Doc/c-api/long.rst
.. highlight:: c
.. _longobjects:
.. index:: pair: object; long integer pair: object; integer
All integers are implemented as "long" integer objects of arbitrary size.
On error, most PyLong_As* APIs return (return type)-1 which cannot be
distinguished from a number. Use :c:func:PyErr_Occurred to disambiguate.
.. c:type:: PyLongObject
This subtype of :c:type:PyObject represents a Python integer object.
.. c:var:: PyTypeObject PyLong_Type
This instance of :c:type:PyTypeObject represents the Python integer type.
This is the same object as :class:int in the Python layer.
.. c:function:: int PyLong_Check(PyObject *p)
Return true if its argument is a :c:type:PyLongObject or a subtype of
:c:type:PyLongObject. This function always succeeds.
.. c:function:: int PyLong_CheckExact(PyObject *p)
Return true if its argument is a :c:type:PyLongObject, but not a subtype of
:c:type:PyLongObject. This function always succeeds.
.. c:function:: PyObject* PyLong_FromLong(long v)
Return a new :c:type:PyLongObject object from v, or NULL on failure.
.. impl-detail::
CPython keeps an array of integer objects for all integers
between ``-5`` and ``1024``. When you create an int in that range
you actually just get back a reference to the existing object.
.. c:function:: PyObject* PyLong_FromUnsignedLong(unsigned long v)
Return a new :c:type:PyLongObject object from a C :c:expr:unsigned long, or
NULL on failure.
.. c:function:: PyObject* PyLong_FromSsize_t(Py_ssize_t v)
Return a new :c:type:PyLongObject object from a C :c:type:Py_ssize_t, or
NULL on failure.
.. c:function:: PyObject* PyLong_FromSize_t(size_t v)
Return a new :c:type:PyLongObject object from a C :c:type:size_t, or
NULL on failure.
.. c:function:: PyObject* PyLong_FromLongLong(long long v)
Return a new :c:type:PyLongObject object from a C :c:expr:long long, or NULL
on failure.
.. c:function:: PyObject* PyLong_FromInt32(int32_t value) PyObject* PyLong_FromInt64(int64_t value)
Return a new :c:type:PyLongObject object from a signed C
:c:expr:int32_t or :c:expr:int64_t, or NULL
with an exception set on failure.
.. versionadded:: 3.14
.. c:function:: PyObject* PyLong_FromUnsignedLongLong(unsigned long long v)
Return a new :c:type:PyLongObject object from a C :c:expr:unsigned long long,
or NULL on failure.
.. c:function:: PyObject* PyLong_FromUInt32(uint32_t value) PyObject* PyLong_FromUInt64(uint64_t value)
Return a new :c:type:PyLongObject object from an unsigned C
:c:expr:uint32_t or :c:expr:uint64_t, or NULL
with an exception set on failure.
.. versionadded:: 3.14
.. c:function:: PyObject* PyLong_FromDouble(double v)
Return a new :c:type:PyLongObject object from the integer part of v, or
NULL on failure.
.. c:function:: PyObject* PyLong_FromString(const char *str, char **pend, int base)
Return a new :c:type:PyLongObject based on the string value in str, which
is interpreted according to the radix in base, or NULL on failure. If
pend is non-NULL, *pend will point to the end of str on success or
to the first character that could not be processed on error. If base is 0,
str is interpreted using the :ref:integers definition; in this case, leading
zeros in a non-zero decimal number raises a :exc:ValueError. If base is not
0, it must be between 2 and 36, inclusive. Leading and trailing
whitespace and single underscores after a base specifier and between digits are
ignored. If there are no digits or str is not NULL-terminated following the
digits and trailing whitespace, :exc:ValueError will be raised.
.. seealso:: :c:func:PyLong_AsNativeBytes() and
:c:func:PyLong_FromNativeBytes() functions can be used to convert
a :c:type:PyLongObject to/from an array of bytes in base 256.
.. c:function:: PyObject* PyLong_FromUnicodeObject(PyObject *u, int base)
Convert a sequence of Unicode digits in the string u to a Python integer value.
