PowerOfSqrtTwoZoomConstraint.cpp

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/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam.
    
    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.  See the file
    COPYING included with this distribution for more information.
*/

#include "PowerOfSqrtTwoZoomConstraint.h"

#include <iostream>
#include <cmath>


size_t
PowerOfSqrtTwoZoomConstraint::getNearestBlockSize(size_t blockSize,
                                                  RoundingDirection dir) const
{
    int type, power;
    size_t rv = getNearestBlockSize(blockSize, type, power, dir);
    return rv;
}

size_t
PowerOfSqrtTwoZoomConstraint::getNearestBlockSize(size_t blockSize,
                                                  int &type, 
                                                  int &power,
                                                  RoundingDirection dir) const
{
//    std::cerr << "given " << blockSize << std::endl;

    size_t minCachePower = getMinCachePower();

    if (blockSize < (1U << minCachePower)) {
        type = -1;
        power = 0;
        float val = 1.0, prevVal = 1.0;
        while (val + 0.01 < blockSize) {
            prevVal = val;
            val *= sqrt(2);
        }
        size_t rval;
        if (dir == RoundUp) rval = size_t(val + 0.01);
        else if (dir == RoundDown) rval = size_t(prevVal + 0.01);
        else if (val - blockSize < blockSize - prevVal) rval = size_t(val + 0.01);
        else rval = size_t(prevVal + 0.01);
//      std::cerr << "returning " << rval << std::endl;
        return rval;
    }

    unsigned int prevBase = (1 << minCachePower);
    unsigned int prevPower = minCachePower;
    unsigned int prevType = 0;

    size_t result = 0;

    for (unsigned int i = 0; ; ++i) {

        power = minCachePower + i/2;
        type = i % 2;

        unsigned int base;
        if (type == 0) {
            base = (1 << power);
        } else {
            base = (((unsigned int)((1 << minCachePower) * sqrt(2) + 0.01))
                    << (power - minCachePower));
        }

//      std::cerr << "Testing base " << base << std::endl;

        if (base == blockSize) {
            result = base;
            break;
        }

        if (base > blockSize) {
            if (dir == RoundNearest) {
                if (base - blockSize < blockSize - prevBase) {
                    dir = RoundUp;
                } else {
                    dir = RoundDown;
                }
            }
            if (dir == RoundUp) {
                result = base;
                break;
            } else {
                type = prevType;
                power = prevPower;
                result = prevBase;
                break;
            }
        }

        prevType = type;
        prevPower = power;
        prevBase = base;
    }

    if (result > getMaxZoomLevel()) result = getMaxZoomLevel();
    return result;
}   

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