logcurve.h

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/*
 * Copyright (C) 2005-2006 Taybin Rutkin <taybin@taybin.com>
 * Copyright (C) 2007-2013 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2009 David Robillard <d@drobilla.net>
 *
 * 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.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
#ifndef __ardour_logcurve_h__
#define __ardour_logcurve_h__
 
#include "pbd/fastlog.h"
#include <glibmm/threads.h>
 
namespace ARDOUR {
 
class LIBARDOUR_API LogCurve {
  public:
        LogCurve (float steepness = 0.2, uint32_t len = 0) {
                l = len;
                S = steepness;
                a = log(S);
                b = 1.0f / log(1.0f + (1.0f / S));
        }
 
        bool operator== (const LogCurve& other) const {
                return S == other.S && l == other.l;
        }
 
        bool operator!= (const LogCurve& other) const {
                return S != other.S || l != other.l;
        }
 
        float value (float frac) const {
                return (fast_log(frac + S) - a) * b;
        }
 
        float value (uint32_t pos) const {
                return (fast_log(((float) pos/l) + S) - a) * b;
        }
 
        float invert_value (float frac) const {
                return (a - fast_log(frac + S)) * b;
        }
 
        float invert_value (uint32_t pos) const {
                return (a - fast_log(((float) pos/l) + S)) * b;
        }
 
        void fill (float *vec, uint32_t veclen, bool invert) const {
                float dx = 1.0f/veclen;
                float x;
                uint32_t i;
 
                if (!invert) {
 
                        vec[0] = 0.0;
                        vec[veclen-1] = 1.0;
 
                        for (i = 1, x = 0; i < veclen - 1; x += dx, i++) {
                                vec[i] = value (x);
                        }
 
                } else {
 
                        vec[0] = 1.0;
                        vec[veclen-1] = 0.0;
 
                        for (i = veclen-2, x = 0.0f; i > 0; x += dx, i--) {
                                vec[i] = value (x);
                        }
                }
        }
 
        float steepness() const { return S; }
        uint32_t length() const { return l; }
 
        void set_steepness (float steepness) {
                S = steepness;
                a = log(S);
                b = 1.0f / log(1.0f + (1.0f / S));
        }
        void set_length (uint32_t len) { l = len; }
 
        mutable Glib::Threads::Mutex lock;
 
  protected:
        float a;
        float b;
        float S;
        uint32_t l;
};
 
class LIBARDOUR_API LogCurveIn : public LogCurve
{
  public:
        LogCurveIn (float steepness = 0.2, uint32_t len = 0)
                : LogCurve (steepness, len) {}
 
        float value (float frac) const {
                return (fast_log(frac + S) - a) * b;
        }
 
        float value (uint32_t pos) const {
                return (fast_log(((float) pos/l) + S) - a) * b;
        }
};
 
class LIBARDOUR_API LogCurveOut : public LogCurve
{
  public:
        LogCurveOut (float steepness = 0.2, uint32_t len = 0)
                : LogCurve (steepness, len) {}
 
};
 
} // namespace ARDOUR
 
#endif /* __ardour_logcurve_h__ */