Include/floatobject.h

   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 */