view data/model/PowerOfSqrtTwoZoomConstraint.cpp @ 537:3cc4b7cd2aa5

* Merge from one-fftdataserver-per-fftmodel branch.  This bit of
reworking (which is not described very accurately by the title of
the branch) turns the MatrixFile object into something that either
reads or writes, but not both, and separates the FFT file cache
reader and writer implementations separately.  This allows the
FFT data server to have a single thread owning writers and one reader
per "customer" thread, and for all locking to be vastly simplified
and concentrated in the data server alone (because none of the
classes it makes use of is used in more than one thread at a time).
The result is faster and more trustworthy code.

/* -*- 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;
}