GNU Radio 2.x: gr_fxpt.h Source File

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# gr_fxpt.h

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    00001 /* -*- c++ -*- */
    00002 /*
    00003  * Copyright 2004 Free Software Foundation, Inc.
    00004  *
    00005  * This file is part of GNU Radio
    00006  *
    00007  * GNU Radio is free software; you can redistribute it and/or modify
    00008  * it under the terms of the GNU General Public License as published by
    00009  * the Free Software Foundation; either version 2, or (at your option)
    00010  * any later version.
    00011  *
    00012  * GNU Radio is distributed in the hope that it will be useful,
    00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
    00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00015  * GNU General Public License for more details.
    00016  *
    00017  * You should have received a copy of the GNU General Public License
    00018  * along with GNU Radio; see the file COPYING.  If not, write to
    00019  * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    00020  * Boston, MA 02111-1307, USA.
    00021  */
    00022 #ifndef INCLUDED_GR_FXPT_H
    00023 #define INCLUDED_GR_FXPT_H
    00024
    00025 #include <gr_types.h>
    00026
    00037 class gr_fxpt
    00038 {
    00039   static const int WORDBITS = 32;
    00040   static const int NBITS = 10;
    00041   static const float s_sine_table[1 << NBITS][2];
    00042   static const float PI = 3.14159265358979323846;
    00043   static const float TWO_TO_THE_31 = 2147483648.0;
    00044 public:
    00045
    00046   static gr_int32
    00047   float_to_fixed (float x)
    00048   {
    00049     return (gr_int32) ((float) x * TWO_TO_THE_31 / PI);
    00050   }
    00051
    00052   static float
    00053   fixed_to_float (gr_int32 x)
    00054   {
    00055     return x * (PI / TWO_TO_THE_31);
    00056   }
    00057
    00061   static float
    00062   sin (gr_int32 x)
    00063   {
    00064     gr_uint32 ux = x;
    00065     int index = ux >> (WORDBITS - NBITS);
    00066     return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1];
    00067   }
    00068
    00069   /*
    00070    * \brief Given a fixed point angle x, return float cosine (x)
    00071    */
    00072   static float
    00073   cos (gr_int32 x)
    00074   {
    00075     gr_uint32 ux = x + 0x40000000;
    00076     int index = ux >> (WORDBITS - NBITS);
    00077     return s_sine_table[index][0] * (ux >> 1) + s_sine_table[index][1];
    00078   }
    00079
    00080 };
    00081
    00082 #endif /* INCLUDED_GR_FXPT_H */