gh-111389: expose _PyHASH_INF/BITS/MODULUS/IMAG macros as public

Doc/c-api/hashing.rst

@@ -0,0 +1,20 @@
+Parameters of the numeric hash implementation
+=============================================
+
+See :ref:`numeric-hash` for more details about hashing of numeric types.
+
+.. c:macro:: PyUnstable_PyHASH_MODULUS
+
+   The Mersenne prime ``P = 2**n -1``, used for numeric hash scheme.
+
+.. c:macro:: PyUnstable_PyHASH_BITS
+
+   The exponent ``n`` of ``P``.
+
+.. c:macro:: PyUnstable_PyHASH_INF
+
+   The hash value returned for a positive infinity.
+
+.. c:macro:: PyUnstable_PyHASH_IMAG
+
+   The multiplier used for the imaginary part of a complex number.

Doc/c-api/utilities.rst

@@ -20,3 +20,4 @@ and parsing function arguments and constructing Python values from C values.
    reflection.rst
    codec.rst
    perfmaps.rst
+   hashing.rst

Include/internal/pycore_pyhash.h

@@ -17,23 +17,6 @@ extern Py_hash_t _Py_HashPointerRaw(const void*);
 // Export for '_datetime' shared extension
 PyAPI_FUNC(Py_hash_t) _Py_HashBytes(const void*, Py_ssize_t);
 
-/* Prime multiplier used in string and various other hashes. */
-#define _PyHASH_MULTIPLIER 1000003UL  /* 0xf4243 */
-
-/* Parameters used for the numeric hash implementation.  See notes for
-   _Py_HashDouble in Python/pyhash.c.  Numeric hashes are based on
-   reduction modulo the prime 2**_PyHASH_BITS - 1. */
-
-#if SIZEOF_VOID_P >= 8
-#  define _PyHASH_BITS 61
-#else
-#  define _PyHASH_BITS 31
-#endif
-
-#define _PyHASH_MODULUS (((size_t)1 << _PyHASH_BITS) - 1)
-#define _PyHASH_INF 314159
-#define _PyHASH_IMAG _PyHASH_MULTIPLIER
-
 /* Hash secret
  *
  * memory layout on 64 bit systems

Include/pyhash.h

@@ -16,6 +16,27 @@ typedef struct {
 PyAPI_FUNC(PyHash_FuncDef*) PyHash_GetFuncDef(void);
 #endif
 
+/* Prime multiplier used in string and various other hashes. */
+#define _PyHASH_MULTIPLIER 1000003UL  /* 0xf4243 */
+
+/* Parameters used for the numeric hash implementation.  See notes for
+   _Py_HashDouble in Python/pyhash.c.  Numeric hashes are based on
+   reduction modulo the prime 2**_PyHASH_BITS - 1. */
+
+#if SIZEOF_VOID_P >= 8
+#  define _PyHASH_BITS 61
+#else
+#  define _PyHASH_BITS 31
+#endif
+
+#define PyUnstable_PyHASH_BITS _PyHASH_BITS
+
+#define _PyHASH_MODULUS (((size_t)1 << _PyHASH_BITS) - 1)
+#define PyUnstable_PyHASH_MODULUS _PyHASH_MODULUS
+#define _PyHASH_INF 314159
+#define PyUnstable_PyHASH_INF _PyHASH_INF
+#define _PyHASH_IMAG _PyHASH_MULTIPLIER
+#define PyUnstable_PyHASH_IMAG _PyHASH_IMAG
 
 /* Cutoff for small string DJBX33A optimization in range [1, cutoff).
  *