.. versionadded:: 3.3
.. c:function:: PyObject* PyLong_FromVoidPtr(void *p)
Create a Python integer from the pointer p. The pointer value can be
retrieved from the resulting value using :c:func:PyLong_AsVoidPtr.
.. c:function:: PyObject* PyLong_FromNativeBytes(const void* buffer, size_t n_bytes, int flags)
Create a Python integer from the value contained in the first n_bytes of buffer, interpreted as a two's-complement signed number.
flags are as for :c:func:PyLong_AsNativeBytes. Passing -1 will select
the native endian that CPython was compiled with and assume that the
most-significant bit is a sign bit. Passing
Py_ASNATIVEBYTES_UNSIGNED_BUFFER will produce the same result as calling
:c:func:PyLong_FromUnsignedNativeBytes. Other flags are ignored.
.. versionadded:: 3.13
.. c:function:: PyObject* PyLong_FromUnsignedNativeBytes(const void* buffer, size_t n_bytes, int flags)
Create a Python integer from the value contained in the first n_bytes of buffer, interpreted as an unsigned number.
flags are as for :c:func:PyLong_AsNativeBytes. Passing -1 will select
the native endian that CPython was compiled with and assume that the
most-significant bit is not a sign bit. Flags other than endian are ignored.
.. versionadded:: 3.13
.. c:macro:: PyLong_FromPid(pid)
Macro for creating a Python integer from a process identifier.
This can be defined as an alias to :c:func:PyLong_FromLong or
:c:func:PyLong_FromLongLong, depending on the size of the system's
PID type.
.. versionadded:: 3.2
.. c:function:: long PyLong_AsLong(PyObject *obj)
.. index:: single: LONG_MAX (C macro) single: OverflowError (built-in exception)
Return a C :c:expr:long representation of obj. If obj is not an
instance of :c:type:PyLongObject, first call its :meth:~object.__index__ method
(if present) to convert it to a :c:type:PyLongObject.
Raise :exc:OverflowError if the value of obj is out of range for a
:c:expr:long.
Returns -1 on error. Use :c:func:PyErr_Occurred to disambiguate.
.. versionchanged:: 3.8
Use :meth:~object.__index__ if available.
.. versionchanged:: 3.10
This function will no longer use :meth:~object.__int__.
.. c:namespace:: NULL
.. c:function:: long PyLong_AS_LONG(PyObject *obj)
A :term:`soft deprecated` alias.
Exactly equivalent to the preferred ``PyLong_AsLong``. In particular,
it can fail with :exc:`OverflowError` or another exception.
.. deprecated:: 3.14
The function is soft deprecated.
.. c:function:: int PyLong_AsInt(PyObject *obj)
Similar to :c:func:PyLong_AsLong, but store the result in a C
:c:expr:int instead of a C :c:expr:long.
.. versionadded:: 3.13
.. c:function:: long PyLong_AsLongAndOverflow(PyObject *obj, int *overflow)
Return a C :c:expr:long representation of obj. If obj is not an
instance of :c:type:PyLongObject, first call its :meth:~object.__index__
method (if present) to convert it to a :c:type:PyLongObject.
If the value of obj is greater than :c:macro:LONG_MAX or less than
:c:macro:LONG_MIN, set *overflow to 1 or -1, respectively, and
return -1; otherwise, set *overflow to 0. If any other exception
occurs set *overflow to 0 and return -1 as usual.
Returns -1 on error. Use :c:func:PyErr_Occurred to disambiguate.
.. versionchanged:: 3.8
Use :meth:~object.__index__ if available.
.. versionchanged:: 3.10
This function will no longer use :meth:~object.__int__.
.. c:function:: long long PyLong_AsLongLong(PyObject *obj)
.. index:: single: OverflowError (built-in exception)
Return a C :c:expr:long long representation of obj. If obj is not an
instance of :c:type:PyLongObject, first call its :meth:~object.__index__ method
(if present) to convert it to a :c:type:PyLongObject.
Raise :exc:OverflowError if the value of obj is out of range for a
:c:expr:long long.
