DECREF(chunks);
    return result;
}

static PyMethodDef rawiobase_methods[] = {
    {"read", rawiobase_read, METH_VARARGS},
    {"readall", rawiobase_readall, METH_NOARGS, rawiobase_readall_doc},
    {NULL, NULL}
};

PyTypeObject PyRawIOBase_Type = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "_io._RawIOBase",                /*tp_name*/
    0,                          /*tp_basicsize*/
    0,                          /*tp_itemsize*/
    0,                          /*tp_dealloc*/
    0,                          /*tp_print*/
    0,                          /*tp_getattr*/
    0,                          /*tp_setattr*/
    0,                          /*tp_compare */
    0,                          /*tp_repr*/
    0,                          /*tp_as_number*/
    0,                          /*tp_as_sequence*/
    0,                          /*tp_as_mapping*/
    0,                          /*tp_hash */
    0,                          /*tp_call*/
    0,                          /*tp_str*/
    0,                          /*tp_getattro*/
    0,                          /*tp_setattro*/
    0,                          /*tp_as_buffer*/
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
    rawiobase_doc,              /* tp_doc */
    0,                          /* tp_traverse */
    0,                          /* tp_clear */
    0,                          /* tp_richcompare */
    0,                          /* tp_weaklistoffset */
    0,                          /* tp_iter */
    0,                          /* tp_iternext */
    rawiobase_methods,          /* tp_methods */
    0,                          /* tp_members */
    0,                          /* tp_getset */
    &PyIOBase_Type,             /* tp_base */
    0,                          /* tp_dict */
    0,                          /* tp_descr_get */
    0,                          /* tp_descr_set */
    0,                          /* tp_dictoffset */
    0,                          /* tp_init */
    0,                          /* tp_alloc */
    0,                          /* tp_new */
};