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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