Returns -1 on error. Use :c:func:PyErr_Occurred to disambiguate.
.. versionchanged:: 3.8
Use :meth:~object.__index__ if available.
.. versionchanged:: 3.10
This function will no longer use :meth:~object.__int__.
.. c:function:: long long PyLong_AsLongLongAndOverflow(PyObject *obj, int *overflow)
Return a C :c:expr:long long representation of obj. If obj is not an
instance of :c:type:PyLongObject, first call its :meth:~object.__index__ method
(if present) to convert it to a :c:type:PyLongObject.
If the value of obj is greater than :c:macro:LLONG_MAX or less than
:c:macro:LLONG_MIN, set *overflow to 1 or -1, respectively,
and return -1; otherwise, set *overflow to 0. If any other
exception occurs set *overflow to 0 and return -1 as usual.
Returns -1 on error. Use :c:func:PyErr_Occurred to disambiguate.
.. versionadded:: 3.2
.. versionchanged:: 3.8
Use :meth:~object.__index__ if available.
.. versionchanged:: 3.10
This function will no longer use :meth:~object.__int__.
.. c:function:: Py_ssize_t PyLong_AsSsize_t(PyObject *pylong)
.. index:: single: PY_SSIZE_T_MAX (C macro) single: OverflowError (built-in exception)
Return a C :c:type:Py_ssize_t representation of pylong. pylong must
be an instance of :c:type:PyLongObject.
Raise :exc:OverflowError if the value of pylong is out of range for a
:c:type:Py_ssize_t.
Returns -1 on error. Use :c:func:PyErr_Occurred to disambiguate.
.. c:function:: unsigned long PyLong_AsUnsignedLong(PyObject *pylong)
.. index:: single: ULONG_MAX (C macro) single: OverflowError (built-in exception)
Return a C :c:expr:unsigned long representation of pylong. pylong
must be an instance of :c:type:PyLongObject.
Raise :exc:OverflowError if the value of pylong is out of range for a
:c:expr:unsigned long.
Returns (unsigned long)-1 on error.
Use :c:func:PyErr_Occurred to disambiguate.
.. c:function:: size_t PyLong_AsSize_t(PyObject *pylong)
.. index:: single: SIZE_MAX (C macro) single: OverflowError (built-in exception)
Return a C :c:type:size_t representation of pylong. pylong must be
an instance of :c:type:PyLongObject.
Raise :exc:OverflowError if the value of pylong is out of range for a
:c:type:size_t.
Returns (size_t)-1 on error.
Use :c:func:PyErr_Occurred to disambiguate.
.. c:function:: unsigned long long PyLong_AsUnsignedLongLong(PyObject *pylong)
.. index:: single: OverflowError (built-in exception)
Return a C :c:expr:unsigned long long representation of pylong. pylong
must be an instance of :c:type:PyLongObject.
Raise :exc:OverflowError if the value of pylong is out of range for an
:c:expr:unsigned long long.
Returns (unsigned long long)-1 on error.
Use :c:func:PyErr_Occurred to disambiguate.
.. versionchanged:: 3.1
A negative pylong now raises :exc:OverflowError, not :exc:TypeError.
.. c:function:: unsigned long PyLong_AsUnsignedLongMask(PyObject *obj)
Return a C :c:expr:unsigned long representation of obj. If obj is not
an instance of :c:type:PyLongObject, first call its :meth:~object.__index__
method (if present) to convert it to a :c:type:PyLongObject.
If the value of obj is out of range for an :c:expr:unsigned long,
return the reduction of that value modulo ULONG_MAX + 1.
Returns (unsigned long)-1 on error. Use :c:func:PyErr_Occurred to
disambiguate.
.. versionchanged:: 3.8
Use :meth:~object.__index__ if available.
.. versionchanged:: 3.10
This function will no longer use :meth:~object.__int__.
.. c:function:: unsigned long long PyLong_AsUnsignedLongLongMask(PyObject *obj)
Return a C :c:expr:unsigned long long representation of obj. If obj
is not an instance of :c:type:PyLongObject, first call its
:meth:~object.__index__ method (if present) to convert it to a
:c:type:PyLongObject.
