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      1 
      2 /* Float object interface */
      3 
      4 /*
      5 PyFloatObject represents a (double precision) floating point number.
      6 */
      7 
      8 #ifndef Py_FLOATOBJECT_H
      9 #define Py_FLOATOBJECT_H
     10 #ifdef __cplusplus
     11 extern "C" {
     12 #endif
     13 
     14 typedef struct {
     15     PyObject_HEAD
     16     double ob_fval;
     17 } PyFloatObject;
     18 
     19 PyAPI_DATA(PyTypeObject) PyFloat_Type;
     20 
     21 #define PyFloat_Check(op) PyObject_TypeCheck(op, &PyFloat_Type)
     22 #define PyFloat_CheckExact(op) (Py_TYPE(op) == &PyFloat_Type)
     23 
     24 /* The str() precision PyFloat_STR_PRECISION is chosen so that in most cases,
     25    the rounding noise created by various operations is suppressed, while
     26    giving plenty of precision for practical use. */
     27 
     28 #define PyFloat_STR_PRECISION 12
     29 
     30 #ifdef Py_NAN
     31 #define Py_RETURN_NAN return PyFloat_FromDouble(Py_NAN)
     32 #endif
     33 
     34 #define Py_RETURN_INF(sign) do					\
     35 	if (copysign(1., sign) == 1.) {				\
     36 		return PyFloat_FromDouble(Py_HUGE_VAL);	\
     37 	} else {						\
     38 		return PyFloat_FromDouble(-Py_HUGE_VAL);	\
     39 	} while(0)
     40 
     41 PyAPI_FUNC(double) PyFloat_GetMax(void);
     42 PyAPI_FUNC(double) PyFloat_GetMin(void);
     43 PyAPI_FUNC(PyObject *) PyFloat_GetInfo(void);
     44 
     45 /* Return Python float from string PyObject.  Second argument ignored on
     46    input, and, if non-NULL, NULL is stored into *junk (this tried to serve a
     47    purpose once but can't be made to work as intended). */
     48 PyAPI_FUNC(PyObject *) PyFloat_FromString(PyObject*, char** junk);
     49 
     50 /* Return Python float from C double. */
     51 PyAPI_FUNC(PyObject *) PyFloat_FromDouble(double);
     52 
     53 /* Extract C double from Python float.  The macro version trades safety for
     54    speed. */
     55 PyAPI_FUNC(double) PyFloat_AsDouble(PyObject *);
     56 #define PyFloat_AS_DOUBLE(op) (((PyFloatObject *)(op))->ob_fval)
     57 
     58 /* Write repr(v) into the char buffer argument, followed by null byte.  The
     59    buffer must be "big enough"; >= 100 is very safe.
     60    PyFloat_AsReprString(buf, x) strives to print enough digits so that
     61    PyFloat_FromString(buf) then reproduces x exactly. */
     62 PyAPI_FUNC(void) PyFloat_AsReprString(char*, PyFloatObject *v);
     63 
     64 /* Write str(v) into the char buffer argument, followed by null byte.  The
     65    buffer must be "big enough"; >= 100 is very safe.  Note that it's
     66    unusual to be able to get back the float you started with from
     67    PyFloat_AsString's result -- use PyFloat_AsReprString() if you want to
     68    preserve precision across conversions. */
     69 PyAPI_FUNC(void) PyFloat_AsString(char*, PyFloatObject *v);
     70 
     71 /* _PyFloat_{Pack,Unpack}{4,8}
     72  *
     73  * The struct and pickle (at least) modules need an efficient platform-
     74  * independent way to store floating-point values as byte strings.
     75  * The Pack routines produce a string from a C double, and the Unpack
     76  * routines produce a C double from such a string.  The suffix (4 or 8)
     77  * specifies the number of bytes in the string.
     78  *
     79  * On platforms that appear to use (see _PyFloat_Init()) IEEE-754 formats
     80  * these functions work by copying bits.  On other platforms, the formats the
     81  * 4- byte format is identical to the IEEE-754 single precision format, and
     82  * the 8-byte format to the IEEE-754 double precision format, although the
     83  * packing of INFs and NaNs (if such things exist on the platform) isn't
     84  * handled correctly, and attempting to unpack a string containing an IEEE
     85  * INF or NaN will raise an exception.
     86  *
     87  * On non-IEEE platforms with more precision, or larger dynamic range, than
     88  * 754 supports, not all values can be packed; on non-IEEE platforms with less
     89  * precision, or smaller dynamic range, not all values can be unpacked.  What
     90  * happens in such cases is partly accidental (alas).
     91  */
     92 
     93 /* The pack routines write 4 or 8 bytes, starting at p.  le is a bool
     94  * argument, true if you want the string in little-endian format (exponent
     95  * last, at p+3 or p+7), false if you want big-endian format (exponent
     96  * first, at p).
     97  * Return value:  0 if all is OK, -1 if error (and an exception is
     98  * set, most likely OverflowError).
     99  * There are two problems on non-IEEE platforms:
    100  * 1):  What this does is undefined if x is a NaN or infinity.
    101  * 2):  -0.0 and +0.0 produce the same string.
    102  */
    103 PyAPI_FUNC(int) _PyFloat_Pack4(double x, unsigned char *p, int le);
    104 PyAPI_FUNC(int) _PyFloat_Pack8(double x, unsigned char *p, int le);
    105 
    106 /* Used to get the important decimal digits of a double */
    107 PyAPI_FUNC(int) _PyFloat_Digits(char *buf, double v, int *signum);
    108 PyAPI_FUNC(void) _PyFloat_DigitsInit(void);
    109 
    110 /* The unpack routines read 4 or 8 bytes, starting at p.  le is a bool
    111  * argument, true if the string is in little-endian format (exponent
    112  * last, at p+3 or p+7), false if big-endian (exponent first, at p).
    113  * Return value:  The unpacked double.  On error, this is -1.0 and
    114  * PyErr_Occurred() is true (and an exception is set, most likely
    115  * OverflowError).  Note that on a non-IEEE platform this will refuse
    116  * to unpack a string that represents a NaN or infinity.
    117  */
    118 PyAPI_FUNC(double) _PyFloat_Unpack4(const unsigned char *p, int le);
    119 PyAPI_FUNC(double) _PyFloat_Unpack8(const unsigned char *p, int le);
    120 
    121 /* free list api */
    122 PyAPI_FUNC(int) PyFloat_ClearFreeList(void);
    123 
    124 /* Format the object based on the format_spec, as defined in PEP 3101
    125    (Advanced String Formatting). */
    126 PyAPI_FUNC(PyObject *) _PyFloat_FormatAdvanced(PyObject *obj,
    127 					       char *format_spec,
    128 					       Py_ssize_t format_spec_len);
    129 
    130 /* Round a C double x to the closest multiple of 10**-ndigits.  Returns a
    131    Python float on success, or NULL (with an appropriate exception set) on
    132    failure.  Used in builtin_round in bltinmodule.c. */
    133 PyAPI_FUNC(PyObject *) _Py_double_round(double x, int ndigits);
    134 
    135 
    136 
    137 #ifdef __cplusplus
    138 }
    139 #endif
    140 #endif /* !Py_FLOATOBJECT_H */
    141