整數物件
********

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 "PyErr_Occurred()" to
disambiguate.

type PyLongObject
    * 為 受限 API 的一部分 （做為一個不透明結構 (opaque struct)）.*

   This subtype of "PyObject" represents a Python integer object.

PyTypeObject PyLong_Type
    * 為 穩定 ABI 的一部分.*

   This instance of "PyTypeObject" represents the Python integer type.
   This is the same object as "int" in the Python layer.

int PyLong_Check(PyObject *p)

   Return true if its argument is a "PyLongObject" or a subtype of
   "PyLongObject".  This function always succeeds.

int PyLong_CheckExact(PyObject *p)

   Return true if its argument is a "PyLongObject", but not a subtype
   of "PyLongObject".  This function always succeeds.

PyObject *PyLong_FromLong(long v)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Return a new "PyLongObject" object from *v*, or "NULL" on failure.

   The current implementation keeps an array of integer objects for
   all integers between "-5" and "256". When you create an int in that
   range you actually just get back a reference to the existing
   object.

PyObject *PyLong_FromUnsignedLong(unsigned long v)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Return a new "PyLongObject" object from a C unsigned long, or
   "NULL" on failure.

PyObject *PyLong_FromSsize_t(Py_ssize_t v)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Return a new "PyLongObject" object from a C "Py_ssize_t", or "NULL"
   on failure.

PyObject *PyLong_FromSize_t(size_t v)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Return a new "PyLongObject" object from a C "size_t", or "NULL" on
   failure.

PyObject *PyLong_FromLongLong(long long v)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Return a new "PyLongObject" object from a C long long, or "NULL" on
   failure.

PyObject *PyLong_FromUnsignedLongLong(unsigned long long v)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Return a new "PyLongObject" object from a C unsigned long long, or
   "NULL" on failure.

PyObject *PyLong_FromDouble(double v)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Return a new "PyLongObject" object from the integer part of *v*, or
   "NULL" on failure.

PyObject *PyLong_FromString(const char *str, char **pend, int base)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Return a new "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 Integer literals definition; in this case, leading zeros in a
   non-zero decimal number raises a "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,
   "ValueError" will be raised.

   也參考:

     Python methods "int.to_bytes()" and "int.from_bytes()" to convert
     a "PyLongObject" to/from an array of bytes in base "256". You can
     call those from C using "PyObject_CallMethod()".

PyObject *PyLong_FromUnicodeObject(PyObject *u, int base)
    *回傳值：新的參照。*

   Convert a sequence of Unicode digits in the string *u* to a Python
   integer value.

   在 3.3 版被加入.

PyObject *PyLong_FromVoidPtr(void *p)
    *回傳值：新的參照。** 為 穩定 ABI 的一部分.*

   Create a Python integer from the pointer *p*. The pointer value can
   be retrieved from the resulting value using "PyLong_AsVoidPtr()".

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 "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 "PyLong_FromUnsignedNativeBytes()". Other flags are
   ignored.

   在 3.13 版被加入.

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 "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.

   在 3.13 版被加入.

long PyLong_AsLong(PyObject *obj)
    * 為 穩定 ABI 的一部分.*

   Return a C long representation of *obj*.  If *obj* is not an
   instance of "PyLongObject", first call its "__index__()" method (if
   present) to convert it to a "PyLongObject".

   Raise "OverflowError" if the value of *obj* is out of range for a
   long.

   Returns "-1" on error.  Use "PyErr_Occurred()" to disambiguate.

   在 3.8 版的變更: Use "__index__()" if available.

   在 3.10 版的變更: This function will no longer use "__int__()".

int PyLong_AsInt(PyObject *obj)
    * 為 穩定 ABI 的一部分 自 3.13 版本開始.*

   Similar to "PyLong_AsLong()", but store the result in a C int
   instead of a C long.

   在 3.13 版被加入.

long PyLong_AsLongAndOverflow(PyObject *obj, int *overflow)
    * 為 穩定 ABI 的一部分.*

   Return a C long representation of *obj*.  If *obj* is not an
   instance of "PyLongObject", first call its "__index__()" method (if
   present) to convert it to a "PyLongObject".

   If the value of *obj* is greater than "LONG_MAX" or less than
   "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 "PyErr_Occurred()" to disambiguate.

   在 3.8 版的變更: Use "__index__()" if available.

   在 3.10 版的變更: This function will no longer use "__int__()".

long long PyLong_AsLongLong(PyObject *obj)
    * 為 穩定 ABI 的一部分.*

   Return a C long long representation of *obj*.  If *obj* is not an
   instance of "PyLongObject", first call its "__index__()" method (if
   present) to convert it to a "PyLongObject".

   Raise "OverflowError" if the value of *obj* is out of range for a
   long long.

   Returns "-1" on error.  Use "PyErr_Occurred()" to disambiguate.

   在 3.8 版的變更: Use "__index__()" if available.

   在 3.10 版的變更: This function will no longer use "__int__()".

long long PyLong_AsLongLongAndOverflow(PyObject *obj, int *overflow)
    * 為 穩定 ABI 的一部分.*

   Return a C long long representation of *obj*.  If *obj* is not an
   instance of "PyLongObject", first call its "__index__()" method (if
   present) to convert it to a "PyLongObject".

   If the value of *obj* is greater than "LLONG_MAX" or less than
   "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 "PyErr_Occurred()" to disambiguate.

   在 3.2 版被加入.

   在 3.8 版的變更: Use "__index__()" if available.

   在 3.10 版的變更: This function will no longer use "__int__()".

Py_ssize_t PyLong_AsSsize_t(PyObject *pylong)
    * 為 穩定 ABI 的一部分.*

   Return a C "Py_ssize_t" representation of *pylong*.  *pylong* must
   be an instance of "PyLongObject".