If the value of obj is out of range for an :c:expr:unsigned long long,
return the reduction of that value modulo ULLONG_MAX + 1.
Returns (unsigned long long)-1 on error. Use :c:func:PyErr_Occurred
to disambiguate.
.. versionchanged:: 3.8
Use :meth:~object.__index__ if available.
.. versionchanged:: 3.10
This function will no longer use :meth:~object.__int__.
.. c:function:: int PyLong_AsInt32(PyObject *obj, int32_t *value) int PyLong_AsInt64(PyObject *obj, int64_t *value)
Set *value to a signed C :c:expr:int32_t or :c:expr:int64_t
representation of obj.
If obj is not an instance of :c:type:PyLongObject, first call its
:meth:~object.__index__ method (if present) to convert it to a
:c:type:PyLongObject.
If the obj value is out of range, raise an :exc:OverflowError.
Set *value and return 0 on success.
Set an exception and return -1 on error.
value must not be NULL.
.. versionadded:: 3.14
.. c:function:: int PyLong_AsUInt32(PyObject *obj, uint32_t *value) int PyLong_AsUInt64(PyObject *obj, uint64_t *value)
Set *value to an unsigned C :c:expr:uint32_t or :c:expr:uint64_t
representation of obj.
If obj is not an instance of :c:type:PyLongObject, first call its
:meth:~object.__index__ method (if present) to convert it to a
:c:type:PyLongObject.
ValueError.OverflowError.Set *value and return 0 on success.
Set an exception and return -1 on error.
value must not be NULL.
.. versionadded:: 3.14
.. c:function:: double PyLong_AsDouble(PyObject *pylong)
Return a C :c:expr:double representation of pylong. pylong must be
an instance of :c:type:PyLongObject.
Raise :exc:OverflowError if the value of pylong is out of range for a
:c:expr:double.
Returns -1.0 on error. Use :c:func:PyErr_Occurred to disambiguate.
.. c:function:: void* PyLong_AsVoidPtr(PyObject *pylong)
Convert a Python integer pylong to a C :c:expr:void pointer.
If pylong cannot be converted, an :exc:OverflowError will be raised. This
is only assured to produce a usable :c:expr:void pointer for values created
with :c:func:PyLong_FromVoidPtr.
Returns NULL on error. Use :c:func:PyErr_Occurred to disambiguate.
.. c:function:: Py_ssize_t PyLong_AsNativeBytes(PyObject pylong, void buffer, Py_ssize_t n_bytes, int flags)
Copy the Python integer value pylong to a native buffer of size
n_bytes. The flags can be set to -1 to behave similarly to a C cast,
or to values documented below to control the behavior.
Returns -1 with an exception raised on error. This may happen if
pylong cannot be interpreted as an integer, or if pylong was negative
and the Py_ASNATIVEBYTES_REJECT_NEGATIVE flag was set.
Otherwise, returns the number of bytes required to store the value. If this is equal to or less than n_bytes, the entire value was copied. All n_bytes of the buffer are written: remaining bytes filled by copies of the sign bit.
If the returned value is greater than n_bytes, the value was truncated: as many of the lowest bits of the value as could fit are written, and the higher bits are ignored. This matches the typical behavior of a C-style downcast.
.. note::
Overflow is not considered an error. If the returned value
is larger than *n_bytes*, most significant bits were discarded.
0 will never be returned.
Values are always copied as two's-complement.
Usage example::
int32_t value;
Py_ssize_t bytes = PyLong_AsNativeBytes(pylong, &value, sizeof(value), -1);
if (bytes < 0) {
// Failed. A Python exception was set with the reason.
return NULL;
}
else if (bytes <= (Py_ssize_t)sizeof(value)) {
// Success!
}
else {
// Overflow occurred, but 'value' contains the truncated
// lowest bits of pylong.
}
Passing zero to n_bytes will return the size of a buffer that would
be large enough to hold the value. This may be larger than technically
necessary, but not unreasonably so. If n_bytes=0, buffer may be
NULL.
