"""Utilities for handling IEEE 754 floating point special values This python module implements constants and functions for working with IEEE754 double-precision special values. It provides constants for Not-a-Number (NaN), Positive Infinity (PosInf), and Negative Infinity (NegInf), as well as functions to test for these values. The code is implemented in pure python by taking advantage of the 'struct' standard module. Care has been taken to generate proper results on both big-endian and little-endian machines. Some efficiency could be gained by translating the core routines into C. See for reference material on the IEEE 754 floating point standard. Further information on this package is available at . Author: Gregory R. Warnes Date:: 2003-04-08 Copyright: (c) 2003, Pfizer, Inc. """ __version__ = "0.6.0" ident = "$Id: fpconst.py,v 1.8 2003/05/12 15:14:00 warnes Exp $" import struct # check endianess _big_endian = struct.pack('i',1)[0] != '\x01' # and define appropriate constants if(_big_endian): _HW = 0 _LW = 1 NaN = struct.unpack('d', '\x7F\xFF\xFF\xFF\xFF\xFF\xFF\xFF')[0] PosInf = struct.unpack('d', '\x7F\xF0\x00\x00\x00\x00\x00\x00')[0] NegInf = -PosInf else: _HW = 1 _LW = 0 NaN = struct.unpack('d', '\x00\x00\x00\x00\x00\x00\xf8\xff')[0] PosInf = struct.unpack('d', '\x00\x00\x00\x00\x00\x00\xf0\x7f')[0] NegInf = -PosInf def _double_as_longs(dval): "Use struct.unpack to decode a double precision float into two longs" tmp = struct.unpack('ll',struct.pack('d', dval)) return (tmp[_HW], tmp[_LW]) ## ## Functions to extract components of the IEEE 754 floating point format ## def _sign(dval): "Extract the sign bit from a double-precision floating point value" ll = _double_as_longs(dval) return ll[0] >> 31 & 0x01 def _exponent(dval): """Extract the exponentent bits from a double-precision floating point value. Note that for normalized values, the exponentdent bits have an offset of 1023. As a consequence, the actual exponentent is obtained by subtracting 1023 for the value returned by this function """ ll = _double_as_longs(dval) return (ll[0] >> 20) & 0x7ff def _mantissa(dval): """Extract the _mantissa bits from a double-precision floating point value.""" ll = _double_as_longs(dval) mantissa0 = (ll[0] & 0x000fffffL) << 32 mantissa1 = ll[1] return mantissa0 + mantissa1 ## ## Functions to test for IEEE 754 special values ## def isNaN(value): "Determine if the argument is a IEEE 754 NaN (Not a Number) value." return (_exponent(value)==0x7ff and _mantissa(value)!=0) def isInf(value): """Determine if the argument is an infinite IEEE 754 value (positive or negative inifinity)""" return (_exponent(value)==0x7ff and _mantissa(value)== 0) def isFinite(value): """Determine if the argument is an finite IEEE 754 value (i.e., is not NaN, positive or negative inifinity)""" return (_exponent(value)!=0x7ff) def isPosInf(value): "Determine if the argument is a IEEE 754 positive infinity value" return (_sign(value)==0 and _exponent(value)==0x7ff and \ _mantissa(value)== 0) def isNegInf(value): "Determine if the argument is a IEEE 754 negative infinity value" return (_sign(value)==1 and _exponent(value)==0x7ff and \ _mantissa(value)== 0) 6f4eb8bc13b2a97b35da1d7a62e91d96680b'>libiconv: fix the wrong mergewoglinde1 2008-10-15libinconv: split up into .inc and version filewoglinde2 2008-10-15[PR] Change PR to FILE_PR and intro PR as FILE_PR + DISTRO_PRHolger Hans Peter Freyther2 2008-10-15mtn2git: remove .mtn2git_empty files in non-empty directoriesJan Luebbe2 2008-06-06libiconv: update to version 1.12 and fixing libtool-2 buildHenning Heinold4 2007-05-24packages/libiconv: Battle libiconv to not use a rpath (and fix the uclibc build)Holger Freyther1 2006-11-10libiconv: fix SECTIONKoen Kooi1 2006-10-10Remove MAINTAINER fields from recipes, add MAINTAINER file to replace them.Koen Kooi1 2005-06-30import clean BK tree at cset 1.3670Koen Kooi1 2005-02-26Merge nslu2-linux@nslu2-linux.bkbits.net:openembeddedg2@giantshoulder.com1 2004-12-31Merge bk://oe-devel.bkbits.net/openembeddednslu2-linux.adm@bkbits.net1 2004-12-09Merge oe-devel@oe-devel.bkbits.net:openembeddedChris Larson1