1+ /*
2+ Copyright 2010 Brent W. Lewis
3+ coder0xff on hotmail
4+
5+ This file is part of QPFloat.
6+
7+ QPFloat is free software: you can redistribute it and/or modify
8+ it under the terms of the GNU General Public License as published by
9+ the Free Software Foundation, either version 3 of the License, or
10+ (at your option) any later version.
11+
12+ QPFloat is distributed in the hope that it will be useful,
13+ but WITHOUT ANY WARRANTY; without even the implied warranty of
14+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15+ GNU General Public License for more details.
16+
17+ You should have received a copy of the GNU General Public License
18+ along with QPFloat. If not, see <http://www.gnu.org/licenses/>.
19+ */
20+
21+ #include " Stdafx.h"
22+ #include " DoubleDecomposition.h"
23+ #include " Helpers.h"
24+
25+ #define DBL_SIGNIFICANT_BITS 52
26+ #define DBL_EXPONENT_BITS 11
27+ #define DBL_EXPONENT_BIAS 0x3FF
28+
29+ #define DBL_MANTISSA_BYTES (DBL_SIGNIFICANT_BITS + 7 ) / 8
30+ #define DBL_EXPONENT_MASK ((1 << DBL_EXPONENT_BITS) - 1 )
31+ #define DBL_EXPONENT_MAX (DBL_EXPONENT_MASK - DBL_EXPONENT_BIAS)
32+ #define DBL_EXPONENT_MIN (-DBL_EXPONENT_BIAS)
33+
34+ #ifdef _MANAGED
35+ #pragma unmanaged
36+ #endif
37+
38+ bool DoubleDecomposition::GetSign ()
39+ {
40+ byte* ptr = (byte*)&value + 7 ;
41+ return (*ptr & (byte)0x80 ) != 0 ;
42+ }
43+
44+ void DoubleDecomposition::SetSign (bool value)
45+ {
46+ byte* ptr = (byte*)&this ->value + 7 ;
47+ if (value)
48+ *ptr |= 0x80 ;
49+ else
50+ *ptr &= 0x7F ;
51+ }
52+
53+ ui16 DoubleDecomposition::GetBiasedExponent ()
54+ {
55+ ui16* ptr = ((ui16*)&this ->value ) + 3 ;
56+ return (ui16)((*ptr >> 4 ) & 0x7FF );
57+ }
58+
59+ void DoubleDecomposition::SetBiasedExponent (ui16 value)
60+ {
61+ const int exponentTruncate = (1 << DBL_EXPONENT_BITS) - 1 ;
62+ ui16* ptr = ((ui16*)&this ->value ) + 3 ;
63+ *ptr = (ui16)(*ptr & 0x800F | (value & exponentTruncate) << 4 );
64+ }
65+
66+ int DoubleDecomposition::GetUnbiasedExponent ()
67+ {
68+ return (int )GetBiasedExponent () - DBL_EXPONENT_BIAS;
69+ }
70+
71+ void DoubleDecomposition::SetUnbiasedExponent (int value)
72+ {
73+ if (value >= DBL_EXPONENT_MAX)
74+ {
75+ bool s = GetSign ();
76+ value = 0 ;
77+ SetSign (s);
78+ SetBiasedExponent ((1 << DBL_EXPONENT_BITS) - 1 ); // infinity
79+ return ;
80+ }
81+ if (value < DBL_EXPONENT_MIN) value = DBL_EXPONENT_MIN; // -1023 results in a subnormal
82+ SetBiasedExponent ((ui16)(value + DBL_EXPONENT_BIAS));
83+ }
84+
85+ void DoubleDecomposition::GetMantissa (byte* data, int byteCount)
86+ {
87+ if (byteCount < DBL_MANTISSA_BYTES) throw -1 ;
88+ BitBlockTransfer (&value, 0 , data, byteCount * 8 - DBL_SIGNIFICANT_BITS, DBL_SIGNIFICANT_BITS); // place in H.O.
89+ }
90+
91+ void DoubleDecomposition::SetMantissa (byte* data, int byteCount)
92+ {
93+ if (GetBiasedExponent () == DBL_EXPONENT_MASK)
94+ {
95+ // cannot set the mantissa while exponent represents infinity
96+ // since it'd create an invalid value
97+ return ;
98+ }
99+ int bitCount = byteCount * 8 ;
100+ double * dptr = &value;
101+ if (bitCount < DBL_SIGNIFICANT_BITS) ClearBlock ((byte*)dptr, 0 , DBL_SIGNIFICANT_BITS);
102+ bool carry = false ;
103+ if (bitCount > DBL_SIGNIFICANT_BITS) carry = ReadBit (data, bitCount - DBL_SIGNIFICANT_BITS - 1 );
104+ // load highest order bits into highest order bits
105+ if (!carry)
106+ {
107+ BitWindowTransfer (data, 0 , bitCount, bitCount, (byte*)dptr, 0 , DBL_SIGNIFICANT_BITS, DBL_SIGNIFICANT_BITS);
108+ }
109+ if (carry)
110+ {
111+ ui64 mantissaMask = ((ui64)1 << DBL_SIGNIFICANT_BITS) - 1 ;
112+ ui64* ui64Ptr = (ui64*)dptr;
113+ if ((*ui64Ptr & mantissaMask) == mantissaMask)
114+ {
115+ // we cannot simply increment because it'd overflow
116+ // instead we clear all the bits and increment the exponent
117+ *ui64Ptr &= ~mantissaMask;
118+ SetBiasedExponent (GetBiasedExponent ()+1 ); // we know it's not ExponentMax already because we checked at the beginning of the func
119+ }
120+ else
121+ {
122+ // we can increment the whole ui64 without it overflowing to the exponent part
123+ // but first we need to copy it in ^^
124+ BitWindowTransfer (data, 0 , bitCount, bitCount, (byte*)dptr, 0 , DBL_SIGNIFICANT_BITS, DBL_SIGNIFICANT_BITS);
125+ (*ui64Ptr)++;
126+ }
127+ }
128+ }
129+
130+ #ifdef _MANAGED
131+ #pragma unmanaged
132+ #endif
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