.. note::
Passing *n_bytes=0* to this function is not an accurate way to determine
the bit length of the value.
To get at the entire Python value of an unknown size, the function can be called twice: first to determine the buffer size, then to fill it::
// Ask how much space we need.
Py_ssize_t expected = PyLong_AsNativeBytes(pylong, NULL, 0, -1);
if (expected < 0) {
// Failed. A Python exception was set with the reason.
return NULL;
}
assert(expected != 0); // Impossible per the API definition.
uint8_t *bignum = malloc(expected);
if (!bignum) {
PyErr_SetString(PyExc_MemoryError, "bignum malloc failed.");
return NULL;
}
// Safely get the entire value.
Py_ssize_t bytes = PyLong_AsNativeBytes(pylong, bignum, expected, -1);
if (bytes < 0) { // Exception has been set.
free(bignum);
return NULL;
}
else if (bytes > expected) { // This should not be possible.
PyErr_SetString(PyExc_RuntimeError,
"Unexpected bignum truncation after a size check.");
free(bignum);
return NULL;
}
// The expected success given the above pre-check.
// ... use bignum ...
free(bignum);
flags is either -1 (Py_ASNATIVEBYTES_DEFAULTS) to select defaults
that behave most like a C cast, or a combination of the other flags in
the table below.
Note that -1 cannot be combined with other flags.
Currently, -1 corresponds to
Py_ASNATIVEBYTES_NATIVE_ENDIAN | Py_ASNATIVEBYTES_UNSIGNED_BUFFER.
.. c:namespace:: NULL
============================================= ======
Flag Value
============================================= ======
.. c:macro:: Py_ASNATIVEBYTES_DEFAULTS -1
.. c:macro:: Py_ASNATIVEBYTES_BIG_ENDIAN 0
.. c:macro:: Py_ASNATIVEBYTES_LITTLE_ENDIAN 1
.. c:macro:: Py_ASNATIVEBYTES_NATIVE_ENDIAN 3
.. c:macro:: Py_ASNATIVEBYTES_UNSIGNED_BUFFER 4
.. c:macro:: Py_ASNATIVEBYTES_REJECT_NEGATIVE 8
.. c:macro:: Py_ASNATIVEBYTES_ALLOW_INDEX 16
============================================= ======
Specifying Py_ASNATIVEBYTES_NATIVE_ENDIAN will override any other endian
flags. Passing 2 is reserved.
By default, sufficient buffer will be requested to include a sign bit. For example, when converting 128 with n_bytes=1, the function will return 2 (or more) in order to store a zero sign bit.
If Py_ASNATIVEBYTES_UNSIGNED_BUFFER is specified, a zero sign bit
will be omitted from size calculations. This allows, for example, 128 to fit
in a single-byte buffer. If the destination buffer is later treated as
signed, a positive input value may become negative.
Note that the flag does not affect handling of negative values: for those,
space for a sign bit is always requested.
Specifying Py_ASNATIVEBYTES_REJECT_NEGATIVE causes an exception to be set
if pylong is negative. Without this flag, negative values will be copied
provided there is enough space for at least one sign bit, regardless of
whether Py_ASNATIVEBYTES_UNSIGNED_BUFFER was specified.
If Py_ASNATIVEBYTES_ALLOW_INDEX is specified and a non-integer value is
passed, its :meth:~object.__index__ method will be called first. This may
result in Python code executing and other threads being allowed to run, which
could cause changes to other objects or values in use. When flags is
-1, this option is not set, and non-integer values will raise
:exc:TypeError.
.. note::
With the default *flags* (``-1``, or *UNSIGNED_BUFFER* without
*REJECT_NEGATIVE*), multiple Python integers can map to a single value
without overflow. For example, both ``255`` and ``-1`` fit a single-byte
buffer and set all its bits.
This matches typical C cast behavior.
.. versionadded:: 3.13
.. c:macro:: PyLong_AsPid(pid)
Macro for converting a Python integer into a process identifier.
