Address Mark's review

vstinner · Mar 11, 2022 · Mar 3, 2022 · Mar 10, 2022 · Mar 10, 2022 · 9371cde337f22333eb31b9a7f9eca255a3b95ab0
commit 9371cde337f22333eb31b9a7f9eca255a3b95ab0
@@ -81,17 +81,18 @@ Floating Point Objects
 Pack and Unpack functions
 =========================
 
-The :mod:`struct` and :mod:`pickle` (at least) modules need an efficient
-platform- independent way to store floating-point values as byte strings. The
-Pack routines produce a bytes string from a C :c:type:`double`, and the Unpack
-routines produce a C :c:type:`double` from such a bytes string. The suffix
-(2, 4 or 8) specifies the number of bytes in the bytes string.
-
-On platforms that appear to use IEEE-754 formats these functions work by
-copying bits. On other platforms, the formats the 4- byte format (32-bit) is
-identical to the IEEE-754 single precision format, and the 8-byte format
-(64-bit) to the IEEE-754 double precision format, although the packing of INFs
-and NaNs (if such things exist on the platform) isn't handled correctly, and
+The pack and unpack functions provide an efficient platform-independent way to
+store floating-point values as byte strings. The Pack routines produce a bytes
+string from a C :c:type:`double`, and the Unpack routines produce a C
+:c:type:`double` from such a bytes string. The suffix (2, 4 or 8) specifies the
+number of bytes in the bytes string.
+
+On platforms that appear to use IEEE 754 formats these functions work by
+copying bits. On other platforms, the 2-byte format is identical to the IEEE
+754 binary16 half-precision format, the 4-byte format (32-bit) is identical to
+the IEEE 754 binary32 single precision format, and the 8-byte format to the
+IEEE 754 binary64 double precision format, although the packing of INFs and
+NaNs (if such things exist on the platform) isn't handled correctly, and
 attempting to unpack a bytes string containing an IEEE INF or NaN will raise an
 exception.
 
@@ -105,40 +106,41 @@ happens in such cases is partly accidental (alas).
 Pack functions
 --------------
 
-The pack routines write 2, 4 or 8 bytes, starting at *p*. *le* is a bool
-argument, true if you want the bytes string in little-endian format (exponent
-last, at ``p+1``, ``p+3`` or ``p+7``), false if you want big-endian format
-(exponent first, at *p*).
+The pack routines write 2, 4 or 8 bytes, starting at *p*. *le* is an
+:c:type:`int` argument, non-zero if you want the bytes string in little-endian
+format (exponent last, at ``p+1``, ``p+3``, or ``p+6`` ``p+7``), zero if you
+want big-endian format (exponent first, at *p*).
 
 Return value: ``0`` if all is OK, ``-1`` if error (and an exception is set,
 most likely :exc:`OverflowError`).
 
 There are two problems on non-IEEE platforms:
 
 * What this does is undefined if *x* is a NaN or infinity.
-* -0.0 and +0.0 produce the same bytes string.
+* ``-0.0`` and ``+0.0`` produce the same bytes string.
 
 .. c:function:: int PyFloat_Pack2(double x, unsigned char *p, int le)
 
-   Pack a C double as 16-bit.
+   Pack a C double as the IEEE 754 binary16 half-precision format.
 
 .. c:function:: int PyFloat_Pack4(double x, unsigned char *p, int le)
 
-   Pack a C double as 32-bit.
+   Pack a C double as the IEEE 754 binary32 single precision format.
 
 .. c:function:: int PyFloat_Pack8(double x, unsigned char *p, int le)
 
-   Pack a C double as 64-bit.
+   Pack a C double as the IEEE 754 binary64 double precision format.
 
 
 Unpack functions
 ----------------
 
-The unpack routines read 2, 4 or 8 bytes, starting at *p*.  *le* is a bool
-argument, true if the bytes string is in little-endian format (exponent last,
-at ``p+1``, ``p+3`` or ``p+7``), false if big-endian (exponent first, at *p*).
+The unpack routines read 2, 4 or 8 bytes, starting at *p*.  *le* is an
+:c:type:`int` argument, non-zero if the bytes string is in little-endian format
+(exponent last, at ``p+1``, ``p+3`` or ``p+6`` and ``p+7``), zero if big-endian
+(exponent first, at *p*).
 