   Raise "OverflowError" if the value of *pylong* is out of range for
   a "Py_ssize_t".

   Returns "-1" on error.  Use "PyErr_Occurred()" to disambiguate.

unsigned long PyLong_AsUnsignedLong(PyObject *pylong)
    * 為 穩定 ABI 的一部分.*

   Return a C unsigned long representation of *pylong*.  *pylong* must
   be an instance of "PyLongObject".

   Raise "OverflowError" if the value of *pylong* is out of range for
   a unsigned long.

   Returns "(unsigned long)-1" on error. Use "PyErr_Occurred()" to
   disambiguate.

size_t PyLong_AsSize_t(PyObject *pylong)
    * 為 穩定 ABI 的一部分.*

   Return a C "size_t" representation of *pylong*.  *pylong* must be
   an instance of "PyLongObject".

   Raise "OverflowError" if the value of *pylong* is out of range for
   a "size_t".

   Returns "(size_t)-1" on error. Use "PyErr_Occurred()" to
   disambiguate.

unsigned long long PyLong_AsUnsignedLongLong(PyObject *pylong)
    * 為 穩定 ABI 的一部分.*

   Return a C unsigned long long representation of *pylong*.  *pylong*
   must be an instance of "PyLongObject".

   Raise "OverflowError" if the value of *pylong* is out of range for
   an unsigned long long.

   Returns "(unsigned long long)-1" on error. Use "PyErr_Occurred()"
   to disambiguate.

   在 3.1 版的變更: A negative *pylong* now raises "OverflowError",
   not "TypeError".

unsigned long PyLong_AsUnsignedLongMask(PyObject *obj)
    * 為 穩定 ABI 的一部分.*

   Return a C unsigned long representation of *obj*.  If *obj* is not
   an instance of "PyLongObject", first call its "__index__()" method
   (if present) to convert it to a "PyLongObject".

   If the value of *obj* is out of range for an unsigned long, return
   the reduction of that value modulo "ULONG_MAX + 1".

   Returns "(unsigned long)-1" on error.  Use "PyErr_Occurred()" to
   disambiguate.

   在 3.8 版的變更: Use "__index__()" if available.

   在 3.10 版的變更: This function will no longer use "__int__()".

unsigned long long PyLong_AsUnsignedLongLongMask(PyObject *obj)
    * 為 穩定 ABI 的一部分.*

   Return a C unsigned long long representation of *obj*.  If *obj* is
   not an instance of "PyLongObject", first call its "__index__()"
   method (if present) to convert it to a "PyLongObject".

   If the value of *obj* is out of range for an unsigned long long,
   return the reduction of that value modulo "ULLONG_MAX + 1".

   Returns "(unsigned long long)-1" on error.  Use "PyErr_Occurred()"
   to disambiguate.

   在 3.8 版的變更: Use "__index__()" if available.

   在 3.10 版的變更: This function will no longer use "__int__()".

double PyLong_AsDouble(PyObject *pylong)
    * 為 穩定 ABI 的一部分.*

   Return a C double representation of *pylong*.  *pylong* must be an
   instance of "PyLongObject".

   Raise "OverflowError" if the value of *pylong* is out of range for
   a double.

   Returns "-1.0" on error.  Use "PyErr_Occurred()" to disambiguate.

void *PyLong_AsVoidPtr(PyObject *pylong)
    * 為 穩定 ABI 的一部分.*

   Convert a Python integer *pylong* to a C void pointer. If *pylong*
   cannot be converted, an "OverflowError" will be raised.  This is
   only assured to produce a usable void pointer for values created
   with "PyLong_FromVoidPtr()".

   Returns "NULL" on error.  Use "PyErr_Occurred()" to disambiguate.

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: large buffers are
   padded with zeroes.

   If the returned value is greater than 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.

   備註:

     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".

   備註:

     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 combintation 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".

   +-----------------------------------------------+--------+
   | Flag                                          | Value  |
   |===============================================|========|
   | Py_ASNATIVEBYTES_DEFAULTS                     | "-1"   |
   +-----------------------------------------------+--------+
   | Py_ASNATIVEBYTES_BIG_ENDIAN                   | "0"    |
   +-----------------------------------------------+--------+
   | Py_ASNATIVEBYTES_LITTLE_ENDIAN                | "1"    |
   +-----------------------------------------------+--------+
   | Py_ASNATIVEBYTES_NATIVE_ENDIAN                | "3"    |
   +-----------------------------------------------+--------+
   | Py_ASNATIVEBYTES_UNSIGNED_BUFFER              | "4"    |
   +-----------------------------------------------+--------+
   | Py_ASNATIVEBYTES_REJECT_NEGATIVE              | "8"    |
   +-----------------------------------------------+--------+
   | 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 "__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 "TypeError".

   備註:

     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.

   在 3.13 版被加入.

PyObject *PyLong_GetInfo(void)
    * 為 穩定 ABI 的一部分.*

   On success, return a read only *named tuple*, that holds
   information about Python's internal representation of integers. See
   "sys.int_info" for description of individual fields.

   在失敗時，會回傳 "NULL" 並設定例外。

   在 3.1 版被加入.

int PyUnstable_Long_IsCompact(const PyLongObject *op)

   *這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。*

   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
   "PyUnstable_Long_CompactValue()"; for others fall back to a
   "PyLong_As*" function or "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.

Py_ssize_t PyUnstable_Long_CompactValue(const PyLongObject *op)

   *這是 不穩定 API，它可能在小版本發布中沒有任何警告地被變更。*

   If *op* is compact, as determined by "PyUnstable_Long_IsCompact()",
   return its value.

   Otherwise, the return value is undefined.
