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1 /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */
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2
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3 /*
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4 Sonic Visualiser
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5 An audio file viewer and annotation editor.
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6 Centre for Digital Music, Queen Mary, University of London.
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7 This file copyright 2006 Chris Cannam.
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8
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9 This program is free software; you can redistribute it and/or
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10 modify it under the terms of the GNU General Public License as
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11 published by the Free Software Foundation; either version 2 of the
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12 License, or (at your option) any later version. See the file
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13 COPYING included with this distribution for more information.
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14 */
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15
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16 #include "PowerOfSqrtTwoZoomConstraint.h"
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17
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18 #include <iostream>
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19 #include <cmath>
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20
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21
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22 size_t
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23 PowerOfSqrtTwoZoomConstraint::getNearestBlockSize(size_t blockSize,
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24 RoundingDirection dir) const
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25 {
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26 int type, power;
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27 size_t rv = getNearestBlockSize(blockSize, type, power, dir);
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28 return rv;
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29 }
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30
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31 size_t
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32 PowerOfSqrtTwoZoomConstraint::getNearestBlockSize(size_t blockSize,
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33 int &type,
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34 int &power,
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35 RoundingDirection dir) const
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36 {
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37 // std::cerr << "given " << blockSize << std::endl;
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38
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39 size_t minCachePower = getMinCachePower();
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40
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41 if (blockSize < (1U << minCachePower)) {
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42 type = -1;
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43 power = 0;
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44 float val = 1.0, prevVal = 1.0;
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45 while (val + 0.01 < blockSize) {
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46 prevVal = val;
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47 val *= sqrt(2.f);
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48 }
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49 size_t rval;
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50 if (dir == RoundUp) rval = size_t(val + 0.01);
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51 else if (dir == RoundDown) rval = size_t(prevVal + 0.01);
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52 else if (val - blockSize < blockSize - prevVal) rval = size_t(val + 0.01);
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53 else rval = size_t(prevVal + 0.01);
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54 // SVDEBUG << "returning " << rval << endl;
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55 return rval;
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56 }
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57
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58 unsigned int prevBase = (1 << minCachePower);
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59 unsigned int prevPower = minCachePower;
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60 unsigned int prevType = 0;
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61
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62 size_t result = 0;
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63
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64 for (unsigned int i = 0; ; ++i) {
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65
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66 power = minCachePower + i/2;
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67 type = i % 2;
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68
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69 unsigned int base;
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70 if (type == 0) {
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71 base = (1 << power);
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72 } else {
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73 base = (((unsigned int)((1 << minCachePower) * sqrt(2.) + 0.01))
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74 << (power - minCachePower));
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75 }
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76
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77 // SVDEBUG << "Testing base " << base << endl;
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78
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79 if (base == blockSize) {
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80 result = base;
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81 break;
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82 }
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83
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84 if (base > blockSize) {
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85 if (dir == RoundNearest) {
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86 if (base - blockSize < blockSize - prevBase) {
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87 dir = RoundUp;
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88 } else {
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89 dir = RoundDown;
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90 }
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91 }
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92 if (dir == RoundUp) {
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93 result = base;
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94 break;
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95 } else {
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96 type = prevType;
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97 power = prevPower;
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98 result = prevBase;
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99 break;
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100 }
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101 }
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102
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103 prevType = type;
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104 prevPower = power;
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105 prevBase = base;
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106 }
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107
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108 if (result > getMaxZoomLevel()) result = getMaxZoomLevel();
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109 return result;
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110 }
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