/*
This file is part of a program that implements a Software-Defined Radio.

Copyright (C) 2007, 2008 Philip A Covington

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

The author can be reached by email at

p.covington@gmail.com

*/

#define WIN32

using System;
using System.Runtime.InteropServices;
using System.Security;

namespace SharpDSP2.Lite
{

    #region FFTW
    internal class FFTW
    {
        private const string library_name = "libfftw3f.dll";

        internal enum fftw_direction : int
        {
            Forward=-1,
            Backward=1
        }

        [Flags]
        internal enum fftw_flags : uint
        {
            Measure=0,
            DestroyInput=1,
            Unaligned=2,
            ConserveMemory=4,
            Exhaustive=8,
            PreserveInput=16,
            Patient=32,
            Estimate=64
        }

        [DllImport(library_name,
        EntryPoint = "fftwf_destroy_plan",
        ExactSpelling = true),
        System.Security.SuppressUnmanagedCodeSecurity]
        internal static extern void destroy_plan(IntPtr plan);

        [DllImport(library_name,
        EntryPoint = "fftwf_cleanup",
        ExactSpelling = true),
        System.Security.SuppressUnmanagedCodeSecurity]
        internal static extern void cleanup();

        [DllImport(library_name,
        EntryPoint = "fftwf_execute",
        ExactSpelling = true),
        System.Security.SuppressUnmanagedCodeSecurity]
        internal static extern void execute(IntPtr plan);

        [DllImport(library_name,
        EntryPoint = "fftwf_plan_dft_1d",
        ExactSpelling = true),
        System.Security.SuppressUnmanagedCodeSecurity]
        internal static extern IntPtr dft_1d(int n, IntPtr input, IntPtr output,
        fftw_direction direction, fftw_flags flags);
    }

    #endregion

    /// <summary>
    /// The DSP Buffer
    /// </summary>

    [Serializable()]
    public class DSPBuffer : IDisposable
    {
        #region Public Members
        public SharpDSP2._1.CPX[] buf_in;
        public SharpDSP2._1.CPX[] buf_out;
        #endregion

        #region Private Members

        private IntPtr plan_fwd_main;
        private IntPtr plan_rev_main;
        private GCHandle h_buf_in;
        private GCHandle h_buf_out;

        private readonly int size;
        private readonly float scalefactor;

        #endregion

        #region Constructor

        public DSPBuffer(int fftSize)
        {
            size = fftSize;

            buf_in = new SharpDSP2._1.CPX[size];
            buf_out = new SharpDSP2._1.CPX[size];

            scalefactor = (float)1.0f/size;

            h_buf_in = GCHandle.Alloc(buf_in, GCHandleType.Pinned);
            h_buf_out = GCHandle.Alloc(buf_out, GCHandleType.Pinned);

            // in: cpx out: tmp_cpx_1
            plan_fwd_main = FFTW.dft_1d(size,
                                        h_buf_in.AddrOfPinnedObject(),
                                        h_buf_out.AddrOfPinnedObject(),
                                        FFTW.fftw_direction.Forward,
                                        FFTW.fftw_flags.Measure);

            // in: tmp_cpx_2 out: tmp_cpx_3
            plan_rev_main = FFTW.dft_1d(size,
                                        h_buf_in.AddrOfPinnedObject(),
                                        h_buf_out.AddrOfPinnedObject(),
                                        FFTW.fftw_direction.Backward,
                                        FFTW.fftw_flags.Measure);
        }

        ~DSPBuffer()
        {
            Dispose(true);
        }

        public void Dispose()
        {
            Dispose(false);
            GC.SuppressFinalize(this);
        }

        private void Dispose(bool bDestructing) // destructor
        {
            FFTW.destroy_plan(plan_fwd_main);
            FFTW.destroy_plan(plan_rev_main);
            h_buf_in.Free();
            h_buf_out.Free();
        }

        #endregion

        #region Public Methods

        public void ClearAll()
        {
            Array.Clear(buf_in, 0, size);
            Array.Clear(buf_out, 0, size);
        }

        public float GetMagnitude(int index)
        {
            return (float)Math.Sqrt(buf_out[index].real *
                                    buf_out[index].real +
                                    buf_out[index].imag *
                                    buf_out[index].imag);

            //if (Math.Abs(cpx[index].real) > Math.Abs(cpx[index].imag))
            //    return (float)(Math.Abs(cpx[index].real) + 0.4 * Math.Abs(cpx[index].imag));
            //else
            //    return (float)(Math.Abs(cpx[index].imag) + 0.4 * Math.Abs(cpx[index].real));
        }

        public void DoFFTForwardMain()
        {
            FFTW.execute(plan_fwd_main);
        }

        public void DoFFTReverseMain()
        {
            FFTW.execute(plan_rev_main);
        }

        public void NormalizeOut()
        {
            for (int i = 0; i < size; i++)
            {
                buf_out[i].real *= this.scalefactor;
                buf_out[i].imag *= this.scalefactor;
            }
        }

        #endregion
    }
}