toFloat.cpp
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00001 
00002 //
00003 // Copyright (c) 2002, Industrial Light & Magic, a division of Lucas
00004 // Digital Ltd. LLC
00005 // 
00006 // All rights reserved.
00007 // 
00008 // Redistribution and use in source and binary forms, with or without
00009 // modification, are permitted provided that the following conditions are
00010 // met:
00011 // *       Redistributions of source code must retain the above copyright
00012 // notice, this list of conditions and the following disclaimer.
00013 // *       Redistributions in binary form must reproduce the above
00014 // copyright notice, this list of conditions and the following disclaimer
00015 // in the documentation and/or other materials provided with the
00016 // distribution.
00017 // *       Neither the name of Industrial Light & Magic nor the names of
00018 // its contributors may be used to endorse or promote products derived
00019 // from this software without specific prior written permission. 
00020 // 
00021 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
00022 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
00023 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
00024 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
00025 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
00026 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
00027 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
00028 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
00029 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
00030 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
00031 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
00032 //
00034 
00035 
00036 
00037 
00038 //---------------------------------------------------------------------------
00039 //
00040 //      toFloat
00041 //
00042 //      A program to generate the lookup table for half-to-float
00043 //      conversion needed by class half.
00044 //      The program loops over all 65536 possible half numbers,
00045 //      converts each of them to a float, and prints the result.
00046 //
00047 //---------------------------------------------------------------------------
00048 
00049 
00050 #include <iostream>
00051 #include <iomanip>
00052 
00053 using namespace std;
00054 
00055 //---------------------------------------------------
00056 // Interpret an unsigned short bit pattern as a half,
00057 // and convert that half to the corresponding float's
00058 // bit pattern.
00059 //---------------------------------------------------
00060 
00061 unsigned int
00062 halfToFloat (unsigned short y)
00063 {
00064 
00065     int s = (y >> 15) & 0x00000001;
00066     int e = (y >> 10) & 0x0000001f;
00067     int m =  y        & 0x000003ff;
00068 
00069     if (e == 0)
00070     {
00071         if (m == 0)
00072         {
00073             //
00074             // Plus or minus zero
00075             //
00076 
00077             return s << 31;
00078         }
00079         else
00080         {
00081             //
00082             // Denormalized number -- renormalize it
00083             //
00084 
00085             while (!(m & 0x00000400))
00086             {
00087                 m <<= 1;
00088                 e -=  1;
00089             }
00090 
00091             e += 1;
00092             m &= ~0x00000400;
00093         }
00094     }
00095     else if (e == 31)
00096     {
00097         if (m == 0)
00098         {
00099             //
00100             // Positive or negative infinity
00101             //
00102 
00103             return (s << 31) | 0x7f800000;
00104         }
00105         else
00106         {
00107             //
00108             // Nan -- preserve sign and significand bits
00109             //
00110 
00111             return (s << 31) | 0x7f800000 | (m << 13);
00112         }
00113     }
00114 
00115     //
00116     // Normalized number
00117     //
00118 
00119     e = e + (127 - 15);
00120     m = m << 13;
00121 
00122     //
00123     // Assemble s, e and m.
00124     //
00125 
00126     return (s << 31) | (e << 23) | m;
00127 }
00128 
00129 
00130 //---------------------------------------------
00131 // Main - prints the half-to-float lookup table
00132 //---------------------------------------------
00133 
00134 int
00135 main ()
00136 {
00137     cout.precision (9);
00138 #ifndef HAVE_IOS_BASE
00139     cout.setf (ios::hex, ios::basefield);
00140 #else
00141     cout.setf (ios_base::hex, ios_base::basefield);
00142 #endif
00143 
00144     cout << "//\n"
00145             "// This is an automatically generated file.\n"
00146             "// Do not edit.\n"
00147             "//\n\n";
00148 
00149     cout << "{\n    ";
00150 
00151     const int iMax = (1 << 16);
00152 
00153     for (int i = 0; i < iMax; i++)
00154     {
00155         cout << "{0x" << setfill ('0') << setw (8) << halfToFloat (i) << "}, ";
00156 
00157         if (i % 4 == 3)
00158         {
00159             cout << "\n";
00160 
00161             if (i < iMax - 1)
00162                 cout << "    ";
00163         }
00164     }
00165 
00166     cout << "};\n";
00167     return 0;
00168 }


threemxl
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autogenerated on Fri Aug 28 2015 13:21:08