.. highlight:: c
PyHash API
----------
See also the :c:member:`PyTypeObject.tp_hash` member and :ref:`numeric-hash`.
.. c:type:: Py_hash_t
Hash value type: signed integer.
.. versionadded:: 3.2
.. c:type:: Py_uhash_t
Hash value type: unsigned integer.
.. versionadded:: 3.2
.. c:macro:: PyHASH_MODULUS
The `Mersenne prime <https://en.wikipedia.org/wiki/Mersenne_prime>`_ ``P = 2**n -1``, used for numeric hash scheme.
.. versionadded:: 3.13
.. c:macro:: PyHASH_BITS
The exponent ``n`` of ``P`` in :c:macro:`PyHASH_MODULUS`.
.. versionadded:: 3.13
.. c:macro:: PyHASH_MULTIPLIER
Prime multiplier used in string and various other hashes.
.. versionadded:: 3.13
.. c:macro:: PyHASH_INF
The hash value returned for a positive infinity.
.. versionadded:: 3.13
.. c:macro:: PyHASH_IMAG
The multiplier used for the imaginary part of a complex number.
.. versionadded:: 3.13
.. c:type:: PyHash_FuncDef
Hash function definition used by :c:func:`PyHash_GetFuncDef`.
.. c::member:: Py_hash_t (*const hash)(const void *, Py_ssize_t)
Hash function.
.. c:member:: const char *name
Hash function name (UTF-8 encoded string).
.. c:member:: const int hash_bits
Internal size of the hash value in bits.
.. c:member:: const int seed_bits
Size of seed input in bits.
.. versionadded:: 3.4
.. c:function:: PyHash_FuncDef* PyHash_GetFuncDef(void)
Get the hash function definition.
.. seealso::
:pep:`456` "Secure and interchangeable hash algorithm".
.. versionadded:: 3.4
.. c:function:: Py_hash_t Py_HashPointer(const void *ptr)
Hash a pointer value: process the pointer value as an integer (cast it to
``uintptr_t`` internally). The pointer is not dereferenced.
The function cannot fail: it cannot return ``-1``.
.. versionadded:: 3.13
.. c:function:: Py_hash_t Py_HashBuffer(const void *ptr, Py_ssize_t len)
Compute and return the hash value of a buffer of *len* bytes
starting at address *ptr*. The hash is guaranteed to match that of
:class:`bytes`, :class:`memoryview`, and other built-in objects
that implement the :ref:`buffer protocol <bufferobjects>`.
Use this function to implement hashing for immutable objects whose
:c:member:`~PyTypeObject.tp_richcompare` function compares to another
object's buffer.
*len* must be greater than or equal to ``0``.
This function always succeeds.
.. versionadded:: 3.14
.. c:function:: Py_hash_t PyObject_GenericHash(PyObject *obj)
Generic hashing function that is meant to be put into a type
object's ``tp_hash`` slot.
Its result only depends on the object's identity.
.. impl-detail::
In CPython, it is equivalent to :c:func:`Py_HashPointer`.
.. versionadded:: 3.13
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