bpo-46906: Add PyFloat_Pack8() to the C API (GH-31657)

Add new functions to pack and unpack C double (serialize and
deserialize):

* PyFloat_Pack2(), PyFloat_Pack4(), PyFloat_Pack8()
* PyFloat_Unpack2(), PyFloat_Unpack4(), PyFloat_Unpack8()

Document these functions and add unit tests.

Rename private functions and move them from the internal C API
to the public C API:

* _PyFloat_Pack2() => PyFloat_Pack2()
* _PyFloat_Pack4() => PyFloat_Pack4()
* _PyFloat_Pack8() => PyFloat_Pack8()
* _PyFloat_Unpack2() => PyFloat_Unpack2()
* _PyFloat_Unpack4() => PyFloat_Unpack4()
* _PyFloat_Unpack8() => PyFloat_Unpack8()

Replace the "unsigned char*" type with "char*" which is more common
and easy to use.

1 files changed, 8 insertions, 9 deletions

diff --git a/Modules/_ctypes/cfield.c b/Modules/_ctypes/cfield.c
index 2992d34..3b769f9 100644
--- a/Modules/_ctypes/cfield.c
+++ b/Modules/_ctypes/cfield.c
@@ -10,7 +10,6 @@
 
 #include "pycore_bitutils.h"      // _Py_bswap32()
 #include "pycore_call.h"          // _PyObject_CallNoArgs()
-#include "pycore_floatobject.h"   // _PyFloat_Pack8()
 
 #include <ffi.h>
 #include "ctypes.h"
@@ -1009,10 +1008,10 @@ d_set_sw(void *ptr, PyObject *value, Py_ssize_t size)
     if (x == -1 && PyErr_Occurred())
         return NULL;
 #ifdef WORDS_BIGENDIAN
-    if (_PyFloat_Pack8(x, (unsigned char *)ptr, 1))
+    if (PyFloat_Pack8(x, ptr, 1))
         return NULL;
 #else
-    if (_PyFloat_Pack8(x, (unsigned char *)ptr, 0))
+    if (PyFloat_Pack8(x, ptr, 0))
         return NULL;
 #endif
     _RET(value);
@@ -1022,9 +1021,9 @@ static PyObject *
 d_get_sw(void *ptr, Py_ssize_t size)
 {
 #ifdef WORDS_BIGENDIAN
-    return PyFloat_FromDouble(_PyFloat_Unpack8(ptr, 1));
+    return PyFloat_FromDouble(PyFloat_Unpack8(ptr, 1));
 #else
-    return PyFloat_FromDouble(_PyFloat_Unpack8(ptr, 0));
+    return PyFloat_FromDouble(PyFloat_Unpack8(ptr, 0));
 #endif
 }
 
@@ -1057,10 +1056,10 @@ f_set_sw(void *ptr, PyObject *value, Py_ssize_t size)
     if (x == -1 && PyErr_Occurred())
         return NULL;
 #ifdef WORDS_BIGENDIAN
-    if (_PyFloat_Pack4(x, (unsigned char *)ptr, 1))
+    if (PyFloat_Pack4(x, ptr, 1))
         return NULL;
 #else
-    if (_PyFloat_Pack4(x, (unsigned char *)ptr, 0))
+    if (PyFloat_Pack4(x, ptr, 0))
         return NULL;
 #endif
     _RET(value);
@@ -1070,9 +1069,9 @@ static PyObject *
 f_get_sw(void *ptr, Py_ssize_t size)
 {
 #ifdef WORDS_BIGENDIAN
-    return PyFloat_FromDouble(_PyFloat_Unpack4(ptr, 1));
+    return PyFloat_FromDouble(PyFloat_Unpack4(ptr, 1));
 #else
-    return PyFloat_FromDouble(_PyFloat_Unpack4(ptr, 0));
+    return PyFloat_FromDouble(PyFloat_Unpack4(ptr, 0));
 #endif
 }