File Objects
************

These APIs are a minimal emulation of the Python 2 C API for built-in
file objects, which used to rely on the buffered I/O ("FILE*") support
from the C standard library.  In Python 3, files and streams use the
new "io" module, which defines several layers over the low-level
unbuffered I/O of the operating system.  The functions described below
are convenience C wrappers over these new APIs, and meant mostly for
internal error reporting in the interpreter; third-party code is
advised to access the "io" APIs instead.

PyFile_FromFd(int fd, const char *name, const char *mode, int buffering, const char *encoding, const char *errors, const char *newline, int closefd)
    *Return value: New reference.*

   Create a Python file object from the file descriptor of an already
   opened file *fd*.  The arguments *name*, *encoding*, *errors* and
   *newline* can be *NULL* to use the defaults; *buffering* can be
   *-1* to use the default. *name* is ignored and kept for backward
   compatibility. Return *NULL* on failure. For a more comprehensive
   description of the arguments, please refer to the "io.open()"
   function documentation.

   Warning: Since Python streams have their own buffering layer,
     mixing them with OS-level file descriptors can produce various
     issues (such as unexpected ordering of data).

   Changed in version 3.2: Ignore *name* attribute.

int PyObject_AsFileDescriptor(PyObject *p)

   Return the file descriptor associated with *p* as an "int".  If the
   object is an integer, its value is returned.  If not, the object’s
   "fileno()" method is called if it exists; the method must return an
   integer, which is returned as the file descriptor value.  Sets an
   exception and returns "-1" on failure.

PyObject* PyFile_GetLine(PyObject *p, int n)
    *Return value: New reference.*

   Equivalent to "p.readline([n])", this function reads one line from
   the object *p*.  *p* may be a file object or any object with a
   "readline()" method.  If *n* is "0", exactly one line is read,
   regardless of the length of the line.  If *n* is greater than "0",
   no more than *n* bytes will be read from the file; a partial line
   can be returned.  In both cases, an empty string is returned if the
   end of the file is reached immediately.  If *n* is less than "0",
   however, one line is read regardless of length, but "EOFError" is
   raised if the end of the file is reached immediately.

int PyFile_SetOpenCodeHook(Py_OpenCodeHookFunction handler)

   Overrides the normal behavior of "io.open_code()" to pass its
   parameter through the provided handler.

   The handler is a function of type "PyObject *(*)(PyObject *path,
   void *userData)", where *path* is guaranteed to be
   "PyUnicodeObject".

   The *userData* pointer is passed into the hook function. Since hook
   functions may be called from different runtimes, this pointer
   should not refer directly to Python state.

   As this hook is intentionally used during import, avoid importing
   new modules during its execution unless they are known to be frozen
   or available in "sys.modules".

   Once a hook has been set, it cannot be removed or replaced, and
   later calls to "PyFile_SetOpenCodeHook()" will fail. On failure,
   the function returns -1 and sets an exception if the interpreter
   has been initialized.

   This function is safe to call before "Py_Initialize()".

   New in version 3.8.

int PyFile_WriteObject(PyObject *obj, PyObject *p, int flags)

   Write object *obj* to file object *p*.  The only supported flag for
   *flags* is "Py_PRINT_RAW"; if given, the "str()" of the object is
   written instead of the "repr()".  Return "0" on success or "-1" on
   failure; the appropriate exception will be set.

int PyFile_WriteString(const char *s, PyObject *p)

   Write string *s* to file object *p*.  Return "0" on success or "-1"
   on failure; the appropriate exception will be set.
