forked from osmocom/wireshark
85 lines
2.1 KiB
C
85 lines
2.1 KiB
C
/**********************************************************************
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*
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* ieee-float.h
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*
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* Implements simple stuff to convert from IEEE float types
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* to 32-bit longs
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*
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* (C) Ashok Narayanan, 2000
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*
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* $Id: ieee-float.h,v 1.2 2001/02/04 08:21:35 guy Exp $
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*
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* For license details, see the COPYING file with this distribution
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*
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**********************************************************************/
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#ifndef IEEE_FLOAT_H
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#define IEEE_FLOAT_H
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/* Stuff for IEEE float handling */
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#define IEEE_NUMBER_WIDTH 32 /* bits in number */
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#define IEEE_EXP_WIDTH 8 /* bits in exponent */
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#define IEEE_MANTISSA_WIDTH 23 /* IEEE_NUMBER_WIDTH - 1 - IEEE_EXP_WIDTH */
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#define IEEE_SIGN_MASK 0x80000000
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#define IEEE_EXPONENT_MASK 0x7F800000
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#define IEEE_MANTISSA_MASK 0x007FFFFF
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#define IEEE_INFINITY IEEE_EXPONENT_MASK
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#define IEEE_IMPLIED_BIT (1 << IEEE_MANTISSA_WIDTH)
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#define IEEE_INFINITE ((1 << IEEE_EXP_WIDTH) - 1)
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#define IEEE_BIAS ((1 << (IEEE_EXP_WIDTH - 1)) - 1)
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#define MINUS_INFINITY (signed)0x80000000L
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#define PLUS_INFINITY 0x7FFFFFFF
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static inline int ieee_float_is_zero (long number)
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{
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return(!(number & ~IEEE_SIGN_MASK));
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}
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/*
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* simple conversion: ieee floating point to long
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*/
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static long tvb_ieee_to_long (tvbuff_t *tvb, int offset)
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{
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long number;
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long sign;
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long exponent;
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long mantissa;
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number = tvb_get_ntohl(tvb, offset);
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sign = number & IEEE_SIGN_MASK;
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exponent = number & IEEE_EXPONENT_MASK;
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mantissa = number & IEEE_MANTISSA_MASK;
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if (ieee_float_is_zero(number)) {
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/* number is zero, unnormalized, or not-a-number */
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return 0;
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}
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if (IEEE_INFINITY == exponent) {
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/* number is positive or negative infinity, or a special value */
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return (sign? MINUS_INFINITY: PLUS_INFINITY);
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}
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exponent = (exponent >> IEEE_MANTISSA_WIDTH) - IEEE_BIAS;
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if (exponent < 0) {
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/* number is between zero and one */
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return 0;
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}
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mantissa |= IEEE_IMPLIED_BIT;
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if (exponent <= IEEE_MANTISSA_WIDTH)
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mantissa >>= IEEE_MANTISSA_WIDTH - exponent;
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else
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mantissa <<= exponent - IEEE_MANTISSA_WIDTH;
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if (sign)
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return -mantissa;
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else
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return mantissa;
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}
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#endif
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