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DGDouble.d

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00001 /*******************************************************************************
00002 
00003         @file DGDouble.d
00004         
00005         Copyright (c) 2004 Kris Bell
00006         
00007         This software is provided 'as-is', without any express or implied
00008         warranty. In no event will the authors be held liable for damages
00009         of any kind arising from the use of this software.
00010         
00011         Permission is hereby granted to anyone to use this software for any 
00012         purpose, including commercial applications, and to alter it and/or 
00013         redistribute it freely, subject to the following restrictions:
00014         
00015         1. The origin of this software must not be misrepresented; you must 
00016            not claim that you wrote the original software. If you use this 
00017            software in a product, an acknowledgment within documentation of 
00018            said product would be appreciated but is not required.
00019 
00020         2. Altered source versions must be plainly marked as such, and must 
00021            not be misrepresented as being the original software.
00022 
00023         3. This notice may not be removed or altered from any distribution
00024            of the source.
00025 
00026         4. Derivative works are permitted, but they must carry this notice
00027            in full and credit the original source.
00028 
00029 
00030                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
00031 
00032         
00033         @version        Initial version, Feb 2005
00034         @author         Kris
00035 
00036 
00037 *******************************************************************************/
00038 
00039 module mango.format.DGDouble;
00040 
00041 private import mango.format.Styled;
00042 
00043 /*******************************************************************************
00044         
00045         External requirements for this package    
00046 
00047 *******************************************************************************/
00048 
00049 extern (C)
00050 {
00051         // these should be linked in via dtoa.c
00052         char*  dtoa (double d, int mode, int ndigits, int* decpt, int* sign, char** rve);
00053         double atod (char* s00, int len, char** se);
00054 
00055 
00056         // callback for dtoa allocation function
00057         void* __dToaMalloc (uint size)
00058         {
00059                 throw new Exception ("unexpected memory request from DGDouble");
00060                 return new byte[2048];
00061         }
00062 }
00063 
00064 
00065 /******************************************************************************
00066 
00067         David Gay's extended conversions between string and floating-point
00068         numeric representations. Use these where you need extended accuracy
00069         for convertions. 
00070 
00071         Note that this class requires the attendent file dtoa.c be compiled 
00072         and linked to the application.
00073 
00074         While these functions are all static, they are encapsulated within 
00075         a class inheritance to preserve some namespace cohesion. One might 
00076         use structs for encapsualtion instead, but then inheritance would 
00077         be lost. Note that the root class, Styled, is abstract to prevent 
00078         accidental instantiation of these classes.
00079 
00080 ******************************************************************************/
00081 
00082 class DGDouble : Styled
00083 {
00084         /**********************************************************************
00085 
00086                 Convert a formatted string of digits to a floating-
00087                 point number. 
00088 
00089         **********************************************************************/
00090 
00091         final static double parse (char[] src, uint* ate=null)
00092         {
00093                 char* end;
00094 
00095                 double x = atod (src.ptr, src.length, &end);
00096                 if (ate)
00097                     *ate = end - src.ptr;
00098                 return x;
00099         }
00100 
00101 
00102         /**********************************************************************
00103 
00104                 Convert float to string based upon Style bits.
00105 
00106         **********************************************************************/
00107 
00108         final static int format (double i, inout Style style)
00109         {
00110                 return style.emit (format (style.workspace, i,
00111                                   (style.flags & Flags.Prec) ? style.precision : 6, 
00112                                    style.type == 'e'));
00113         }
00114 
00115 
00116         /**********************************************************************
00117 
00118                 Convert a floating-point number to a string. Parameter 'mode'
00119                 should be specified thusly:
00120 
00121                 0 ==> shortest string that yields d when read in
00122                         and rounded to nearest.
00123 
00124                 1 ==> like 0, but with Steele & White stopping rule;
00125                         e.g. with IEEE P754 arithmetic , mode 0 gives
00126                         1e23 whereas mode 1 gives 9.999999999999999e22.
00127 
00128                 2 ==> max(1,ndigits) significant digits.  This gives a
00129                         return value similar to that of ecvt, except
00130                         that trailing zeros are suppressed.
00131 
00132                 3 ==> through ndigits past the decimal point.  This
00133                         gives a return value similar to that from fcvt,
00134                         except that trailing zeros are suppressed, and
00135                         ndigits can be negative.
00136 
00137                 4,5 ==> similar to 2 and 3, respectively, but (in
00138                         round-nearest mode) with the tests of mode 0 to
00139                         possibly return a shorter string that rounds to d.
00140                         With IEEE arithmetic and compilation with
00141                         -DHonor_FLT_ROUNDS, modes 4 and 5 behave the same
00142                         as modes 2 and 3 when FLT_ROUNDS != 1.
00143 
00144                 6-9 ==> Debugging modes similar to mode - 4:  don't try
00145                         fast floating-point estimate (if applicable).
00146 
00147         **********************************************************************/
00148 
00149         static final char[] format (char[] dst, double x, uint decimals = 6, bool scientific = false, uint mode=3)
00150         in {
00151            assert (dst.length >= 32);
00152            }
00153         body
00154         {
00155                 char*   end,
00156                         str;
00157                 int     sign,
00158                         decpt;
00159                   
00160                 str = dtoa (x, mode, decimals, &decpt, &sign, &end);
00161                 
00162                 char *p = dst;
00163                 int len = end - str;
00164 
00165                 if (sign)
00166                     *p++ = '-';
00167 
00168                 if (decpt == 9999)
00169                     p[0..len] = str[0..len];
00170                 else
00171                    {
00172                    int exp = decpt - 1;
00173                    sign = 0;
00174                    if (exp < 0)
00175                       {
00176                       exp = -exp;
00177                       sign = 1;
00178                       }
00179 
00180                    // force scientific format if too long ...
00181                    if ((exp + len + 2) > dst.length)
00182                         scientific = true;
00183 
00184                    if (scientific)
00185                       {
00186                       *p++ = *str++;
00187                       *p++ = '.';
00188                       while (str < end)
00189                              *p++ = *str++;
00190                       *p++ = 'e';
00191                       *p++ = (sign) ? '-' : '+';
00192    
00193                       if (exp >= 100)
00194                          {
00195                          *p++ = exp / 100 + '0';
00196                          exp %= 100;
00197                          }
00198                       *p++ = exp / 10 + '0';
00199                       *p++ = exp % 10 + '0';
00200                       }
00201                    else
00202                       {
00203                       if (decpt <= 0)
00204                           *p++ = '0';
00205                       else
00206                          {
00207                          while (decpt > 0)
00208                                {
00209                                *p++ = (str < end) ? *str++ : '0';
00210                                --decpt;
00211                                }
00212                          }
00213                       if (str < end)
00214                          {
00215                          *p++ = '.';
00216                          while (decpt < 0)
00217                                {
00218                                *p++ = '0';
00219                                ++decpt;
00220                                }
00221                          while (str < end)
00222                                 *p++ = *str++;
00223                          }
00224                       } 
00225                    }
00226                          
00227                 return dst[0..(p - dst.ptr)];
00228         }
00229 }
00230 
00231 

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