This can be defined as an alias to :c:func:PyLong_AsLong,
:c:func:PyLong_FromLongLong, or :c:func:PyLong_AsInt, depending on the
size of the system's PID type.
.. versionadded:: 3.2
.. c:function:: int PyLong_GetSign(PyObject *obj, int *sign)
Get the sign of the integer object obj.
On success, set *sign to the integer sign (0, -1 or +1 for zero, negative or positive integer, respectively) and return 0.
On failure, return -1 with an exception set. This function always succeeds
if obj is a :c:type:PyLongObject or its subtype.
.. versionadded:: 3.14
.. c:function:: int PyLong_IsPositive(PyObject *obj)
Check if the integer object obj is positive (obj > 0).
If obj is an instance of :c:type:PyLongObject or its subtype,
return 1 when it's positive and 0 otherwise. Else set an
exception and return -1.
.. versionadded:: 3.14
.. c:function:: int PyLong_IsNegative(PyObject *obj)
Check if the integer object obj is negative (obj < 0).
If obj is an instance of :c:type:PyLongObject or its subtype,
return 1 when it's negative and 0 otherwise. Else set an
exception and return -1.
.. versionadded:: 3.14
.. c:function:: int PyLong_IsZero(PyObject *obj)
Check if the integer object obj is zero.
If obj is an instance of :c:type:PyLongObject or its subtype,
return 1 when it's zero and 0 otherwise. Else set an
exception and return -1.
.. versionadded:: 3.14
.. c:function:: PyObject* PyLong_GetInfo(void)
On success, return a read only :term:named tuple, that holds
information about Python's internal representation of integers.
See :data:sys.int_info for description of individual fields.
On failure, return NULL with an exception set.
.. versionadded:: 3.1
.. c:function:: int PyUnstable_Long_IsCompact(const PyLongObject* op)
Return 1 if op is compact, 0 otherwise.
This function makes it possible for performance-critical code to implement
a “fast path” for small integers. For compact values use
:c:func:PyUnstable_Long_CompactValue; for others fall back to a
:c:func:PyLong_As* <PyLong_AsSize_t> function or
:c:func:PyLong_AsNativeBytes.
The speedup is expected to be negligible for most users.
Exactly what values are considered compact is an implementation detail and is subject to change.
.. versionadded:: 3.12
.. c:function:: Py_ssize_t PyUnstable_Long_CompactValue(const PyLongObject* op)
If op is compact, as determined by :c:func:PyUnstable_Long_IsCompact,
return its value.
Otherwise, the return value is undefined.
.. versionadded:: 3.12
Export API ^^^^^^^^^^
.. versionadded:: 3.14
.. c:type:: PyLongLayout
Layout of an array of "digits" ("limbs" in the GMP terminology), used to represent absolute value for arbitrary precision integers.
Use :c:func:PyLong_GetNativeLayout to get the native layout of Python
:class:int objects, used internally for integers with "big enough"
absolute value.
See also :data:sys.int_info which exposes similar information in Python.
.. c:member:: uint8_t bits_per_digit
Bits per digit. For example, a 15 bit digit means that bits 0-14 contain
meaningful information.
.. c:member:: uint8_t digit_size
Digit size in bytes. For example, a 15 bit digit will require at least 2
bytes.
.. c:member:: int8_t digits_order
Digits order:
- ``1`` for most significant digit first
- ``-1`` for least significant digit first
.. c:member:: int8_t digit_endianness
Digit endianness:
- ``1`` for most significant byte first (big endian)
- ``-1`` for least significant byte first (little endian)
.. c:function:: const PyLongLayout* PyLong_GetNativeLayout(void)
Get the native layout of Python :class:int objects.
See the :c:type:PyLongLayout structure.
The function must not be called before Python initialization nor after Python finalization. The returned layout is valid until Python is finalized. The layout is the same for all Python sub-interpreters in a process, and so it can be cached.
.. c:type:: PyLongExport
Export of a Python :class:int object.
