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, 13 insertions, 7 deletions

diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index 91ca848..736ddc9 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -2033,7 +2033,7 @@ _PyFloat_DebugMallocStats(FILE *out)
 
 
 /*----------------------------------------------------------------------------
- * _PyFloat_{Pack,Unpack}{2,4,8}.  See floatobject.h.
+ * PyFloat_{Pack,Unpack}{2,4,8}.  See floatobject.h.
  * To match the NPY_HALF_ROUND_TIES_TO_EVEN behavior in:
  * https://github.com/numpy/numpy/blob/master/numpy/core/src/npymath/halffloat.c
  * We use:
@@ -2044,8 +2044,9 @@ _PyFloat_DebugMallocStats(FILE *out)
  */
 
 int
-_PyFloat_Pack2(double x, unsigned char *p, int le)
+PyFloat_Pack2(double x, char *data, int le)
 {
+    unsigned char *p = (unsigned char *)data;
     unsigned char sign;
     int e;
     double f;
@@ -2148,8 +2149,9 @@ _PyFloat_Pack2(double x, unsigned char *p, int le)
 }
 
 int
-_PyFloat_Pack4(double x, unsigned char *p, int le)
+PyFloat_Pack4(double x, char *data, int le)
 {
+    unsigned char *p = (unsigned char *)data;
     if (float_format == unknown_format) {
         unsigned char sign;
         int e;
@@ -2255,8 +2257,9 @@ _PyFloat_Pack4(double x, unsigned char *p, int le)
 }
 
 int
-_PyFloat_Pack8(double x, unsigned char *p, int le)
+PyFloat_Pack8(double x, char *data, int le)
 {
+    unsigned char *p = (unsigned char *)data;
     if (double_format == unknown_format) {
         unsigned char sign;
         int e;
@@ -2384,8 +2387,9 @@ _PyFloat_Pack8(double x, unsigned char *p, int le)
 }
 
 double
-_PyFloat_Unpack2(const unsigned char *p, int le)
+PyFloat_Unpack2(const char *data, int le)
 {
+    unsigned char *p = (unsigned char *)data;
     unsigned char sign;
     int e;
     unsigned int f;
@@ -2446,8 +2450,9 @@ _PyFloat_Unpack2(const unsigned char *p, int le)
 }
 
 double
-_PyFloat_Unpack4(const unsigned char *p, int le)
+PyFloat_Unpack4(const char *data, int le)
 {
+    unsigned char *p = (unsigned char *)data;
     if (float_format == unknown_format) {
         unsigned char sign;
         int e;
@@ -2524,8 +2529,9 @@ _PyFloat_Unpack4(const unsigned char *p, int le)
 }
 
 double
-_PyFloat_Unpack8(const unsigned char *p, int le)
+PyFloat_Unpack8(const char *data, int le)
 {
+    unsigned char *p = (unsigned char *)data;
     if (double_format == unknown_format) {
         unsigned char sign;
         int e;