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New private API functions _PyFloat_{Pack,Unpack}(4,8}. This is a

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refactoring to get all the duplicates of this delicate code out of the
cPickle and struct modules.
This commit is contained in:
Tim Peters 2003-03-20 20:53:32 +00:00
parent d50ade68ec
commit 9905b943f7
4 changed files with 382 additions and 446 deletions
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42
Include/floatobject.h
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@ -47,6 +47,48 @@ PyAPI_FUNC(void) PyFloat_AsReprString(char*, PyFloatObject *v);
preserve precision across conversions. */
PyAPI_FUNC(void) PyFloat_AsString(char*, PyFloatObject *v);
/* _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.
*
* Excepting NaNs and infinities (which aren't handled correctly), 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. 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 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+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).
* Bug: What this does is undefined if x is a NaN or infinity.
* Bug: -0.0 and +0.0 produce the same string.
*/
PyAPI_FUNC(int) _PyFloat_Pack4(double x, unsigned char *p, int le);
PyAPI_FUNC(int) _PyFloat_Pack8(double x, unsigned char *p, int le);
/* The unpack routines read 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+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).
* Bug: What this does is undefined if the string represents a NaN or
* infinity.
*/
PyAPI_FUNC(double) _PyFloat_Unpack4(const unsigned char *p, int le);
PyAPI_FUNC(double) _PyFloat_Unpack8(const unsigned char *p, int le);
#ifdef __cplusplus
}
#endif