There are two cases:
digits is NULL, only use the :c:member:value member.digits is not NULL, use :c:member:negative,
:c:member:ndigits and :c:member:digits members... c:member:: int64_t value
The native integer value of the exported :class:`int` object.
Only valid if :c:member:`digits` is ``NULL``.
.. c:member:: uint8_t negative
``1`` if the number is negative, ``0`` otherwise.
Only valid if :c:member:`digits` is not ``NULL``.
.. c:member:: Py_ssize_t ndigits
Number of digits in :c:member:`digits` array.
Only valid if :c:member:`digits` is not ``NULL``.
.. c:member:: const void *digits
Read-only array of unsigned digits. Can be ``NULL``.
.. c:function:: int PyLong_Export(PyObject *obj, PyLongExport *export_long)
Export a Python :class:int object.
export_long must point to a :c:type:PyLongExport structure allocated
by the caller. It must not be NULL.
On success, fill in *export_long and return 0.
On error, set an exception and return -1.
:c:func:PyLong_FreeExport must be called when the export is no longer
needed.
.. impl-detail::
This function always succeeds if *obj* is a Python :class:`int` object
or a subclass.
.. c:function:: void PyLong_FreeExport(PyLongExport *export_long)
Release the export export_long created by :c:func:PyLong_Export.
.. impl-detail::
Calling :c:func:PyLong_FreeExport is optional if export_long->digits
is NULL.
PyLongWriter API ^^^^^^^^^^^^^^^^
The :c:type:PyLongWriter API can be used to import an integer.
.. versionadded:: 3.14
.. c:type:: PyLongWriter
A Python :class:int writer instance.
The instance must be destroyed by :c:func:PyLongWriter_Finish or
:c:func:PyLongWriter_Discard.
.. c:function:: PyLongWriter* PyLongWriter_Create(int negative, Py_ssize_t ndigits, void **digits)
Create a :c:type:PyLongWriter.
On success, allocate *digits and return a writer.
On error, set an exception and return NULL.
negative is 1 if the number is negative, or 0 otherwise.
ndigits is the number of digits in the digits array. It must be greater than 0.
digits must not be NULL.
After a successful call to this function, the caller should fill in the
array of digits digits and then call :c:func:PyLongWriter_Finish to get
a Python :class:int.
The layout of digits is described by :c:func:PyLong_GetNativeLayout.
Digits must be in the range [0; (1 << bits_per_digit) - 1]
(where the :c:type:~PyLongLayout.bits_per_digit is the number of bits
per digit).
Any unused most significant digits must be set to 0.
Alternately, call :c:func:PyLongWriter_Discard to destroy the writer
instance without creating an :class:~int object.
.. c:function:: PyObject* PyLongWriter_Finish(PyLongWriter *writer)
Finish a :c:type:PyLongWriter created by :c:func:PyLongWriter_Create.
On success, return a Python :class:int object.
On error, set an exception and return NULL.
The function takes care of normalizing the digits and converts the object to a compact integer if needed.
The writer instance and the digits array are invalid after the call.
.. c:function:: void PyLongWriter_Discard(PyLongWriter *writer)
Discard a :c:type:PyLongWriter created by :c:func:PyLongWriter_Create.
If writer is NULL, no operation is performed.
The writer instance and the digits array are invalid after the call.
Deprecated API ^^^^^^^^^^^^^^
These macros are :term:soft deprecated. They describe parameters
of the internal representation of :c:type:PyLongObject instances.
Use :c:func:PyLong_GetNativeLayout instead, along with :c:func:PyLong_Export
to read integer data or :c:type:PyLongWriter to write it.
These currently use the same layout, but are designed to continue working correctly
even if CPython's internal integer representation changes.
.. c:macro:: PyLong_SHIFT
This is equivalent to :c:member:~PyLongLayout.bits_per_digit in
the output of :c:func:PyLong_GetNativeLayout.
.. c:macro:: PyLong_BASE
This is currently equivalent to :c:expr:1 << PyLong_SHIFT.
.. c:macro:: PyLong_MASK
This is currently equivalent to :c:expr:(1 << PyLong_SHIFT) - 1