-Return value:  The unpacked double.  On error, this is ``-1.0`` and
+Return value: The unpacked double.  On error, this is ``-1.0`` and
 :c:func:`PyErr_Occurred` is true (and an exception is set, most likely
 :exc:`OverflowError`).
 
@@ -147,12 +149,12 @@ represents a NaN or infinity.
 
 .. c:function:: double PyFloat_Unpack2(const unsigned char *p, int le)
 
-   Unpack 16-bit as a C double.
+   Unpack the IEEE 754 binary16 half-precision format as a C double.
 
 .. c:function:: double PyFloat_Unpack4(const unsigned char *p, int le)
 
-   Unpack 32-bit as a C double.
+   Unpack the IEEE 754 binary32 single precision format as a C double.
 
 .. c:function:: double PyFloat_Unpack8(const unsigned char *p, int le)
 
-   Unpack 64-bit as a C double.
+   Unpack the IEEE 754 binary64 double precision format as a C double.
diff --git a/Include/cpython/floatobject.h b/Include/cpython/floatobject.h
@@ -12,50 +12,10 @@ typedef struct {
 #define PyFloat_AS_DOUBLE(op) (((PyFloatObject *)(op))->ob_fval)
 
 
-/* PyFloat_{Pack,Unpack}{4,8}
- *
- * The struct and pickle (at least) modules need an efficient platform-
- * independent way to store floating-point values as byte strings.
- * The Pack routines produce a string from a C double, and the Unpack
- * routines produce a C double from such a string.  The suffix (4 or 8)
- * specifies the number of bytes in the string.
- *
- * On platforms that appear to use (see _PyFloat_Init()) IEEE-754 formats
- * these functions work by copying bits.  On other platforms, the formats the
- * 4- byte format is identical to the IEEE-754 single precision format, and
- * the 8-byte format to the IEEE-754 double precision format, although the
- * packing of INFs and NaNs (if such things exist on the platform) isn't
- * handled correctly, and attempting to unpack a string containing an IEEE
- * INF or NaN will raise an exception.
- *
- * On non-IEEE platforms with more precision, or larger dynamic range, than
- * 754 supports, not all values can be packed; on non-IEEE platforms with less
- * precision, or smaller dynamic range, not all values can be unpacked.  What
- * happens in such cases is partly accidental (alas).
- */
-
-/* The pack routines write 2, 4 or 8 bytes, starting at p.  le is a bool
- * argument, true if you want the string in little-endian format (exponent
- * last, at p+1, p+3 or p+7), false if you want big-endian format (exponent
- * first, at p).
- * Return value:  0 if all is OK, -1 if error (and an exception is
- * set, most likely OverflowError).
- * There are two problems on non-IEEE platforms:
- * 1):  What this does is undefined if x is a NaN or infinity.
- * 2):  -0.0 and +0.0 produce the same string.
- */
 PyAPI_FUNC(int) PyFloat_Pack2(double x, char *p, int le);
 PyAPI_FUNC(int) PyFloat_Pack4(double x, char *p, int le);
 PyAPI_FUNC(int) PyFloat_Pack8(double x, char *p, int le);
 
-/* The unpack routines read 2, 4 or 8 bytes, starting at p.  le is a bool
- * argument, true if the string is in little-endian format (exponent
- * last, at p+1, p+3 or p+7), false if big-endian (exponent first, at p).
- * Return value:  The unpacked double.  On error, this is -1.0 and
- * PyErr_Occurred() is true (and an exception is set, most likely
- * OverflowError).  Note that on a non-IEEE platform this will refuse
- * to unpack a string that represents a NaN or infinity.
- */
 PyAPI_FUNC(double) PyFloat_Unpack2(const char *p, int le);
 PyAPI_FUNC(double) PyFloat_Unpack4(const char *p, int le);
 PyAPI_FUNC(double) PyFloat_Unpack8(const char *p, int le);