Add low level unstable API for fast access to 'small' ints.

Author: markshannon

Include/cpython/longobject.h

@@ -93,3 +93,8 @@ PyAPI_FUNC(PyObject *) _PyLong_GCD(PyObject *, PyObject *);
 
 PyAPI_FUNC(PyObject *) _PyLong_Rshift(PyObject *, size_t);
 PyAPI_FUNC(PyObject *) _PyLong_Lshift(PyObject *, size_t);
+
+
+PyAPI_FUNC(int) PyUnstable_Int_IsCompact(const PyLongObject* op);
+PyAPI_FUNC(Py_ssize_t) PyUnstable_Int_CompactValue(const PyLongObject* op);
+

Include/internal/pycore_long.h

@@ -137,6 +137,8 @@ _PyLong_IsCompact(const PyLongObject* op) {
     return op->long_value.lv_tag < (2 << NON_SIZE_BITS);
 }
 
+#define PyUnstable_Int_IsCompact _PyLong_IsCompact
+
 static inline int
 _PyLong_BothAreCompact(const PyLongObject* a, const PyLongObject* b) {
     assert(PyLong_Check(a));
@@ -159,6 +161,8 @@ _PyLong_CompactValue(const PyLongObject *op)
     return sign * (Py_ssize_t)op->long_value.ob_digit[0];
 }
 
+#define PyUnstable_Int_CompactValue _PyLong_CompactValue
+
 static inline bool
 _PyLong_IsZero(const PyLongObject *op)
 {

Objects/longobject.c

@@ -6366,3 +6366,17 @@ _PyLong_FiniTypes(PyInterpreterState *interp)
 {
     _PyStructSequence_FiniBuiltin(interp, &Int_InfoType);
 }
+
+#undef PyUnstable_Int_IsCompact
+
+int
+PyUnstable_Int_IsCompact(const PyLongObject* op) {
+    return _PyLong_IsCompact(op);
+}
+
+#undef PyUnstable_Int_CompactValue
+
+Py_ssize_t
+PyUnstable_Int_CompactValue(const PyLongObject* op) {
+    return _PyLong_CompactValue(op);
+}