PEP 757: misc edits (#3984)

Author: skirpichev

peps/pep-0757.rst

@@ -129,6 +129,11 @@ Export API
 
       Read-only array of unsigned digits. Can be ``NULL``.
 
+   If :c:member:`digits` not ``NULL``, a private field of the
+   :c:struct:`PyLongExport` structure stores a strong reference to the Python
+   :class:`int` object to make sure that that structure remains valid until
+   :c:func:`PyLong_FreeExport()` is called.
+
 
 .. c:function:: int PyLong_Export(PyObject *obj, PyLongExport *export_long)
 
@@ -146,11 +151,6 @@ Export API
    On CPython 3.14, no memory copy is needed, it's just a thin wrapper to
    expose Python int internal digits array.
 
-   If :c:member:`~PyLongExport.digits` not ``NULL``, a private field of
-   the :c:struct:`PyLongExport` structure stores a strong reference to
-   the Python :class:`int` object to make sure that that structure
-   remains valid until :c:func:`PyLong_FreeExport()` is called.
-
 
 .. c:function:: void PyLong_FreeExport(PyLongExport *export_long)
 
@@ -183,9 +183,9 @@ create a Python :class:`int` object from a digits array.
    greater than or equal to 0.
 
    The caller must initialize the array of digits *digits* and then call
-   :c:func:`PyLongWriter_Finish` to get a Python :class:`int`. Digits must be
-   in the range [``0``; ``PyLong_BASE - 1``]. Unused digits must be set to
-   ``0``.
+   :c:func:`PyLongWriter_Finish` to get a Python :class:`int`.  Digits must be
+   in the range [``0``; ``(1 << sys.int_info.bits_per_digit) - 1``].  Unused digits must
+   be set to ``0``.
 
    On CPython 3.14, the implementation is a thin wrapper to the private
    :c:func:`!_PyLong_New()` function.
@@ -238,6 +238,18 @@ Implementation
 Benchmarks
 ==========
 
+Code::
+
+    /* Query parameters of Python’s internal representation of integers. */
+    const PyLongLayout *layout = PyLong_GetNativeLayout();
+
+    size_t int_digit_size = layout->digit_size;
+    int int_digits_order = layout->digits_order;
+    size_t int_bits_per_digit = layout->bits_per_digit;
+    size_t int_nails = int_digit_size*8 - int_bits_per_digit;
+    int int_endianness = layout->endianness;
+
+
 Export: :c:func:`PyLong_Export()` with gmpy2
 --------------------------------------------
 
@@ -246,28 +258,26 @@ Code::
     static void
     mpz_set_PyLong(mpz_t z, PyObject *obj)
     {
-        const PyLongLayout* layout = PyLong_GetNativeLayout();
         static PyLongExport long_export;
 
         PyLong_Export(obj, &long_export);
         if (long_export.digits) {
-            mpz_import(z, long_export.ndigits, layout->digits_order,
-                       layout->digit_size, layout->endianness,
-                       layout->digit_size*8 - layout->bits_per_digit,
-                       long_export.digits);
+            mpz_import(z, long_export.ndigits, int_digits_order, int_digit_size,
+                       int_endianness, int_nails, long_export.digits);
             if (long_export.negative) {
                 mpz_neg(z, z);
             }
             PyLong_FreeExport(&long_export);
         }
         else {
-            if (LONG_MIN <= long_export.value && long_export.value <= LONG_MAX) {
-                mpz_set_si(z, long_export.value);
+            const int64_t value = long_export.value;
+
+            if (LONG_MIN <= value && value <= LONG_MAX) {
+                mpz_set_si(z, value);
             }
             else {
-                mpz_import(z, 1, -1, sizeof(int64_t), 0, 0,
-                           &long_export.value);
-                if (long_export.value < 0) {
+                mpz_import(z, 1, -1, sizeof(int64_t), 0, 0, &value);
+                if (value < 0) {
                     mpz_t tmp;
                     mpz_init(tmp);
                     mpz_ui_pow_ui(tmp, 2, 64);
@@ -324,20 +334,17 @@ Code::
             return PyLong_FromLong(mpz_get_si(obj->z));
         }
 
-        const PyLongLayout *layout = PyLong_GetNativeLayout();
         size_t size = (mpz_sizeinbase(obj->z, 2) +
-                       layout->bits_per_digit - 1) / layout->bits_per_digit;
+                       int_bits_per_digit - 1) / int_bits_per_digit;
         void *digits;
         PyLongWriter *writer = PyLongWriter_Create(mpz_sgn(obj->z) < 0, size,
                                                    &digits);
         if (writer == NULL) {
             return NULL;
         }
 
-        mpz_export(digits, NULL, layout->endianness,
-                   layout->digit_size, layout->digits_order,
-                   layout->digit_size*8 - layout->bits_per_digit,
-                   obj->z);
+        mpz_export(digits, NULL, int_digits_order, int_digit_size,
+                   int_endianness, int_nails, obj->z);
 
         return PyLongWriter_Finish(writer);
     }
@@ -389,11 +396,11 @@ Open Questions
   :c:func:`PyLong_GetNativeLayout()` function returns a C structure
   which is more convenient to use in C than :data:`sys.int_info` which uses
   Python objects.
-* Currenly, all required information for :class:`int` import/export is
+* Currently, all required information for :class:`int` import/export is
   already available via :c:func:`PyLong_GetInfo()` or :data:`sys.int_info`.
   Native endianness of "digits" and current order of digits (least
   significant digit first) --- is a common denominator of all libraries
-  for aribitrary precision integer arithmetic.  So, shouldn't we just remove
+  for arbitrary precision integer arithmetic.  So, shouldn't we just remove
   from API both :c:struct:`PyLongLayout` and :c:func:`PyLong_GetNativeLayout()` (which
   is actually just a minor convenience)?